EW E BASIC CIVIL ENGINEERING S.S. BHAVIKATTI NEWAGEINTERNATIONAL PUBLISILIERSL BASIC CIVIL ENGINEERING This page intentionally left blank BASIC CIVIL ENGINEERING S.S. BHAVIKATTI Emeritus Fellow (AICTE) BVB College of Engineering and Technology, Hubli (Formerly Principal, RYMEC, Bellary Professor & Dean SDMCET, Dharwad and NITK, Surathkal) PUBLISHING FORONEWORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS New Delhi - Bangalore - Chennai - Cochin - Guwahati - Hyderabad Jalandhar - Kolkata - Lucknow»-gMumbaié Ranchi Visit usat wwW.newagepublishers.com M Copyright © 2010, New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publishers All rights reserved. No part of this ebook may be reproduced in any form, by photostat, microlm, xerography, or any other means, or incorporated into any information retrieval system, electronic or mechanical, without the written permission of the publisher. All inquiries should be emailed to rights@newagepublishers.com ISBN (13) : 978-81-224-2853-7 PUBLISHING FORONEWORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS 4835/24,Ansari Road, Daryaganj, New Delhi 110002 Visit us at www.newagepublishers.com All engineeringstudentsshouldknow basiccivil engineeringsincethey needinteractionwith civil engineersin their routine works. Hence all important aspectsof civil engineeringare taught as elements of civil engineering in all over the world. It covers entire syllabus on Basic Civil Engineering.The author has tried to make it studentsfriendly by providing neat sketchesand illustrations with practicalproblems,wherevernecessary. Author hopesthat studentsand faculty will receivethis book wholeheartedly.Corrections,if any and suggestionsfor improvementare Welcome. S.S. BHAVIKATTI This page intentionally left blank Contents Preface v UNIT - I: CIVIL ENGINEERINGMATERIALS 1 TRADITIONAL MATERIALS 1.1 Stones 3 1.2 Bricks II 1.3 Lime 1.4 Cement 18 1.5 Timber 23 1-70 3-32 16 Questions 31 2 MORTARS 2.1 Sand 33-38 33 2.2 Cement Mortar 2.3 Lime Mortar 35 34 2.4 Mud Mortar 36 2.5 Special Mortar 37 2.6 Tests on Mortar 37 Questions 38 3 CONCRETE 39-54 3.1 Plain Concrete 39 3.2 3.3 3.4 3.5 Reinforced Cement Concrete (R.C.C.) 49 Reinforced Brick Concrete(RBC) 50 PrestressedConcrete (PSC) 50 Fibre-Reinforced Concrete (FRC) 51 3.6 Cellular Concrete 3.7 Ferro-Cement 52 52 Questions 53 M ETALS AS BUILDING 4.l Ferrous Metals 4.2 Aluminium 4.3. Copper 58 MATERIALS 55 57 Questions 58 M ISCELLAN EOUS BUILDING 5.l Glass 5.2 Plastics MATERIALS 59-69 59 60 5.3 Bitumen 62 5.4 Asbestos 62 5.5 Paints 63 5.6 Distempers 65 5.7 Vamishes 5.8 Solid and Hollow 5.9 Roong and Flooring Tiles 67 Questions 68 65 Concrete Blocks 66 UNIT - II: BUILDING CONSTRUCTION BUILDING 55-58 PLANNING 6.l 6.2 6.3 6.4 Elements of a Building 73 Basic Requirementsof a Building 76 Planning 77 Planning Suitable Orientation 77 6.5 6.6 6.7 Planning for Energy Efficiency 78 Planning for Suitable Utility 78 Planning for Meeting Other Requirements 79 Questions 71-135 73-81 81 FOUNDATIONS 7.1 Dimensions of Foundation 82 7.2 7.3 Conventional SpreadFootings 83 R.C.C. Footings 84 7.4 Grillage Footing 86 82-91 7.5 Arch Foundation 87 7.6 Pile Foundations 87 7.7 Foundations in Black Questions 8 SJPER Cotton Soil 89 91 STRUCTURES 92-127 8.1 Types of Super StructuresBasedon the Method of Load Transfer 92 8.2 Walls 8.3 8.4 8.5 8.6 8.7 StoneMasonry 94 Brick Masonry 97 Plastering 100 Pointing 101 Flooring 101 8.8 Roof 8.9 Doors and Windows 8.10 Lintels 8.1 1 Stairs 93 105 113 122 I 23 Questions 126 9 DAM PN ESS AND 9.1 9.2 9.3 9.4 9.5 ITS PREVENTION Causesof Dampness 128 Ill-Effects of Dampness 129 Requirementsof an Ideal Material for Damp Proong Materials for Damp Proong 130 Methods of Damp Proong 130 Questions 132 10 COST EFFECTIVE CONSTRUCTION IN MASS HOUSING 10.1 128-132 Minimum 129 TECHNIQUES 133-135 SCHEMES Standards 133 10.2 Approach to Cost Effective Mass Housing Schemes 134 10.3 Cost Effective Construction Techniques 135 Questions 135 UNW-I":SUmEYmG 11 INTRODUCTION TO SURVEYING 11.1 Object and Uses of Surveying 139 11.2 Primary Divisions in Surveying 140 137-236 139-148 11.3 FundamentalPrinciples of Surveying 141 11.4 Classication of Surveying 142 11.5 Plans and Maps 143 11.6 Scales 144 11.7 Types of Graphical Scales 145 11.8 Units of Measurements 148 Questions 148 12 UNEAR MEASUREMENTSAND of Linear CHAIN 12.1 Methods 12.2 12.3 12.4 12.5 12.6 12.7 12.8 Instrumentsused in Chaining 154 Chain Surveying 156 Ranging I 62 Obstaclesin Chaining 163 Errors in Chaining I 67 Tape Corrections 168 Conventional Symbols 173 Questions 175 Measurements SURVEYING 149 13 COM PASS SURVEYING 176-194 13.1 13.2 13.3 13.4 13.5 Types of Compass 176 Method of Using a Compass 180 Bearing 180 Whole Circle Bearing and ReducedBearing 180 Computation of Angles I 82 13.6 Declination 13.7 Local Attraction and DIP 149-175 I 84 18 7 13.8 Chain and CompassSurveying Field Work 190 Questions 14 PLAN E TABLE 193 SU RVEYIN G 195-208 14.1 Plane Table and its Accessories 14.2 14.3 14.4 14.5 Working Operations 198 Methods of Plane Tabling 199 Errors in Plane Table Surveying 206 Advantagesand Limitations of Plane Table Survey 207 Questions 207 195 15 LEVEL AND 15.1 15.2 15.3 15.4 15.5 15.6 LEVELUNG 209-225 Object and Uses of Levelling 209 Terms Used in Levelling 209 Levelling Instruments 21] Levelling Staff 213 Methods of Levelling 214 Terms Used in Direct Method of Levelling 215 15.7 TemporaryAdjustments of a Level 216 15.8 Types of Direct Levelling 21 7 Questions 225 16 MODERN 16.1 TOOLSOF Theodolite SURVEYING 226-236 226 16.2 Electromagnetic Distance Measuring Instruments 23] 16.3 Total Station 233 16.4 Global Positioning System 235 Questions 236 UNIT - IV: MAPPING AND SENSING 17 MAPPING AND CONTOURING 237-268 17.1 Mapping 239 17.2 Contours 241 17.3 Methods of Contouring 243 Drawing Contours 246 Questions 246 18 AREAS AND 239-246 VOLUMES 18.1 Computation of Areas from Field Notes 24 7 18.2 Computing Areas from Maps 252 18.3 Computation of Volumes 256 Questions 19 REMOTE 264 SENSING 247-265 AND ITS APPUCATIONS 19.1 Remote sensing 266 19.2 GeographicalInformation System(GIS) 267 Questions 268 266-268 UNIT - V: DISASTER RESISTANT BUILDING 20 20.1 DISASTER RESISTANT BUILDINGS 21 22 20.2 20.3 CIVIL ENGINEERING MATERIALS This page intentionally left blank lliatliliunal Materials Stones, bricks, cement, lime and timber are the traditional materials used for civil engineering constructionsfor several centuries.In this chaptertypes, properties,testsand usesof thesematerials is explained. 1.1 STONES Stoneis a naturally available building material which hasbeenusedfrom the early age of civilization. It is available in the form of rocks, which is cut to required size and shapeand used as building block. It hasbeen usedto construct small residential buildings to large palacesand templesall over the World. Red Fort, Taj Mahal, Vidhan Sabhaat Bangaloreand severalpalacesof medieval age all over India are the famous stonebuildings. 1.1.1 Type of Stones Stonesused for civil engineeringWorksmay be classified in the following three Ways: 0 Geological 0 Physical 0 Chemical Geological Classication Basedon their origin of formation stonesare classified into three main groupsIgneous, sedimentary and metamorphic rocks. (i) Igneous Rocks: Theserocks are formed by cooling and solidifying of the rock massesfrom their molten magmatic condition of the material of the earth. Generally igneous rocks are strong and durable. Granite, trap and basalt are the rocks belonging to this category,Granites are formed by slow cooling of the lava under thick cover on the top. Hence they have crystalline surface.The cooling of lava at the top surfaceof earth results into noncrystalline and glassy texture. Trap and basalt belong to this category. (ii) Sedimentary Rocks: Due to weathering action of water, wind and frost existing rocks disintegrates.The disintegratedmaterial is carried by Wind and Water;the Waterbeing most powerful medium. Flowing Waterdepositsits suspendedmaterials at somepoints of obstaclesto its ow. These depositedlayersof materialsget consolidatedunderpressureandby heat.Chemical agentsalso contribute to the cementingof the deposits.The rocks thus formed are more uniform, ne grained and compact in their nature. They representa bedded or stratied structure in general. Sand stones,lime stones,mud stonesetc. belong to this class of rock. (iii) Metamorphic Rocks: Previously formed igneous and sedimentaryrocks under go changes due to metamorphicaction of pressureand internal heat.For exampledue to metamorphicaction granite becomesgreisses,trap and basalt changeto schist and laterite, lime stonechangesto marble, sandstone becomesquartzite and mud stonebecomesslate. PhysicalClassication Based on the structure, the rocks may be classified as: 0 Stratified rocks 0 Unstratified rocks (i) Stratified Rocks: These rocks are having layered structure. They possess planes of stratification or cleavage.They can be easily split along theseplanes.Sandstones,lime stones,slateetc. are the examplesof this class of stones. (ii) Unstratied Rocks: These rocks are not stratified. They possesscrystalline and compact grains. They cannot be split in to thin slab. Granite, trap, marble etc. are the examplesof this type of rocks. (iii) Foliated Rocks: These rocks have a tendency to split along a definite direction only. The direction need not be parallel to each other as in caseof stratified rocks. This type of structure is very common in caseof metamorphicrocks. Chemical Classication On the basis of their chemical composition engineersprefer to classify rocks as: 0 Silicious rocks 0 Argillaceous rocks and 0 Calcareous rocks (i) Silicious rocks: The main contentof theserocks is silica. They arehard and durable.Examples of such rocks are granite, trap, sand stonesetc. (ii) Argillaceous rocks: The main constituent of theserocks is argil i.e., clay. These stonesare hard and durable but they are brittle. They cannot Withstandshock. Slatesand laterites are examplesof this type of rocks. (iii) Calcareous rocks: The main constituent of these rocks is calcium carbonate. Limestone is a calcareousrock of sedimentaryorigin While marble is a calcareous rock of metamorphicorigin. 1.1.2 Properties of Stones The following properties of the stones should be looked into before selecting them for engineering works: (i) Structure: The structure of the stone may be stratified (layered) or unstratified. Structured stonesshould be easily dressedand suitable for superstructure.Unstratied stonesare hard and difficult to dress.They are preferred for the foundation works. (ii) Texture: Fine grained stoneswith homogeneousdistribution look attractive and hencethey are used for carving. Such stonesare usually strong and durable. (iii) Density: Denserstonesare stronger.Light weight stonesareweak. Hencestoneswith specific gravity less than 2.4 are consideredunsuitable for buildings. (iv) Appearance: A stone with uniform and attractive colour is durable, if grains are compact. Marble and granite get very good appearance,when polished. Hence they are used for face works in buildings. (v) Strength: Strengthis an important property to be looked into before selectingstoneasbuilding block.Indianstandardcoderecommends, a minimumcrushingstrengthof 3.5N/mmzfor anybuilding block. Table 1.1 shows the crushing strength of various stones.Due to nonuniformity of the material, usually a factor of safety of 10 is usedto find the permissible stressin a stone.Hence even laterite can be used safely for a single storey building, becausein such structuresexpectedload can hardly give a stressof 0.15N/mm2.Howeverin stonemasonrybuildingscareshouldbe takento checkthe stresses when the beams(ConcentratedLoads) are placed on laterite wall. 3Table1.1.Crushing strength of common buildingstones 31 Nameof Stone CrushingStrengthin N/mmz Trap 300 to 350 Basalt 153 to 189 Granite 104 to 140 Slate 70 to 210 Marble 72 Sand stone 65 Lime stone 55 Laterite 1.8 to 3.2 (vi) Hardness: It is an important property to be consideredwhen stone is used for ooring and pavement.Coefficient of hardnessis to be found by conducting test on standardspecimen in Dorys testing machine.For road works coefcient of hardnessshouldbe at least 17.For building works stones with coefficient of hardness less than 14 should not be used. (vii) Percentagewear: It is measuredby attrition test. It is an important property to be considered in selecting aggregatefor road works and railway ballast. A good stone should not show wear of more than 2%. (viii) Porosity and Absorption: All stoneshave pores and hence absorb water. The reaction of water with material of stone causedisintegration. Absorption test is specied as percentageof water absorbedby the stone when it is immersed under water for 24 hours. For a good stone it should be as small as possible and in no casemore than 5. (ix) Weathering: Rain and wind cause loss of good appearanceof stones.Hence stoneswith good weatherresistanceshould be used for face works. (x) Toughness: The resistanceto impact is called toughness.It is determined by impact test. Stoneswith toughnessindex more than 19 are preferred for road works. Toughnessindex 13 to 19 are consideredas medium tough and stoneswith toughnessindex less than 13 are poor stones. (xi) Resistance to Fire: Sand stonesresist fire better. Argillaceous materials, though poor in strength,are good in resisting fire. (xii) Ease in Dressing: Cost of dressing contributes to cost of stone masonry to a great extent. Dressing is easy in stoneswith lesser strength.Hence an engineer should look into sufficient strength rather than high strength while selecting stonesfor building works. (xiii) Seasoning: The stonesobtained from quarry contain moisture in the pores.The strength of the stoneimproves if this moisture is removedbefore using the stone.The processof removing moisture from pores is called seasoning.The best way of seasoningis to allow it to the action of nature for 6 to 12 months. This is very much required in the caseof laterite stones. 1.1.3 Requirementsof Good Building Stones The following are the requirementsof good building stones: (i) Strength: The stone should be able to resist the load coming on it. Ordinarilly this is not of primary concernsinceall stonesare having good strength.However in caseof large structure,it may be necessaryto check the strength. (ii) Durability: Stonesselectedshould be capableof resisting adverseeffects of natural forces like wind, rain and heat. (iii) Hardness: The stone used in floors and pavementsshould be able to resist abrasive forces causedby movement of men and materials over them. (iv) Toughness: Building stones should be tough enough to sustain stressesdeveloped due to vibrations. The vibrations may be due to the machinery mounted over them or due to the loads moving over them. The stone aggregatesused in the road constructionsshould be tough. (v) Specific Gravity: Heavier variety of stones should be used for the construction of dams, retaining walls, docks and harbours.The specific gravity of good building stoneis between2.4 and 2.8. (vi) Porosity and Absorption: Building stone should not be porous. If it is porous rain water entersinto the pour and reacts with stone and crumbles it. In higher altitudes, the freezing of water in pores takes place and it results into the disintegration of the stone. (vii) Dressing: Giving required shapeto the stoneis called dressing.It should be easyto dressso that the cost of dressingis reduced.However the care should be taken so that, this is not be at the cost of the required strength and the durability. (viii) Appearance: In caseof the stonesto be used for face works, where appearanceis a primary requirement,its colour and ability to receive polish is an important factor. (ix) Seasoning: Good stonesshould be free from the quarry sap. Laterite stonesshould not be used for 6 to 12 months after quarrying. They are allowed to get rid of quarry sap by the action of nature. This processof removing quarry sap is called seasoning. (x) Cost: Cost is an important consideration in selecting a building material. Proximity of the quarry to building site brings down the cost of transportationand hencethe cost of stonescomesdown. However it may be noted that not a single stone can satisfy all the requirements of a good building stones, since one requirement may contradict another.For example, strength and durability requirementcontradictseaseof dressingrequirement.Hence it is necessarythat site engineerlooks into the properties required for the inteded work and selectsthe stone. 1.1.4 Tests on Stones To acertain the required properties of stones,the following tests can be conducted: (i) crushing strength test (ii) water absorption test (iii) abrasion test (iv) impact test (v) acid test. (i) Crushing Strength Test: For conducting this test, specimenof size 40 x 40 x 40 mm are prepared from parent stone. Then the sides are finely dressedand placed in water for 3 days. The saturatedspecimenis provided with a layer of plaster of paris on its top and bottom surfacesto get even surface so that load applied is distributed uniformly. Uniform load distribution can be obtained satisfactorily by providing a pair of 5 mm thick playwood instead of using plaster of paris layer also. The specimenso placedin the compression testingmachineis loadedat the rate of 14 N/mmzper minute. The crushing load is noted. Then crushing strengthis equal to the crushing load divided by the areaover which the load is applied. At least three specimenshould be testedand the averageshould be taken as crushing strength. (ii) Water Absorption Test: For this test cube specimenweighing about 50 grams are prepared and the test is carried out in the stepsgiven below: (a) Notethe weightof dry specimentasW1. (b) Place the specimenin water for 24 hours. (c) Takeout the specimen,wipe out the surfacewith a piece of cloth and weigh the specimen. Let its weightbeW2. (d) Suspendthe specimenfreelyin waterandweightit. Let its weightbeW3. (e) Place the specimenin boiling water for 5 hours. Then take it out, wipe the surface with cloth andweighit. Let this weightbeW4.Then, Percentageabsorptionby weight = W2 W1 W1 W2 W Percentageabsorptionby volume = l W2 X 100 x 100 w3 ...(l) ...(2) Percentageporosity by volume = W2 x 100 W3 Density = -W-1 Specificgravity =l Saturation W2 W1 W W2 - W3 coefficient ...(3) ...(4) ...(5) _ Waterabsorption , Total porosity w2w1 W4W1 (iii) Abrasion Test: This test is carried out on stones which are used as aggregatesfor road construction. The test result indicate the suitability of stones against the grinding action under trafc. Any one of the following test may be conductedto find out the suitability of aggregates: (i) Los Angeles abrasiontest (ii) Deval abrasion test (iii) Dorrys abrasiontest. However Los Angelesabrasiontest is preferredsincethesetest resultsarehaving good correlation with the performanceof the pavements. The Los Angeles apparatus[Fig 1.1] consists of a hollow cylinder 0.7 m inside diameter and 0.5 m long with both ends closed. It is mounted on a frame so that it can be rotated about horizontal axis. IS codehasstandardisedthe test procedurefor different gradationof specimen.Along with specied weight of specimena specied number of cast iron balls of 48 mm diameter are placed in the cylinder. Fig. 1.1. Los Angelestesting machine Then the cylinder is rotated at a speedof 30 to 33 rpm for specified numberof times (500 to 1000).Then the aggregateis removed and sieved on 1.7 mm. IS sieve. The Weight of aggregatepassing is found. Then Los Angeles value is found as _ Weight of aggregatepassingthrough sieve _ x 100. Original Weight The following values are recommendedfor road Works: For bituminous mixes For base course 30% 50% (iv) Impact Test: The resistanceof stonesto impact is found by conducting tests in impacting testing machine (Fig. 1.2). It consistsof a frame with guides in which a metal hammerWeighing 13.5to 15 kg can freely fall from a height of 380 mm. Hammer of weight 132-137 N Cup 102 mm Dia and height 50 mm Circular base Fig. 1.2. Aggregateimpact testing machine Aggregatesof size 10 mm to 12.5 mm are filled in cylinder in 3 equal layers; each layer being tamped 25 times. The sameis then transferred to the cup and again tamped 25 times. The hammer is then allowed to fall freely on the specimen 15 times. The specimenis then sieved through 2.36 mm sieve. Then, W Impactvalue= 2 W1 Where W2= Weightof fines W 1 = original Weight. The recommendedimpact values for various works are: (i) for Wearingcourse :4 30% (ii) for bituminous mechadam :9 35% (iii) for water bound mechadam )4 40% (v) Acid Test:This test is normally carried out on sand stonesto check the presenceof calcium carbonate,which weakensthe weather resisting quality. In this test, a sample of stone weighing about 50 to 100 gm is taken and kept in a solution of one per cent hydrochloric acid for seven days. The solution is agitated at intervals. A good building stone maintains its sharp edgesand keeps its surface intact. If edgesare broken and powder is formed on the surface,it indicates the presenceof calcium carbonate.Such stoneswill have poor weather resistance. 1.1.5 Uses of Stones Stonesare used in the following civil engineering constructions: (i) Stonemasonry is used for the construction of foundations, walls, columns and arches. (ii) Stonesare used for ooring. (iii) Stoneslabs are used as damp proof courses,lintels and even as roofing materials. (iv) Stoneswith good appearanceare used for the face works of buildings. Polishedmarbles and granite are commonly used for face works. (v) Stonesare used for paving of roads, footpaths and open spacesround the buildings. (vi) Stonesare alsousedin the constructionsof piers and abutmentsof bridges,damsandretaining walls. (vii) Crushedstoneswith graved are used to provide basecoursefor roads.When mixed with tar they form finishing coat. (viii) Crushed stonesare used in the following works also: (a) As a basic inert material in concrete (1))For making articial stonesand building blocks (c) As railway ballast. 1.1.6 Common Building Stones The following are the someof commonly used stones: (i) Basalt and trap (iii) Sand stone (v) Laterite (vii) Gneiss (ii) Granite (iv) Slate (vi) Marble (viii) Quartzite. Their qualities and usesare explained below: (i) Basalt and Trap: The structureis medium to ne grained and compact.Their colour varies fromdarkgrayto black.Fractures andjointsarecommon.Theirweightvariesfrom 18kN/m3to 29kN/m3. The compressive strengthvariesfrom 200 to 350N/mmz.Theseareigneousrocks.They areusedas road metals, aggregatesfor concrete.They are also used for rubble masonry works for bridge piers, river walls and dams.They are used as pavement. (ii) Granite: Granites are also igneous rocks. The colour varies from light gray to pink. The structure is crystalline, ne to coarsegrained. They take polish well. They are hard durable. Specific gravityis from 2.6 to 2.7 andcompressive strengthis 100to 250N/mm2.Theyareusedprimarily for bridge piers, river walls, and for dams. They are used as kerbs and pedestals.The use of granite for monumental and institutional buildings is common. Polished granites are used as table tops, cladding for columns and wall. They are used as coarseaggregatesin concrete. (iii) Sand stone: These are sedimentaryrocks, and hence stratified. They consist of quartz and feldspar. They are found in various colours like white, grey, red, buff, brown, yellow and even dark gray.Thespecificgravityvariesfrom 1.85to 2.7andcompressive strengthvariesfrom20to 170N/mm2. Its porosity varies from 5 to 25 per cent. Weatheringof rocks rendersit unsuitable as building stone.It is desirableto use sand stoneswith silica cement for heavy structures,if necessary.They are used for masonry work, for dams, bridge piers and river walls. (iv) Slate: Theseare metamorphicrocks. They are composedof quartz, mica and clay minerals. The structure is ne grained. They split along the planes of original bedding easily. The colour varies from dark gray, greenish gray, purple gray to black. The specific gravity is 2.6 to 2.7. Compressive strengthvariesfrom 100to 200N/mmz.Theyareusedasroong tiles, slabs,pavements etc. (v) Laterite: It is a metamorphicrock. It is having porous and spongesstructure.It containshigh percentageof iron oxide. Its colour may be brownish, red, yellow, brown and grey. Its specific gravity is 1.85andcompressive strengthvariesfrom 1.9to 2.3N/mmz.It canbeeasilyquarriedin blocks.With seasoningit gains strength.When used as building stone, its outer surface should be plastered. (vi) Marble: This is a metamorphic rock. It can take good polish. It is available in different pleasing colours like white and pink. Its specic gravity is 2.65 and compressivestrength is 70~75 N/ mm2.It is usedfor facingandornamentalworks.It is usedfor columns,ooring, stepsetc. (vii) Gneiss: It is a metamorphic rock. It is having ne to coarse grains. Alternative dark and white bands are common. Light grey, pink, purple, greenishgray and dark grey coloured varieties are available. These stonesare not preferred becauseof deleteriousconstituentspresentin it. They may be used in minor constructions. However hard varieties may be used for buildings. The specic gravity variesfrom 2.5to 3.0 andcrushingstrengthvariesfrom 50 to 200N/mmz. (viii) Quartzite: Quartzites are metamorphic rocks. The structure is fine to coarse grained and often granular and branded.They are available in different colours like white, gray, yellowish. Quartz is the chief constituentwith feldspar and mica in small quantities.The specic gravity varies from 2.55 to 2.65.Crushingstrengthvariesfrom 50to 300N/mmz.Theyareusedasbuildingblocksandslabs.They are also used as aggregatesfor concrete. I1.2 BRICKS Brick is obtainedby moulding good clay into a block, which is dried and then burnt. This is the oldest building block to replace stone. Manufacture of brick started with hand moulding, sun drying and burning in clamps. A considerableamount of technological development has taken place with better knowledgeaboutto propertiesof raw materials,better machinariesand improved techniquesof moulding drying and burning. The size of the bricks are of 90 mm x 90 mm x 90 mm and 190 mm x 90 mm x 40 mm. With mortar joints, the size of thesebricks are taken as 200 mm x 100 mm X 100 mm and 200 mm X 100 mm 2/ 1 5,, X50mm. However theoldsize of8Z x4-2 X2-2-g giving amasonary size of9x4 1,, x3' isstill commonly used in India. 1.2.1 Typesof Bricks Bricks may be broadly classified as: (i) Building bricks (ii) Paving bricks (iii) Fire bricks (iv) Special bricks. (i) Building Bricks: Thesebricks are used for the construction of walls. (ii) Paving Bricks: Theseare vitried bricks and are used as pavers. (iii) Fire Bricks: Thesebricks are specially madeto withstand furnacetemperature.Silica bricks belong to this category. (iv) Special Bricks: These bricks are different from the commonly used building bricks with respectto their shapeand the purpose for which they are made. Some of such bricks are listed below: (a) Specially shapedbricks (b) Facing bricks (c) Perforatedbuilding bricks (d) Burnt clay hollow bricks (e) Sewer bricks (f) Acid resistant bricks. (a) Specially Shaped Bricks: Bricks of special shapes are manufactured to meet the requirementsof different situations. Some of them are shown in Fig. 1.3. EE Bull nosed brick Cant brick Channel brick \ \\ Coping brick Plinth brick Cornice brick Fig. 1.3. Specialshapedbricks (b) Facing Bricks: Thesebricks are usedin the outer face of masonry.Oncethesebricks are provided, plastering is not required. The standardsize of these bricks are 190 x 90 x 90mmor l90><90><40mm. (c) Perforated Building Bricks: Thesebricks are manufacturedwith area of perforation of 30to 45percent.Theareaof eachperforationshouldnotexceed500ml. Theperforation should be uniformly distributed over the surface.They are manufacturedin the size 190 X l90><90mmand290><90x90mm. (d) Burnt Clay Hollow Bricks: Figure 1.4 shows a burnt clay hollow brick. They are light in weight. They areusedfor the constructionof partition walls. They provide goodthermal insulation to buildings. They are manufactured in the sizes 190 x 190 X 90 mm, 290 X 90 x 90 mm and 290 x 140 x 90 mm. The thicknessof any shell should not be less than 11 mm and that of any web not less than 8 mm. WEBS 8 mm minimum thick Fig. 1.4. Hollow bricks (e) Sewer Bricks: These bricks are used for the construction of sewage lines. They are manufacturedfrom surface clay, re clay shale or with the combination of these.They are manufacturedin the sizes 190 X 90 x 90 mm and 190 x 90 x 40 mm. The average strength of thesebricks shouldbe a minimumof 17.5N/mm2. The waterabsorption should not be more than 10 per cent. (f ) Acid Resistant Bricks: Thesebricks are used for oorings likely to be subjectedto acid attacks,lining of chambersin chemical plants, lining of sewerscarrying industrial wastes etc. These bricks are made of clay or shale of suitable composition with low lime and iron content, int or sandand vitried at high temperaturein a ceramic kiln. 1.2.2 Properties of Bricks The following are the required properties of good bricks: (i) Colour: Colour should be uniform and bright. (ii) Shape: Bricks should haveplane faces.They shouldhave sharpand true right angledcorners. (iii) Size: Bricks should be of standardsizesas prescribedby codes. (iv) Texture: They should possessne, dense and uniform texture. They should not possess ssures, cavities, loose grit and unburnt lime. (v) Soundness: When struck with hammer or with another brick, it should produce metallic sound. (vi) Hardness: Finger scratching should not produce any impression on the brick. (vii) Strength: Crushingstrengthof brick shouldnot be less than 3.5 N/mm2' A field test for strengthis that when droppedfrom a height of 0.9 m to 1.0 mm on a hard ground, the brick should not break into pieces. (viii) Water Absorption: After immercing the brick in water for 24 hours, water absorptionshould not be more than 20 per cent by weight. For classI works this limit is 15 per cent. (ix) Eforescence: Bricks should not show white patcheswhen soakedin water for 24 hours and then allowed to dry in shade.White patches are due to the presenceof sulphateof calcium, magnesium and potassium.They keep the masonrypermanently in damp and wet conditions. (x) Thermal Conductivity: Bricks should have low thermal conductivity, so that buildings built with them are cool in summer and warm in winter. (xi) Sound Insulation: Heavier bricks arepoor insulatorsof soundwhile light weight and hollow bricks provide good sound insulation. (xii) Fire Resistance: Fire resistanceof bricks is usually good. In fact bricks are used to encase steel columns to protect them from fire. 1.2.3 Tests on Bricks The following laboratory tests may be conductedon the bricks to find their suitability: (i) Crushing strength (ii) Absorption (iii) Shapeand size and (iv) Eforescence. (i) Crushing Strength: The brick specimenare immersedin water for 24 hours.The frog of the brick is filled flush with 1:3 cementmortar and the specimenis storedin dampjute bag for 24 hours and then immersed in clean water for 24 hours. The specimenis placed in compressiontesting machine with 6 mm plywood on top and bottom of it to get uniform load on the specimen.Then load is applied axially at a uniformrateof 14N/mmz. The crushingload is noted.Thenthe crushingstrengthis the ratio of crushing load to the area of brick loaded. Average of ve specimenis taken as the crushing strength. (ii) Absorption Test: Brick specimenare weighed dry. Then they are immersed in water for a period of 24 hours. The specimenare taken out and wiped with cloth. The weight of each specimenin wet condition is determined.The difference in weight indicate the water absorbed.Then the percentage absorptionis the ratio of water absorbedto dry weight multiplied by 100.The averageof five specimen is taken. This value should not exceed20 per cent. (iii) Shape and Size: Bricks should be of standardsize and edgesshould be truely rectangular with sharp edges.To check it, 20 bricks are selectedat random and they are stackedalong the length, along the width and then along the height. For the standardbricks of size 190 mm X 90 mm x 90 mm. IS code permits the following limits: Lengthwise: 3680 to 3920 mm Widthwise: 1740 1860 mm Heightwise: 1740 to to 1860 mm. The following eld tests help in acertainingthe good quality bricks: (i) uniformity in size (ii) uniformity in colour (iii) structure (iv) hardness test (v) sound test (vi) strength test. (i) Uniformity in Size: A good brick should have rectangularplane surfaceand uniform in size. This check is made in the field by observation. (ii) Uniformity in Colour: A good brick will be having uniform colour throughout. This observationmay be made before purchasingthe brick. (iii) Structure: A few bricks may be broken in the eld and their crosssectionobserved.The section should be homogeneous,compact and free from defects such as holes and lumps. (iv) Sound Test: If two bricks are struck with eachother they should produceclear ringing sound. The sound should not be dull. (v) Hardness Test: For this a simple field test is scratch the brick with nail. If no impression is marked on the surface,the brick is sufciently hard (vi) Elorescense: The presenceof alkalies in brick is not desirablebecausethey form patches of gray powder by absorbingmoisture. Henceto determinethe presenceof alkalies this test is performed as explained below: Placethe brick specimenin a glassdish containing water to a depth of 25 mm in a well ventilated room. After all the water is absorbedor evaporatedagain add water for a depth of 25 mm. After second evaporation observe the bricks for white/grey patches.The observation is reported as nil, slight, moderate, heavy or seriousto mean (a) Nil: No patches (b) Slight: 10% of area covered with deposits (c) Moderate: 10 to 50% areacoveredwith depositbut unaccompaniedby aking of the surface. (d) Heavy: More than 50 per cent area covered with depositsbut unaccompaniedby aking of the surface. (e) Serious:Heavy depositsof salt accompaniedby aking of the surface. 1.2.4 Classication of Bricks Basedon their Quality The bricks used in construction are classified as: (i) First class bricks (ii) Second class bricks (iii) Third class bricks and (iv) Fourth class bricks (i) First Class Bricks: These bricks are of standard shapeand size. They are burnt in kilns. They fulll all desirableproperties of bricks. (ii) Second ClassBricks: Thesebricks are ground moulded and burnt in kilns. The edgesmay not be sharpand uniform. The surfacemay be somewhat rough. Suchbricks are commonly usedfor the construction of walls which are going to be plastered. (iii) Third Class Bricks: Thesebricks are ground moulded and burnt in clamps. Their edgesare somewhatdistorted. They produce dull sound when struck together.They are used for temporary and unimportant structures. (iv) Fourth Class Bricks: Theseare the over burnt bricks. They are dark in colour. The shapeis irregular. They are used as aggregatesfor concretein foundations, oors and roads. 1.2.5 Uses of Bricks Bricks are used in the following civil works: (i) As building blocks. (ii) For lining of ovens, furnacesand chimneys. (iii) For protecting steel columns from fire. (iv) As aggregatesin providing water proofing to R.C.C. roofs. (v) For pavers for footpaths and cycle tracks. (vi) For lining sewer lines. l1.3 LIME It is an important binding material used in building construction.Lime hasbeen used asthe material of construction from ancient time. When it is mixed with sandit provides lime mortar and when mixed with sandand coarseaggregate,it forms lime concrete. 1.3.1 Typesof Limesand their Properties The limes are classified as fat lime, hydraulic lime and poor lime: (i) Fat lime: It is composedof 95 percentageof calcium oxide. When water is added,it slakes vigorously anditsvolume increases to2to23 times. It iswhiteincolour. Itsproperties are: (a) hardensslowly (b) has high degreeof plasticity (c) setsslowly in the presenceof air (d) white in colour (e) slakes vigorously. (ii) Hydraulic lime: It contains clay and ferrous oxide. Depending upon the percentageof clay present, the hydraulic lime is divided into the following three types: (a) Feebly hydraulic lime (5 to 10% clay content) (b) Moderately hydraulic lime (11 to 20% clay content) (c) Eminently hydraulic lime (21 to 30% clay content) The properties of hydraulic limes are: 0 Sets under water 0 Colour is not perfectly white 0 Forms a thin pastewith water and do not dissolve in water. 0 Its binding property improves if its fine powder is mixed with sand and kept in the form of heap for a week, before using. (iii) Poor lime: It containsmore than 30% clay. Its colour is muddy. It haspoor binding property. The mortar made with such lime is used for inferior works. IS 712-1973 classifies lime as class A, B, C, D and E. ClassA Lime: It is predominently hydraulic lime. It is normally supplied as hydratedlime and is commonly used for structural works. Class B Lime: It contains both hydraulic lime and fat lime. It is supplied as hydrated lime or as quick lime. It is used for making mortar for masonry works. Class C Lime.It is predorninentlyfat lime, suppliedboth as quick lime and fat lime. It is usedfor finishing coat in plastering and for white washing. Class D Lime: This lime contains large quantity of magnesiumoxide and is similar to fat lime. This is also commonly used for white washing and for finishing coat in plastering. Class E Lime: It is an impure lime stone,known as kankar. It is available in modular and block form. It is supplied as hydrated lime. It is commonly used for masonry mortar. 1 .3.2 Tests on Limestones The following practical tests are made on limestonesto determine their suitability: (i) Physical tests (ii) Heat test (iii) Chemical test (iv) Ball test. (i) Physical Test:Purelimestoneis white in colour. Hydraulic limestonesarebluish grey,brown or are having dark colours. The hydraulic lime gives out earthy smell. They are having clayey taste.The presenceof lumps give indication of quick lime and unburnt lime stones. (ii) HeatTest:A pieceof dry stoneweighingW1is heatedin anopenfire for few hours.If weight of sampleaftercoolingis W2,thelossof weightis W2 WI.Thelossof weightindicatestheamountof carbon dioxide. From this the amount of calcium carbonate in limestone can be worked out. (iii) Chemical Test: A teaspoonfull of lime is placed in a test tube and dilute hydrochloric acid is poured in it. The content is stirred and the test tube is kept in the stand for 24 hours. Vigourous effervescenceand less residue indicates pure limestone. If effervescenceis less and residue is more it indicates impure limestone. If thick gel is formed and after test tube is held upside down it is possibleto identify classof lime as indicated below: 0 ClassA lime, if gel do not ow. 0 Class B lime, if gel tends to ow down. 0 Class C lime, if there is no gel formation. (iv) Ball Test: This test is conductedto identify whether the lime belongsto classC or to classB. By adding sufficient water about 40 mm size lime balls are made and they are left undisturbed for six hours. Then the balls are placed in a basin of water. If within minutes slow expansion and slow disintegration startsit indicates classC lime. If there is little or no expansion,but only cracks appearit belongs to class B lime. 1.3.3 Uses of Lime The following are the usesof lime in civil works: (i) For white washing. (ii) For making mortar for masonry works and plastering. (iii) To produce lime sandbricks. (iv) For soil stabilization. (v) As a refractory material for lining open hearth furnaces. (vi) For making cement. I 1.4 CEMENT Cementis a commonly usedbinding material in the construction.The cement is obtainedby burning a mixture of calcarious (calcium) and argillaceous (clay) material at a very high temperatureand then grinding the clinker so producedto a fine powder. It was first produced by a masonJoseph Aspdin in England in 1924. He patentedit as portland cement. 1.4.1 Types of Cement In addition to ordinary portland cement there are many varieties of cement. Important varieties are briey explained below: (i) White Cement: The cement when made free from colouring oxides of iron, maganeseand chlorium results into white cement. In the manufacture of this cement, the oil fuel is used instead of coal for burning. White cementis usedfor the oor nishes, plastering, ornamentalworks etc. In swimming pools white cement is used to replace glazed tiles. It is used for fixing marbles and glazed tiles. (ii) Coloured Cement: The cements of desired colours are produced by intimately mixing pigments with ordinary cement. The chlorium oxide gives green colour. Cobalt produce blue colour. Iron oxide with different proportion producebrown, red or yellow colour.Addition of manganesedioxide gives black or brown coloured cement.These cementsare used for giving finishing touchesto oors, walls, window sills, roofs etc. (iii) Quick Setting Cement: Quick setting cement is produced by reducing the percentageof gypsum and adding a small amount of aluminium sulphate during the manufacture of cement. Finer grinding also adds to quick setting property. This cement starts setting within 5 minutes after adding water and becomeshard mass within 30 minutes. This cement is used to lay concreteunder static or slowly running water. (iv) Rapid Hardening Cement: This cement can be produced by increasing lime content and burning at high temperaturewhile manufacturingcement.Grinding to very fine is also necessary.Though the initial and nal setting time of this cementis the sameasthat of portland cement,it gains strengthin early days. This property helps in earlier removal of form works and speedin construction activity. (v) Low Heat Cement: In massconcreteworks like construction of dams,heatproduceddue to hydration of cementwill not get dispersedeasily.This may give rise to cracks.Hencein suchconstructions it is preferableto uselow heatcement.This cementcontainslow percentage(5%) of tricalcium alurninate (C3A)andhigherpercentage (46%)of dicalciumsilicate(CZS). (vi) Pozzulana Cement: Pozzulanais a volcanic power found in Italy. It can be processedfrom shalesand certain types of clay also. In this cementpozzulanamaterial is 10 to 30 per cent. It can resist action of sulphate.It releasesless heat during setting. It imparts higher degree of water tightness. Its tensile strength is high but compressivestrength is low. It is used for mass concrete works. It is also used in sewageline works. (vii) Expanding Cement: This cement expandsas it sets.This property is achieved by adding expanding medium like sulpho aluminate and a stabilizing agent to ordinary cement.This is used for filling the cracks in concrete structures. (viii) High Alumina Cement: It is manufacturedby calcining a mixture of lime and bauxite. It is more resistant to sulphate and acid attack. It develops almost full strength within 24 hours of adding water. It is used for under water works. (ix) Blast Furnace Cement: In the manufactureof pig iron, slag comes out as a waste product. By grinding clinkers of cement with about 60 to 65 per cent of slag, this cement is produced. The propertiesof this cementare more or less sameas ordinary cement,but it is cheap,since it utilise waste product. This cementis durablebut it gains the strengthslowly and henceneedslonger period of curing. (x) Acid Resistant Cement: This cement is produced by adding acid resistant aggregatedsuch as quartz, quartzite, sodium silicate or soluble glass.This cement has good resistanceto action of acid and water. It is commonly used in the construction of chemical factories. (xi) SulphateResistantCement:By keepingthepercentage of tricalciumaluminateC3Abelow ve per cent in ordinary cement this cement is produced. It is used in the construction of structures which are likely to be damagedby alkaline conditions. Examplesof such structuresare canals,culverts etc. (xii) Fly Ash Blended Cement: Fly ashis a byproduct in thermal stations.The particles of y ash are very minute and they y in the air, creating air pollution problems. Thermal power stationshave to spendlot of money to arresty ashand disposesafely.It is found that one of the best way to disposey ash is to mix it with cement in controlled condition and derive some of the beneficiary effects on cement. Nowadays cement factories produce the y ash in their own thermal stations or borrow it from other thermal stationsand further processit to make it suitableto blend with cement.20 to 30% y ash is used for blending. Fly ash blended cementshave superior quality of resistanceto weathering action. The ultimate strengthgainedis the sameasthat with ordinary portland cement.However strengthgainedin the initial stageis slow. Birla plus, Birla star,A.C.C. Surakshaare someof the brand mame of blended cement. 1.4.2 Properties of Ordinary Portland Cement (i) Chemical properties: Portland cement consistsof the following chemical compounds: (a) Tricalciumsilicate 3 CaO.SiO2(C3S) 40% (b) Dicalciumsilicate 2CaO.SiO2(CQS) 30% (c) Tricalciumaluminate 3CaO.Al2O3 (C3A) 11% (d) Tetracalciumaluminate 4CaO.Al2O3.Fe2O3 (C3AF) 11% There may be small quantitiesof impurifies presentsuchascalcium oxide (CaO) and magnesium oxide (MgO). Whenwateris addedto cement,C3Ais the first to reactandcauseinitial set.It generates great amountof heat.C38hydratesearlyanddevelopsstrengthin thefirst 28 days.It alsogenerates heat.CZS is the nextto hydrate.It hydratesslowly andis responsiblefor increasein ultimatestrength.C4AF is comparatively inactive compound. (ii) Physical properties: The following physical properties should be checkedbefore selecting a portland cement for the civil engineering works. IS 269l967 specifies the method of testing and prescribesthe limits: (at)Fineness ([2)Setting time (c) Soundness (d) Crushing strength. (a) Fineness: It is measuredin terms of percentageof weight retained after sieving the cement through 90 micron sieve or by surface area of cement in squarecentimetersper gramme of cement. According to IS code specification weight retained on the sieve should not be more than 10 per cent. In termsof specificsurfaceshouldnot be lessthan2250cm2/gm. (12)Settingtime: A period of 30 minutesasminimum settingtime for initial settingand a maximum period of 600 minutes as maximum settingtime is specied by IS code,provided the testsare conducted as per the procedureprescribedby IS 269-1967. (c) Soundness: Once the concrete has hardened it is necessaryto ensure that no volumetric changestakesplace.The cementis saidto be unsound,if it exhibits volumetric instability after hardening. IS code recommendstest with Le Chatelier mould for testing this property. At the end of the test, the indicator of Le Chatelier mould should not expandby more than 10 mm. (a) Crushing strength: For this mortar cubes are made with standard sand and tested in compressiontesting machine as per the specification of IS code. The minimum strength specied is 16N/mmzafter3 daysand22 N/mmzafter7 daysof curing. 1.4.3 PhysicalTests on Cement (a) SoundnessTest: It is conductedby sieve analysis. 100 gms of cement is taken and sieved through IS sieve No. 9 for fteen minutes. Residueon the sieve is Weighed.This should not exceed 10 per cent by Weight of sampletaken. (12)Setting Time: Initial setting time and nal setting time are the two important physical properties of cement. Initial setting time is the time taken by the cement from adding of Waterto the starting of losing its plasticity. Final settingtime is the time lapsedfrom adding of the water to complete loss of plasticity. Vicat apparatusis used for finding the setting times [Ref. Fig. 1.5]. Vicat apparatus consists of a movable rod to which any one of the three needlesshown in figure can be attached.An indicator is attachedto the movable rod. A vicat mould is associatedwith this apparatuswhich is in the form of split cylinder. Movable rod weight 300 g T 1mm sq 8 Air 1 vent\A 6-4 Front view Side view Vicalapparatuswith needle for initial section time test Fig. 1.5. Vicat apparatus ->l10¢lUJl\J . For other permanentworks like for railway sleepers,fencing poles, electric poles and gates. . For temporaryworks in constructionlike scaffolding, centering,shoringand strutting, packing of materials. For decorative works like showcases and furnitures. oo\)O\_U1 . For body works of buses,lorries, trains and boats . For industrial useslike pulps (usedin making papers),card boards,wall papers . For making sports goods and musical instruments. IQUESTIONS Discuss the geological classification of stones. 0 Briey explain physical and chemical classification of rocks. 0 Discuss the characteristicsof good building stones. §°.°°.°S" Explain any three tests performed on stonesto find their properties. Write Varioususesof stonesin civil engineering works. Name any four stonesalong with their characteristicsand uses. 0 What do you understandby the term brick? Explain different types of bricks. Describe the properties of good bricks. Explain briey any four types of tests conductedon bricks in the laboratories to acertain their qualities. 10. What are the field tests carried out to determinethe qualities of the brick? 11. Explain classification of bricks basedon their quality. 12. What are the different uses of bricks? 13. Differentiate between fat lime and hydraulic lime. 14. Briey explain IS code classification of lime as classA, B, C, D and E. 15. What are the test carried on lime? Briey explain. 16. List the Various uses of lime. 17. What is cement?How quick setting and rapid hardening cement differs from portland cement? 18. Write short notes on (1') Low heat cement (ii) Pozzulana cement (iii) Coloured cement and (iv) Expanding cement. 19. Statechemical and physical properties of portland cement. 20. What is standardconsistencyof cement?How it is determinedin the laboratory? 21. Explain the terms initial setting time and final setting time of cement.How they are determined? 22. Explain the following test procedure on cement: (1') Soundness test (ii) Crushing strength test 23. List Various uses of cement. 24. Explain the terms: timber, standingtimber, rough timber and convertedtimber. 25. Draw and explain crosssectionof an exogeneoustree. 26. 27. 28. Differentiate between (i) exogeneousand endogeneoustrees (ii) soft Wood and hard Wood. 29. What are the requirementsof good timber? What is meant by seasoningof timber? Distinguish between natural and articial seasoning. Write short notes on: (i) Air seasoning (ii) Water seasoning (iii) Kiln seasoningand (iv) Chemical seasoning. 30. Explain Variousdefects in timber due to natural forces. 31. Write short notes on defects in timber due to (i) defective seasoningand conversion (ii) attack by fungi and insects. 32. What do you understandby the term preservationof timber? Briey explain the different methods of preservation adopted. 33. State different uses of timber. CHAPTER Mortar is an intimate mixture of binding material, fine aggregateand water.When water is addedto the dry mixture of binding material and the inert material, binding material developsthe property that binds not only the inert material but also the surrounding stones and bricks. If the cement is the binding material, then the mortar is known as cementmortar. Other mortars commonly usedare lime mortar and mud mortar. The inert material used is sand.In this chapter, first an introduction is given to the inert material sand and then the proportioning, mixing, curing, properties and uses of different mortars is explained.At the end of the chapter various tests conductedon mortars is presented. 2.1 SAND Sand is a natural product which is obtained as river sand, nalla sand and pit sand. However sea sand should not be used for the following reasons: 1. It containssalt andhencestructurewill remain damp.The mortar is affectedby eforenscence and blisters appear. 2. It contains shells and other organic matter, which decomposeafter some time, reducing the life of the mortar. Sandmay be obtainedarticially by crushing hard stones.Usually artificial sandis obtained as a byproduct while crushing stonesto get jelly (coarseaggregate). Sand is used in mortar and concretefor the following purpose: 1. It subdividesthe pasteof binding material into thin films and allows it to adhereand spread. 2. It fills up the gap betweenthe building blocks and spreadsthe binding material. 3. It adds to the density of the mortar. 4. It preventsthe shrinkageof the cementing material. 5. It allows carbon dioxide from the atmosphereto reach some depth and thereby improve setting power. 6. The cost of cementingmaterial per unit volume is reducedas this low cost material increases the volume of mortar. 33 7. Silica of sand contributesto formation of silicates resulting into the hardenedmass. The properties of good sandare: 1. It should be chemically inert. 2. It should be free from organic or vegetablematter. 3. It should be free from salt. 4. It should contain sharp,angular and coarsegrains. 5. It should be well graded. 6. It should be hard. I2.2 CEMENT MORTAR For preparingmortar,first a mixture of cementand sandis madethoroughly mixing them in dry condition. Water is gradually added and mixed with shovels. The cement to sand proportion recommendedfor various works is as shown is Table 2.1 Table 2.1. Cement to sandproportions for various works Works Cement: Sand Masonry works 1:6 to 1:8 Plastering masonry 1:3 to 1:4 Plastering concrete 1:3 Pointing 1:2 to 1:3 Curing: Cement gains the strength gradually with hydration. Hence it is necessaryto seethat mortar is wet till hydration hastaken place.The processto ensuresufficient moisture for hydration after laying mortar/concreteis called curing. Curing is ensuredby spraying water. Curing normally starts 624 hours after mortar is used. It may be noted that in the initial period water requirement is more for hydration and gradually it reduces.Curing is recommendedfor 28 days. Properties of Cement Mortar: The following are the important properties of cement mortar: 1. When water is addedto the dry mixture of cementand sand,hydration of cement startsand it binds sandparticles and also the surrounding surfacesof masonry and concrete. 2. A mix richer than 1:3 is prone to shrinkage. 3. Well proportioned mortar provides impervious surface. 4. Leaner mix is not capable of closing the voids in sand and hence the plastered surface is porous. 5. The strength of mortar dependsupon the proportion of cement and sand.Strengthsobtained with various proportion of cement and sand is shown in Table 2.2. Table 2.2 Cement: Sand Uses Mortar of Cement CompressiveStrength Mortar is used 1. to bind masonry units like stone,bricks, cement blocks. . to plaster slab and Walls make them impervious. . to give neat finishing to Walls and concreteWorks. OO\lO\UI-i . for pointing masonryjoints. . for preparing building blocks. . as a filler material in ferro cement Works. . to ll joints and cracks in Walls. . as a filler material in stone masonry. 2.3 LIME MORTAR Fat lime and hydraulic limes are usedfor making lime mortar. If fat lime is used sandmixed is normally 2 to 3 times its volume. If hydraulic lime is used sandmixed is only 2 times the volume of lime. Lime is preparedby pounding, if quantity required is small or by grinding, if the required quantity is more. Pounding: For pounding pits are formed in hard grands.The size of pit is usually 1.80 m long, 0.4 m Wideand 0.5 m deep.It is provided with lining of bricks or stones.Lime and sanddry mixed with required proportion is placed in the pit. Small quantity of Wateris addedat intervals. In eachinterval the mix is poundedwith Woodenpoundersand mortar is turned up and down. The processis continued till uniform colour and desired consistancyis achieved. Grinding: This is the better Wayof getting good mix. The grinding may be carried out in bullock driven grinding mill or in power driven grinding mill. Figure 2.1 shows a typical bullock driven grinding mill. It consistsof a circular trench of radius 3 to 4.5 m, 0.3 m Wideand 0.4 m deep.A Woodenshaft pivoted at centre carries a stoneWheelof Width just 50 mm to 100 mm less than that of trench. Bullock drive this Wheel in the trench for grinding mortar. The dry mix is placed in the trench. Water is addedgradually and bullock driven stone Wheels grind the mix. A Workerturns the mix up and down regularly. This method of preparing mortar needs6 hoursandcanproduceabout1.7m3of mortar. Bullock to be attached at this end Fig. 2.1. Bullock driven grinding mill Figure 2.2 shows a typical power driven grinding mill used for preparing lime mortar. Two rollers rotate in a pan of diameter 1.8 to 2.4 In. Either pan or roller is rotated with the help of oil engine or electric power. During mixing required quantity of water is addedgradually. Fig. 2.2. Powerdriven grinding mill Lime mortar is also having good grinding property. Fat lime mortar is used for plastering while hydraulic lime mortar is used for masonry construction. This mortar was consideredcheap in olden days and was commonly used in small towns. However the combersomeprocess of preparation and easein availibility of cement in market has almost replacedthe use of lime mortar. l2.4 MUDMORTAR Clay lumps are collected and are wetted with water and allowed to mature for 1 or 2 days. It is kneeded well until it attains required consistancy.Sometimesbrous materials like gobber is addedin the mix. It prevents cracks in the plaster. If plaster is to be used for outer walls, it is sprayed or painted with bitumen. It is cheap mortar. Its durability is less. It is normally used for the construction of temporary shedsand cheaphousesin rural areas. l2.5 SPECIAL MORTAR The following are some of the special mortars: 1. Cement clay mortar 2. Gauged mortar 3. Decorative mortar. 1. Cement Clay Mortar: Quality of clay mortar can be improved by adding cementto the mix. Normal proportion of clay to cement is 1:1. It maintains the economy to some extent and there is sufficient improvements in the durability of mudmortar. 2. Gauged Mortar: It is the mortar obtained by adding cement to lime mortar. The usual proportion of cement,lime and sandare 1:1:6, 1:2:9 and 1:3:12.This mortar is to be usedwithin half an hour after mixing cement.Obviously, it is cheaperthan cementmortar and its quality is betweenthat of cement mortar and lime mortar. 3. Decorative Mortar: Thesemortars are obtainedby using coloured cement.They are usedto give pleasantappearanceto outer walls. I2.6 TESTS ON MORTAR The following tests are conductedon the preparedmortars to ensuretheir quality: 1. Crushing Test 2. Tensile StrengthTest 3. Adhesive Test. 1. Crushing Test: This test is carried out on a brick work with the mortar. This brick work is crushed in a compressiontesting machine and the load is noted down. Then the crushing strength is obtained as load divided by crosssectionalarea. 2. TensileStrength Test: The mortar preparedis placed in a mould of bricket which has central crosssectional area as 38 mm X 38 mm. After curing the briquette [Fig. 2.3] is pulled under the grips of tensile testing machine. The ultimate load noted.Then the tensile strengthof mortar is load divided by the central crosssectional Elevation area. I<§>1 >1 L 3. Adhesive Test: Two bricks arejoined together with mortar to be tested as shown in Fig. 2.4. The upper brick is 70)mm suspended from an overhead support. Aboard ishung from the lower brick. Then weights are addedto the board till the bricks separate. Theadhesive strength istheloaddivided byarea of contact. 15F?|;,m Fig. 2.3. Briquette for tensile test Suspander Elevation Heme Side view Fig. 2.4. Adhesivenesstest arrangement QUESTIONS Why seasand should not be used for making mortar? What are the different types of sandused in making mortar? S":E*!°" Why sandis used in mortars? List the properties of good sand. What proportion of cementto sanddo you recommendfor the following Works? (a) Masonry works (b) Plastering masonry (c) Plastering concrete surface (d) Pointing. Statethe important properties of cement mortar. °?°>.° Where do you use cement mortar? Explain with sketchesthe methodsof grinding lime mortar. Write 10. short notes on mud mortar. Briey explain tests conductedon mortar. 4---90 CHAPTER lmncrele Plain concrete,commonly known as concrete,is an intimate mixture of binding material, ne aggregate, coarse aggregateand water. This can be easily moulded to desired shape and size before it looses plasticity and hardens.Plain concrete is strong in compressionbut Very weak in tension. The tensile property is introduced in concrete by inducting different materials and this attempt has given rise to RCC, RBC, PSC, FRC, cellular concrete and Ferro cement. In this chapter proportioning, mixing, curing, properties, tests and uses of plain concrete is dealt in detail. The other improved Versionsof concreteare explained and their special properties and usesare pointed out. 3.1 PLAIN CONCRETE Major ingredients of concreteare: 1. Binding material (like cement, lime, polymer) 2. Fine aggregate(sand) 3. Coarseaggregates(crushedstone,jelly) 4. Water. A small quantity of admixtures like air entraining agents, water proong agents, workability agentsetc. may also be addedto impart special propertiesto the plain concretemixture. Depending upon the proportion of ingredient, strength of concrete Varies. It is possible to determine the proportion of the ingredients for a particular strength by mix design procedure. In the absence ofmix design the ingredients are proportioned as1:1:2, 1:121:3, 1:2:4, l:3:6 and 1:4:8, which is the ratio of weights of cementto sandto coarseaggregate. In proportioning of concreteit is kept in mind that Voidsin coarseaggregatesare filled with sand and the Voidsin sandare filled with cementpaste.Proportion of ingredientsusually adoptedfor Various works are shown in Table 3.1. 39 Table 3.1. Proportion of cement, sandand coarseaggregatesin concrete S. No. 1 2 Proportion 131:2 Nature of Work For machine foundation, footings for steel columns and concreting under water. 1 1:13:3 Water tanks, shells andfolded plates, forother water retaining structures. 3 1:214 Commonly used for reinforced concrete works like beams, slabs, tunnel lining, bridges 4 1:3:6 Piers, abutments, concrete walls, sill of windows, oors. 1:418 Mass concreteslike dam, foundation course for walls, for making concrete blocks. Functionsof Various Ingredients Cement is the binding material. After addition of water it hydrates and binds aggregatesand the surroundingsurfaceslike stoneandbricks. Generallyricher mix (with more cement)gives more strength. Setting time starts after 30 minutes and ends after 6 hours. Hence concreteshould be laid in its mould before 30 minutes of mixing of water and should not be subjectedto any external forces till final setting takes place. Coarse aggregate consistsof crushedstones.It should be well gradedand the stonesshould be of igneous origin. They should be clean, sharp, angular and hard. They give massto the concreteand prevent shrinkage of cement. Fine aggregate consists of river sand. It prevents shrinkage of cement. When surroundedby cement it gains mobility enters the voids in coarse aggregatesand binding of ingradientstakesplace. It addsdensity to concrete,since it lls the voids. Denserthe concretehigher is its strength. Water used for making concreteshould be clean. It activatesthe hydration of cementand forms plastic mass.As it sets completely concretebecomeshard mass.Water gives workability to concrete which meanswater makes it possibleto mix the concretewith easeand place it in final position. More the water better is the workability. However excesswater reducesthe strength of concrete.Figure 3.1 shows the variation of strength of concrete with water cement ratio. To achieve required workability and at the sametime good strengtha water cementratio of 0.4 to 0.45 is used,in caseof machinemixing and water cementratio of 0.5 to 0.6 is used for hand mixing. Compressiv strength Water/cement ratio Fig. 3.1. Variation of strength of concretewith w/c ratio Preparing and Placingof Concrete The following stepsare involved in the concreting: 1. Batching 2. Mixing 3. Transporting and placing and 4. Compacting. 1. Batching: The measurementof materials for making concrete is known as batching. The following two methodsof batching is practiced: (a) Volume batching (b) Weight batching. (a) VolumeBatching: In this method cement,sandand concreteare batchedby volume. A gauge box is madewith woodenplates,its volume being equalto that of one bag of cement.One bag of cement has volume of 35 litres. The required amount of sandand coarseaggregateis addedby measuringon to the gaugebox. The quantity of water required for making concreteis found after deciding water cement ratio. For example,if water cementratio is 0.5, for one bag of cement(50 kg), water required is 0.5 X 50 = 25 kg, which is equal to 25 litres. Suitable measureis used to selectrequired quantity of water. Volume batching is not ideal method of batching. Wet sand has higher volume for the same weight of dry sand.It is called bulking of sand.Hence it upsetsthe calculated volume required. (b) Weight Batching: This is the recommendedmethod of batching. A weighing platform is used in the field to pick up correct proportion of sand and coarse aggregates.Large weigh batching plants have automatic weighing equipments. 2. Mixing: To produce uniform and good concrete, it is necessaryto mix cement, sand and coarseaggregate,first in dry condition and then in wet condition after adding water. The following methodsare practiced: (a) Hand Mixing (11)Machine Mixing. (a) Hand Mixing: Required amount of coarseaggregatefor a batch is weighed and is spreadon an impervious platform. Then the sandrequired for the batch is spreadover coarseaggregate.They are mixed in dry condition by overturning the mix with shovels.Then the cementrequired for the batch is spreadover the dry mix and mixed by shovels.After uniform texture is observedwater is addedgradually and mixing is continued. Full amount of water is addedand mixing is completed when uniform colour and consistancyis observed.The processof mixing is completed in 68 minutes of adding water. This method of mixing is not very good but for small works it is commonly adopted. (b) Machine Mixing: In large and important works machine mixing is preferred. Figure 3.2 shows a typical concrete mixer. Required quantities if sand and coarse aggregatesare placed in the drum of the mixer. 4 to 5 rotations are made for dry mixing and then required quantity of cement is added and dry mixing is made with another 4 to 5 rotations. Water is gradually added and drum is rotated for 2 to 3 minutes during which period it makes about 50 rotations. At this stageuniform and homogeneousmix is obtained. C) c 7-70) SE &9 3.. CD Fig. 3.2. Concretemixer 3. 'Iransporting and Placing of Concrete. After mixing concreteshould be transportedto the nal position. In small Worksit is transportedin iron pans from hand to hand of a set of Workers.Wheel barrow and hand carts also may be employed. In large scale concreting chutes and belt conveyors or pipeswith pumpsareemployed.In transportingcareshouldbe takento seethat seggregationof aggregate from matrix of cement do not take place. Concrete is placed on form Works. The form Works should be cleaned and properly oiled. If concreteis to be placed for foundation, the soil bed should be compactedWell and is made free from loose soil. Concrete should be dropped on its nal position as closely as possible. If it is dropped from a height, the coarse aggregatesfall early and then mortar matrix. This segregationresults into Weaker concrete. 4. Compaction of Concrete: In the processof placing concrete,air is entrapped.The entrapped air reducesthe strengthof concreteup to 30%. Hence it is necessaryto remove this entrappedair. This is achievedby compactingthe concreteafter placing it in its final position. Compaction can be carried out either by hand or with the help of vibrators. (a) Hand Compaction: In this method concreteis compactedby ramming, tamping, spadingor by slicing with tools. In intricate portions a pointed steelrod of 16 mm diameterand about a metre long is used for poking the concrete. (b) Compaction by Vibrators: Concrete can be compactedby using high frequency vibrators. vibrators are used for compaction, water cement ratio can be less, which also help in improving the strength of concrete. Vibration should be stopped as soon as cement paste is seen on the surface of concrete.Over vibration is not good for the concrete. The following types of vibrators are commonly used in concreting: (a) Needle or immersion vibrators (b) Surface vibrators (c) Form or shutter vibrators (d) Vibrating tables. Needle vibrators are usedin concretingbeamsand columns. Surfacevibrators and form vibrators are useful in concreting slabs.Vibrating tables are useful in preparing precastconcreteelements. Curing of Concrete Curing may be defined as the processof maintaining satisfactory moisture and temperatureconditions for freshly placedconcretefor somespecifiedtime for proper hardeningof concrete.Curing in the early agesof concreteis more important. Curing for 14 daysis very important. Better to continue it for 7 to 14 daysmore. If curing is not doneproperly, the strengthof concretereduces.Cracksdevelopdue shrinkage. The durability of concretestructure reduces. The following curing methodsare employed: (a) Spraying of water (b) Covering the surfacewith wet gunny bags, straw etc. (c) Ponding (d) Steamcuring and (e) Application of curing compounds. (a) Spraying of water: Walls, columns, plasteredsurfacesare cured by sprinkling water. (b) Wet covering the surface: Columns and other vertical surfacesmay be cured by covering the surfaceswith wet gunny bags or straw. (c) Ponding: The horizontal surfaceslike slab and oors are cured by stagnatingthe water to a height of 25 to 50 mm by providing temporary small hunds with mortar. (d) Steam curing: In the manufactureof prefabricated concreteunits steamis passedover the units kept in closedchambers.It acceleratescuring process,resulting into the reduction of curing period. (e) Application of curing compounds: Compounds like calcium chloride may be applied on the curing surface.The compound shows affinity to the moisture and retains it on the surface.It keeps the concretesurface wet for a long time. Properties of Concrete Concretehas completely different properties when it is the plastic stageand when hardened.Concrete in the plastic stageis also known as green concrete.The properties of green concreteinclude: 1. Workability 2. Segregation 3. Bleeding 4. Harshness. The properties of hardenedconcreteare: 1. Strength 2. Resistance to wear 3. Dimensional changes 4. Durability 5. Impermeability. Properties of Green Concrete 1. Workability: This is dened asthe easewith which concretecan be compactedfully without seggregatingand bleeding. It can also be defined as the amount of internal work required to fully compactthe concreteto optimum density.The workability dependsupon the quantity of water, grading, shapeand the percentageof the aggregatespresentin the concrete. Workability is measuredby (a) The slump observedwhen the frustum of the standardcone filled with concreteis lifted and removed. (b) The compactionfactor determinedafter allowing the concreteto fall through the compaction testing machine. (c) The time taken in secondsfor the shapeof the concreteto changefrom coneto cylinder when tested in VeeBee consistometer. The suggestedvalues of workability for different works are as shown in Table 3.2. Table 3.2. Suggestedvalues of workability Application Slump Compaction Factor Concreting of shallow sectionswith vibrations - 0.75 3. Concreting of lightly reinforced sectionswithout vibrations and heavily reinforced sections with vibrations 25 75 mm 0.85 4. Concreting of heavily reinforced sections without 75 - 125 mm 2. Concreting of light reinforced sections with vibrators 0.80 0.80 0.85 0.92 Time in VeeBee 10 20 5 l0 2- 5 More than 0.92 vibration 2. Segregation: Separationof coarseparticles from the green concrete is called segregation. This may happendue to lack of sufficient quantity of finer particles in concreteor due to throwing of the concrete from greater heights at the time of placing the concrete. Because of the segregation, the cohesivenessof the concrete is lost and honey combing results. Ultimately it results in the loss of strength of hardenedconcrete.Hence utmost care is to be taken to avoid segregation. 3. Bleeding: This refers to the appearanceof the water along with cement particles on the surfaceof the freshly laid concrete.This happenswhen there is excessivequantity of water in the mix or due to excessivecompaction. Bleeding causesthe formation of pores and renders the concrete weak. Bleeding can be avoided by suitably controlling the quantity of water in the concreteand by using finer grading of aggregates. 4. Harshness: Harshnessis the resistanceoffered by concreteto its surfacefinish. Harshnessis due to presenceof lesser quantity of fine aggregates,lesser cement mortar and due to use of poorely graded aggregates.It may result due to insufficient quantity of water also. With harsh concrete it is difficult to get a smooth surface nish and concretebecomesporous. Properties of HardenedConcrete 1. Strength: The characteristic strength of concrete is defined as the compressivestrength of 150 mm size cubesafter 28 days of curing below which not more than 5 per cent of the test results are expectedto fail. Theunit of stressusedis N/mmz.IS 456gradestheconcretebasedon its characteristic strength as shown in Table 3.3. Table 3.3. Grades of concrete Characteristic strengthin M N/mm2 Till year2000,M15concretewas permittedto be usedfor reinforcedconcreteworks. But IS 4562000speciesminimumgradeof M20to be usedfor reinforcedconcreteworks. Strength of concrete depends upon the amount of cement content, quality and grading of aggregates,water cement ratio, compaction and curing. Strength of concrete is gained in the initial stages.In 7 days the strengthgainedis as much as 60 to 65 per cent of 28 days strength.It is customary to assumethe 28 days strengthasthe full strengthof concrete.However concretegains strengthafter 28 days also. The characteristicstrength may be increasedby the as factor given in Table 3.4. Table 3.4. Effect of age factor on strength of concrete Minimum age of member when design load is expected. Age factor 1 month 3 months 6 months 12 months 1.0 l.l0 1.15 1.20 Thetensilestrength maybeestimated fromtheformulaft = 0.7 fck N/mmz,wherefckis the characteristic compressive stress. The modulus of elasticity may be estimated from the formula: E = 50 f.;. N/mmz. 2. Dimensional Change: Concrete shrinks with age. The total shrinkage dependsupon the constituents of concrete, size of the member and the environmental conditions. Total shrinkage is approximately 0.0003 of original dimension. The permanentdimension changedue to loading over a long period is termed as creep. Its value dependsupon the stressin concrete,the ageof the concreteat the time of loading and the duration of the loading. The ultimate creep strain may be estimated from the values of creep coefficient. The creep coefficient is defined as ultimate creep strain divided by the elastic strain at the age of loading. These values are listed in Table 3.5. Table 3.5. Creep coefficient basedon the age of loading Age of Loading The size of concrete may change due to thermal expansion also. The coefficient of thermal expansiondependsupon the natureof cement,the type of aggregates,cementcontent,relative humidity andthe sizeof the sectionsof the structuralelements.Table3.6 showsthe coefficient of thermal expansion of concretewith different types of aggregates. Table 3.6. Coefficient of thermal expansion Type of Aggregate Coeicient of Thermal Expansion/C° l. Quartzite (1.2to 1.3)x 10'5 2. Sand stone (0.9 to 1.2) X 10'5 3. Granite (0.7 to 0.95) X l05 4. Basalt (0.8 to 0.95) x 10- 5 3. Durability: Environmental forces such as weathering, chemical attack, heat, freezing and thawing try to destroy concrete.The period of existanceof concretewithout getting adverselyaffected by theseforces is known as durability. Generally denseand strong concreteshave better durability. The cube crushing strengthalone is not a reliable guide to the durability. Concrete should have an adequate cement content and should have low water cement ratio. 4. Impermeability: This is the resistanceof concrete to the flow of water through its pores. Excesswater during concreting leavesa large number of continuous pores leading to the permeability. Sincethe permeability reducesthe durability of concrete,it should be kept very low by using low water cement ratio, dense and well graded aggregates, good compaction and continuous curing at low temperatureconditions. The cement content used should be sufficient to provide adequateworkability with low water cement ratio and the available compaction method. Tests on Concrete The following are some of the important tests conductedon concrete: 1. Slump test. 2. Compaction factor test. 3. Crushing strength test. 1. Slump Test: This test is conductedto determinethe workability of concrete.It needsa slump cone for test (Fig. 3.3). Slump cone is a vessel in the shapeof a frustum of a cone with diameter at bottom 200 mm and 50 mm at top and 300 mm high. This cone is kept over a impervious platform and is lled with concretein four layers. Each layer is tampedwith a 16 mm pointed rod for 25 times. After filling completely the cone is gently pulled up. The decreasein the height of the concrete is called slump. Higher the slump, more workable is the concrete. The desired values of slumps for various works have been shown in Table 3.2. +| 50r:nm 1< |+ 200mm-->| Fig. 3.3. Slump test 2. Compaction Factor Test: This is another test to identify the workability of concrete.This test is conductedin the laboratory.The test equipmentconsistsof two hoppersand a cylinder xed to a stand,the dimensions and the distancesbetween the three vesselsbeing standardized.VesselA and B are having hinged bottoms whereascylinder C is having xed bottom. [Ref. Fig. 3.4] Top vesselA is lled with the concreteto be tested.As soon as it is lled, the hinged door is opened.Concrete is collected in vessel B. Then the hinged door of B is openedto collect concretein cylinderC. The concretein cylinderC is weighted.Let it beW1. Now cylinder is again lled with the sampleof concretein 50 mm layers, which is compactedby rammingandvibrating.Thenthe weightof compactedconcreteis determined. Let this weightbeW2. Theratio W1/W2is termedascompactionfactor.The speciedvaluesof compactionfactorfor different works are already listed in Table 3.2. g<25o mm~>| >| 44: 280 mm >|<2oo mm >|< 230 mm >|<2oo mm |< 300 mm Fig. 3.4. Compaction Factortest 3. Crushing Strength Test: Metallic moulds of size 150 mm x 150 mm x 150 mm are usedfor casting concretecubes.Before filling mould, it is properly oiled on its inner surfaces,so that cubescan be easily separated.Fresh cube is filled with concreteto be testedin 3 layers and kept in the room. After 24 hours, cube is removed from the mould and kept under Waterfor curing. After 28 days of curing cubes are tested in the compression testing machine. In this test cubes are placed over the smooth surfacewhich is in contact with side plates of mould. The crushing load is noted and crushing strength is foundasloaddividedby surfacearea(150X 150m2). Code specify the desirable strength of concretefor 3 days and 7 days for quick assessmentof strength of concrete. Desirable Properties of Concrete Appropriate quality and quantity of cement,ne aggregate,coarseaggregateand Watershould be used so that the green concretehas the following properties: (a) Desired workability (b) No seggregationin transporting and placing (c) No bleeding and (d) No harshness. Hardened concrete should have (a) required characteristic strength (b) minimum dimensional changes (c) good durability (d) impermeable (e) good resistanceto wear and tear. Uses of Concrete 1. As bed concretebelow column footings, wall footings, on wall at supportsto beams 2. As sill concrete 3. Over the parapetwalls as coping concrete 4. For flagging the area around buildings 5. For pavements 6. For making building blocks. However major use of concreteis as a major ingradient of reinforced and prestressedconcrete. Many structural elementslike footings, columns, beams, chejjas, lintels, roofs are made with R.C.C. Cementconcreteis usedfor making storagestructureslike water tanks,bins, silos, bunkersetc. Bridges, dams,retaining walls are R.C.C. structuresin which concreteis the major ingradient. l3.2 REINFORCED CEMENT CONCRETE (R.C.C.) Concreteis good in resisting compressionbut is very weak in resisting tension. Hencereinforcement is provided in the concrete wherever tensile stress is expected. The best reinforcement is steel, since tensile strength of steel is quite high and the bond between steel and concrete is good. As the elastic modulus of steelis high, for the sameextensionthe force resistedby steelis high comparedto concrete. However in tensile zone, hair cracks in concrete are unavoidable. Reinforcementsare usually in the form of mild steelor ribbed steelbars of 6 mm to 32 mm diameter.A cageof reinforcementsis prepared asper the designrequirements,kept in a form work and then greenconcreteis poured.After the concrete hardens,the form work is removed. The composite material of steel and concrete now called R.C.C. acts as a structural member and can resist tensile as well as compressivestressesvery well. Properties of R.C.C./Requirementof Good R.C.C. 1. It should be capableof resisting expectedtensile, compressive,bending and shearforces. 2. It should not show excessivedeection and spoil serviceability requirement. 3. There should be proper cover to the reinforcement, so that the corrossionis prevented. 4. The hair cracks developedshould be within the permissible limit. 5. It is a good re resistant material. 6. When it is fresh, it can be moulded to any desired shapeand size. 7. Durability is very good. 8. R.C.C. structure can be designedto take any load. Uses of R.C.C. It is a widely used building material. Some of its important usesare listed below: 1. R.C.C. is used as a structural element,the common structural elementsin a building where R.C.C. is used are: (a) Footings (b) Columns (c) Beams and lintels (d) Chejjas, roofs and slabs. (e) Stairs. 2. R.C.C. is used for the construction of storagestructureslike (a) Water tanks ([2) Dams (c) Bins (d) Silos and bunkers. 3. It is used for the construction of big structureslike (a) Bridges (b) Retaining walls (c) Docks and harbours (d) Under water structures. 4. It is used for precasting (a) Railway sleepers (1))Electric poles 5. R.C.C. is used for constructing tall structureslike (a) Multistorey buildings (b) Chimneys (c) Towers. 6. It is used for paving (a) Roads (b) Airports. 7. R.C.C. is used in building atomic plants to prevent danger of radiation. For this purpose R.C.C. walls built are 1.5 m to 2.0 m thick. '33 REINFORCED BRICKCONCRETE (RBC) It is the combination of reinforcement, brick and concrete. It is well known fact that concrete is very weak in tension. Hence in the slabs,lintels and beamsthe concretein the portion below the neutral axis do not participate in resisting the load. It acts as a filler material only. Hence to achieve economy the concretein tensile zone may be replacedby bricks or tiles. Dense cement mortar is used to embedthe reinforcement. The reinforcement may be steel bars, expandedmesh etc. l3.4 PRESTRESSED CONCRETE (PSC) Strengthof concretein tension is very low and henceit is ignored in R.C.C. design.Concretein tension is acting as a cover to steel and helping to keep steel at desireddistance.Thus in R.C.C. lot of concrete is not properly utilized. Prestressingthe concreteis one of the method of utilizing entire concrete.The principle of prestressedconcreteis to introduce calculated compressivestressesin the zonesWherever tensile stressesare expectedin the concrete structural elements.When such structural element is used stressesdeveloped due to loading has to rst nullify these compressive stressesbefore introducing tensile stress in concrete. Thus in prestressedconcrete entire concrete is utilized to resist the load. Another important advantageof PSC is hair cracks are avoided in the concreteand hencedurability is high. The fatigue strengthof PSC is also more. The deections of PSC beamis much lessand hencecan be used for longer spansalso. PSC is commonly used in the construction of bridges, large column free slabs and roofs. PSC sleepersand electric piles are commonly used. The material used in PSC is high tensile steel and high strength steel. The tensioning of Wires may be by pretensioning or by post tensioning. Pretensioningconsists in stretching the wires before concreting and then releasing the wires. In case of post tensioning, the ducts are made in concrete elements.After concreteof hardens,prestressingWiresare passedthrough ducts.After stretchingWires, they are anchoredto concreteelementsby special anchors. l3.5 FIBRE-REINFORCED CONCRETE (FRC) Plain concretepossessesdeficiencies like low tensile strength, limited ductility and low resistanceto cracking. The cracks develop even before loading. After loading micro cracks Widen and propagate, exposing concreteto atmosphericactions. If closely spacedand uniformly disperedfibres are provided While mixing concrete, cracks are arrested and static and dynamic properties are improved. Fibre reinforced concrete can be defined as a composite material of concrete or mortar with discontinuous and uniformly distributed fibres. Commonly usedfibres are of steel,nylon, asbestos,coir, glass,carbon and polypropylene. The length to lateral dimension of fibres range from 30 to 150. The diameter of fibres vary from 0.25 to 0.75 mm. Fibre reinforced concreteis having better tensile strength, ductility and resistanceto cracking. Uses of FRC 1. For wearing coat of air elds, roads and refractory linings. 2. For manufacturingprecastproductslike pipes, stairs, Wall panels,manholecovers and boats. 3. Glass fibre reinforced concrete is used for manufacturing doors and Window frames, park benches, bus shelters etc. 4. Carbon FRC is suitable for structureslike cladding and shells. 5. AsbestosFRC sheetsare commonly used as roofing materials. l3.6 CELLULAR CONCRETE It is a light weight concreteproduced by introducing large voids in the concreteor mortar. Its density variesfrom 3 kN/m3to 8 kN/m3whereasplainconcretedensityis 24 kN/m3.It is alsoknownasaerated, foamed or gas concrete. Properties of cellular concrete: It has the following properties: 1. It has low weight. . It has good fire resistance. . It has good thermal insulation property. .°.U:>*N Thermal expansionis negligible. Freezing and thawing problems are absent. Sound absorption is good. 7. It has less tendencyto spall. Uses of Cellular Concrete 1. It is used for the construction of partition walls. 2. It is used for partitions for heat insulation purposes. 3. It is used for the construction of hollow filled oors. I 3.7 FERRO-CEMENT The term ferrocement implies the combination of ferrous product with cement. Generally this combination is in the form of steel wires meshesembeddedin a portland cement mortar. Wire mesh is usually of 0.8 to 1.00 m diameter steel wires at 5 mm to 50 mm spacing and the cement mortar is of cement sand ratio of 1:2 or 1:3. 6 mm diameter bars are also used at large spacing, preferably in the corners. Sand may be replacedby baby jelly. The water cement ratio used is between 0.4 to 0.45. Ferrocementreinforcementis assembledinto its final desiredshapeand plastereddirectly. There is no need for form work. Minimum two layers of reinforcing steel meshesare required. According to American Concrete Institute Ferro cement is a thin walled reinforced concrete construction where usually a hydraulic cement is reinforced with layers of continuous and relatively small diameter mesh. The meshused may be metallic or any other suitable material. Ferrocement is fast emerging as an alternate material for timber. The history of ferrocement goes back to 1843 (even before RCC). JosephLouis Lambet constructedseveral rowing boats, plant plots and garden seatsusing ferrocement. In early 1940s noted Italian engineer and architect Pier Luigi Nervi carried out scientific tests on ferrocement and used it to replace wood wherever possible. He built small tonnage vessels, the largest being 165 tons motor sailor. Nervi also pioneered the architectural use of ferrocement in buildings. Ferrocementcan be given the finish of teak wood, rose wood etc. and even for making tables, chairs and benchesit can be used. Properties of Ferro-cement 1. Its strengthper unit massis high. 2. It has the capacity to resist shock laod. 3. It can be given attractive finish like that of teak and rose Wood. 4. Ferro cement elementscan be constructedWithout using form Work. 5. It is impervious. Uses of Ferro-cement It can be used for making: 1. Partition Walls . VV1ndoW frames, chejjas and drops . Shelf of cupboards Door and window shutters :C3\OOO Domestic Water tanks Precast roof elements . Reapersand raffers required for supporting roof tiles. . Pipes . Silos Furnitures pit pit. Manhole covers > I\). Boats. IQUESTIONS 1. 2.What is cementconcrete?Explain the function of eachingradient and statecommonproportions of the ingradients used for different Works. do you understandby batching of concrete?Briey explain different methodsof batching. 3.What Explain different methodsof mixing aggregates. Why concrete should be compacted after placing? Explain different methods of compaction. Bring out their advantagesand disadvantages. What is meantby curing of concrete?Why it is necessaryand how it is made? Write short notes on (a) Workability of concrete (b) Segregationof concreteand (c) Bleeding of concrete. 11. 12. Write E;I.NEEtuN short note on Water cement ratio. Whatdo you understand by M20concrete?How this gradeis determined? Explain the Variouscausesfor dimensional changesin the hardenedconcrete. 13. Write short notes on the following tests on concrete: (a) Slump test (b) Compaction factor test ((3)Crushing strength test. What are the desired properties of concrete? 14. List the Various Works Where concrete is used. What is R.C.C.? Briey Write on desirableproperties and usesof concrete. Write short notes on (a) Reinforced brick concrete (b) Prestressed concrete (c) Fibre reinforced concrete (d) Cellular concrete and (e) Ferrocement. CHAPTER MetalsasBuilding Materials Various metals used for building Worksbe broadly classified as ferrous metals and nonferrous metals. The properties and usesof ferrous metals and someof important non-ferrous materials like aluminium and copper are explained in this chapter. 4.1 FERROUS METALS A ferrous material is the one in which iron is a main constituent.Iron ore is first convertedinto pig iron and then pig iron is subjectedto Variousmetallurgical processesto mix different percentageof carbon and to get the following three useful ferrous materials: 1. Cast ironcarbon content 1.7% to 4.5% 2. Wrought ironcarbon content 0.05% to 0.15% 3. Steelcarbon content 0.25% to 0.25%. All ferrous materialscontain about 0.5 to 3% silica, lessthan 2% manganese,0.15% sulphur and 0.6% phosphorous. 1. Cast Iron: Important properties of cast iron are: (a) Compression strengthis 700N/mmzandtensilestrengthis 150N/mm2. (b) It is brittle and does not absorb shocks (c) Its specific gravity is 7.5. (d) Its structure is coarse,crystalline and fibrous. (e) It cannot be magnetised. Q)It does not rusteasily. (g) It has low melting point of about 1200°C. Uses of Cast Iron: (a) 1. It is used for making rain Waterand sanitarypipes, sanitary ttings and manholecovers. 2. It is used for making railings and spiral stair cases. 3. Fire gratings, cover for pumps and motors and brackets are made with cast irons. 55 2. Wrought Iron: It is almost pure iron. It containsless than 0.15% carbon. Attempts are made to reduce the other impurities during the processof manufacturing. Properties of Wrought Iron: 1. Its ultimatecompressive strengthis 200N/mm2andultimatetensilestrengthis 375N/mmz. 2. It is ductile and brittle. 3. Its unit Weightis 77 kN/m3. 4. It melts at about 1500°C. It becomes so soft at 900°C that two pieces can be joined by hammering. 5.Itcan absorb shocks very Well. 6. It forms temporary magnetsbut it cannot be magnetisedpermanently. 7. It rusts more easily. Uses of Wrought Iron: 1. It is used for making nails nuts and botts, Wiresand chains. 2. It is used for making roofing sheets,grills, fences,window gaurds etc. 3. Steel: It is extensively used building material. The following three varieties of steel are extensively used: (a) Mild steel (b) High carbon steel and (c) High tensile steel. (a) Mild Steel: It contains a maximum of 0.25% carbon, 0.055% of sulphur and 0.55% of phosphorus. Properties of Mild Steel: (i) It is malleable and ductile (ii) It is more elastic (iii) It can be magnetizedpermanently. (iv) Its specic gravity is 7.8. (v) Its Youngsmodulusis 2.1 X 105N/mmz. (vi) It can be Weldedeasily. (vii) It is equally strong in tension and in compression. Uses of Mild Steel: (i) Round bars are extensively used as reinforcement in R.C.C. works. (ii) Rolled sectionslike I, T, L, C, plates etc. are used to build steel columns, beams,trussesetc. (iii) Tubular sectionsare used as poles and membersof trusses. (iv) Plain and corrugatedmild steel are used as roofing materials. (v) Mild steel sectionsare used in making parts of many machineries. (b) High Carbon Steel: The carbon containts in this steel is 0.7% to 1.5%. Properties of Carbon Steel: (1') It is more tough and elastic comparedto mild steel. (ii) Welding is difcult. (iii) It can be magnetizedpermanently. (iv) It is stronger in compressionthan in tension. (v) It withstands shocks and vibrations better. Uses of High Carbon Steel: (i) It is used for making tools such as drills, files, chisels. (ii) Many machine parts are made with high carbon steel since it is capable of withstanding shocks and vibrations. (c) High Tensile Steel: It contains 0.8% carbon and 0.6% manganese.The strength of this steel is quite high. High tensile steel wires are used in prestressedconcreteworks. |4.2 ALUMINIUM It is presenton the surfaceof earth crust in most of the rooks and clay. But to produce the metal bauxite (A1203.2H2O)is ideally suitedore. Properties of Aluminium 1. It is having silver colour and bright lustre. . It is very light in weight. . It is good conductor of electricity. \}O\_U1-I>m . It has very good resistanceto corrosion. It melts at 66°C. . It is highly ductile and malleable. . It has high strengthto weight ratio. Uses of Aluminium 1. It is used to make door and window frames. 2. Aluminium structural membersare becoming popular. 3. Aluminium wires are used as conductorsof electricity. 4. It is used as a foil. 5. Aluminium powder servesas pigments in paints. I 4.3.COPPER It is a naturally available metal in the form of ores which contain small amount of iron and sulphur. After removing impurities, it is processedelectrolytically to get purest metal. This metal is almost indestructible. Copper scrap can be processedto get original copper. Properties of Copper 1. It is having reddish brown colour. . Its structure is crystalline. . It is highly ductile and malleable. O0\]_O\U1 It resists corrossion. . It can be welded easily at red heat condition. Dents on the copper can be hammeredout. . It has high electric and thermal conductivity. . Its melting point is at 1083°C. Uses of Copper 1. It is used as electric wire and cable. 2. It is used as lighting conductor. 3. For water proofing the constructionjoints copper plates are used. 4. Copper tubes are used for hot and cold water supply, gas and sanitation connections. 5. It forms a major constituent of brassand bronze. IQUESTIONS 1. Statethe engineeringproperties and use of the following: (a) Cast iron ([2)Wrought iron (d) Aluminium and 2. Differentiate (c) Steel (e) Copper. between cast iron and steel. 3. Differentiate between wrought iron and steel. 4. Bring out the differences among mild steel, high carbon steel and high tensile steel. Miscellaneous BuiIingMalePIals Glass,plastics,bitumen,asbestos,paints,distemperandvarnishesare someof the miscellaneousmaterials used in building constructions.Their properties and usesare briey presentedin this chapter. 5.1 GLASS Silica is the main constituent of glass. But it is to be addedwith sodium potassiumcarbonateto bring down melting point. To make it durable lime or lead oxide is also added.Manganeseoxide is addedto nullify the adverseeffects of unwanted iron presentin the impure silica. The raw materials are ground and sieved. They are mixed in specific proportion and melted in furnace. Then glass items are manufacturedby blowing, flat drawing, rolling and pressing. Important Properties of Glass 1. It absorbs,refracts or transmits light. It can be made transparentor translucent. . It can take excellent polish. . It is an excellent electrical insulator. It is strong and brittle. \Ooo\)_O It can be blown, drawn or pressed. It is not affected by atmosphere. . It has excellent . It is available resistance to chemicals. in various beautiful colours. . With the advancementin technology,it is possible to make glasslighter than cork or stronger than steel. 10. Glass panescan be cleanedeasily. Typesof Glass The glass may be broadly classified as: 1. Sodalime glass 2. Potashlime glass 59 . Potashlead glass 4. Common glass and . Special glasses. . SodaLime Glass: It is mainly a mixture of sodium silicate and calcium silicate. It is fusible at low temperature.In the fusion condition it can be blown or welded easily. It is colourless. It is used as window panesand for the laboratory tubes and apparatus. . Potash Lime Glass: It is mainly a mixture of potassiumsilicate and calcium silicate. It is also known as hard glass. It fuses at high temperature. It is used in the manufacture of glass articles which have to with standhigh temperatures. . Potash Lead Glass: It is mainly a mixture of potassiumsilicate and lead silicate. It possesses bright lustre and great refractive power. It is used in the manufacture of artificial gems, electric bulbs, lenses,prisms etc. . CommonGlass: It is mainly a mixture of sodium silicate, calcium silicate and iron silicate. It is brown, green or yellow in colour. It is mainly usedin the manufactureof medicine bottles. . Special Glasses:Propertiesof glassescan be suitably altered by changing basic ingradients and adding few more ingradients. It has now emergedas versatile material to meet many special requirement in engineering.The following is the list of someof the special glasses: (a) Fibre glass ([2)Foam glass (c) Bullet proof glass (d) Structural glass (e) Glass black (f) Wired glass (g) Ultraviolet ray glass (11)Perforated glass. I 5.2 PLASTICS Plastic is an organic material preparedout of resin. It may or may not contain llers, plasticisers and solvents.Plastic may be defined as a natural or synthetic organic material which are having the property of being plastic at some stage of their manufacture when they can be moulded to required size and shape. Shellac and bitumen are the natural resins used as plastic for a long time. In 1907, Blackland produced synthetic resin from the reaction of phenol and formaldehyde.The resin was hardenedunder pressureand heat to produce useful plastic articles. Types of Plastics Primarily there are two types of plastics: 1. Thermosetting and 2. Thermoplastic. 1. Thermosetting Plastics: It needs momentary heated condition and great pressure during shaping.When heatedcrosslinkage is establishedbetweenthe moleculesandchemicalreaction takesplace.During this stageshapecanbe changedwith pressure.This changeis not reversible. The scrapof such plastic is not reusable.Bakelite is an example of such plastic. 2. Thermoplastic: In this variety, the linkage betweenthe moleculesis very loose. They can be softenedby heating repeatedly.This property helps for reuse of Wasteplastic. These plastic needtime to cool down and harden.Theseplastics are to be kept in moulds till cooling takes place completely. Bitumen, cellulose and shellac are the examplesof this variety of plastics. Properties of Plastics 1. Colour: Someplastics are completely transparent.Using pigments plastics of any attractive colour can be produced. Dimensional Stability: It is dimensionally stable to a great extent. .U.->."°!\ Durability: Plastic offers greatresistanceto moisture and chemicalsand hencemore durable. Electrical Insulation: The plastics possessexcellent electrical insulating property. Fire Resistance:The phenolformaldehyde and urea-formaldehydeplastics resist fire to a great extent and hencethey are used as fire proofing materials. Strength:The plastics are reasonablystrong. Their strengthmay be increasedby reinforcing with various fibrous materials.Attempts arebeing madeto producestructurally soundplastics. . Specific Gravity: The specific gravity of plastics is very low and henceconvenientto handle. 8. Ductility: The plastics are not ductile and hencethey fail Without giving Warning. 9. 10. Fixing: Plastics can be bolted, drilled, glued, clamped or simply push fitted in position. Maintenance: There is no maintenancecost for plastic articles i. e., they do not needpainting and polishing. Uses of Plastics There are variety of plastics madeto suit different uses.The typical usesof plasticsin buildings is listed below: . Corrugatedand plain sheetsfor roong. For making jointless ooring. Flooring tiles. .\°.°°.\.°. Overhead Water tanks. Bath and sink units. Cistern ># hall oats. Decorative laminates and mouldings. .0 VV1ndoW and door frames and shutters for bathroom pit Lighting fixtures. pit Electrical > . Electrical l\). conduits. insulators. Pipes to carry cold Waters. doors. I 5.3 BITUMEN Ashalt, bitumen andtar arereferredasbituminous materials,which areessentiallyhydrocarbonmaterials. The asphalt is a mixture of inert mineral matter lime alumina, lime, silica etc. and a hydrocarbon known as asphaltic bitumen. In someplaces like Trinidad and Bermudez,asphalt is available in nature at a depth of 3 to 60 metres.It is known as natural asphalt. Common variety used all over the world is residual asphalt, which is obtained by fractional distillation of crude petroleum oil. Bitumen is the binding material which is presentin asphalt.It is a hydrocarbon. It is obtained by partial distillation of crude oil. It contains 87 per cent carbon, 11 per cent hydrogen and 2 per cent oxygen. separatingand cooling volatile product gives tar. Comparisonbetween asphalt,bitumen and tar is presentedin Table 5.1. Table 5.1. Comparisonbetween asphalt,bitumen and tar S. No. Asphalt Property Colour Blackish brown Carbon content Low State Effect on heating Bitumen Tar is obtainedin the distructive distillation of coal, wood or other organic materials.When coal or wood is heatedto rednessin an closed chamber,it yields volatile product and residue coke. After Dark with slight Solid orsemisolid Setting time Burns with a smoke reddish tinge P°.\'.°S-" Less Solid Adhesive power ame and becomes Resistance to acid plastic Moderate Use Less Deep dark Melts High More As damp proof course, for paints, as roofing felt and for road works. Tar Less More Viscous liquid Becomes more uid. More As damp proof course and as roofing felt. More Most 4. When it is mixed with cement and water, it retains shapermly. 5. Its colour is brown or grey. 6. It can be cut into pieces or can be drilled. 7. It possesseshigh tensile strength in the direction of its fibres. 8. Its specic gravity is 3.10. Uses of Asbestos 1. Asbestoscement sheetsare the cheapestroofing materials. 2. Asbestoscementpipes are used as down take pipes of rain water from the roof. 3. With bitumen it forms good damp proof layer. 4. It is used for preparing re proof ropes and clothes. 5. It is used as covering material for fuse and electric switch boxes. 6. It is useful for insulating boilers, furnacesetc. I5.5 PAINTS Paints are applied on the surfacesof timber, metals and plastered surfacesas a protective layer and at the same time to get pleasant appearance.Paints are applied in liquid form and after sometime the volatile constituent evaporatesand hardenedcoating acts as a protective layer. Constituents of Paint The essentialconstituentsof paints are: 1. Base 2. A vehicle 4. A drier and 5. A thinner. 3. A pigment 1. Bases: It is a principal constituent of paint. It also possessesthe binding properties. It forms an opaquecoating. Commonly usedbasesfor paints are white lead, red lead, zinc oxide, iron oxide, titanium white, aluminium powder and lithophone.A lead paint is suitablefor painting iron and steel works, as it sticks to them well. However it is affected by atmosphereaction and hence should not be used as final coat. While zinc forms good base but is costly. Lithophone, which is a mixture of zinc sulphateandbarytes,is cheap.It gives good appearance but is affected by day light. Hence it is used for interior works only. 2. Vehicles: The vehicles are the liquid substanceswhich hold the ingredients of a paint in liquid suspensionand allow them to be applied on the surface to be painted. Linseed oil, Tung oil and Nut oil are used as vehicles in paints. Of the above four oils, linseed oil is very commonly used vehicles. Boiling makes the oil thicker and darker. Linseed oil reacts with oxygen and hardensby forming a thin film. 3. Pigment: Pigments give required colour for paints. They are fine particles and have a reinforcing effect on thin film of the paint. The common pigments for different colours are: BlackLamp black, suit and charcoal black. Redvenedion red, red lead and Indian red. Brown-burned timber, raw and burned sienna Greenchrome green, copper sulphate. Blueprussian blue and ultra marine Yellow-ochre and chrome yellow. . The Drier: Theseare the compoundsof metal like lead, manganese,cobalt. The function of a drier is to absorb oxygen from the air and supply it to the vehicle for hardening.The drier should not be addeduntil the paint is about to be used.The excessdrier is harmful becauseit destroyselasticity and causesaking. . The Thinner: It is known as solvent also. It makes paint thinner and hence increasesthe coverage.It helps in spreadingpaint uniformly over the surfaceTerpentine and neptha are commonly used thinners. After paint applied, thinner evaporatesand paint dries. Properties of an Ideal Paint 1. It should be possible to apply easily and freely. . It should dry in reasonabletime. . It should form hard and durable surface. It should not be harmful to the health of workers. \DO0\)_O It should not be easily affected by atmosphere. It should possessattractive and pleasing appearance. . It should form a thin film of uniform nature i. 2., it should not crack. . It should possessgood spreadingpower. . It should be cheap. Types of Paints Dependingupon their constituentsthere are various types of paints.A brief description of someof them which are commonly used are given below: 1. Oil Paint: Thesepaints are applied in three coatsprimer,undercoatand nishing coat. The presenceof dampnesswhile applying the primer adversely affect the life of oil paint. This paint is cheapand easyto apply. 2. Enamel Paint: It containswhite lead, oil, petroleum spirit and resinousmaterial. The surface provided by it resists acids, alkalies and water very well. It is desirable to apply a coat of titanium white before the coat of enamel is applied. It can be used both for external and internal walls. 3. Emulsion Paint: It containsbinding materials suchas polyvinyl acetate,syntheticresins etc. It driesin 1%to 2 hoursandit is easyto apply.It is moredurableandcanbecleaned with water. For plastered surfaces,first a coat of cement paint should be applied and then the emulsion point. Emulsion paint needssound surfaces. 4. Cement Paint: It is available in powder form. It consistsof white cement,pigment and other additives. It is durable and exhibits excellent decorative appearance.It should be applied on DD: it ,.;liiM*5CELL5NE rough surfacesrather than on smooth surfaces.It is applied in two coats.First coat is applied on wet surfacebut free from excesswater and allowed to dry for 24 hours. The secondcoat is then applied which gives good appearance. 5. Bituminous Paints: This type of paint is manufacturedby dissolving asphalt or vegetable bitumen in oil or petroleum. It is black in colour. It is used for painting iron works under water. 6. Synthetic Rubber Paint: This paint is prepared from resins. It dries quickly and is little affected by weather and sunlight. It resists chemical attack well. This paint may be applied even on fresh concrete.Its cost is moderateand it can be applied easily. 7. Aluminium Paint: It containsnely ground aluminium in spirit or oil varnish. It is visible in darknessalso. The surfacesof iron and steel are protected well with this paint. It is widely used for painting gas tanks, water pipes and oil tanks. 8. Anti-corrossive Paint: It consistsessentially of oil, a strong dier, lead or zinc chrome and finely ground sand.It is cheapand resists corrossion well. It is black in colour. Application of Paint Preparationof surfacefor application of paint is the most important part in painting. The surfaceto be painted should not be oily and it should be from akes of the old paint. Cracks in the surfaceshould be lled with putty and then with sandpaper.Then primer is applied. Painting work should be carried out in dry weather.The under coats and first coats must be allowed to dry before nal coat is applied. l5.6 DISTEMPERS Distempersare the cheapervariety of paints in which chalk is usedasbaseand water is usedas a carrier. The emulsifying agent which is commonly used is glue or casein.Distempersare available in powder form or in the form of paste.They are to be mixed with hot water before use. The surface to be distempered should be thoroughly rubbed and cleaned. The cracks, if any should be lled by lime putty. The surface should be kept dry for about two months before applying distemper.Thus a primary coat is applied and is allowed to dry. Distemper is usually applied in two coats. Properties of Distemper 1. They are generally light in colour. 2. The coatings are generally thick. 3. They give reective coating. 4. They are less durable than oil paints but are cheaper. | 5.7 VARNISHES Varnish is the solution of resins or resinous substanceslike amber, copal, shellac, gum resin etc. in solvents like oil, turpentile, alcohol etc. Depending upon the solventsused varnishesare classied as, oil varnishes,turpentile varnishes,spirit varnishesand water varnishes.The desirablecharacteristicsof an ideal varnish are 1. It should give glossy surface. 2. Should be durable. 3. It should dry rapidly after application. 4. It should not develop cracks after drying. It is commonly used on wooden surfaces. I5.8 SOLIDAND HOLLOW CONCRETE BLOCKS Solid and hollow concreteblocks are manufacturedin factories to meet the requirementsof building blocks in cities and towns. Theseblocks may be called as artificial stones,sincethey replacethe stones in the masonry construction.They are manufacturedwith lean mixes of cement,sandand aggregatesof sizes less than 12 mm. Instead of sharp edged aggregates,round aggregatesare professed in the manufactureof theseblocks. The properties and usesof theseblocks is given in this article. (i) Solid Concrete Blocks: Solid concrete blocks of size 400 mm X 200 mm X 150 mm are commonly manufactured.To reduce the weight of the block no fine concretesare preferred. No fine concrete is the concrete in which fine aggregateis not used, but round aggregatesof size less than 12 mm are used. IS:2185 (part I) 1983 covers the requirement,for such blocks. Theblocksshouldsatisfythe strengthrequirementof 4 N/mmz.Their densityshouldbe aslow as possible, so that handling is not difficult. They should have sharpedgeswhich are at right anglesto each other. Theseblocks are used for load nearing wall construction also. (ii) Hollow Concrete Blocks: To reducethe weight of concreteblocks, they may be madehollow as shown in Fig. 5.1. Hollow blocks of sizes400 mm X 200 mm X 190 mm (nominal size 400 X 200 X 200 mm) and also of sizes 400 mm X 300 mm X 190 mm (nominal size 400 X 300 X 200 mm) are manufactured.IS:2185 (part I) 1983 covers the specifications for theseblocks. Theseblock need richer mixes. Fine aggregatesupto 60% and coarseaggregatesupto 40% are used. 10 190+ mm /vl A09 mm |<200 mm>|/ Fig. 5.1. Hollow concrete block Theseblocksalsoshouldsatisfythe strengthrequirementof 4 N/mmz.Theyshouldhavetruely right angled corners. Advantage of using concreteblocks is that the construction activity is fast. Mortar requirement for finishing the surfaceis less. Pointing alone is sufficient, in other words plastering is not necessary. Table 5.2 gives the differencesbetween solid and hollow concreteblocks. Table 5.2. Differences S. No. between solid and hollow concrete blocks Solid Concrete Blocks Hollow Concrete Blocks 1. Solid in nature Hollow in nature 2. More in weight Less in weight 3. Conductivity of heat is high (less thermal Conductivity of heat is low (more thermal insulation) insulation) 4. It does not provide facility to conceal conduits etc. It provides facility to conceal conduits etc. 5. No ne concrete is preferred. Fine aggregateis more (as high as 60%) 6. Lean mixes are used Needs richer mix. Both solid and hollow blocks can be usedfor the construction of load bearing as well aspartition walls. They are ideally suited for the construction of compound walls. 5.9 ROOFING AND FLOORING TILES These are also clay products like brick but are thin. Depending upon their use, building tiles may be further classified as 1. Roofing tiles 2. Flooring tiles and wall tiles. 1. Roofing Tiles: Roong tiles are used to cover sloping roofs. They are supportedon wooden reapers.Sometimeslight gaugesteel or steedrods are also used as reapers.After supporting on reapers thesetiles shouldbe strongenoughto take load of a man safely.The tiles should he leak proof. Normally thesetiles are having curved surfacehaving ribbed sections,sothat with thin sectionthey are sufficiently VIIIIIIIA L\\\\\\\V VIIIIIIIA L§\\\\\\V L\\\\\\\V (a) Allahabad tiles (b) Mangalore tile Fig. 5.2 (c) Corrugated tiles strong to resist the load. However many times at tiles are used under curved/ribbed tiles. Thesetiles are not subjectedto load directly. They servein reducing adversethermal effects.Mangalore, Allahabad tiles, and corrugatedtiles are popularly used roong tiles [Ref. Fig. 5.2]. Allahabad tiles are generally laid side by side and the joints are covered with half round tiles. Mangalore tiles are red in colour and they are of interlocking type. These tiles are manufacturedin Mangalore, Calicut, Cochin and Gujarat. Corrugated tiles satisfy the requirements of appearanceand leak proof but they can be easily blown away by wind. The desirable properties of the roofing tiles are: . they should not absorbmoisture more than 20 per cent by weight. . they should give pleasing look. .°.V:'>P they should be capableof taking load of a man safely, after they are supportedon reapers. they should be durable. they should be uniform in shapeand size. warpageshould not exceed2% along the edgesand 1.5% along the diagonal. 2. Flooring Tiles and Wall Tiles: These tiles are manufacturedby burning pressedgreen tiles twice. First they are burnt at 700°C. Then they are dipped in the glaze solution and again burnt at 1250°Cto fuse them with glaze.The thicknessof thesetiles vary from 15 to 20 mm. Thesetiles are at and they have pleasing appearance.There are two types of flooring tiles: (a) Glazed Tiles: These tiles are used as finish surfaces for oors and walls in kitchen and bath- rooms. Thesetiles are glazed and are provided with attractive colours and designs. (b) Mosaic Tiles: These are precast concrete tiles with marble chips on the top surface.After xing thesetiles polishing is done. The desirableproperties of flooring and roofing tiles are: 1. Tolerancefor length = i 5 mm. 2. Tolerance for thickness = i 2 mm. 3. Should be uniform in shapeand colour. 4. They should be sound,hard and durable. 5. They should have very low percentageof water absorption. 6. They should give a clear ringing sound when struck with each other. 7. They should show good resistanceto abrassion. IQEUSTIONS 1. List the important properties of glass. 2. Write short notes on any four types of glasses. . Dene Plastic. Differentiate between thermosetting and themoplastic. 0 List the usesof plastic as building material. 0 Explain the term bitumen and statetheir properties and uses. Differentiate between plastics and bitumen. 0 What is asbestos? Statetheir properties and uses. Briey explain the function of essentialconstituentsof paints. What are the requirementsof an ideal paint .7 10. Bring out the differences among oil paints, enamel paints and emulsion paints. 11. Distinguish between paints and varnishes. 12. Write short note on: (a) distemper (b) solid and hollow concrete blocks (c) ooring and roofing tiles. 13. Distinguish between solid and hollow concreteblocks. 14. Neatly sketchAllahabad and Mangalore tiles. List their desirableproperties. 15. What are the requirementsof good ooring tiles ? 16. Distinguish between glazed tiles and mossaictiles. This page intentionally left blank 1 UNIT - ll BUILDING CONSTRUCTION This page intentionally left blank CHAPTER BuiIlIingPlanning Every family needs a building to reside. Apart from residential purposesbuildings are required for educational,institutional, business,assemblyand for industrial purposes.Buildings are required for the storageof materials also. In this chapter basic requirementsof buildings are presentedand then planning of the building With respectto orientation, utility of space,energy efficiency and other requirementsare explained. 6.1 ELEMENTS OF A BUILDING The following are the basic elementsof a building: 1. Foundation . Plinth . Walls and columns Sills, lintels and chejjas \D00\J_O Doors and windows Floors . Roofs . Steps,stairs and lifts . Finishing work ># Building services. The functions of theseelementsand the main requirement of them is presentedin this article. :9 1. Foundation: Foundation is the most important part of the building. Building activity starts with digging the ground for foundation and then building it. It is the lower most part of the building. It transfersthe load of the building to the ground. Its main functions and requirementsare: (a) Distribute the load from the structure to soil evenly and safely. (b) To anchor the building to the ground so that under lateral loads building will not move. 73 (c) It preventsthe building from overturning due to lateral forces. (d) It gives level surfacefor the construction of super structure. 2. Plinth: The portion of the wall betweenthe ground level and the ground oor level is called plinth. It is usually of stonemasonry.If the foundation is on piles, a plinth beam is cast to support wall above oor level. At the top of plinth a damp proof courseis provided. It is usually 75 mm thick plain concrete course. The function of the plinth is to keep the ground oor above ground level, free of dampness.Its height is not lessthan 450 mm. It is required that plinth level is at least 150 mm abovethe road level, so that connectionsto undergrounddrainage systemcan be made. 3. Walls and Columns: The function of walls and columns is to transfer the load of the structure vertically downwardsto transfer it to foundation. Apart from this wall performs the following functions also: (a) It enclosesbuilding area into different compartmentsand provides privacy. (b) It provides safety from burglary and insects. (c) It keepsthe building warm in winter and cool in summer. 4. Sills, Lintels and Chejjas: A window frame should not be directly placed over masonry.It is placed over 50 mm to 75 mm thick plain concrete course provided over the masonry.This course is called as sill. Lintels are the R.C.C. or stone beamsprovided over the door and window openings to transfer the load transverselyso as to seethat door or window frame is not stressedunduly. The width of lintels is equal to the width of wall while thickness to be provided dependsupon the opening size. Chejja is the projection given outside the wall to protect doors and windows from the rain. They are usually made with R.C.C. In low cost housesstone slabs are provided as chejjas. The projection of chejja variesfrom 600 mmto 800 mm. Sometimesdropsarealsoprovided to chejjasto improve acsethetic look and also to get additional protection from sun and rain. 5. Doors and Windows: The function of a door is to give accessto different rooms in the building and to deny the accesswhenever necessary.Number of doors should be minimum possible. The size of the door should be of such dimension as will facilitate the movement of the largest object likely to use the door. Windows are provided to get light and ventilation in the building. They are located at a height of 0.75 m to 0.9 m from the oor level. In hot and humid regions, the window areashould be 15 to 20 per cent of the oor area.Another thumb rule used to determine the size and the number of windows is for every 30 m3of insidevolumethereshouldbe 1 m2windowopening. 6. Floors: Floors are the important componentof a building. They give working/useful areafor the occupants.The ground floor is preparedby filling brick bats,wastestones,gravel and well compacted with not lessthan 100 mm sandlayer on its top. A lean concreteof 1 : 4 : 8, 100 mm thick is laid. On this a damp proof coursemay be provided. Then oor nishing is done as per the requirementof the owner. Cheapestfloor finish for a moderatehouse is with 20 to 25 mm rich mortar course finished with red oxide. The costliest oor finish is mossaicor marble nishing. Other oors are usually of R.C.C. nished as per the requirementsof the owner. 7. Roof: Roof is the top most portion of the building which provide top cover to the building. It should be leak proof. Sloping roof like tiled and A.C. sheetgive leak proof cover easily.But they do not give provision for the construction of additional oor. Tiled roof give good thermal protection. Flat roofs give provision for additional floors. Terrace adds to the comfort of occupants.Water tanks can be easily placed over the at roofs. 8. Step, Stairs and Lifts: Stepsgive convenientaccessfrom ground level to ground floor level. They are required at doors in the outer wall. 250 to 300 mm wide and 150 mm rise is ideal size for steps.In no casethe size of two consecutivestepsbe different. Number of stepsrequired dependsupon the difference in the levels of the ground and the oor. Stairs give accessfrom oor to oor. They should consistsof stepsof uniform sizes. In all public buildings lifts are to be provided for the conveniencesof old and disabledpersons. In hostels G + 3 floors can be built without lifts, but in residential ats maximum oors permitted without lifts is only G + 2. Lift is to be located near the entrance. Size of the lift is decided by the number of usersin peak hours. Lifts are available with capacity 4 to 20 persons. 9. Finishing: Bottom portion of slab (ceiling), walls and top of floor need smooth finishing with plaster. Then they are provided with white wash, distemper or paints or tiles. The function of nishing work is: (a) Give protective cover (b) Improve aestheticview (c) Rectify defective workmanship (d) Finishing work for plinth consistsin pointing while for floor it consistsin polishing. 10. Building Services: Water supply, sanitation and drainage works, electric supply work and construction of cupboardsand show casesconstitute major building services. For storing water from municipal supply or from tanker a sump is built in the house property near street.From the sumpwater is pumpedto over headtanks placed on or aboveroof level so asto get water all the 24 hours. Plumbing work is made so as to get water in kitchen, bathrooms,water closets, sinks and garden taps. For draining rain water from roofs, down take pipes of at least 100 mm diameters should be used. Proper slopesshould be given to roof towards down take pipe. Thesepipes should be xed at 10 to 15 mm below the roof surface so that rain water is directed to the down take pipe easily. The sanitary fittings are to be connectedto stone ware pipes with suitable traps and chambers. Stoneware pipes are then connectedto undergrounddrainageof municipal lines or to the septic tank. Many carpentry works are required for building service. They are in the form of showcases, cupboards,racks etc. Electric supply is essential part of building services. The building should be provided with sufficient points for supply of lights, fans and other electric gadgets. l6.2 BASICREQUIREMENTS OFA BUILDING The planning and construction of a building should be aimed at fulfilling the following requirements: 1. Strength and stability Dimensional stability Resistanceto dampness Resistance to fire \°.°°.\.°.U: Heat insulation Sound insulation Protection against termite attack Durability . Security against burglary ># .9 Lighting and ventilation tit tit. Comforts and convenience > [9. Economy. 1. Strength and Stability: Building should be capableof transferring the expectedloads in its life period safely to the ground. Design of various structural components like slabs, beams, walls, columns and footing should ensuresafety.None of the structural componentsshould buckle, overturn and collapse. 2. Dimensional Stability: Excessive deformation of structural components give a senseof instability and result into crack in Walls, ooring etc. All structural components,should be so designed that deflections do not exceedthe permissible values specified in the codes. 3. Resistanceto Dampness: Dampnessin a building is a great nuisanceand it may reducethe life of the building. Great care should be taken in planning and in the construction of the building to avoid dampness. 4. Resistanceto Fire: Regardingachieving resistanceto fire, the basic requirementslaid down in the codes are: (a) the structure should not ignite easily. (b) building orientation should be such that spreadof fire is slow. (c) In caseof fire, there should be meansof easy accessto vacatebuilding quickly. 5. Heat Insulation: A building should be so oriented and designed that it insulates interior from heat. 6. Sound Insulation: Buildings should be planned against outdoor and indoor noises. 7. Protection from Termite: Buildings should be protected from termites. 8. Durability: Each and every componentof the building should be durable. 9. Security against Burglary: This is the basic need the owner of the building expects. 10. Lighting and Ventilation: For healthy and happy living natural light and ventilations are required. Diffused light and good cross ventilation should be available inside the building. 11. Comforts and Conveniences: Various units in the building should be properly grouped and integratedkeeping in mind the comfort and convenienceof the user. 12. Economy: Economy without sacricing comfort, convenienceand durability is anotherbasic requirement of the building. I 6.3 PLANNING All buildings should be properly planned,keeping in view the various requirementsof a good building. Except strength requirement, all other requirementsof a good buildings are taken care at the stageof planning. Strengthrequirementis taken care during structural design of building components.However in planning the building bylaws of the statutory authorities should not be violated. Planning of the building is an art combined with science. Principles of planning of buildings may be grouped into: 1. Orientation 2. Energy efficiency 3. Utility 4. Other requirementsof the building. Theseprinciples are briey explained in the articles 6.4 to 6.7. l6.4 PLANNING SUITABLE ORIENTATION Orientation meanssetting out the plan of the building with respectto northsouthand eastwestdirections to provide an opportunity to user to enjoy sunshine and breezewhen required and to avoid the same whenevernot required.This is alsoknown asplanning the aspectof a building. Aspectmeansarrangement of doors, windows in the external wall to make good use of nature.This term has nothing to do with the architecturalaspectof outlook of building. Kitchen shouldhaveeasternaspectto enjoy morning sunshine, means,kitchen should be located on the easternside of the building to make use of morning sun rays. The following are the required aspectsfor various parts of the building in the northern hemisphereof earth: (a) Kitcheneastern aspect. (b) Dining roomsouthern aspectto enjoy winter sun. (c) Drawing and living room~southernor southeasternaspectto enjoy winter sun. (d) Bed roomswestern or southwesternaspectto enjoy breez in summer. (e) Reading room, class room, stairs, northern aspectto enjoy diffused light. The following suggestionsshould be kept in mind in the orientation of a building in India: (a) Place long walls towards northsouth and short walls in eastwestdirections so as to reduce the area exposedto direct sun rays. (12)Provide verandahand balcony on east and west. (c) Provide chejjas on doors and Windowson southernside to protect them from sunsrays. |6.5 PLANNING FORENERGY EFFICIENCY A building should be plannedin sucha mannerthat it gives maximum day lighting, ventilation and heat insulation. If theserequirementsare fullled, requirement of electric energy comes down. (a) Light: Natural light provides hygenic atmosphere.Light should not be glaring but it should be uniformly distributed. Providing Windows and ventilators of appropriate size at suitable positions contributes a lot for natural lighting. For residential buildings Window areato oor area should not be less than 1/10th while for school buildings it should not be less than 1/5th of oor area. For factory buildings north light trussesshould be provided to get maximum diffused light. (b) Ventilation: Ventilation is the circulation of the air in the building. Natural ventilation can be achieved by selecting and positioning of doors, Windows and ventilators at suitable places. Always cross ventilations should be planned suitably. Provision of ventilators at roof level helps in driving out hot airs. In case it is not possible to achieve natural ventilation for any part of the building provide ordinary or exhaustfans. (c) Heat Insulation: Thicker exterior Walls provide insulation against heat. Proper ventilation also helps in achieving heat insulation. Sun shadesprovided to doors, Windowsand ventilators help in achieving heat insulation. In factories and assemblyhalls height should be more to reduce temperature inside the building. The position of furnacesin the factories shouldbe located away from the other parts of the factory. The openings should be provided at higher level in the Wall to remove hot air. |6.6 PLANNING FORSUITABLE UTILITY Principles of planning for suitable utility are: 1. Roominess 2. Furniture Requirements 3. Groupings 4. Circulation. 1. Roominess: It refers to suitable proportioning of length, width and height of rooms in the building to get maximum benefit from the minimum dimensions.Length to Width ratio should be 1.2 to 1.5. If it is nearly squarelot of area is Wastedfor movement, While, it is more than 1.5, it gives the tunnel effect. Doors for rooms should be properly located so that utility and privacy are maximum. Cupboardsand lofts should be provided to increaseroominess. Proper colours to Wall and floor also give roominesseffect. Light colour gives effect of more space. 2. Furniture Requirements: In planning residential, office, laboratory, hospital buildings positions of required furniture should be drawn and then room dimensions,positions of doors,windows, wardsities etc. planned.In caseof planning a hostel room for two studentsit may needcentrally placed door while if it is for three students,it should be near the end of front wall. Positions of cots, study tables and cupboard should be drawn and room planned. In designing a living room, positions of sofa, chairs,T.V. show caseetc. shouldbe drawn and sizeof the room and positions of doorsfixed. Availability of circulation area should be checked. Thus the furniture requirement inuences the planning of a building to a great extent. 3. Grouping: Grouping meansdisposition of various rooms in the building for the convenience of usersand their utility. A dining room should be close to the kitchen, white sanitary block should be away from kitchen, but convenientto bedrooms.In caseof offices, administrative departmentis located centrally. In factories, various sections are located such that product moves in one direction to get nally assembledafter least movement.In residential buildings grouping is to achievecomfort, privacy and efficiency while in the caseof other buildings it is to achieve economical service. 4. Circulation: Circulation meansthe spaceto be provided for movement from room to room or oor to oor. Passages,lobbies, halls provided serve horizontal circulation while stairs and lifts serve vertical circulation. Within a room also a portion of it serve for circulation while some other portion serve for utility. The following points should be consideredin planning circulation: (a) They should be straight. (b) They should be sufficient. (c) They should be sufficiently lighted and ventilated. (d) Stairs should be easily accessibleto all the users. (e) Sanitary servicesshould have accessfor every user through passage lobby. I6.7 PLANNING FORMEETING OTHERREQUIREMENTS Principle of planning involves planning for meeting the following requirementsalso: 1. Sanitary convenience . Prospects . Elegance \ooo\3_m Flexibility Privacy Resistance to fire . Sound insulation . Protection from termite . Security against burglary ># .0 Economy pit pit. Provisions for future alterations. 1. Sanitary Convenience: Sanitary conveniencesinclude provision of bathrooms, lavatories, urinals etc. Provision of these are not only necessitiesbut statutory requirement also. These facilities should be located giving free accessto all users.In theseblocks, suitable slopesshould be given to the oors to drain out water easily. 2. Prospects: It is about locating and selecting types of doors and windows so as to reveal pleasantfeaturesand concealundesirablefeaturesof the buildings from a personviewing from outside. 3. Elegance: Elegance means general effect produced for a viewer from outside. It depends upon proper positioning of doors, windows, ventilators, chejjas, balconies etc. Elevations should be attractive. The width, height and the projections in the building contribute a lot for the elegance.Taj Mahal is an example famous for its elegance. 4. Flexibility: This aspectof planning meansa room designedfor a specific purposeshould be possibleto use for other purposes,if necessary.A study room may be plannedfor using as a guestroom. If partition is provided betweenliving room and dining room, it is possibleto remove partition and use living room plus dining room for the family functions. If independentaccessis given to backyard from kitchen, backyardcanbe usedfor dinner functions.Thus in planning exibility also shouldbe considered. 5. Privacy: Planning should take care of privacy of one room from other room in a building as well as someparts of a building from neighbouring buildings and from streets.It is ensuredby proper grouping of rooms and by suitably providing doors, windows and ventilators. Planning the entranceat appropriateposition also contributes a lot in providing privacy. 6. Resistance to Fire: It may be noted that concreteand masonry (stone or brick) have better resistance to fire while steel and wood have lesser resistance. Hence reduce use of steel and wood in kitchen and bathrooms with electric heaters.Kitchen should be so located that if fire is caught it is directed away from the building by the wind rather than towards the building. In public buildings and assemblyhalls stair casesshould be easily accessibleand always more than one is provided. 7. Sound Insulation: Noise pollution can be reduced by suitable planning of the building. Some of them are: (a) Orienting the building suitably so that rooms are kept away from road side. (b) Using hollow blocks for the walls. (c) Plugging door and window openingstightly. (d) Using false ceilings. (e) By fixing water closet cisterns on outer walls instead on wall common to rooms. (f) By xing water closet pan on a thin pad. (g) Holding pipes passing through walls and oors by insulated clips. 8. Protection from Termite: Building should be protected from termite attack by (a) Treating the foundation with chemicals at the time of construction. (b) Using well seasonedand well treated wood in the building. 9. Security against Burglary: By providing thicker walls, using stronger doors and windows in outer walls, security againstburgling is improved. Providing grills to windows and additional shutters to doors are some of the methods of improving security. Alarms tted in Walls, roofs also improve security of the buildings. 10. Economy: Economy Without sacrificing comfort, conveniencesand durability is another basic principle of planning a building. For this circulation area should be minimised. Materials should be so selected that maintenance cost is minimized. ll. Provision for Future Expansion: Building should be planned making suitableprovision for future expansion.Someof the stepsrequired for it are: (a) Improving elevations without dismantling any part during future expansion. (b) Extending building horizontally or vertically Without damagingthe existing building. (c) Improving the ooring. IQUESTIONS 1. What are the basic componentsof a building? Discussthe main requirementsof eachpart to fulll its primary function. Briey explain the principles of building planning. ':'9! Dene orientation of a building. Explain the various aspectsof orientation. Describe the principles of planning with respectto utility. Write short notes on energy efficiency in planning of building. CHAPTER raunuauiuns The definition and functions of foundation have beengiven in chapter6. In this chapterbroad guidelines for fixing the dimensions of foundation are given and different types of foundations are explained. 7.1 DIMENSIONS OF FOUNDATION Guidelines for minimum dimensionsare given below: using Rankines Formula: (a) Depth of Foundation: For all types of foundations minimum depth required is calculated H=p[lsin(pT w l+sin(p where p = safe bearing capacity of soil w = unit weight of soil (p= angle of reposeof soil. However in any caseit is not less than 0.9 m. Finding safebearing of the soil is an expertsjob, and it is found after conducting tests in eld or in Laboratories. However general values for common soils are listed in Table 7.1. Table 7.1 S.No. Typeof Soil SBCin kN/m2 1. Igneous rocks (granite, troy etc.) 3300 2. Sedimentaryrocks (sand, stone etc.) 1650 3. Residual deposits,hard shale, cementedmaterials 900 4. Soft rock, coarse sand 450 5. Medium sand 250 6. Fine sand 150 7. Loose gravel or sand gravel 250 8. Soft shale,hard clay 450 9. Medium clay, readily indented with thumb nail 250 10. Moist clay, clay and sand mixture 150 11. Soft clay 100 12. Black cotton soil, peat and made up of ground to be found after investigations (b) VVdthof Foundation: Width of wall foundations or size of column footing is determinedby first calculating the expectedload and then dividing that with SBC. Thus, Width of wall foundation Load per unit length of wall = S.B.C.of soil Load carried by column Area ofcolumn footing = 7.2 CONVENTIONAL S. B.C.0 f S01.1 SPREAD FOOTINGS This type of foundations are commonly used for walls and masonry columns. These foundations are built after openingthe trenchesto required depth. Suchfootings are economicalup to a maximum depth of 3 In. As thesefoundations are suitable depth, they are groupedunder shallowfoundations. Figure 7.1 shows a conventional spreadfooting for a wall and Fig. 7.2 shows it for a masonry column. FiS. 7.1. Wall footin 8 FiS. 7.2. Foundation for masonr Y Pier Before building thesefooting trenchesare openedto required depth and the soil is rammed well. Then a plain concreteof mix 1 : 4 : 8 is provided. Its thickness varies from 150 to 200 mm. Over this bed, stone masonry footing is built. It is built in courseseach courseprojecting 50 to 75 mm from the top course and height of each coursebeing 150 to 200 mm. In caseof wall footing the projections are only one direction while in caseof columns, they are in both directions. The projection of bed concrete from the lowest courseof foundation masonry is usually 150 mm. I7.3 R.C.C.FOOTINGS There are mainly two types of R.C.C. footings: 1. One way reinforced footings. 2. Two way reinforced footings. 1. One Way Reinforced Footing: These footings are for the walls. In these footings main reinforcements are in the transverse direction of wall. In longitudinal directions there will be only nominal reinforcement. 2. Two Way Reinforced Footings: For columns two way reinforced footings are provided. The following types of the footings are common: (i) Isolated Column Footings: If separatefootings are provided for each column, it is called isolated column footing. Figure 7.3 shows a typical isolated column footing. The size of footing is basedon the arearequired to distribute the load of the columns safely over the soil . Thesefootings are provided over a 100 to 150 mm bed concrete. Required reinforcements and thickness of footing are found by the design engineers.Thickness may be uniform or varying. R.C.C. column R.C.C. footing Plan concrete bed (a) Footing with uniform thickness (b) Sloping footing Fig. 7.3. isolated R.C.C.footing (ii) Combined Footings: Common footings may be provided for two columns. This type of footing is necessarywhen a column is very close to the boundary of the property and hencethere is no scopeto project footing much beyond the column face. Figure 7.4 shows a typical combined footing. The footing is to be designed for transferring loads from both columns safely to the soil. The two columns may or may not be connectedby a strap beam. Fig. 7.4. Combined footing [Strap beam may or may not be provided] (iii) Continuous Footings: If a footing is common to more than two columns in a row, it is called continuousfooting. This type of footing is necessary,if the columns in a row are closer or if SBC of soil is low. Figure 7.5 shows this type of footing. Fig. 7.5. Continuous footing (iv) Mat Footing/Raft Footing: If the load on the column is quite high (Multistorey columns) or when the SBC of soil is low, the sizesof isolated columns may work out to be to suchan extent that they overlap eachother. In such situation a common footing may be provided to severalcolumns as shown in Fig. 7.6. Such footings are known as raft footings. If the beamsare provided in both directions over the footing slab for connecting columns, the raft foundations may be called as grid foundation also. The addedadvantageof suchfooting is, settlementis uniform andhenceunnecessarystressesarenot produced. Fig. 7.6. Raft foundation I7.4 GRILLAGE FOOTING High rise buildings are built with steel columns encasedin concrete. Such columns carry Very heavy load andhencethey needspecialfoundationsto spreadthe load to a larger areaof soil. Grillage foundation is one such special foundation. It consistsof one tier or more tiers of Isections steelbeams.Figure 7.7 showsa typical two tier grillage foundation. Top tier consistsof less number but large size steel section while lower tier consistsof larger number but smaller size steel sections.Column load is transferredto the top tier through a base plate. The grillage beams are unpainted and are encasedin concrete with minimum cover of 100 mm beyond the edgesof steel sections.A minimum clear spaceof 75 mm should be maintainedbetweenthe anges of adjacentgrillage beamsso that concreting can be madeproperly. To maintain spacing,pipe separatorsare used. Steel column Gusset plate Pipe separators E .5.-. .g. so .3 IIIIIIIIIIIJ 7 VIIIIIIIIIIIII1 . V//////////////////////////////////////////0 .' .' .' - Second E E E . E E E = I7.S ARCHFOUNDATION Inverted arch foundations are provided in the placeswhere the SBC of the soil is very poor and the load of the structure is through walls. In such casesinverted archesare constructedbetweenthe walls. End walls should be sufficiently thick and strong to withstand the outward horizontal thrust due to arch action. The outer walls may be provided with buttress walls to strengthenthem. Figure 7.8 shows a typical inverted arch footing. inverted arch Fig. 7.8. inverted arch Footing 7.6 PILE FOUNDATIONS Thesefoundations are known as deep foundations.A pile is a slendercolumn made of wood, concrete or steel.A pile is either driven into the soil or formed in situ by excavatinga hole and then filling it with concrete.A group of piles are driven to the required depth and are cappedwith R.C.C. slab, over which super structure is built. The pile transfer the load to soil by friction or by direct bearing, in the latter case,piles being taken up to hard strata.This type of foundations is used when top soil is not capableof taking the load of the structure even at 3-4 m depth. Hard strata (a) Bearing pile (b) Friction pile Fig. 7.9. Pile Foundations Pile foundations are classified according to the materials used and also on the nature of load transfer. Classification According to Materials Used: Piles may be classified as: (a) Timber piles (b) Concretepiles (C) Steelpiles and (c0 Composite piles. (a) Timber piles: Circular seasonedwood can be used as piles. Their diameter may vary from 200 mm to 400 mm. Similarly squarepiles of sizes 200 mm to 400 mm are also used. The length of timber pile should not be more than 20 times its lateral dimension. The bottom of the pile is sharpened and is provided with iron shoe,so that it can be driven in the ground easily by hammering.Thesepiles should be always kept below water table; otherwise alternating wet and dry condition causethe decay. These piles are cheap and can be easily driven rapidly. The main disadvantageis their load carrying capacity is low and are likely to be damagedduring driving in the soil. (b) Concrete piles: Thesepiles may be further classified as precastpiles and cast in situ piles. Precast piles are reinforced with steel and are manufactured in factories. The crosssection diameter/dimension varies from 200 mm to 500 mm. Square, circular and octagonal sections are commonly used.The length of piles may be up to 20 m. They are provided with steel shoeat the lowest end. Thesepiles can carry fairly large loads. Thesepiles are highly resistantto biological and chemical actions of the soil. The disadvantageof thesepiles is they needmore time to manufactureand are heavy to handle. Figure 7.10(a) and (b) show concretepiles. III%lII Beam Pile f Under ream Under ream (a) Pressure pile (b) Under-reamed pile Fig. 7.10. Cast in situ concrete piles Cast in situ concretepiles are formed rst by boring the holes in the soil and then concreting them. Concreting is usually made using casing tubes. If the hole is lled with only plain concreteit is pressurepile. The load carrying capacity of the piles may be increasedby providing enlargedbase. The reinforcementcagingmay be insertedin the boredholesandto increaseload carrying capacity one or two under reamsmay be formed. After that concreting may be carried out. Suchpiles are known as under reamed piles. These piles are provided at regular interval of 2 to 4 m and capping beam is provided over them. (c) Steel Piles: A steelpile may be a rolled steel1 sections,tubesor fabricated in the form of box. These piles are mostly used as bearing piles since surface available for friction is less and also the coefficient of friction is less. If tubes are used the soil inside the tube is driven out by compressedair and concrete is filled. These piles are very useful for driving close to existing structures since they disturb the soil least. (d) Composite Piles: Composite piles may be of concrete and timber or of concrete and steel. Wooden piles should not be subjectedto alternating wet and dry conditions. Hence they are preferred for the portion below water table. The portion abovewater table are built with cast in situ concretepiles. If the required length of steel piles is less than the depth of pile, many times upper portions are built with concrete.Thus steel and concretecompositepiles are sometimesused. Classification of Piles According to Load Transfer: According to the load transfer to the soil piles may be classified as (a) Bearing piles and (b) Friction piles. Bearing piles rest on hard strataand transfer the load by bearing. Suchpiles are preferred.These piles are used if the hard stratais available at reasonabledepth. Friction piles transfer the load to the soil by the friction betweensoil and the pile. Suchpiles are used if hard strata is not available to a considerabledepth. The friction developed is to be properly assessedbefore deciding the length of the pile. The surfaceof such piles is maderough to increasethe skin friction so that required length of pile is reduced. |7.7 FOUNDATIONS IN BLACK COTTONSOIL Black cotton soil swells during rainy seasonand cracks in summer due to shrinkage.These shrinkage cracks are 100 mm to 150 mm wide and 0.5 m to 2 m deep. Swelling createsupwards pressureon the structure and shrinkage creates downward pull. It results into cracks in foundations wall and roof. Hence foundation in black cotton soil need special care. In caseblack cotton soil is only to a depth of 1.0 m and 2.0 m it is economical to remove entire black cotton soil from the site and build the foundation on red soil. Apart from this black cotton soil should be removed from the sidesof the foundation and filled with sand and gravel. In casethe depth of black cotton soil is more, the following type of foundation may be provided 1. Strip or pad foundation 2. Pier foundation with arches and 3. Under reamedpile foundation. 1. Strip or Pad Foundation: Strip foundation are for walls while pad foundations are for columns. In these foundation the attempt is to keep black cotton soil from foundation by interposing layers of sand and gravel. These foundations should be constructedduring dry season.Suitable plinth protection should be made around external walls with its slops away from the wall, so that moisture do not penetratethe foundation during rainy season.Figure 7.11 shows such foundations. Linth beam Plinth protection Plinth beam Plinth protection 60 to 90 cm L (a)Simple sand-fill structure (b)Fillofalternate layers ofsand andmooram Fig. 7.11. Strip or Pad foundation 2. Pier Foundation with Arches: A pier is a vertical columns of relatively larger crosssection than piles. For walls carrying heavy loads,piers aredug at regular intervals and filled with plain concrete. Thesepiers are taken up to good bearing strata.Then the piers are connectedby concreteor masonry arch. Over thesearchesregular masonryis built. Figure 7.12 showsa typical pier foundation with arches. I---:-_-Z Wall Hard soil (a) L-section (b) Crosssection Fig. 7.12. Pier foundation with arches Under ReamedFile Foundations: Under reamedpiles are bored and then concretedat the sites. Their length may Vary from 3 to 6 m. They are provided with reamsand reinforcement.The pile spacing varies from 2 to 4 m. The top of piles are provided with capping beams over which Walls are built. [Ref. Fig. 7.10 (b)]. IQUESTIONS Briey explain how depth and Width of foundations are fixed. With neat sketchesexplain conventional spreadfooting. Neatly sketchthe following types of R.C.C. footings and explain the situationsin which they are used (a) Isolated column footings (b) Combined footings (c) Mat foundations. What is grillage footing? When do you go for such footings? Neatly sketch a typical grillage footing. Write short notes on (a) Arch foundations (b) Foundation in black cotton soil (c) Pile foundations. SlI'IItII|'eS The portion above the ground level and below the ground oor level is known as plinth. The portion above the ground floor level is known as super structure. It includes walls, columns, beams, oors, roofs, doors, windows, lintels, staircasesetc. In this chapter types of super structures based on the method of load transfer is first presentedand then the various componentsare discussedgiving their functions and types. I8.1 TYPES OFSUPER STRUCTURES BASED ONTHEMETHOD OF LOAD TRANSFER On this basis there are two types 1. Load Bearing Structures 2. Framed Structures. 1. Load Bearing Structures: In this type of structure the load on the structure is transferred vertically downward through walls. Loads from roof and oors gets transferredto wall and then wall has to transfer these loads as well as self weight. Such constructions are used in residential buildings where dimension of rooms is less. Residentialbuildings up to ground + 2 floors can be built economically with such structures. 2. Framed Structures: In this type of structuresa frame work of columns, beamsand oors are built first. Then walls are built to partion the living area.The walls are subjectedto selfweight only. This type of super structuresare required when number of stories in a building is more and also when larger areasare to be covered free from walls. Table 8.1 showsthe comparisonbetweenR.C.C. framed structuresand load beaming structures. Table 8.1. Comparisonbetween load bearing and framed structures Load Bearing Structure Framed Structure Cost is less. 2. Cost is more. Suitable up to three stories. Suitable for any number of stories. Walls are thicker and hence floor area Walls are thinner and hence more oor area is reduced. available for use. 92 4. Slow construction. Speedy construction. 5. Not possible to alter the position of walls, after the construction. Position of walls may be changed,whenever necessary. 6. Resistanceto earthquakeis poor. Resistanceto earthquakeforces is good. I8.2 WALLS Walls are built to partition living area into different parts. They impart privacy and protection against temperature,rain and theft. Walls may be classified as 1. Load bearing walls 2. Partition Walls. 1. Load Bearing Walls: If beams and columns are not used, load from roof and floors are transferredto foundation by Walls. Such Walls are called load bearing Walls.They are to be designedto transfer the load safely.The critical portion of the Wallsare near the openingsof doors and Windowsand the positions Whereconcretebeamsrest. Minimum wall thickness used is 200 mm. It is also recommended that the slenderness ratio of wall dened asratio of effective length or effective height to thicknessshould not be more than 27. The effective height and effective length of a Wall may be taken as shown in tables 8.2 and 8.3 respectively. Table 8.2. Effective height of Walls in terms of actual height H S. No. End Condition 1. 2. Eective Height Lateral as well as rotational restraint 0.75 H Lateral as well as rotational restraint at one end and only lateral 0.85 H restraint at other 3. Lateral restraint but no rotational restraint at both ends 1.0 H 4. Lateral and rotational restraint at one end and no restraint at other 1.5 H ends (compound walls, parapet walls etc.). Table 8.3. Effective length of Walls of length L S. No. End Condition Eective Length 1. Continuous and supportedby cross walls 0.8 L 2. Continuous at one end and supportedby cross walls at 0.9 L the other end 3. Wall supportedby cross walls at each end 1.0 L 4. Free at one end and continuous at other end 1.5 L 5. Free at one end and supportedby cross wall at other end 2.0 L 2. Partition Walls: In framed structurespartition walls arebuilt to divide floor areafor different utilities. They rest on oors. They do not carry loads from oor and roof. They have to carry only selfweight. Hence normally partition walls are thin. Table 8.4 shows the differences betweenload bearing walls and partition walls. Dependingupon the requirementthesewalls may be brick partition, clay block partition, glass partition, wood partition, and aluminium and glass partition. Table 8.4. Differences between load bearing and partition walls S. No. Load Bearing Walls Partition Walls 1. They carry loads from roof, oor, self-weight etc. They carry selfweight only. 2. They are thick and hence occupy more oor area. These walls are thin and hence occupy less oor area. 3. As the material required is more, As the material required is less, the the construction cost is more. construction cost is less. 4. Stones or bricks are used Stones are not used for for the construction. the construction of partition walls. '83 STONEMASONRY Masonry meansconstruction of buildings using building blocks like stone,bricks, concreteblocks etc. Masonry is used for the construction of foundation, plinth, walls and columns. Mortar is the binding material for the building blocks. In this article different types of stonemasonry used are explained and points to be observedwhile supervising stonemasonry works are listed. Types of Stone Masonry Mainly there are two types of stonemasonry: 1. Rubble Masonry 2. Ashlar Masonry. 1. Rubble Masonry: In this type of constructionsstonesof irregular sizesand shapesare used. To remove sharp shapesthey may be hammered.The r11bblemasonry may be coursed or nncoursed [Fig. 8.1 and 8.2]. In nncoursed rubble masonry the wall is brought to level at every 300 mm to 500 mm. The mortar consumed in these construction is more. Course rubble masonry is used for the construction of public and residential buildings. Uncoursed rubble masonry is usedfor the construction of foundations,compoundwalls, garages,labour quartersetc. A skilled masonmay arrangethe facing stonesin polygonal shapesto improve the aesthetic of the wall. (T) Through (a) Elevation (b) Section x x Fig. 8.1. Uncoursedrubble masonry Fig. 8.2. Coursedrubble masonry 2. Ashlar Masonry: In this type of masonry stonesare dressedto get suitable shapesand sizes. The height of the stonesVariesfrom 250 mm to 300 mm. The length should not exceedthree times the height. The dressing of the stone need not be Very accurateon all sides.Usually good dressing is made on facing side. In such construction mortar consumption is less comparedto rubble masonry. There are different types of ashlar masonry dependingupon the type of dressing such as Ashlar ne dressed,Ashlar rough dressed,Ashlar rock or quarry faced, Ashlar facing, Ashlar chamferedetc. Figure 8.3 show someof such masonry. (b) Ashlar chamfered (a) Fine finished ashlar Fig. 8.3. Ashlar masonry Supervisionof Stone Masonry Construction The following points should be kept in mind in supervising stonemasonry Work: 1. 2. Hard and durable stones, free from defects like aws, cavities veins etc. should be used. of the stonesshould be as per the requirement. 3.Dressing Stonesshould be properly Wettedbefore they are used so as to avoid sucking of Waterfrom mortar. . Stones should be laid on their natural bed. . Facingandbacking facesshouldbe laid neatly andlevelled andcheckedwith Woodentemplate. 6. The heart of masonry should be lled with stone chips and mortars. To thick mortar joints should be avoided. . Verticality of the Wall should be frequently checkedwith plumbbob. 8. Mortars with correct proportion of sand and cement should be used. . Continuous vertical joints should be avoided. 10. 11. 12. Through stonesshould be used within 1.5 m distances. 14. The height of masonry should be raised uniformly. Under the beams,trusses,sills etc large at stonesshould be used. 13. Before continuing Work,the masonrybuilt on previous day should be Well cleanedand freed from loose particles. Curing should be done properly for 2 to 3 Weeks. 8.4 BRICK MASONRY Brick masonry is built with bricks bondedtogether with mortar. For temporary shedsmud mortar may be used but for all permanentbuildings lime or cement mortars are used. The various types of bonds generally used in brick masonry are 1. Stretcher bond 2. Header bond 3. English bond and 4. Flemish bond. 1. Stretcher Bond: A stretcher is the longer face of the brick as seenin the elevation. In the brick of size 190 mm x 90 mm x 90 mm, 190 mm X 90 mm face is the stretcher. In stretcher bond masonryall the bricks are arrangedin stretchercoursesas shown in Fig. 8.4. However care should be taken to break vertical joints. This type of construction is useful for the construction half brick thick partition wall. (a) Elevation 1, 3, 5 Courses (b) Plan Fig. 8.4. Stretcherbond 2. Header Bond: A header is the shorter face of the brick as seen in the elevation. In a standard brick it is 90 mm x 90 mm face. In headerbond brick masonryall the bricks are arrangedin the headercoursesas shown in Fig. 8.5. This type of bond is useful for the construction of one brick thick walls. 4 IIIIIIIII 3'. = I ZIIIIIIIIII H .r>|o2 IIIIIIII 3 U: I Bat B U) 1,3, 6 (a) Elevation Courses (b) Plan Fig. 8.5. Header bond 3. English Bond: In this alternatecoursesconsist of headersand stretchers.This is considered to be the strongestbond. Hence it is commonly usedbond for the walls of all thicknesses.To break continuity of vertical joints a brick is cut lengthwise into two halves and used in the beginning and end of a wall after first header.This is called queen closer. [Ref. Fig. 8.6]. Figure 8.6 shows typical one brick and one and half brick thick wall with English bond. Back I Back Face Elevation Plan of stretcher course Face Plan of header course (a) Back Back Face Elevation Plan of stretcher course Face Plan of Header course (b) Fig. 8.6. Englishbond 4. Flemish Bond: In this type of bond each coursecomprisesof alternateheaderand stretcher [Fig. 8.7]. Alternate coursesstart with stretcherand header.To break the vertical joints queen closersare required, if a coursestartswith header.Every headeris centrally supportedon the stretcher below it. Flemish bonds may be further classified as (a) Double Flemish Bond ([2) Single Flemish Bond. In caseof doubleemish bond, both facesof the wall have emish look, i.e. eachcourseconsist of alternateheader and stretcher,whereassingle emish bond outer faces of walls have emish look whereasinner faces have look of English bond [Fig. 8.7 (a), (b)]. Construction of emish bond needsgreaterskill. It gives more pleasing appearance.But it is not as strong as English bond. If only pointing is to be used for finished wall, emish bond may be usedto get good aestheticview. If plastering is going to be used, it is better to use English bond. BackBack 1% Brick waii Front 11 Brickwall 2 (i) odd courses F'°"* (ii) even courses (a)Double emish bond (1%brick thick) i BackBack 1% Brick wall F° 1% Bflck Wa" F'° (b) Single emish bond Fig. 8.7. Flemishbond Points to be Observed in SupervisingBrick Masonry Constructions The following points should be observedin the construction of brick masonry: 1. Use bricks of good quality with uniform colour, well burnt, with exact shapeand size. 2. Before using the bricks in masonry,they should be soakedin water for 2 hours so that bricks do not absorb water from the mortar. . Bricks should be laid with the frog pointing upward. . Construction of brick wall should start from the end or corner. \DOO\lO\U . Brick coursesshould be perfectly horizontal. . Verticality of the wall should be ensuredby frequently checking with plumbbob. . Mortar used should be as per specification. . Whenever work is stoppedbrick masonry should be left with toothed end. . Use of brick bats should be avoided. 10. Walls should be raised uniformly. In no case difference between adjoining walls be more than 1 m. In a day no wall should be raised by more than 1.5 m. ll. To get proper key for plastering or pointing, the facejoints should be raised to a depth of 12 to 20 mm, when the mortar is green.If plastering or pointing is not to be provided, facejoints should be stuck ush and finished neatly. 12. Holdfasts for doors and windows should be embeddedin brick masonry with cementmortar or concrete,at the time of constructing the wall itself. 13. Brick masonry should be regularly cured for 2 weeks. 14. For carrying out brick work at higher levels, only single scaffolding should be used. Advantagesand Disadvantagesof Brick Masonry Over Stone Masonry Advantages: 1.Since shape and size ofbricks are uniform, itdo not need skilled labour for the construction. 2. Bricks are light in weight and hencehandling them is easy. 3. Bricks are easily available around cities and their transportation cost is less becausetheir Weight is less. Stonesare to be brought from quarries which are located only at few places. 4. It is possibleto use all types of mortar in brick masonry.For unimportant buildings even mud mortar can be used. . Thinner Walls can be constructed with bricks but it is not so with stones. OO\lO\Ul . It is easyto form openingsfor doors and Windows. . Dead load of brick masonry is less. . In brick masonry mortar joints are thin and henceconstruction cost is reducedconsiderably. 9. Brick masonry has better fire and Weatherresistancecomparedto stone masonry. Disadvantages. 1.Strength ofbrick masonry isless than that ofstone masonry. 2. Durability of brick masonry is less. 3. Brick masonry needsplastering and plasteredsurfaceneedscolour Washing.Stonemasonry dont need them and hencemaintenancecost is more in brick masonry. 4. Brick masonryabsorbsWaterand there arepossibility of dampness.There is no suchproblem in stonemasonry. 5. More architectural effects can be given in stonemasonrycomparedto that in brick masonry. 6. Stonemasonrygives massiveappearanceand hencemonumentalbuildings are built in stone masonry. I8.5 PLASTERING Applying mortar coats on the surfacesof Walls, columns, ceiling etc. to get smooth finish is termed as plastering. Mortar used for plastering may be lime mortar, cementmortar or lime-cement mortar. Lime mortar used shall have fat lime to sandratio of 1 : 3 or 1 : 4. If hydraulic lime is used mix proportion (lime: sand)is 1 : 2. Cementmortar of 1 : 4 or 1 : 6 mix is very commonly usedfor plastering,richer mix being usedfor outer Walls.To combine the cost effectivenessof lime mortar and good quality of cement mortar many use lime-cement mortar of proportion (cement : lime : sand) of 1 : 1 : 6 or 1 : 1 : 8 or 1 : 2 : 8. The objective of plastering are: 1. to conceal defective workmanship 2. to give smooth surfaceto avoid catching of dust. 3. to give good look. 4. to protect the wall from rain water and other atmosphericagencies. 5. to protect surfacesagainst vermit. Requirement of good plaster are: 1. It should adhereto the background easily. 2. It should be hard and durable. 3. It should prevent penetrationby moisture 4. It should be cheap. Lime mortar is usually applied in 3 coatswhile cementmortar is applied in two or three coatsfor the stoneand brick masonry.For concretesurfacescementmortar may be applied in two or three coats. For concretebuilding blocks many times only one coat of cement mortar is applied. The first coat provides meansof getting level surface.The nal coat provides smooth surface.If three coats are used secondcoat is known as oating coat. The averagethickness of rst coat is 10 to 15 mm. Middle coat thicknessis 6~8 mm. The final coat is just 2 to 3 mm thick. If single coat is usedits thickness is kept between 6 to 12 mm. Such coats are used on concretesurfacesnot exposedto rain. l8.6 POINTING Insteadof plastering entire surfaceof the masonry,special mortar finishing work is done to the exposed joints. This is called pointing. It consistsof raking the joints to a depth of 10 mm to 20 mm and filling it with richer mortar mixes. In case of lime mortar pointing mix used is 1 : 2 and in case of cement mortar pointing mix usedis 1 : 3. Pointing is ideally suited for stonemasonrybecausestonesare having attractive colours and good resistanceto penetrationby water. Pointing gives prefection to weaker part of masonry (i. e. to joints) and it addsto aestheticview of the masonry. The table 8.5 gives the comparisonbetweenplastering and pointing. Table 8.5. Comparisonbetween plastering and pointing Plastering It is applied to entire surface. It is provided only at exposedjoints. 2. It provides smooth surface. It does not provide smooth surface. 3. It concealsdefective workmanship in the masonry construction. It is used to exposebeauty of well built masonry work. 4. It provides a base for applying white/ White washing or colour washing are colour washing. ruled out. I8.7 FLOORING Purpose of ooring is to get a good hard, level and beautiful surface for living. The oors directly resting on the ground are known as ground oors while the oors of each storey are known as upper oors. Ground Floor Apart from giving good nished surface,these oors should have good damp resistance.The ground surfaceis rammed well and a layer of red earth or sandis placed which is compacted.A layer of broken bricks, stonesetc. is provided up to 150 mm below oor finish level and rammed.While ramming the surface is kept moist to get good compaction. Then 1 : 4 : 8 concrete of 100 to 150 mm thickness is provided as basecourse. Over this bed oor finish is laid. The types of ooring used are: 1. 3. 5. 7. 9. Mud and moorum 2. Brick Flag stone 4. Cement concrete 11. Terrazo 6. Mosaic Marble 8. Tiles Timber 10. Rubber 1.Mud and Moorum Flooring: These oorings are used in low cost housing, specially in P.V.C. villages. Over the hard layer of earth lling mud or moorum layer is provided. The floor needsa thin wash of cow dung at least once a weak. Brick Flooring: This is also a cheapoor construction.It is commonly usedin godownsand factories. Bricks are laid at or on edges. Bricks of good quality should be used for the construction. Brick layer is provided on sandbed or on lean concrete(1 : 8 : 16) bed. In both casesjoints are renderedush and nished with cement mortar. . Flag Stone Flooring: Laminated sandstonesor slatesof 20 mm to 40 mm thick in the form of slabs of 300 mm X 300 mm or 450 mm x 450 mm or in the form of rectanglesof size 450 mm x 600 mm are used as floor finishes. The stone slabs are laid on 20 to 25 mm thick mortar spreadover concretebed. The joints are to be nished with rich mortar. . Cement Concrete Floors: It is modestly cheapand durable floor and hencecommonly used in residential, commercial and industrial buildings. It consists of two coursesbasecourse and wearing coat. Base course is laid over well compactedsoil. Its thickness is usually 75 mm to 100 mm. It consistsof lean cementconcretemix (1 : 4 : 8) or lime concretecontaining 40% of 1 : 2 lime mortar and 60% of coarseaggregateof 40 mm size. After base coarseis hardenedwearing coat of 40 mm is laid. It consistsof panelsof 1 m x 1 m, 2 m x 2 m or 1 m x 2 m. Alternate panels are laid with 1 : 2 : 4 concreteusing wooden, glass or asbestosstrip separatorsof 1.5mm to 2.0 mm thickness.To get good bond betweenbasecoarseand wearing coat cement slurry wash is given before laying wearing coat panels.After 34 days of laying Marble chips are mixed in cementin the proportion 1 : 1.25 to 1 : 2 and about 6 mm terrazo topping is laid. The top is tamped and rolled. Additional marble chips are spread during tamping to get proper distribution of marble chips on the surface.After drying it for 12 to 20 hours, it is cured for 2-3 days. Then grinding is made in the following three steps: Ist grindingUsing coarsegrade (No. 60) carborundum stones. Ilnd grinding-Using medium grade (No. 120) carborundum stones. IIIrd grinding~Using fine grade (No. 320) carborundum stones. Plenty of water is used during grinding. After each grinding cement grout of creamlike consistency is applied and cured for 6-7 days. After final grinding and curing the oor is washedwith plenty of water and then with dilute oxalic acid solution. Then oor is finished with polishing using machinesand wax polish. Mosaic Flooring: It consists of a nishing coat of small pieces of broken tiles of China glazed or of marble arrangedin different patterns set in limesurkhi or cement mortar. The base coarse is concrete flooring and on it 30 to 40 mm mortar layer is provided. On this mortar layer broken piecesof China glazedor marble are setto get different attractivepatterns. After 20 to 24 hours of drying the top is rubbed with carborundum stoneto get smooth and polished surface. . Marble Flooring: Marble slabs are cut to get marble tiles of 20 to 25 mm thickness.They are laid on floors similar to other tiles. \V1thpower driven machine surfaceis polished to get even and shining surface.This type of flooring is widely used in hospitals and temples. . Tiled Flooring: This is an alternativeto terrazo ooring, usedcommonly usedin residential, office and commercial buildings. Tiles of clay, cement or terrazo of standard sizes are manufactured in factories under controlled conditions. On the concrete base, 25 mm to 30 mm thick mortar is laid and these tiles are placed and pressedwith trowel or wooden mallet. Before placing tiles care is taken to seethat, neat cement slurry is applied to bottom side and sidesof tiles to get good bond. Next day joints are cleanedof loose mortar and raked up to 5 m depth. Then that is lled with coloured cement slurry to get uniform colour on the top surface. After curing for 7 days grinding and polishing is made as in the case of terrazo ooring. . Timber Flooring: Timber ooring are used in dancing halls and in auditoriums. Timber platesmay be directly placed on concretebed or may be provided over timber frame work. In latter caseit is necessaryto provide proper ventilation below the oor. This ooring is costly. 10. Rubber Flooring: Tiles or sheetsof rubber with fillers such as cotton fibres, asbestosfibre or granulatedcork are manufacturedin variety of patternsand colours. These sheetsor tiles may be fixed to concreteor timber oors. Thesefloors areattractive and noiseproof. However they are costly. 11. P.V.C.Flooring: PolyVinylChloride (PVC) is a plastic which is available in different colour and shade.Nowadaystiles of this material areusedwidely. Adhesivesare applied on concrete base as well as on bottom of PVC tiles. Then the tile is pressedgently with 5 kg wooden roller till the oozing of adhesiveis seen.The oozed out adhesiveis wiped and the floor is washedwith warm soapwater.The oor nish is smooth,attractive and canbe easily cleaned. However it is slippery and costly. Upper Floors In olden days upper oors were made of timber floors or steeljoist and stone slabs. For larger spans jack arch oorings were used.Jack archoor consistedof Isection steelbeamssupportedon walls and gap between Isections beamsfilled with concretearch. Figure 8.8 shows a typical jack arch ooring. _'°'_' U1 "-1" heed ' Cement concrete (1 £14) R.S.J. Fig. 8.8.jack arch ooring NowadaysR.C.C.floors are commonly used.It may consist of only slab, if spanis lessor it may be beam and slab ooring. In halls of hotels and assembly,many provide at slabs i.e. slabs directly supportedover columns. The columns are provided with widened portion called column head. They give elegantlook to halls, particularly when the headroom is high. R.C.C. oors needproper thickness and reinforcements.They are arrived at by structural design engineers.Figure 8.9 showstypical R.C.C. slabs. V /J/I/I/I/I/I/I/I/I/I/I/Z V /I/I/I/I/I/I/I/I/I/I/I/Z \\\\\\\.x\\\\\\1\ \\\\\\x&\\\\\ Reinforced cement concrete 40 mm Fig. 8.10. Reinforcedbrick slab In ribbed or hollow tiled ooring, the concrete in tension portion is replaced by hollow tiles. Figure 8.11 shows a typical floor of this type. Distribution reinforcement / /////////////////// ///////////////////5 / ._. \ 5 4 4 4 4 4 \\\\\\\\\\\\\\\\\ \\\ S ////////// '\\' Flat roofs are used in plains where rainfall is less and climate is moderate.Pitched roofs are preferred wherever rainfall is more. Shells and folded plate roofs are used to cover large column free areasrequired for auditoriums, factories etc. Brief description of theseroofs is presentedbelow: 1. Flat Roofs: Theseroofs are nearly at. However slight slope (not more than 10°) is given to drain out the rain water. All types of upper storey oors can serve as at roofs. Many times top of these roofs are treated with water proofing materialslike mixing water proofing chemicals in concrete, providing coba concrete. With advent of reliable water proofing techniquessuch roofs are constructedeven in areaswith heavy rain fall. The advantages of at roofs are: (a) The roof can be used as a terrace for playing and celebrating functions. (b) At any latter stagethe roof can be converted as a oor by adding another storey. (c) They can suit to any shapeof the building. (d) Overheadwater tanks and other servicescan be located easily. (e) They can be made fire proof easily comparedto pitched roof. The disadvantages of at roofs are: (a) They cannot cover large column free areas. (b) Leakageproblem may occur at latter date also due to developmentof cracks. Once leakage problem starts, it needscostly treatments. (c) The dead weight of at roofs is more. (d) In places of snow fall at roofs are to be avoided to reduce snow load. (e) The initial cost of construction is more. (f) Speedof construction of at roofs is less. Types of Flat Roofs: All the types listed for upper oors can be used as at roofs. 2. Pitched Roofs: In the areasof heavy rain falls and snow fall sloping roof are used.The slope of roof shall be more than 10°. They may have slopesas much as 45° to 60° also. The sloped roofs are known as pitched roofs. The sloping roofs are preferred in large spannedstructures like workshops, factory buildings and ware houses.In all these roofs covering sheetslike A.C. sheet, G.I. sheets,tiles, slates etc. are supported on suitable structures.The pitched roofs are classified into (a) Single roofs (b) Double or purlin roofs (c) Trussed roofs. (a) Single Roof: If the span of roof is less than 5 m the following types of single roofs are used. (i)Lean toroofs (ii)Coupled roofs (iii) Coupledcloseroof (iv) Collar beam roof In all theseroofs rafters placed at 600 mm to 800 mm spacing are main members taking load of the roof. Battens run over the rafters to support tiles. Figure 8.13 shows various types of single roofs. Ridge cover Root covering Knee strap Main wall Wall plate Verandahwall 2.40 m (a) Lean toroof (b) Coupled roof Ridge piece Ridge piece Rafters Wall plate Wall plate Tie beam (c) Coupled close roof Fig. 8.13. Singleroofs (12)Double or Purlin Roofs: If span exceeds,the cost of rafters increaseand single roof becomesuneconomical.For spansmore than 5 m double purlin roofs are preferred.The intermediatesupportis given to raftersby purlins supportedover collar beams.Figure 8.14 shows a typical double or purlin roof. Ridge piece Fig. 8.14. Double or purlins roofs (c) Trussed Roof: If span is more, a frame work of slender membersare used to support sloping roofs. These frames are known as trusses.A number of trussesmay be placed lengthwise to get wall free longer halls. Purlins are provided over the trusseswhich in turn supportroof sheets.For spansup to 9 m wooden trussesmay be used but for larger spanssteel trussesare a must. In case of wooden trusses suitable carpentry joints are made to connect Variousmembersat a joint. Bolts and strapsare also used. In case of steeltrussesjoints aremadeusing gussetplatesandby providing bolts or rivets or welding. Dependingupon the span,trussesof different shapesareused.End of trussesaresupported on walls or on column. Figure 8.15 shows different shapesof trussesused. Figure 8.16 shows a typical wooden truss details and Fig. 8.17 shows the details of a typical steel (a) Kingpostspansupto 8 m 4 (b) Queenpostspansupto 10 m (c) Howetrusswith4 and8 panelsspans6 m to 30 m (d) Pratttrussspans6 m to 100m Modifiedpratttruss 4&8 (e) Finkor frenchrooftrussesspansupto 10 m (f) Compoundfrenchtruss span20 m to 30 m (g) Fantrussspans10 m to 15 m (i) Quadrangular truss Camberedfrenchrooftruss span20 m to 30 m (h) Northlightrooftrussspan8 m to 10 m (j)Trussusedfor largespan (k)Trussusedfor largespans Fig. 8.15. Typesof trusses Ridge tile Common rafters Baens Eaves board Fig. 8.16. A typical wooden truss (king past) Fig. 8.17. Steelroof truss 3. Shells and Folded Plate Roofs: Shell roof may be defined as a curved surface,the thickness of which is small comparedto the other dimensions.In theseroofs lot of load is transferred by membranecompressioninstead of by bending as in the case of conventional slab and beamconstructions.Cavesarehaving natural shell roofs. An examinationof placesof worships built in India, Europe and Islamic nations show that shell structureswere in usagefor the last 800 to 1000 years. However the shells of middle ageswere massivemasonry structuresbut nowadays thin R.C.C. shell roofs are built to cover large column free areas.Figure 8.18 shows commonly used shell roofs. Tfl/1 (a) Cylindrical (b) Butterfly (C) North light (d) Spherical dome Parabola Q (e) Paraboloid (f) Ellipsoidal (i) Hyperbolic paraboloid [inverted umbrella type] Parab (g) Elliptic paraboloid [vertical section parabola horizontal sections ellipse] (j) Conoid (k) Corrugated shells (h) Hyperbola of revolution (l) Funicular shell Fig. 8.18. Typesof shell roof Advantagesand Disadvantagesof Shell Roofs Advantagesof shell roofs are: (a) Good from aestheticpoint of view (12)Material consumption is quite less (c) Form work can be removed early (d) Large column free areascan be covered. Disadvantagesare: (a) Top surfaceis curved and henceadvantageof terrace is lost. (b) Form work is costly. Folded plate roofs may be looked as slab with a number of folds. Theseroofs are also known as hipped plates,prismatic shells and faltwerke. In thesestructuresalso bending is reducedand lot of load gets transferred as membrane compression. However folded plates are not so efficient as shells. Figure 8.19 shows typical folded plate roofs. @ mm Prismatic VType -7 , I , Trough type --I I I I I I i --I I I I I I North light Fig. 8.19. Typesof folded plateroofs Advantagesand Disadvantages of FoldedPlate RoofsOver ShellRoofs Advantagesare: (a) Form work requiredis relativelysimpler. (la)Movable form work canbe employed. (c) Design involvessimplercalculations. Disadvantages are: (a) Foldedplateconsumemorematerialthan shells. (b) Form work canbe removedafter 7 dayswhile in caseof shellsit canbe little earlier. RoofCoveringsfor PitchedRoofs Varioustypesof coveringmaterialsare availablefor pitchedroofsandtheir selectiondependsuponthe climaticconditions, fabricationfacility,availabilityof materialsandaffordabilityof theowner.Commonly usedpitchedroof coveringmaterialsare: (a) Thatch (b) Shingle (c) Tiles (d) Slates (e) Asbestos cement (A.C.) sheets (f) Galvanised iron (G.I.) sheets (a) Thatch Covering: These coveringsare providedfor small spans,mainly for residential buildingsin villages.Thatch is a roof coveringof straw,reedsor similar materials.The thatchis wellsoakedin wateror fire resistingsolutionandpackedbundlesarelaid with their butt endspointingtowardseves.Thicknessvariesfrom 150 mm to 300 mm. They are tied with ropesor twines to supportingstructures.The supportingstructureconsistsof round bambooraftersspacedat 200 mm to 300 mm overwhichsplitbambooslaid at rightanglesat closespacing.It is claimedthatreedthatchcanlast50 to 60 yearswhile strawthatchmay last for 20-25 years. The advantageof thatch roof is they are cheapand do not need skilled Workersto build them. The disadvantagesare they are very poor fire resistant and harbour rats and other insects. (b) Shingles: Wood shingles are nothing but the split or sawn thin pieces of Wood.Their size varies from 300 mm to 400 mm and length from 60 mm to 250 mm. Their thickness varies from 10 mm at one end to 3 mm at the other end. They are nailed to supporting structures. They are commonly used in hilly areasfor low cost housing. They have very poor fire and termite resistance. (c) Tiles: Variousclay tiles are manufacturedin different localities. They serveas good covering materials.Tiles are supportedover battenswhich are in turn supportedby rafters/trussesetc. Allahabad tiles, Mangalore tiles are excellent interlocking tiles. They give good appearance also. (d) Slates: A slate is a sedimentaryrock. Its colour is gray. It can be easily split into thin sheets. Slates of size 450 mm to 600 mm Wide, 300 mm long and 4 to 8 mm thick are used as covering materials of pitched roofs in the areasWhereslate quarries are nearby.A good slate is hard, tough, durable. They are having rough texture and they give ringing bell like sound when struck. They do not absorb Water. (e) A.C. Sheets: Asbestoscement is a material which consistsof 15 per cent of asbestosfibres evenly distributed and pressedWith cement.They are manufacturedin sufficiently large size. The Width of a A.C. sheetvaries from 1.0 to 1.2 m and length from 1.75 to 3.0 m. To get sufficient strengthwith thin sectionsthey are manufacturedwith corrugation or with traffords [Fig. 8.20]. They are fixed to the steelpurlins using Jbolts. The roofing is quite economical, waterproof. However not very good thermal resistant.They are commonly used as covering materials in Warehouses,godowns or for larger halls. In auditorium etc., if these sheetsare used, false ceilings are provided to get good thermal resistance. 44 -45 mm /\/\/\/\/\/\/V Side lap r tmzjzszit ' Nut ' G.|. washer Hook bolt (a) Corrugated sheet covers (b) Trafford sheet covers Fig. 8.20. A.C. sheetroofing (f) G.I. Sheets: Galvanised iron corrugated sheetsare manufacturedin the sizes 1.0 to 1.2 m wide and 1.65 m length. Galvanisationof iron makesthem rust proof. They are fixed to steel purlins using Jbolts and Washers.They are durable, re proof, light in weight and need no maintenance.They are commonly usedascovering materialsfor Warehouses,godown, sheds etc. Table 8.6 gives comparisonbetweenGI and AC sheetsfor roof covering. Table 8.6. Comparisonbetween GI and AC sheets GI Sheets A. C. Sheets Sheets are thin. Not as thin as GI sheets. Light in weight. Slightly heavier. Do not break while handling. Chancesof breaking are there during handling. Chancesof corrosion can not be ruled out No problem of corrosion. More noisy, if something falls over them. Less noisy, if something falls over them. Less fire resistant. More fire resistant. Less resistance to acids and fumes. More resistant to acids and fumes. Cost is more. Less costly. I8.9 DOORS ANDWINDOWS The function of a door is to give accessto building and to different parts of the building and to deny the accesswhenevernecessary.Number of doors should be minimum possible.The size of the door should be of such dimension as will facilitate the movement of the largest object likely to use the doors. In caseof the residental buildings, the size of the door should not be less than 0.9 m X 2.0 m. Larger doors may be provided at main entranceto the building to enhancethe aestheticview. Minimum sized doors are used for bath rooms and water closets. The size recommended is 0.75 m x 1.9 m. As a thumb rule height of door should be 1 In more than its width. Windows are provided to give light and ventilation. They are located at a height of 0.75 m to 0.90 m from the floor level. In hot and humid regions, the window area should be 15 to 20 per cent of the floor area.It is preferable to have at least two openings in two different walls. Another thumb rule usedto determinethe sizeof thewindowopeningis for every30 m3insidevolumethereshouldbe at least1 m2windowopening. Types of Doors Various types of doors are in use which may be classified on the basis of arrangementof shutters, method of constructions,principles of working operations and materials used. Commonly used doors are briefly explained below: 1. Battened and Ledged Doors: Battens are 100 mm to 150 mm wide and 20 mm thick wooden boards.Their length is that of door opening.The battensare connectedby horizontal planks, known as ledges of size 100 to 200 mm wide and 30 mm thick. Usually three ledges are used one at top, one at bottom and the third one at midheight. This is the simplest form of door and the cheapestalso. Battens are securedby tongued and groovedjoint. Top ledge Frame , ; a) . E (5 E . . . ~! Middle [edge Bottom ledge Fig. 8.21. Battenedand Iedgeddoor 2. Battened, Ledged and Braced Doors: If doors are wide apart from using battensand ledges diagonal members,known as braces,are provided to strengthenthe door. Figure 8.22 shows a typical battened,ledged and braced door. Fig. 8.22. Battened, Iedgedand braced door Sometimes abovetwo types of shuttersare provided within wooden frame work and in those casesthey may be called as battened,ledges andframed doors. 3. Framed and Panelled Doors: This type of door consistsof vertical members,called styles and horizontal members called rails. The styles and rails are suitably grooved to receive panels. The panels may be of wood, A.C. sheet, glassesetc. The panels may be at or of raised type to get good appearance.These are very commonly used doors. They may be of single shutter or of double shutter.Figure 8.23 show few types of panelled doors. If glass panels are used they may be called as glazed doors. EU (a) Four panel Bottomrail (d) Doubleshuttered panelleddoors (e) Fully glazed single shutter door (f) Partly glazed, partly panelled double shutter door Fig. 8.23. Panelledand Iazeddoors 4. Flush Doors: The shuttersof thesedoors are made of plywood or block boards.They are of uniform thickness. These shutters are available with different attractive Vineer nishes. The time consumedin making suchdoors at site is quite less.Thesedoors are suitable for interior portion of a building. Nowadays ush doors are commonly used in residential and office buildings. Figure 8.24 showstypical ush door. Door frame Shutter Peep hole Fig. 8.24. Flush door 5. Louvered Doors: Whenever privacy as well as ventilation is required such doors can be used. Louvers are the glass, wooden or A.C. sheet strips fixed in the frame of shutter such that they prevent vision but permit free passageof air. The doors may be fully or partially louvered. Such doors are commonly used for public bathroomsand latrines. [Fig. 25] CD are-. '2 U) S 0 CD 72 U) E Louvers (b) Section 3#..;..._,_.»._._.;.J.;.. (a) Elevation Fig. 8.25. Louvereddoor 6. Revolving Doors: It consist of a centrally placed pivot to which four radiating shuttersare attached.The central pivot is supportedon ball bearing at the bottom and has a bush bearing at the top. The shuttersmay be partly or fully madeupof glass.A circular spaceof entranceis provided within which shuttersrotate. As shuttersrotate they give entranceon one side and exit on other side. These doors are preferred in public buildings like stores,banks, hotels, theatresWherecontinuoususe of doors is necessary.They are very much required in entrance to air conditioned public buildings. Figure 8.26 shows a typical revolving door. . ......... Corner post __._ ........ 4-Rubber piece Fig. 8.26. Revolvingdoor 7. Swing Doors: Swing door has its shutter attachedto the frame by meansof double action springs. Hence shutter can move both inward and outward. They may be single shutteredor double shuttered.Such doors are preferred in ofces and banks. Since thesedoors can open on both sides it is desirableto provide glass panels or peep holes to enable user to seethe personsfrom other side. [Fig. 8.27] Double action spring hinge Flush shutter Fig. 8.27. Plan of swing door 8. Sliding Doors: In this type of doors, shutter slides on the sides.For this purposerunners and guide rails are provided. Sliding shuttersmay be one, two or even three. Such doors are used in banks, offices etc. The arrangementof such shuttersin plan is shown in Fig. 8.28 Type (C) Fig. 8.28. Plan of sliding door 9. Collapsible Doors: Steel channels 16 to 20 mm wide are used as verticals. They are placed with 12 to 20 mm gap. Steelats 16 mm to 20 mm Wideand 5 mm thick are hinged to them Top of opening Elevation Fig. 8.29. Collapsible steel door as shown in Fig. 8.29. The rollers are provided at their top as well as at bottom so that shutter can be pulled or pushedside ways with slight force. There may be single or double shutters. Usually thesedoors are used for additional safety.They are commonly used for front doors, bank locker rooms, school and college entrancedoors. 10. Rolling Shutters: Figure 8.30 show a typical rolling shutter door. It consists of a frame, a drum and a shutter made of thin steel plates.The width of the door may vary from 2 to 3 m. The shutter moves on steel guidesprovided on sidesand can easily roll up. For this counterbalancing is made with helical springs on the drum. The shutter can be easily pulled down. This type of doors are commonly used as additional doors to shops,offices, banks, factory, buildings from the point of safety. Drum Guide Channel OutsideGuide Channel Plan - E4-Handles-><| - Locking arrangement Section Elevation Fig. 8.30. Rolling shutter Table 8.7 gives the differencesbetween collapsible and revolving doors. Table 8.7. Difference between collapsible and revolving doors S. No. 1. Collapsible Doors These doors do not provide privacy inside Revolving Doors Provide privacy inside a room. a room. 2. 4. These doors operate side ways. These doors revolve These doors provide exit and entry from same side. These doors provide exit from one side and entry from the other side These doors are not suitable for entry to These doors are suitable for A.C. halls. air conditioned halls. 5. These doors do not close automatically These doors close openings automatically when not in use. when not in use. Types of Windows Various windows used may be classified on the basis of materials used, types of shutters, types of openingsof shuttersand the position of windows. Timber, steel and aluminium are commonly used to make window frames. Timber may get termite attacks, steel may rust but aluminium do not have any such defects.However they are costly. Shuttersof windows may be panelled,glazed or louvered. Louvered windows are generally used for bathrooms and toilets where vision is not to be allowed but ventilation is required. Lower parts panelled and upper parts glazed windows are commonly used. Instead of panelled one may think of using translucentglasses.Figure 8.31 show a louvered windows. Frame Fig. 8.31. Louveredwindow Window shuttersmay be fixed, centrally pivoted, sliding type or double hung. Figure 8.32 shows a typical double hung window. Counterweight for bottom sash Counterweight for top sash (T.S) Elevation Fig. 8.32. Double hung window Depending upon the position of windows, they may be classified as: (a) Casement windows (b) Bay windows (c) Corner windows (d) Clear storey windows (e) Gable windows (D Sky light windows (g) Dormer windows (h) Ventilators Casementwindows are commontype of windows, provided in the outer walls. They areprovided over 50 to 75 mm sill concreteat a height of 750 to 900 mm from floor level. Bay windows are provided on the projected portion of walls. Corner windows are provided in the corner of a room. They need heavy lintels. Corner post of window should be strong enough to take load due to deection of lintel and impact load from the shutters. Clear storey windows are provided when the height of the room is much more than adjacent room/varandah.It is provided between the gap of low height room and the top of room with greater height. Gable windows are provided in the gable portion of the building. They are required in the stair casesor in the halls with gable walls. Sky light windows are provided on a sloping roof. It projects above the top sloping surface.The common rafters are to be trimmed suitably. Dormer windows are vertical windows on the sloping roof. Ventilators are provided close to roof level or over the door frames. They help in pushing out exhaustair. They may be provided with two split and separatedglassesor with hung shutters. Various type of windows basedon their positions are shown in Fig. 8.33 Frame Window Si" (a)Casement window Window frame (b)Baywindow Brickwall Sunshade .- ;-pi-«.,, Window frame Windowframe Shutter /\ Glazing Frame Shutter Frame (d) Clear storey window Copper clips Rm. t Common rafter Trimming 'IInna.\m\w . (e) Dormer window and gable window (f) Sky light (b) Plan (g) Ventilator Fig. 8.33. Typesof window on their position Ceiling piece I 8.10 LINTELS Lintel is a horizontal exural member which spansover the openingsin the walls for doors, windows, ventilators, cupboardsetc. The load of masonryabove the opening is transferredto the wall by exural action of the lintel so that frames of doors, windows etc are not unduly loaded.The end bearingsfor the lintel should be at least 200 mm. The width of lintels is same as that of wall. Lintels of various materials are used.They are: (a) Wood (b) Stone (c) Brick (d) R.C.C. and (e) Steel. (a) Wood Lintel: It may be a singlepieceor may be assembledby joining 2 to 3 pieces.Sometimes the wooden lintels are strengthenedby steel plates at top and bottom. Such lintels are called as flitched beams. (12)Stone Lintels: Wherever stones are available stone beams are used as lintels. As stone is weak intension they can be used only forsmall spans. Their depth iskept about 116th span. Stonesare cut to the width of wall and dressedbefore using as lintels. (c) Brick Lintels: Well burnt, good quality lintels are laid on ends or edgesto form lintels as shown in Fig. 8.34. It needstemporary form work at the time of construction.The lintel is to be cured for 714 days before form work is removed. Such lintels are useful to span small openings. Fig. 8.34. Brick lintel (d) R.C.C. Lintels: It is possible to provide R.C.C. lintels of any spanrequired in the building. They can be isolated or continuous over the openings. They are provided with suitable reinforcementmain reinforcementsbeings on lower side in the opening. Nowadays these lintels are used very commonly in buildings. (e) Steel Lintels: Steel anglesor rolled steel Isections are used as lintels. Tube separatorsmay be provided to maintain the spacing between the sections. If the sections are opened to atmosphericaction, regular painting is necessary.Many times they are encasedin concreteto avoid maintenanceproblem. Theselintels can be used for large openings. I8.11 STAIRS Stairs give accessfrom oor to oor. The space/roomhousing stairs is called staircase.Stairs consists of a number of stepsarrangedin a single ight or more number of ights. The requirement of good stairs are (a) Width: 0.9 m in residential buildings and 1.5 m to 2.5 m in public buildings. (b) Number of Steps in a Flight: Maximum number of stepsin a ight should be limited to 12 to 14, while minimum is 3. (c) Rise: Rise provided should be uniform. It is normally 150 mm to 175 mm in residential buildings while it is kept between 120 mm to 150 mm in public buildings. However in commercial buildings more rise is provided from the considerationof economic oor area. (d) Tread: Horizontal projection of a stepin a stair caseis called tread. It is also known asgoing. In residential buildings tread provided is 250 mm while in public buildings it is 270 mm to 300 mm. The following empirical formula is used to decide rise and tread: 2R+T> whereR 550mmbut<700to 600mm is rise in mm and T is tread in m. (e) Head Room: Head room available in the stair case should not be less than 2.1 m. (f) Hand Rails: Hand rails should be provided at a convenient height of a normal personwhich is from 850 mm to 900 mm. Typesof Stairs The stairs may be built with wood, concrete masonry or with cast iron. Wooden stairs are not safe, becauseof the dangerof re. However they are used in unimportant buildings to accessto small areas in the upper oors. Cast iron or steel stairs in the spiral forms were used commonly to reduce stair case area. In many residential buildings masonry stairs are also used. Reinforced concrete stairs are very commonly used in all types of buildings. Basedon the shapesstairs may be classified as: (a) Straight stairs (b) Dog legged stairs (c) Well or opennewel stairs (d) Geometrical stairs (e) Spiral stairs 0) Turning stairs. (a) Straight Stairs: If the spaceavailable for stair caseis narrow and long, straight stairs may be provided. Such stairs are commonly used to give accessto porch or as emergencyexits to cinema halls. In this type all stepsare in one direction. They may be provided in single ight or in two ights with landing betweenthe two ights [Fig. 8.35]. Fig. 8.35. Straight stairs (b) Dog Legged Stairs: It consistsof two straight ights with 180° turn betweenthe two. They are very commonly usedto give accessfrom oor to oor. Figure 8.36 showsthe arrangement of stepsin such stairs. Landing % 3 ._ 9 3 C) c cc 4-0 o co (e) Spiral Stairs: These stairs are commonly used as emergencyexits. It consists of a central post supportinga seriesof stepsarrangedin the form of a spiral.At the end of stepscontinuous hand rail is provided. Such stairs are provided where spaceavailable for stairs is very much limited. Figure 8.39 showsa typical spiral stair. Cast iron, steelor R.C.C. is usedfor building these stairs. Fig. 8.39. Spiral stairs (f ) Turning Stairs: Apart from dog legged and open newel type turns, stairs may turn in various forms. They dependupon the available spacefor stairs. Quarter turned, half turned with few steps in between and bifurcated stairs are some of such turned stairs. Figure 8.40 shows a bifurcated stair. Fig. 8.40. Bifurcated stairs SalientPointsto be Consideredin LocatingStairs The followingpointsshouldbe consideredin locatingstairsin a building: (a) They should be locatednearthe main entranceto the building. (12)There should be easyaccessfrom all the roomswithoutdisturbingthe privacyof the rooms. (c) There should be spaciousapproach. (d) Good light andventilationshouldbe available. IQUESTIONS 1. 10. 11. 12. 13. 19. Explain the advantagesand disadvantagesof (i) Shell roofs over beamslab construction (ii) Folded plate roof over shell roof. 20. Write short notes on the following roof coverings (i) thatch (iii) tiles (ii) shingle (iv) slates. 21. ComparebetweenA.C. and GI. sheetcoverings. 22. Write short notes on sizes of doors and windows. 23. Sketch the following types of doors (i) Battenedand ledged (ii) Battened,ledged and braced (iii) Louvered. 24. Write short notes on (i) revolving doors (ii) swing doors (iii) sliding doors 25. Distinguish between (i) Collapsible and rolling shutters (ii) Collapsible and revolving door. 26. Explain any four types of windows classified on the basis of their position. 27. Sketch gable, dormer, skylight and clear storey windows. 28. What is lintel ? Where do you use lintel? Briey explain different types of lintels used. 29. Explain the terms rise and tread of stairs. Give the desirablerelationship betweenthem. 30. Sketch dog legged, open newel and geometric stairs. 31. Write short notes on straight stairs and spiral stairs. 32. What are the salient points to be consideredin locating stairs? CHAPTER amines:andIts Prevention. Dampnessin a building is the presenceof moisture in various parts of building like oor, Wall, roof etc. The continuous dampnessof building give rise to unhygenic condition, hence care should be taken to prevent such situation. In this chapter causesand effects of dampnessare presented.Ideal materials required for prevention of dampnessare discussedand various methods of preventing dampnessare presented. 9.1 CAUSES OF DAMPNESS Dampnessmay be causedby: (a) Ground water (b) Rain Water and (c) Leakagesfrom pipes. (a) Dampness due to Ground Water: All buildings are founded on soils. Soil holds water for a long time. SometimesWater level may rise and come in contact with foundation. Due to capillary action moisture from ground rises into foundation, oor and even in Wall. (b) Rain Water: May enter the building componentsdue to various reasons. (i) From wall top: If top of wall is not protected with impervious course like concrete, Watercan enter the Wall and keep it damp for a long time. (ii) From face of external walls: Splashingof outer wall by rain resultsinto moistureentering the Wall. Poor plaster coat is the main sourceof this type of dampness. (iii) Improper xing of downtake pipes: If downtake pipes from roof are not properly xed, a thin layer of Waterstagnatesnear the mouth of downtakepipes. This results into entry of rain Waterinto roof and Wall. (iv) Improper slopes to roof: In at roofs, many times this is the causefor the dampnessof roofs. If slope is not given properly, water ponds are formed on the at roof, which results into entry of Waterinto slab. Once Waterentersthe slab it remains for long time creating dampness. 128 (v) Defective construction: Imperfect wall joints, improper slopes to chejja, construction joints in roof etc. causedampnessin buildings. (c) Leakage from Pipes: From over head tanks, pipes are taken over roof and along the Wall. From bathrooms,toilets and kitchen Wateris drained out with different types of pipes. The pipes are joined to get required length and turns. Many times Water leaks through joints resulting into moisture in building components. I9.2 ILL-EFFEC.TS OF DAMPNESS Illeffects of dampnessare as listed below: 1. . Colour Wash,White Washand paintings are damaged. Patchesdevelop and destroy the appearanceof the building. . Plaster crumbles. Bricks and stonesdisintegrate endangeringthe building. xooo\1_o Steel in the slabs and beam start rusting. It reducesthe life of structure. Electric short circuits may takes place. > . Flooring CD tit may settle. . Floor covers are damaged. tit. Woodencomponentsof > . Dry rotting of Woodtakes place. l\3. Termite > buildings like door frames, cupboard Warp. becomes active and attack Wooden articles. . Mosquito breeding takes place. U). Darknessalong with Warmthand darknessbreed germs giving rise to many diseases. I 9.3 REQUIREMENTS OFANIDEALMATERIAL FORDAMPPROOFING The requirementsof an ideal materials for damp proong are: 1. It should be impervious. .Itshould be exible. . It should be easyto carry out leak proofing joints. oo\1_ox_u It should be stable. It should be durable. Its life should be as much as the life of building itself. It should resist the load safely. . It should not contain sulphates,chloride and nitrates. . It should be cheap. l9.4 MATERIALS FORDAMPPROOFING The materials used for damp proong are: 1. Bitumen: In hot condition it is highly exible and can be applied with brush to the bedding of concreteor mortar. Thickness of coat provided is about 3 mm. . Mastic asphalt: It is a semirigid material. It is obtained by heating asphalt with sand and mineral llers. It is perfectly impervious. It should be laid very carefully. . Bituminous or asphaltic felt: It is a exible material which is available in rolls. It is provided on roof slabsand parapetwalls with an overlap of 100 mm on sides.The laps are sealedwith bitumen. They do not withstand heavy movements. . Bricks: Good bricks with water absorption less than 5 per cent are sometimesused to make damp proof courses.The bricks are laid in two to four coursesin cement mortar. . Stones: Stoneslike granite, trap and slatesmay be laid over wall to its full width as damp proof course. . Mortar: Cement mortar of proportion 1 : 3 with small quantity of lime and water proofing agentsare used to make a water proofing course to foundations, ground floor slabs,top of parapetwalls etc. It may be used for plastering external walls. . Concrete: To check the rise of water into walls a course of 75 mm to 100 mm cement 1 concrete 1 : 1- : 3 or 1 : 2 : 4 is provided before starting constructing walls. These courses 2 may be provided with hot bitumen paint as an additional precaution. . Metal sheets:Aluminium, copper or lead sheetsare provided to seal the constructionjoints. Over these sheetsbituminous seal is provided. . Plastic sheets: Plastic sheetsare very good coursefor damp proofing. They are made up of black polythene of thickness 1 mm. l9.5 METHODS OF DAMPPROOFING Various methodsof damp proong are as given below: 1. 2. 3. 4. 5. material like bitumen, mastic asphalt, cement concrete,metal or plastic sheets.DPC should cover full width of wall. It should be laid on levelled surface of mortar. Joints should be minimum and should not be at critical points. When horizontal DPC on roof is continued on vertical face of parapetwall, the junction should be filled with about 75 mm llet of cement concrete.Figure 9.1 shows details of providing water proof course at plinth level. Whereas Figure 9.2 shows the details of water proong course for wall and oor. Figure 9.3 shows details of water proofing course for basement. \ GL Fig. 9.1. DPCat plinth level k\\\\V GL Basement Fig. 9.3. DPC for basement Fig. 9.4. Providingcavity wall 2. Providing cavity wall: Cavity wall may be constructedto protect foundation masonry and the wall as shown in Fig. 9.4. The cavity prevents moisture travelling from outer to inner wall. 3. Surface treatment: If moisture is only supercial and not under pressurethis method is useful. It consistsof application of layer of water repellant compoundson the surface.Some of the water proofing agentsusedfor suchtreatmentare silicates of sodium or potassiumand sulphatesof aluminium, zinc and magnesium. 4. Integral treatment: It consistsin mixing commercially available compoundsin Waterbefore concreteis Wetmixed. Thesecompoundsare madefrom chalk, talc, utter earth or chemical compoundslike calcium chloride, aluminium sulphate,calcium chloride etc. Somecompounds contain compoundslike soap,petroleum oils, fatty acids etc. 5. Guniting: In this method a mixture of cement and water is forced by cement gun on the surfaceto be made Waterproof. Later 1 : 3 or 1 : 4 cement mortar is applied to the surface with pressureusing compressedair. Thus an impervious layer of mortar is provided. 6. Pressure grouting: This is the method used to seal cracks in the concretesurfaces.In this method cement grout is forced under pressure. | QUESTIONS . What is dampness?Give various reasonsfor dampness. . List various ill effects of dampness. yr-hp-)l~)>t What are the requirementsof an ideal material for damp proofing? . Write short notes on the materials used for damp proof course. With neat sketchesexplain various methodsof damp proof Workstaken up in buildings. CHAPTER l:unslrucliun Housing scheme Large per cent of the population of India is residing in temporary housesof mud, bamboo,thatched or erectedfrom waste products in a very crude form. The temporary houses(Jhuggi) are not only unsafe but unhygenic to live in. Government of India and all state governments in India are aware of this massiveproblem and hencehave establishedhousingboardsfor developmentof housing sites and mass construction of houses.The national housing policy emphasiseson the following: 1. Arrangement for selection and promotion of proven technology. 2. Promotion of manufactureof building materialsand componentsthrough nancial assistance, technical help, scal concessions. 3. Support extensive network of building centres. 4. Setting up of dedicated organization for technology, research, application and promotion concerning the following areas: (a) Building materials and components. ([2) Selective approachto technology. (c) Marketing through building centres. (d) Franchising of the building centres. (e) Development of appropriate standards. As a result of this housing policy, a lot of fund ows to educational institutions and research centresfor developinglow cost housingtechnology,establishmentof Nirmithi Kendrasand good number of masshousing works coming under Ashraya Yojana. I10.1 MINIMUMSTANDARDS It is obvious that cost of construction is directly proportional to the area covered. In low cost housing economyin the construction is a vital factor, but one should not lose sight of the fact that any economies effected are not worth, if the minimum requirementsof basic physical comfort in the dwellings are not met. In order to meetthesetwin requirementsof economyandcomfort, onehasto dependto the maximum extent on the cost effective construction technology to provide minimum standardaccommodation.On the recommendationsof the planning commission,the Governmentof India has adoptedthe following minimum standards: 133 11.1 m[Q 1. A living room 2. A varandah and kitchen 6.5 m2 3. A bathroom 1.3 m2 4. A Lavatory 1.1m2 20.0 m2 ! Figure 10.1 shows typical plans for low cost passing. / \\\\\\\\\'\& '7 lggn O I\I\I I . Cos"r EFFECTIVE CONSTIRVU(.II'IiyON;'TECl-INlQtJ§CVIN:I_VI_i__If _ 2. Financial Assistance: Poor people should be given nancial assistancein the form of grant and cheaploan to build the low cost houses. 3. Construct Model Low Cost Houses: Few model low cost houses should be built to show the technology of building low cost houses. 4. Self Help Schemes:Low income peoplearecapableof helping themselvesin building shelter at acceptablecost. Self help housing programmesconsists of motivating the beneciaries, extending technical know how and skilled worker required for some works. 5. Skeleton Housing: Technical know how for building skeleton of housing should be made known to beneciary. They should be allowed to make certain changesand improvementsin nal finishing to suit their nancial position and taste. |10.3 COSTEFFECTIVE CONSTRUCTION TECHNIQUES Extensive researchand development works have been taken place at various researchcentres to use local materials,wastematerialsandprefabricatedstructuralcomponentsto reducethe costof construction. Some of the improved cost effective technology are listed below: 1. Foundation: Under reamedpiles for foundations have been developedfor housing in black cotton soil area. . Damp Proof Courses: Use of polythene,bituminous materialsand cementmortar with water proofing agentshave been suggestedfor damp proof courses. . Walls: Fly ash bricks, precast hollow concrete blocks (without plaster), brick panels and precastwall panels may be used to get reasonablygood comfort with little cost. . Doors and Windows: PrecastR.C.C. frames can save25 to 30 per cent cost when composed with wooden frames. Instead of wooden shuttersparticle board shuttersmay be used. . Lintels and Chejja: Locally available stonesand slatescan serveas lintels and chejja. . Precast Structural Elements: In mass constructions works precast membersmay be used for columns, beams,reapersand stair cases.One can think of using wall panels also. . Roof Units: A.C. sheets,cementbonded bre sheets,paper corrugated sheets,lime and y ash cellular slabs, solid planks, slates,ferrocementroof units etc. may be used for low cost housing roofs. . Flooring: Low cost housing ooring may be with soil cementbase,thin clay tiles, bricks on edgesor with agstones. If group housing is taken up automatically there is cost reduction, since mobilization of men, material cost is reduced and continuity of labour work is maintained. IQUESTIONS 1. Write explanatory note on cost effective construction techniques. 2. What are the minimum standardsrecommendedfor low cost housing? 3. What is the suitable approachto cost effective masshousing works? This page intentionally left blank UNIT - Ill SURVEYING This page intentionally left blank CHAPTER Surveying is the art of making measurementsof objects on, above or beneaththe ground to show their relative positions on paper The relative position required is either horizontal, or vertical, or both. Less precisely the term Surveying is used to the measurementof objects in their horizontal positions. Measurementsto detereminetheir relative vertical positions is known as levelling. I11.1 OBJECT ANDUSES OFSURVEYING As statedin the definition, object of surveying is to show relative positions of various objects of an area on paper and produce plan or map of that area.Various usesof surveying are listed below: (i) Planspreparedto recordpropertylines of private,public andgovernmentlandshelp in avoiding unnecessarycontroversies. (ii) Maps preparedfor marking boundariesof countries, states,districts etc., avoid disputes. (iii) Locality plans help in identifying location of housesand offices in the area. (iv) Road maps help travellers and tourist. (v) Topographicmapsshowing natural featureslike rivers, streams,hills, forestshelp in planning irrigation projects and ood control measures. (vi) For planning and estimatingproject works like roads,bridges,railways, airports, water supply and waste water disposal surveying is required. (vii) Marine and hydrographic survey helps in planning navigation routes and harbours. (viii) Military survey is required for strategic planning. (ix) Mine surveys are required for exploring Ininearl wealth. (x) Geological surveys are necessaryfor determining different strata in the earth crust so that proper location is found for reservoirs. (xi) Archeological surveys are useful for unearthing relics of antiquity. (xii) Astronomical survey helps in the study of movementsof planets and for calculating local and standard times. 139 11.2 PRIMARY DIVISIONS IN SURVEYING The earth is an oblate spheroid, length of equatorial axis being 12756.75 km and polar axis being 12713.80km. Since the difference between these two axes and irregularities on the earth surface are very small (Note. Height of Mount Everest is 8.79 km) comparedto thesetwo axes,the earth may be treated as a sphere,Figure 11.1 shows a circular plane passingthrough a point A on the earth surface. The gravitational force is always directed towards the centre of the earth. Hence, the plumbline shown in Fig. 11.1 is a vertical line. Line perpendicular to vertical line (tangential to earth surface)is known as horizontal line. In surveying all measurementat any point are in the direction of these two lines. A. Verticallines Horizontal line at A Horizontal line at B Fig. 11.1. Vertical and horizontal lines Fig. 11.2. Planeand sphericaltriangles Obviously, the vertical and horizontal lines at another point B are not parallel to the respective lines at A. It should be noted that all lines lying on the earths surfaceare curved lines and all triangles are spherical triangles as shown in Fig. 11.2. Hence, surveying involves spherical trigonometry. If the area to be surveyed is small, the curvature of the earth may be neglected and all plumb lines treated as the same vertical. Hence, the lines normal to plumb line at any point in the area are treated as the samehorizontal. All triangles in the area may be treated as plane triangles. The survey in which earth curvature is neglected is called Plane Surveying and the survey in which earths curvature is considered is known as Geodetic Surveying. No denite value can be assignedto the areaup to which a survey may be treatedas plane, since the degreeof accuracyrequired forms the controlling factor. However, the following points should be noted: (i) The length of an arc of 1.2 km on earthsmean surfaceis only 1 mm more than the straight line connecting those two points. (ii) The sum of the interior anglesof a geometrical gure laid on the surfaceof the earth differs from that of the correspondinggure only to the extent of one secondfor about 200 square kilometres of area. Hence, in most of engineeringprojects plane surveying is used.The geodetic surveying is used to determinethe precise positions of control stations on the surface of the earth to which plane survey details are connectedin works of larger magnitudelike preparing mapsof countries.Thus, in surveying there are two primary divisions viz. Geodetic Surveyingand Plane Surveying. I11.3 FUNDAMENTAL PRINCIPLES OFSURVEYING To get accurateresults in surveying one should follow the following fundamentalprinciples: (1') Work from whole to part (ii) Take extra care in fixing new control points. 1 1 .3.1 Work from Whole to Part In surveyinglarge areas,a systemof control points areidentied andthey arelocatedwith high precision. Then secondarycontrol points are located using lesser precise methods. The details of the localised areasare measuredand plotted with respectto the secondarycontrol points. This is called working from whole to part. This principle in surveying helps in localising the errors. If the surveying is carried out by adding localised areaserrors accumulatedand may becomeunacceptablewhen large area is covered. 11.3.2 Extra Care in Fixing New Control Points A A A A \\ e2\ \ \ \ \ \ l11.4 CLASSIFICATION OFSURVEYING Surveying may be classified on the following basis: (i) Nature of the survey eld (ii) Object of survey (iii) Instruments used and (iv) The methodsemployed. 11.4.1 Classication Basedon Nature of SurveyField On this basis survey may be classified as land survey, marine or hydraulic survey and astronomical survey. Land Survey. It involves measurementof various objects on land. This type of survey may be further classified as given below: (a) Topographic Survey: It is meant for plotting natural features like rivers, lakes, forests and hills as well as man made featureslike roads, railways, towns, villages and canals. (b) CadestalSurvey:It is for marking the boundariesof municipalities, villages, talukas,districts, statesetc. The survey madeto mark propertiesof individuals also come under this category. (c) City Survey: The survey made in connection with the construction of streets,water supply and sewagelines fall under this category. Marine or Hydrographic Survey. Survey conductedto nd depth of water at various points in bodies of water like sea,river and lakes fall under this category.Finding depth of water at specied points is known as sounding. Astronomical Survey. Observationsmadeto heavenlybodieslike sun,starsetc.,to locateabsolute positions of points on the earth and for the purposeof calculating local time is known as astronomical survey. 11.4.2 Classification Based on Object of Survey On the basis of object of survey the classification can be as engineering survey, military survey, mines survey, geological survey and archeological survey. (a) Engineering Survey:The objective of this type of survey is to collect data for designing civil engineeringprojects like roads,railways, irrigation, water supply and sewagedisposals.Thesesurveys are further subdivided into: ReconnaissanceSurvey for determining feasibility and estimation of the scheme. Preliminary Survey for collecting more information to estimatethe cost of the project, and Location Surveyto set the work on the ground. (b) Military Survey: This survey is meant for working out plans of strategic importance. (c) Mines Survey: This is used for exploring mineral wealth. (d) Geological Survey: This survey is for finding different strata in the earths crust. (e) Archeological Survey: This survey is for unearthing relics of antiquity. 11.4.3 Classication Based on Instruments Used Basedon the instruments used,surveyingmay be classifiedas: (i) Chain survey (ii) Compasssurvey (iii) Planetable survey (iv) Theodolitesurvey (v) Tacheometricsurvey (vi) Modern surveyusingelectronicdistancemetersandtotal station (vii) Photographic andAerial survey The surveyis taughtto studentsmainlybasedon this classification. 11.4.4 Classication Basedon MethodsEmployed On thisbasissurveyingis classied as triangulationandtraversing. (i) Triangulation:In this methodcontrolpointsare established througha networkof triangles. (ii) Traversing:In this schemeof establishingcontrolpointsconsistsof a seriesof connected pointsestablished throughlinearandangularmeasurements. If the lastline meetsthe startingpointit is calledas closedtraverse.If it doesnot meet,it is knownas opentraverse[Ref. Fig. 11.5]. D B (a) Closedtraverse (b) Open traverse Fig. 11.5. Traversing l11.5 PLANS ANDMAPS As statedin the definitionof surveyingthe objectiveof measurements is to showrelativepositionsof variousobjectson paper.Suchrepresentations onpaperis calledplanor map.A plan maybe dened as the graphical representation of thefeatures on, near or below the surface of the earth as projected on a horizontalplane to a suitablescale. However,sincethe surfaceof the earthis curvedand that of the paperis plane,no part of the earthcan be represented on suchmapswithoutdistortion.If the areato be representedis small,the distortion is less and large scale can be used. Such representationsare called plans. If the area to be representedis large, small, scalesare to be used and distortion is large. Representationof larger areas are called maps.Representationof a particular locality in a municipal areais a plan while representation of a state/countryis a map. There is no exact demarcationbetween a plan and map. I11.6 SCALES It is not possible and also not desirable to make maps to one to one scale. While making maps all distancesare reducedby a fixed proportion. That fixed proportion is called scaleof the map. Thus, if 1 mm on the paper represents1 metre on the ground, then the scaleof the map is 1 mm = 1 m or 1 mm = 1000mm or 1 : 1000.To make scaleindependentof the units it is preferableto userepresentativefactor which may be defined asthe ratio of one unit on paperto the number of units it representon the ground. Thus 1 mm = 1 m is equivalent to _ 1 " 1000 Apart from writing scaleon map, it is desirableto show it graphically on it. The reasonis, over the time, the papermay shrink and the scaling down the distancesfrom map may mislead.The graphical scale should be sufficiently long (180 mm to 270 mm) and the main scale divisions should represent one, ten or hundred units so that it can be easily read. The scaleof a map is consideredas (i) large if it is greaterthan 1 cm = 10 m i.e., RF >1 1000 (ii) intermediate ifitisbetween 1 RF = and 1000 10,000 (iii)small if RF< 10,000 In general,scaleselectedshould be as large as possible, since it is not possiblefor human eye to distinguish betweentwo point if distancebetweenthem is less than 0.25 mm. The recommendedscales for Varioustypes of surveys are as shown in Table 11.1. Table 11.1. Recommendedscalesfor various types of surveys Typeof Survey 1. Building sites Scale RF 1cm= 10morless 1000orless 1 (1:1000 orless) 1 2. Town planning schemes andreservoirs 1 1cm=50mto100 m 5000 to10000 1 cm = 5 m to 500 m 110 (1:5000 to1: 10000) 1 3. Cadastral maps 4. Location surveys (1:5000 to1; 50000) 1cm=50mto200m (1: 5000 to1; 20000) 5. Topographic surveys ' V 6. Geographic maps 1em=250mto2500 m (1; 25000 to1: 250000) 1cm= 5000 mto160000 in (1:500000 to1: 16000000) 1 500 50000 1 to 1 5000 20000 1 to I 25000 250000 1 1 t 0________ 500000 16000000 1 7. Route surveys 1cm= 100m 10000 (1 : 10000) 8. Longitudinal sections 1 (2') Horizontal scale 1 cm = 10 m to 200 m (1 : 1000 to 1 : 20000) (ii)Vertical scale 1000 1 t0 20000 1cm= 1m to2m 1to1 (1; 100to 1; 200) 100 200 9. Cross-sections 1cm= 1mto2m __1_ to_i_ (Bothhorizontal and (1 ; 100to 1;200) 100 200 vertical scales same) I 11.7 TYPES OFGRAPHICAL SCALES The following two types of scalesare used in surveying: (1) Plain Scale (ii) Diagonal Scale. 11.7.1 Plain Scale On a plain scale it is possible to read two dimensionsdirectly such as unit and tenths. This scaleis not drawn like ordinary foot rule (30 cm scale).If a scaleof 1 : 40 is to be drawn, the markings are not like 4 m, 8 m, 12 In etc. at every 1 cm distance.Construction of such a scaleis illustrated with the example given below: I I Example 11.1: Construct aplainscale ofRF= -5-0-6 andindicate 66monit. Solution. If the total length of the scaleis selectedas 20 cm, it representsa total length of 500 X 20 = 10000cm = 100 m. Hence, draw a line of 20 cm and divide it into 10 equal parts. Hence,eachpart correspondto 10 m on the ground. First part on extreme left is subdivided into 10 parts, each subdivision representing 1 m on the field. Then they are numberedas 1 to 10 from right to left as shown in Fig. 11.6.If a distanceon the ground is between 60 and 70 m, it is picked up with a divider by placing one leg on 60 m marking and the other leg on subdivision in the first part. Thus field distanceis easily convertedto map distance. «Tasman 5 0 10 20 30 40 50 60 70 80 90 Fig. 11.6 IS 1491-1959 recommendsrequirementsof metric plain scalesdesignatedasA, B, C, D, E and F as shown in Table 11.2. Such scalesare commonly available in the market. They are made of either varnishedcardboardor of plastic materials.Suchscalesare commonly usedby surveyorsand architects. Table 11.2. Recommendedplain scales Designation Scale RF Full size 1/1 (1:1) 50 cm to a metre 1/2 (1:2) 40 cm to a metre 1/2.5 (1:25) 20 cm to a metre 1/5 (1:5) 10 cm toa metre 1/10 (1:10) 5 cm to a metre 1/20 (1:20) 2 cm to a metre 1/50 (1:50) 1 cm to a metre 1/100 (l:100) 5 mm to a metre 1/200 (1:200) 2 mm to a metre 1/500 (1:500) 1 mm to a metre 1/1000 (1:l000) 0.5 mm to a metre 1/2000 (112000) 11.7.2 Diagonal Scale In plain scaleonly unit and tenths can be shown whereasin diagonal scalesit is possible to show units, tenths and hundredths. Units and tenths are shown in the same manner as in plain scale. To show hundredths,principle of similar triangle is used.If AB is a small length and its tenths are to be shown, it can be shown as explained with Fig. 11.7below. Draw the line AC of convenient length at right angles to plain scale AB.Divide it into10equal parts. JoinBC.Fromeach tenth pointonlineAC 1 draw lines parallel toABtillthey meet lineBC. Then line1-1represent R)th 0 1 2 3 4 6 a a 5 ofAB, 6-6 represent E thofAB and so on. Figure 11.8 shows the construction 5 7 ofdiagonal scale with RF =3-6-6 and indicates 62.6 m. 8 1 9 1O A Fig. 11.8. Diagonal scale IS 15621962 recommendsdiagonal scales A, B, C, and D as shown in Table 11.3. Table 11.3. Indian standarddiagonal scales(recommended) Designation RF A I Total Graduated Length 1 150cm 1 100000 1 B 3% _1_ 25000 100cm l11.8 UNITSOFMEASUREMENTS According to Standardsof Weights and MeasurementsAct, India decided to give up FPS systemused earlier and switched over to MKS in 1956. In 1960 System International (SI units) unit was approved by the conference of weights and measures.It is an international organisation of which most of the countries are the members.In this system also unit of linear measurementis metre. However, in this systemuse of centimetersand decametersare discouraged.Of course major difference betweenMKS and SI is in the use of unit of force. In MKS unit of force is kgwt (which is commonly called askg only) while in SI it is newton. The recommendedmultipliers in SI units are given below Gigaunit: 1 x 109units Megaunit = 1 x 106units Kilo unit = 1 X 103 units unit: 1 X 100 units Milli unit = 1 x 103 unit Micro unit = 1 X 106 unit Commonly used linear units in surveying are kilometre, metre and millimetres. However centimetre is not yet fully given up. For measuringangles sexagesimalsystemis used. In this system: 1 circumference = 360° 1 degree= 60 (minutes of arc) 1 minute = 60" (secondsof arc) IQUESTIONS What is surveying?State its objects and uses. Distinguish between geodetic surveying and plain surveying. Explain the terms topographical surveying and cadastralsurveying. What are the fundamentalprinciples of surveying? Explain briey. Discussthe classifications of surveying basedon S":>S"!°." (i) instruments used (ii) objective of survey and (iii) methods employed. 6. Distinguish betweenplans and maps. 7. Explain with a neat sketchthe construction of a diagonal scaleto represent1 cm = 5 m and show 53.6 m on it. CHAPTER earMeasurements and I All the distancesrequired for making a plan are the horizontal distances.Hence in the field horizontal distancesare measuredor sufficient readingsare taken to calculate horizontal distances.In this chapter the methodsused for linear measurementsare explained.Method of preparing a plan using only linear measurementsis by conducting chain surveying. This method is also explained in this chapter and Indian StandardConventions for showing objects on the map are presentedat the end of the chapter. l12.1 METHODS OF LINEAR MEASUREMENTS Various methodsused for linear measurementsmay be grouped as: (i) Approximate (ii) Using chain or tape (iii) By optical meansand (iv) Using electromagneticdistance measurementinstruments. 12.1.1 Approximates Methods of Linear Measurements Thesemethodsareusedin reconnaissancesurveyor to detectmajor mistakescommitted Whilemeasuring with better methods.On smooth roads they can give results Within 1 per cent error. Theseapproximate measurementsmay be by: (i) pacing (ii) using passometer (iii) using pedometer (iv) using odometeror by (v) using speedometer. (i) Pacing: In this method surveyor Walksalong the line to be measuredand countsthe number of steps.Then the distancemeasuredis equal to number of stepsx averagelength of a step. Averagelength of a step can be found by walking along a known length. A normal man takes a step of length 0.75 m to 0.8 m. 149 (ii) Using Passometer:A passometeris a Watchlike instrument Which is carried vertically in the pocket of shirt or tied to a leg. It recordsnumber of stepstaken.Thus the problem of counting number of stepsis eliminated in this approximate method of linear measurement. (iii) Using Pedometer: This instrument is similar to passometerbut it can record the distance instead of number of steps. In this, zero setting and setting of step length is made before Walking. (iv) Odometer: This instrument is attachedto the wheel of a cycle or other vehicle. It recordsthe number of revolutions made by the Wheel. Knowing the circumference of the Wheel, the distancetravelled may be found. (v) Speedometer: Odometercalibratedto give distancedirectly is called speedometer.This is to be used for particular vehicle only. All automobiles are provided With speedometers.By running the vehicle along the line to be measureddistancecan be found. 12.1.2 Measurementwith Chains or Tapes Measurementof distancesusing chain or tape is termed as chaining. This is the accurateand commonly employed method in surveying: These instruments can be classified as (i) chain (ii) steel band and (iii) tapes. (i) Chains: The chains are composedof 100 pieces of 4 mm diameter galvanised mild steel Wiresbent into rings at the end and joined to each other by three circular or oval shapedrings. These rings give exibility to the chain. The endsof chains are provided with swivel joints (Ref. Fig. l2.l(a)), 3+--1o links---->i<1O links >l<1o nnks>l<1olinks 16 10/90 links 20/80 links 80/70 links (b) Fig. 12.1. Chain 40/60 links 50 links so that the chain can be turned without twisting. To facilitate easyreading of the chain, brasstallies are provided. End of 10th link from each end is provided with a talley of one tooth, 20th link is provided with a talley of two teeth; 30th link with a talley of three teeth; 40th link with a talley of 4 teeth and the middle of chain is provided with a talley of circular shape[Ref. Fig. l2.l(b)]. It is to be noted that (i) length of a link is the distancebetweencentresof two consecutivemiddle rings. (ii) the length of the chain is from outside of one handle to the outside of the other handle. Commonly usedmetric chains are of 20 in length. They have 100 links with talleys at every 2 In. Each link is of 0.2 m length. Simple rings are provided at every one metre length except wherevertallies are provided. The total length of chain is marked on the brasshandle. However 30 in chainsare also in use.Length of eachlink is 0.3 m. It is not so convenientas20 m chain to read, since no rings can be provided at one metre distanceand eachlink needsmultiplication with 0.3 to arrive at metre units. However as a result the inuence of using 100 ft chain in olden days, this type of chain are also in market. Steel Band: It is also known as band chain. It consists of steel of 12 to 16 mm width and 0.3 to 0.6 mm thickness.The steelribbon is wound aroundan open steelcrossor in a metalreel (Ref. Plate 12.1). Metric steelbandsare available in lengths of 20 m and 30 In. Any one of the following two methodsof markings are used: (i) Providing brass studs at every 0.2 m and numbering at every metre. Last links from either end are subdivided in cm and mm. (ii) Etching graduations as meters,decimetersand centimeterson one side of the band and 0.2 in links on the other side. Plate 12.1 Tapes: Depending upon the materials used, they are classified as: (1') cloth or linen tape (ii) metallic tape (iii) steel tape and (iv) invar tape. (i) Cloth or Linen Tape: 12 to 15 mm wide cloth or linen is varnished and graduations are marked. They are provided with brass handle at the ends.They are available in length of 10 m, 20 m, 25 m and 30 m. These tapes are light and exible. However becauseof the following disadvantages they are not popular: (i) Due to moisture they shrink. (ii) Due to stretching they extend. (iii) They are not strong. (iv) They are likely to twist. (ii) Metallic Tape: They are made up of varnished strip of waterproof linen interwooven with small wires of brass,copperor bronze.End 100 mm length of tapesare provided with leatheror suitable strong plastic materials.Tapesof length 10 m, 20 m, 30 m and 50 m are available in a caseof leather or corrosion resistant metal tted with a winding device. Red and black coloured markings are used for indicating full metres and its fractions in centimetres.A typical metallic tape is shown in Fig. 12.2. Thesetapesare light, exible and not easily broken. Thesetapesare commonly used in surveying. i 16mm 25 E33]CE] mm? K Hard Leather strengthening tobe drawn securely stitched places Efl lllillileillllllllllllllj brass loop Stitching lines Fig. 12.2. Metallic tape (iii) Steel Tape: A steel tape consists of 6 to 10 mm wide strip with metal ring at free end and wound in a leatheror corrosion resistantmetal case.It is provided with a suitable winding device.Tapes are marked indicating 5 mm, centimetres,decimetresand metres.The end 10 cm length is marked with millimetres also. 10 m, 20 m, 30 m, or 50 m tapes are used in surveying. Figure 12.3 shows a typical steeltape (Ref. Plate 12.1also). Steeltapesare superiorto metallic tapesasfar as accuracyis concerned. However they are delicate. Care should be taken to wipe clean before winding. They should be oiled regularly to prevent corrosion. 56789° Fig. 12.3. Steeltape (iv) Invar Tape: Invar is an alloy of nickel (36%) and steel. Its coefficient of thermal expansion is low. Hence errors due to variation in temperaturedo not affect measurementsmuch. The width of tape is 6 mm. It is available in length 30 m, 50 m and 100 m. It is accuratebut expensive. 12.1.3 Measurementsby Optical Means In this system, the telescopeof the angle measuring instrument called theodolite (to be explained in Ch. 16) is provided with two additional cross hairs at a and b which are at distance i [Ref. Fig. 12.4]. To measuredistance D betweentwo point P and Q instrument is set at P and a graduatedstaff is held vertically at Q and vertical intercept AB is recorded.Then distance D can be computed as explained below: But from the law of optics, _1_=l+l f u v Multiplying throughout by uf, we get u=f+it-f=f+ 5.f=f+ 1. s V l l If the distancebetweenobjective lence at O and centre of telescopeis d then D=u+d =f+¬s+d =ks +c where ...(l2. =§andc=f+d k and c are constantsfor a given instrument and hencecan be found once for all. Thus distancebetween P and Q can be found by measuringvertical intercept s. Thus distanceis measuredby optical means easily. This is called Tacheometricmeasurement.But this measurementis not that accurateas obtained by measuring with chain or tape. For details of this method of survey, reader has to refer specialised books on surveying and levelling. l12.2 INSTRUMENTS USEDIN CHAINING The following instrumentsare required for measurementswith chain and tape: (i) Arrows (ii) Pegs (iii) Ranging rods and ranging poles (iv) Offset rods (v) Laths (vi) Whites (vii) Plumb bobs and (viii) Line ranger. 1 2.2.1 Arrows When the length of the line to be measuredis more than a chain length, there is needto mark the end of the chain length. Arrows are used for this purpose.A typical arrow is shown in Fig. 12.5. Arrows are madeup of 4 mm diameteredsteel wire with one end sharpenedand other end bent into a loop. Length of an arrow is approximately 400 mm. 400 mmi 5 B Fig. 12.5. Arrows 12.2.2 Pegs Woodenpegs are used in measuringa length of a line to mark the end points of the line. The pegs are made of hard wood of 25 mm x 25 mm section, 150 mm long with one end tapered as shown in Fig. 12.6. When driven in ground to mark station points they project about 40 mm. T is |<>|25 .yLiNEARlMEAsiuRgMi[igi T _ T mm EJ 125 mm H--150m Fig. 12.6. Pegs 12.2.3 Ranging Rods and RangingPoles For ranging intermediatepoints along the line to be measured,ranging rods and ranging poles are used. Ranging rods are 2 to 3 In long and are madeof hard wood. They are provided with iron shoeat one end as shown in Fig. 12.7. They are usually circular in section with 30 mm diameter and are painted with 200 mm colour bandsof red and white or with black and white. If distanceis more than 200 m, for clear visibility they may be provided with multicoloured ags at their top. The ranging rods are occasionallyusedto measure short distancessince they are painted with alternatecolour of band 200 mm. Ranging poles are similar to ranging rods except that they are longer. Their length varies from 4 In to 8 In and diameterfrom 60 mm to 100 mm. They are made of hard wood or steel.They are fixed in the ground by making 0.5 m holes and then packed to keep them vertical. Narrow slit Black or Red bands White bands Fig. 12.7 Rangingrod 12.2.4 Offset Fig. 12.8. Offset rod Rods Theserods are also similar to ranging rods and they are 3 In long. They are madeup of hard wood and are provided with iron shoeat one end.A hook or a notch is provided at other end.At height of eye, two narrow slits at right anglesto eachother are also provided for using it for setting right angles.A typical offset rod is shown in Fig. 12.8. 12.2.5 Laths Laths are 0.5 to 1.0 m long sticks of soft wood. They are sharpenedat one end and are painted with white or light colours. They areusedasintermediatepoints while ranging or while crossingdepressions. 12.2.6 Whites Whites are the piecesof sharpenedthick sticks cut from the nearestplace in the field. One end of the stick is sharpenedand the other end is split. White papers are inserted in the split to improve the visibility. Whites are also used for the samepurposeas laths. 1 2.2.7 Plumb Bob A typical plumb bob is shownin Fig. 12.9.In measuringhorizontal distances along sloping ground plumb bobs areusedto transferthe position to ground. They arealso used tocheck theverticality ofranging poles. Fig129 Plumb bob 12.2.8 Line Ranger It is an optical instrument used for locating a point on a line and henceuseful for ranging. It consistsof two isoscelessprisms placed one over the other and fixed in an instrument with handle. The diagonals of the prisms are silvered so as to reect the rays. To locate point C on line AB (ref. Fig. 12.10) the surveyor holds the instrument in hand and standsnear the approximateposition of C. If he is not exactly on line AB, the ranging rods at A and B appearseparatedas shown in Fig. 12.10 (b). The surveyor moves to and fro at right angles to the line AB till the images of ranging rods at A and B appear in a single line as shown in Fig. 12.10 (c). It happensonly when the optical squareis exactly on line AB. Thus the desiredpoint C is located on the line AB. Its advantageis it needsonly one personto range. The instrument should be occasionally tested by marking three points in a line and standingon middle point observing the coincidenceof the ranging rods. If the imagesof the two ranging rods do not appearin the sameline, one of the prism is adjusted by operating the screw provided for it. (b) Fig. 12.10. Line ranger 12.3 CHAIN SURVEYING Chain survey is suitable in the following cases: (1') Area to be surveyedis comparatively small 1,x if i (ii) Ground is fairly level (iii) Area is open and (iv) Details to be filled up are simple and less. In chain surveying only linear measurementsare made i.e. no angular measurementsare made. Since triangle is the only figure that can be plotted with measurementof sidesonly, in chain surveying the area to be surveyed should be covered with a network of triangles. Figure 12.11 shows a typical schemeof covering an areawith a network of triangles.No angle of the network triangles should be less than 30° to precisely get plotted position of a station with respect to already plotted positions of other station. As far as possible angles should be close to 60°. However, the arrangementsof triangles to be adopteddependson the shape,topography,natural and artificial obstaclesin the eld. Fig. 12.11. Network of triangles 12.3.1 Technical Terms Varioustechnical terms used in connectionwith the network of the triangles in surveying are explained below: Station: Station is a point of importance at the beginning or at the end of a survey line. Main station: Thesearethe stationsat the beginning or at the end of lines forming main skeleton. They are denotedas A, B, C etc. Subsidiary or tie stations.Thesearethe stationsselectedon main lines to run auxiliary/secondary lines for the purposeof locating interior details. Thesestationsare denotedas a, b, c, ...., etc., or as 1, 2, 3, etc. Base line: It is the most important line and is the longest. Usually it is the line plotted first and then frame work of triangles are built on it. Detail lines: If the important objects are far away from the main lines, the offsets are too long, resulting into inaccuraciesand taking more time for the measurements.In such casesthe secondary lines are run by selecting secondarystations on main lines. Such lines are called detail lines. Checklines: Theseare the lines connectingmain station and a substationon opposite side or the lines connecting to substationson the sides of main lines. The purpose of measuring such lines is to check the accuracywith which main stationsare located. 12.3.2 Selection of Stations The following points should be consideredin selecting station points: (i) It should be visible from at least two or more stations. (ii) As far as possible main lines should run on level ground. (iii) All triangles should be well conditioned (No angle less than 30°). (iv) Main network should have as few lines as possible. (v) Each main triangle should have at least one check line. (vi) Obstaclesto ranging and chaining should be avoided. (vii) Sides of the larger triangles should passas close to boundary lines as possible. (viii) Tresspassingand frequent crossing of the roads should be avoided. 1 2.3.3 Offsets Lateral measurementsto chain lines for locating ground featuresare known as offsets. For this purpose perpendicularor oblique offsets may be taken (Ref. Fig. 12.12). If the object to be located (say road) is curved more number of offsets should be taken. For measuringoffsets tapesare commonly used. Oblique offsets \ Perpendicular offsets A \ >4. ' \ . \ (3) (b) Fig. 12.12. Offsets For setting perpendicularoffsets any one of the following methodsare used: (i) Swinging (ii) Using cross staffs (iii) Using optical or prism square. Lmm . Perpendicular Offset by Swinging II \ / W Perpendicularoffset f Chain line Foot of perpendicular Fig. 12.13 Chain is stretchedalong the survey line. An assistantholds the end of tapeon the object. Surveyor swings the tape on chain line and selectsthe point on chain where offset distanceis the least (Fig. 12.13) and notes chain reading as well as offset reading in a field book on a neat sketch of the object. PerpendicularOffsets Using Cross Staffs (a) (b) (c) Fig. 12.14. Crossstaff Figure 12.14showsthree different types of crossstaffs usedfor setting perpendicularoffsets.All cross staffs are having two perpendicular lines of sights. The cross staffs are mounted on stand. First line of sight is set along the chain line and without disturbing setting right angle line of sight is checked to locate the object. With open cross staff (Fig. 12.14 (a)) it is possible to set perpendicularonly, while with french cross staff (Fig. 12.14 (b)), even 45° angle can be set.Adjustable cross staff can be used to set any angle also, since there are graduationsand upper drum can be rotated over lower drum. PerpendicularOffsets Using Optical Squareand Prism Square These instruments are basedon the optical principle that if two Inirrors are at angle G to each other, they reect a ray at angle 26. Figure 12.15 shows a typical optical square. Fig. 12.15. Optical square Optical squareconsistsof a metal box about 50 mm in diameter and 125 mm deep.In the rim of the box there are three openings: (i) a pin hole at E (ii) a small rectangular slot at G, and (iii) a large rectangular slot at F. A and B are the two mirrors placed at 45° to eachother. Hencethe image of an object at F which falls on A gets reected and emergeat E which is at right anglesto the line FA. The mirror A which is oppositeto the opening at F is fully silvered. It is fitted to a frame which is attachedto the bottom plate. If necessarythis mirror can be adjustedby inserting a key on the top of the cover. The mirror B which is in the line with EG is silvered in the top half and plain in the bottom half. It is firmly attachedto the bottom plate of the box. The ranging rod at Q is directly sighted by eye at E in the bottom half of the B which is a plain glass. At the same time in the top half of B, the reected ray of the object at P is sighted. When the image of P is in the sameVerticalline as the object at Q, then the lines PAis at right anglesto the line EB. This instrument can be used for nding foot of the perpendicular or to set a right angle. In prism square,insteadof two mirrors at 45° to eachother a prism which hastwo facesat 45° to each other is used [Fig. 12.16.]. Its advantageis it will not go out of adjustmenteven after long usage. , /I I II OII X 45 . P Fig. 12.16. Prism square 1 2.3.4 Field Book All observationsand measurementstaken during chain surveying are to be recordedin a standardfield book. It is a oblong book of size 200 mm x 120 mm, which can be carried in the pocket. There are two forms of the book (i) single line and (ii) double line. The pagesof a single book are having a red line along the length of the paper in the middle of the width. It indicatesthe chain line. All chainagesare written acrossit. The spaceon either side of the line is used for sketching the object and for noting offset distances.In double line book there are two blue lines with a spaceof 15 to 20 mm is the Huddle of each book. The space between the two lines is utilised for noting the chainages. Figure 12.17 showstypical pagesof a field books. Line AB ends station B Line AB ends station B ToH Station A line AB starts ToC Station A line AB starts Fig. 12.17 12.3.5 Field Work As soon as the survey party arrives in the field the following details are enteredin the field book: (i) Title of the survey work (ii) The date of survey (iii) The namesof the membersof the party. The field work may be divided into the following: (i) Reconnaissancesurvey. (ii) Marking stations,drawing referencesketches. (iii) Line by line surveying. Reconnaissancesurvey consistsin going round the field and identifying suitable stationsfor the network of triangles. Neat sketch of network is drawn and designated.The typical key plan drawn is similar to one shown in Fig. 12.11. All main stations should be marked on the ground. Someof the methodsused for marking are: (a) Fixing ranging poles (12)Driving pegs (c) Marking a cross if ground is hard (d) Digging and xing a stone. Then referencesketchesaredrawn in the field book so asto identify stationswhenthe development works are taken up. For this measurementswith respect to three permanent points are noted. The permanentpoints may be (a) Corner of a building (b) Postsof gates (c) Corners of compound walls (d) Electric poles (e) A tree. After that, line by line surveying is conducted to locate various objects with respect to chain lines. 12.3.6 Ofce Work It consistsin preparing the plan of the areato a suitable scalemaking useof measurementsand sketches noted in the field book. I12.4 RANGING When a survey line is longer than a chain length, it is necessaryto align intermediate points on chain line so that the measurementsare along the line. The processof locating intermediatepoints on survey line is known as ranging. There are two methodsof ranging viz., direct ranging and reciprocal ranging. i 1 LlNEAR.iM_EASUREM 12.4.1 Direct Ranging If the first and last points are intervisible this method is possible. Figure 12.18 shows the intervisible stations A and B in which an intermediate point C is to be located. Point C is selectedat a distance slightly less than a chain length. At points A and B ranging rods are xed. The assistantholds another ranging rod near C. Surveyor positions himself approximately 2 m behind station A and looking along line AB directs the assistantto move at right anglesto the line AB till he aligns the ranging rod along AB. Then surveyor instructs the assistantto mark that point and stretch the chain along AC. (a) Plan view , (b) Sectional view Fig. 12.18. Direct ranging 12.4.2 Indirect or ReciprocalLevelling Due to intervening ground, if the ranging rod at B is not visible from stationA, reciprocal ranging may be resorted. Figure 12.19 shows this schemeof ranging. It needs two assistantsone at point M and another at point N, where from those points both station A and station B are visible. It needs one surveyorat A andanotherat B. To startwith M andN areapproximatelyselected,sayM1 andN1.Then surveyornearendA rangespersonnearM to positionM2 suchthatAM2N1arein a line. Thensurveyor at B directspersonat N, to moveto N2suchthatBNZM2arein a line.Theprocessis repeatedtill AMNB are in a line. M N (a) Sectional view _ A$41111W====I;;;:t.::::::::rrr= " B R/:::::\: N2 M, \~\l\l, (b) Plan view Fig. 12.19. Reciprocalranging I12.5 OBSTACLES IN CHAINING Though it is desirableto selectstationssoasto avoid obstacles,occasionallythe obstaclesareunavoidable. Various obstaclesto chaining may be grouped into: (i) Obstacles to ranging (chaining freeVision obstructed) (ii) Obstaclesto chaining (chaining obstructedvision free) (iii) Obstaclesto both ranging and chaining. Various methodsof overcoming theseobstaclesare explained is this article. 12.5.1 Obstaclesto Ranging These obstaclescan be further classified into the following categories: (a) Both ends of the line are Visible from some intermediate points. Intervening ground is an example of such obstacle.By resorting to reciprocal ranging this difficulty can be overcome. (b) Both ends of the line may not be Visible from intermediate points on the line, but may be Visible from a point slightly away from the line. Intervening trees and bushesare the examplesof such obstacles.This obstacleto chaining may be overcome by measuring along a random line as shown in Fig. 12.20. In this caserequired length EB= ,lEC2+CB2 Fig. 12.20. Obstacleto ranging 12.5.2 Obstaclesto Chaining In this type the ends of lines are Visible but chaining is obstructed.Examples of such obstructions are ponds, lakes, marshy land etc. Various geometric properties may be used to find obstructedlength CB as shown in Fig. 12.21. (c) (d) F A DAE CO B D H" E (e) (f) Fig. 12.21. Obstaclesto chaining B (a) Set CD and BE perpendicularsto AB, such that CD = BE. Then CB = DE [Fig. 12.22 (a)] (b) Set perpendicularCD to AB. MeasureCD and DB. Then CB= /BD2__CD2 [Fig.12.22 (b)] (c) Set CD and DB such that DB J. CD. Measure them. Then CB= /CD2+ BD2 [Fig.12.22 (c)] (d) Select a convenientpoint F. Set FE = CF and FD = BF. Then CB = DE [Fig. 12.22 (d)] (e) Select a convenient point F. Locate D and E such that CF = 11DF and BF = n EF. Measure DE. Then, 2 _E__Q DF EF _ n DE CB = n DE [Fig. 12.22 (e)] (f) Select points D and E on line passing through C [Fig. 12.22 (b)]. Measure CD, CE, DB and EB. Then, from ABDE, BD2 + DE2 - EB2 COS 9= BEm and from ABDC, 2 cos6: §P:t2CD 2 2 - BD From eqn. (a), cos 9 can be found and substituting it in eqn. (b), the obstructedlength CB can be found. 12.5.3 Obstaclesto Both Chaining and Ranging Building is a typical exampleof this obstacle.Referring to Fig. 12.22,line AB is to be continuedbeyond the obstacle,say as GH. Four possible methodsare presentedbelow: (a) Set perpendicularsAC, BD such that AC = BD [Fig. 12.22 (a)]. Extend line CD to F. Drop perpendicularsEG and FH to line CF such that EG = FH = AC. GH is the continuation of line AB and DE = BG. (b) Referring to Fig. 12.22([2),setBC J. to AB. SelectD on extendedline of AC. Setperpendicular DH suchthat AD = DH. Selectpoint E on DH suchthat DE = DC. Then arcs of length EG = BC and are of length HG = AB are drawn from E and H respectivelyand G is located.GH is continuation of AB and BG = CE. (c) Referring to Fig. 12.22 (c), C is located such that AC = BC = AB. Extend AC to D and construct equilateral triangle DEF. Extend DF to H such that DH = DA. Locate convenient point I on HD and constructequilateraltriangle to locate G. Then GH is the continuation of line AB and length BG isgiven by BG=AHAB GH=ADABGH D A B-"CG H A B"'G (3) H (b) Fig. 12.22. Obstaclesto both ranging and chaining (d) In the method shown in Fig. 12.22(d), points C and D are selectedsuchthat CBD is in a line. Extend AC to E and I suchthat AE = n x AC andAI = m X AC. Similarly Extend AD to F and J suchthat, AF = n X AD and AJ = m x AD. Locate G and H on lines EF and U such that, EG = n X BC and 1H = m x BC. Then GH is the continuation of line AB. Now, AG = n X AB BG=nxABAB=(n l)AB I Example 12.1: In chaining past a pond, stations C and B were taken on the opposite sides of the pond. A line DCE was set by selecting CD = 220 m and CE = 280 m. Thelines DB and ED which are on the oppositesidesof thepond are measured.If DB = 500 m and EB = 600 m,nd obstructedlength CD. Solution: Referring to Fig. 12.21 (f), .. CD=220m CE=280m DB=500m EB=600m DE=DC+CE=220+280=500m From ABDE, cos0= D132 +13132 _E132 5002 +5002 -6002 =-- 2DE-BD =0.28 2><500><500 From ABDC, CD2 +BD2 BC2 COS9 = -*----?---2CD-BD I* 61600 = 2202 + 5002 BC = 486.62 In .L,"4EARiMEAstuREM[. BC2 Ans. |12.6 ERRORS IN CHAINING Errors in chaining may be classified as: (i) Personal errors (ii) Compensatingerrors, and (iii) Cumulating errors. 12.6.1 Personal Errors Wrong reading, wrong recording, reading from wrong end of chain etc., are personal errors. These errors are seriouserrors and cannot be detectedeasily. Care should be taken to avoid such errors. 12.6.2 Compensating Errors Theseerrorsmay be sometimespositive and sometimesnegative.Hencethey arelikely to get compensated when large number of readings are taken. The magnitude of such errors can be estimatedby theory of probability. The following are the examplesof such errors: (i) Incorrect marking of the end of a chain. (ii) Fractional part of chain may not be correct though total length is corrected. (iii) Graduationsin tape may not be exactly samethroughout. (iv) In the method of stepping while measuringsloping ground, plumbing may be crude. 1 2.6.3 Cumulative Errors The errors, that occur always in the same direction are called cumulative errors. In each reading the error may be small, but when large number of measurementsare madethey may be considerable,since the error is always on one side. Examples of such errors are: (i) Bad ranging (ii) Bad straightening (iii) Erroneouslength of chain (iv) Temperaturevariation (v) Variation in applied pull (vi) Nonhorizontality (vii) Sag in the chain, if suspendedfor measuringhorizontal distanceon a sloping ground. Errors (i), (ii), (vi) and (vii) are always +ve since they make measuredlength more than actual. Errors (iii), (iv) and (v) may be +ve or ve. I12.7 TAPECORRECTIONS The following five corrections may be found for the measuredlengths of tape: (i) Corrections for absolute length (ii) Corrections for pull (iii) Corrections for temperature (iv) Corrections for slope and (v) Corrections for sag. 12.7.1 Corrections for Absolute Length Let, I = designated lengthof tape,la = actuallengthof tape. Then correction for chain length c=lal Hence, if the total length measuredis L, the total correction C 2 F. l L ...(l2.2) Correctedlength= L + Ca If A is the measuredarea with incorrect tape, the correct area 2 =(1+ A:(1+ A,since Cissmall. ...(12.3) 1 2.7.2 Corrections for Pull If pull applied While standardisingthe length of tape and pull applied in the field are different, this correction is required. Let, P0= Standardpull P = Pull applied in the field A = Crosssectionalareaof the tape L = Measuredlength of line. E = Youngs modulus of the material of tape, then Cp=L AE The above expressiontakes care of sign of the correction also. 12.7.3 Correction for Temperature Let T0 = Temperature at whichtapeis standardised Tm= Meantemperature duringmeasurement ...(l2.4) OL= Coefficient of thermal expansionof the material of the tape and L = Measuredlength, Thenthetemperature correctionCt is givenby, Ct=L0c(TmT0) ...(12.5) The above expressiontakes care of sign of the correction also. 12.7.4 Correction for Slope If the length measuredis L and the difference in the levels of first and the last point is h, then slope correction Csl=L' VL2 h2 =L[1 1-(h/2)2] = ...(12.6) If measuredlength is L and slope is 6, then CSl=LLcos6=L(1cos6) ...(l2.7) This correction is always ve. 12.7.5 Correction for Sag While measuring on unevenly sloping ground, tapes are suspendedat shorter length and horizontal distancesaremeasured.This techniqueeliminateserrorsdueto measurementalong slopes,but necessitates correction for sag [Fig. 12.23]. Hence, measuredlength is more than actual length. Thus the correction is ve. The correction, which is difference betweenthe length of catenaryand true length is given by 1 2 CS:-iZ(-1:1) L ...(l2.8) where, W = the weight of the tape of spanlength P = the pull applied and L = measuredlength It may be noted that if pull is more than standardpull, the correction for pull is +ve, while correction for sagis always ve. The pull for which thesetwo correctionsneutraliseeachother is called normaltension.HencenormaltensionP maybe foundas, cp=cS Catenary P Heme P length TH Fig. 12.23 2 (Pn 130)]= __1___ E L AE ll 24 P P0)Pf=E1ZW2AE 0.204w s/AE P =- 01 ,/P - P0 ...(12.9) The valueof P is to be determinedby trial anderrormethod. I Example 12.2: A distance of 1500 m was measured with a 20 m chain. After the measurement chain wasfound to be 80 mm longer. If the length of chain wasperfectly correct while starting measurement, what is the true length of the line measured? Solution: Average correction per chain length c=M280 =40mm=0.04m Chain length = 20 m Correction for measured length 0.04 Cu=L E = 1500 l 20 = 3.0 m True length = 1500 + 3.0 = 1503 m Ans. I Example 12.3: A survey was conductedwith a 20 m chain and plan of theeld was drawn to a scale of] cm = 5 m. Theareaof theplan wasfound to be62.8cm2.Howeverwhenthechainwastestedat the end of work, it was wound to be 20.10 m. Assuming the length was exactly 20.0 m in the beginning of survey work, determine the true area of thefield. Solution: Initial length of the chain = 20 111 Length at the end of Work = 20.1 m , 20 + 20.1 Average length ofchain = 2- = 20.05 m Average correction per chain length = 20.05 20.00 = 0.05 m Measuredareaon plan = 62.8cm? Scale 1 cm = 5 III Measured area on eld = 62.8 X 52 = 1570 m2 1 20.05 2 Corrected area ontheground =A 7 = 1570am =1577.860 m2 Ans. I Example 12.4: A 20 m tape was usedfor measuring a line at an average temperatureof 65 F. The measureddistanceson the ground and slope of the ground are as given below: 2 18 for 125 m 3" 30'for 250 m 1" 42 a distance of I 70 m for If the temperature at which tape was standardised is 80" F, find the true length of the line. Take OL= 6.2 X I05/"F. Solution: Measured horizontal distance = 2L cos 6 = 125 cos 2°18 + 250 cos 3° 30 +170 cos 1° 42 = 544.367 m Temperature correction Ct =Lot (Tm T0) = 544.367x 6.2 x 10* (65 = 80) 0.051 m Correct horizontal length = 544.367 0.051 = 544.316 m Ans. I Example 12.5: To measurea base line, a steel tape 30 m long, standardisedat 15 C with a pull of 80 N was used Find the correction per tape length, if the temperature at the time of measurement is 25 C and the pull exertedis 150 N. TakeYoungsmodulusE = 2 X 105N/mmzand coeicient of thermalexpansion06 = 11.2 X 105/°C. Cross-sectional areaof tapeis 8 mmz. Solution: l: 30m, on= 11.2x 106/°C,To = 15°C, P0= 80N Tm= 25°C, P = 150N Correction for temperature Ct=l0c(TmT0) _ (150 80) x 30 2 X105 x 8 = 1.3125 x103 m [Note.' Unit of AE comesout to be Newtononly, if A is in cm2or m2 and E in N/cm2or N/mmz]. Total correction for temperatureand pull = Ct+ Cp= 3.360 x103+ 1.3125 x1O3 = 4.6725x 10-3111 per chainlength I Example 12.6: Calculate sag correctionfor a 30 m steel tape under a pull of 80 N, if it is suspended in threeequalspans.Unit weightof steelis 78.6kN/m3.Areaof cross-section of tapeis 8 mmz. Solution: Length of each span= 10 In W = Wt. of taper per spanlength = 78.6x 10x (8 ><10"6) = 6288 x 104 kN = 6.288 N [Note.' 1 mm2= (0.00l)2m2= l X 106 m2] P = 80 N L = 10 m Correction for each span _;(§-BEE X10 24 80 = 2.574 x 103 m Correction for three spans = 3 x 2.574 ><103 m = 7.722 x 103 m Ans. I Example 12.7: A 30 m steel tape was standardised under 60 N pull at 65 F. It was suspendedin 5 equal span during measurement.The mean temperature during measurementwas 90" F and the pull exertedwas100N. Thearea of the cross-section of the tapewas8 mm2.Find the true lengthof the tape, OL= 6.3 X I06/"E E = 2 X 105N/mmzandunit weightof steel= 78.6kN/m3. Solution: Correction for temperature. Ct=l0L(TmT0) =30 X6.3 xl06 (90 -65) = 4.725 X l03 II1 Vb VLINEAR,i'MEASUl?i.iEMi_ Correction for sag: 30 = -5- = Weightof tapeper span,W = 78.6X 6 X 8 X 106 = 3772.8 X 104 kN Each spanlength = 3.7728 6Nm Correction for sag per span __1_(3.7728T X6 24 100 = 0.3559 x 103 m Corrections for 5spans CS =5X0.3559 X10*3 = 1.779X 1O3In ( Ve) Notingthatcorrection Ct andCpare+ve,whilecorrection CSis Ve,weget Total correction = 4.725 X 103 + 0.75 X 1073 1.779 X 103 = 3.696 X 103 In = 3.696 mm True length of tape = 30 + 3.696 x103 = 30.003696 In Ans. I 12.8 CONVENTIONAL SYMBOLS IS 9621989, codeof practice for architecturaland building drawings has specified standardsymbols for Variousobjects as shown in Table 12.1 on next page. If coloured plans are to be made, the code recommendslight washesof the following shades: For roads Burnt sienna For buildings - Light grey For compound walls Indigo For water Borders edgedwith Prussianblue For trees Green. Table 12.1 Chain line Road under railway Triangulation station Boundaries without Boundaries with pillars Traverse station Township or taluka boundaries Building River Shed with open side Shed with closed side Temple, mosque and church Electric line Path Unfenced road Fenced road Railway line: Single Railway line: Double Road bridge Level crossing Road over railway Embankment North line pillars 5 LtNEAR'MEASUREhn:i 5 IQUESTIONS 0 Briey explain the various approximate methodsof measurementof distances. :5S'!' Briey explain featuresof metric chain. Distinguish between metallic tape and steel tape. Write short notes on (i) Steel band (iii) Ranging rods Explain the terms (i) Check line and tie line (ii) Invar tape (iv) Line ranger. (ii) Reference sketch. List the various points to be consideredin selecting stations for surveying. Explain the use and working of (i) Open cross staff (ii) Prism square. Explain the method of reciprocal levelling. When do you needit? Explain any two methodsof overcoming chaining problem in the following cases: (i) the obstruction is in the form of a pond. (ii) the obstruction is in the form of a building. 10. There is an obstaclein the form of a pond on the main chain line AB. Two points C and D were taken on the opposite sidesof the pond. On the left of CD, a line CE was laid out 65 min length and a secondline CF of 85 long was laid on the right of CD suchthat ECF are in a line. Determine the obstructedlength CD. Given ED = 110 m and DF = 120 m. [ Ans. CD = 87.015 in] 11. Distinguish between comulative error and compensatingerrors. Give examplesfor each case. 12. A 30 In tape usedfor measuringa line was found to be 30.01m at the beginning and 30.026 m at the end of the work. The areaof plan drawnto a scale1:1000was found to be 5625m2. Computethe correctareaof the field. [Ans. 5631.752m2] 13. A steeltape 30 In long, standardisedat 18°Cat a pull of 100N was used.Find the correction per tape length, if the temperatureat the time of measurementis 24°C and the pull exertedis 140 N. Crosssectional areaof thetapeis 8 m2. TakeE = 2 x 105N/mm2andOL = 11.2x 106/°C.Tape was stretchedover 4 equal spans.If measuredlength is 200 In, what is the actual length? Take unit weightof steel= 78.6kN/m3. 14. [Ans. L = 199.979m] With neat sketchesindicate conventional symbol used for the following objects in surveying: (i) Building (iii) Cultivated land (v) River. (ii) Double line railway track (iv) Temple, mosqueand church Disadvantageof chain surveying is that, in it only distances are measuredand hence area is to be coveredwith a network of triangles. If the length as well as angle of a line can be measuredwith respect to a known direction then it is possibleto plot a line, independentof length of other lines. Hence,in such casesthere is no compulsion of going for a network of triangles only. Compassis an instrument which can be usedto measurethe direction of a survey line with respectto magneticnorthsouth.The magnetic northsouth direction which is the reference direction is called meridian (reference direction) and the angle betweenthe line and the meridian is called bearing. Use of compassfor measuringdirection of a line simplities the surveying to a great extent. In this chapterconstruction of different types of compasses,the systemof noting bearingsof the lines, some problems associatedwith measurementwith compassare explained and then field work involved in compasssurvey is presented. |13.1 TYPES OFCOMPASS The types of compassthat are used commonly are: (i) prismatic compass;and (ii) surveyor compass. The essentialparts of both type are: (i) a magnetic needle, (ii) a graduatedcircle, (iii) a line of sight, and (iv) a box to house them. There are somedifferences in the essentialparts of the two type of compass.The construction of the two types of compassis explained and the difference in them is pointed out in this article. 13.1.1 Prismatic Compass Figure 13.1 shows the crosssectionof a typical prismatic compass[seeplate 13.1 also]. A magneticneedleof broad form (1) is balancedon a hard and pointed steelpivot (2). The top of the pointed pivot is protected with agatecap (3). 176 _ 10 R\\\\\\\\\ x\\\\\\\\\\\\\\\\\\\\\\\\\\V K! .\\\\\\\\\\\\\\\\ V m...- _. 12 1. 2. 3. 4. 5. 6. 7. 8. Needle Pivot Agate cap Graduated disc Slit metal frame Horse hair Mirror Reflecting prism with cap 9. Eye vane 10. 11. 12. 13. 14. 15. 16. 17. Fooussing stud Dark sunglasses Box Glass cover Lifting pin Light spring Brake pin or knob Lifting lever 18. Support to fit on tripod Fig. 13.1. Prismaticcompass Plate 13.1 Prismaticcompass An aluminium graduateddisk (4) is xed to the top of the needle.The graduationsare from zero to 360° in clockwise direction when read from top. The direction of north is treatedas zero degrees,east as 90°, south as 180° and Westas 270°. However, while taking the readingsobservationsare at the other end of line of sight. Hence, the readings are shifted by 180° and graduationsare marked as shown in Fig. 13.2. The graduationsare marked inverted becausethey are read through a prism. Direction of sight Reading end (a) (b) Fig. 13.2 The line of sight consistsof object unit and the reading unit. Object unit consistsof a slit metal frame (5) hinged to the box. In the centre the slit is provided with a horse hair or a fine wire or thread (6). The metal frame is provided with a hinged mirror (7), which can be placedupward or downward on the frame. It can be slided along the frame. The mirror can be adjustedto view objects too high or too low from the position of compass.Readingunit is provided at diametrically oppositeedge.It consistsof a prism (8) with a sighting eye vane (9). The prism magnifies the readings on the graduation disk just below it. For focussing, the prism is lowered or raised on the frame carrying it and then xed with the stud (10). Dark sunglasses(11) provided near the line of sight can be interposed if the object to be sighted is bright (e.g., sun). The bottom of the box (12) which is about 85 mm to 110mm supportsthe pivot of needlefirmly at its centre.The object vane and the prism are supportedon the sides of the box. The box is provided with a glass (13) lid which protectsthe graduation disc at the sametime permit the direct reading from the top. When the object vane is folded on the glass top it pressesa lifting pin (14) which activates lifting lever (15) lifts the needleoff the pivot. Thus, it preventsundue wear of pivot point. While taking reading, if graduation disc vibrates, it can be dampenedwith a spring (16). For pressing spring a knob or brake pin (17) is provided on the box. When not in use prism can be folded over the edgeof the box. The box is provided with a lid to close it when the compassis not in use. The box is provided with a socketto fit it on the top of a tripod. 13.1.2 Surveyors Compass In this type of compassgraduationdisc is xed to the box and magnetic needleis free to rotate aboveit. There is no prism provided at viewing end, but has a narrow slit. After fixing the line of sight, the reading is directly taken from the top of the glass cover. Hence, graduations are written directly (not inverted). In this compassgraduationsare from zero to 90°, zero being to north or south and 90° being to eastand west. An angle of 20° to north direction to the eastis written as N 20° E, and an angle of 40° to eastfrom south is written as S 40° E. Always first direction indicated is north or south and the last letter indicates east or west direction. In this systemgraduatedcircle rotates with line of sight and magnetic needle is always towards north. The reading is taken at the tip of needle. Hence, on the compass east and west are marked interchanged and marked [Ref. Fig. 13.3] Plate 13.2 shows the photograph of a surveyors compass. Line of sight Pointof reading (b) Fig. 13.3 Plate 13.2 Surveyorscompass DifferenceBetweenPrismaticCompassand SurveyorsCompass The differencebetweenprismaticand surVeyorscompassare listedin Table 13.1. Table 13.1. Differencesbetweenprismaticand surveyorscompass Sr No. Prismatic Compass SurveyorsCompass Graduationcircle is fixed to broadtype needle. Graduation circle is fixed to the box. Hence, it Hence,it will not rotatewith the line of sight. rotateswith the line of sight. At Viewingend thereis no prism.There is only There is a prismat Viewingend. a slit. Sightingandreadingcanbe donesimultaneously.Sighting and Viewing cannot be done The magneticneedledo not act as an index. simultaneously. Magneticneedleactsas index while reading. The graduationsare in whole circlebearing. The graduationsare in quadrantalsystem. Graduations Graduationsare markeddirectly.They are not are marked inverted since its reection is read throughprism. inverted. The readingis takenthrougha prism. The readingis takenby directly Viewingfrom top glass. Tripod may or may not be used.It can be held Tripod is essentialfor usingit. on a stretched hand also. l13.2 METHODOF USINGA COMPASS To take a reading from a compass,the following temporary adjustmentsare required: (i) Centring: The compassshould be xed to the stand and set over the station. To centre the compasslegs of the tripod standshould be moved inwardoutward or in a circumferential direction. To check centring plumb may be used or a pebble dropped from the centre of the compass. (ii) Levelling: In compasssurvey perfect levelling is not necessary,but it should be sufficient to permit free suspensionof magnetic needle.For checking levelling a bubble level is provided in many compasses.After centring bubble should be ensuredin the middle of the circle provided for it in the level. If it is not within that circle, circumferential movementsmay be provided to the legs of tripod so that without disturbing centring the levelling is achieved. (iii) Focussing the prism: In prismatic compass, to focus the prism on graduated circle, its attachmentis slided up or down till the readings are clearly visible. There is no such requirement in surveyors compass. The following stepsare required for observing bearing of a line, say,AB: (i) Centre the compassover A. (ii) Level the compass. (iii) Focus the prism, if prismatic compassis used. (iv) Rotate the box till ranging rod at B is sighted through the line of sight. (v) Bring the needleto rest using knob. (vi) Take the reading and note it in the field book. Care should be taken to seethat the line of sight is not disturbed betweenthe line of sighting the object and the time of reading the bearing. I13.3 BEARING As statedearlier a bearing of a line is the angle madeby the line with respectto a referencedirection, the referencedirection being known as meridian. The direction shown by a freely suspendedand properly balancedmagnetic needle is called magnetic meridian and the horizontal angle made by a line with this meridian is known as magnetic bearing. The points of intersectionof earthsaxis with surfaceof the earth are known as geographicnorth and south pole. The line passingthrough geographicnorth, south and the point on earth is called true meridian at that point and the angle made by a line passingthrough that point is called true bearing. While traversing along lines A, B, C, D ..., the bearing of lime AB is called fore bearing of AB and the bearing of BA is called back bearing. Fore bearing and back bearing differ by 180°. l13.4 WHOLECIRCLE BEARING AND REDUCED BEARING In whole circle bearing (WCB) the bearing of a line at any point is measuredwith respectto a meridian. Its value varies from zero to 360°, increasingin clockwise direction. Zero is north direction, 90° is east, 180° is south and 270° is west (Ref. Fig. 13.2). This type of bearing is used in prismatic compass. In reduced bearing (RB) system,bearings are measuredfrom north or south direction towards eastor west. Hence, anglesare from 0 to 90° as shown in Fig. 13.3. This systemof measuringbearings is used in Surveyors compassand it is also known as QuadrantalBearing (QB). The bearing measured is designatedwith letter N or S in the beginning to indicate whether it is from north or south.The letter E or W written after the angle indicates whether the bearing read is towards east or west, respectively. The conversion of the bearing from one systemto the other systemcan be easily carried out by drawing a sketchto indicate WCB or RB as shown in Fig. 13.4.It may be observedthat conversiontable is as given below: Quadrant in which bearing lies Conversion relation NE a=0 SE oc= 180° SW on= 0 NW oc= 360° 0 180° 0 Fig. 13.4 I Example 13.1: Convert thefollowing reducedbearings into whole circle bearings. (i)N65°E (ii)S43°15E (iii) S 52° 30 W (iv) N32° 42 W Solution: Let 0 be whole circle bearing. (i)Since itisinNE quadrant, 0=OL =65° Ans. (ii) Since it is in south east quadrant 43° 15 = 180° or 0 = 180° 0 43° 15 = 136° 45 Ans. (iii) Since itisinSW quadrant 52° 30=0~180° or 0 = 180° + 52° 30 = 232° 30 Ans. (iv) Since itisinNW quadrant, 32° 42=360° 6 or 9 = 360° 32° 42 = 327° 18 respectively.Determine their back bearings. (i) 148° (ii) 65° (iii) 285° Ans. (iv) 215° I Example 13.2: Thefollowing fore bearings were observedfor lines, AB, BC, CD, DE, EF and FG (v) N36° W (vi) S 40° E Solution: The difference betweenfore bearing and the back bearing of a line must be 180°. Noting that in WCB angle is from 0° to 360°, we find back bearing = fore bearing i 180° + 180° is used if 6 is less than 180° and 180° is used when 6 is more than 180°. Hence (i)BB ofAB =145° +180° =325° (ii) BB of BC = 65° + 180° = 245° (iii) BB of CD = 285° 180° = 105° (iv) BB of DE = 215° 180° = 35° In caseof RB, back bearing of a line can be obtainedby interchangingN and S at the sametime E and W. Thus (v) BB ofEF = S 36° E (vi) BB of FG = N 40° W. I13.5 COMPUTATION OFANGLES At any point, if bearings of any two lines are known, the angle between thesetwo lines can be easily found by drawing a neat sketch, and then noting the difference. The procedure is illustrated with the examplesgiven below. I Example 13.3: In a closed traverse thefollowing bearings were observedwith a compass.Calculate the interior angles. Line Fore bearing AB 65 ° 00 BC 125° 30 CD 200° 00 DE 265° 15 EA 330° 00 Solution: Figure 13.5 showsthe anglesobserved.Back bearingsof all the lines may be Workedout and noted on the figure. Then calculation of interior angles can be easily carried out. M "g 65° 00 245° 00 125° 30 305° 30 200° 00 20° 00 265° 15 85° 15 330° 00 150° 00 Fig. 13.5 Referring to gure: AA = 150° 00 65° 00 = 85° 00 AB = 245° 00 125° 30 = 119° 30 AC = 305° 30 200° 00 = 105° 30 AD = (360° 265° 15) + 20° 00 = 114° 45 LE = (360° 330° 00) + 85° 15 = 115° 15 I Example 13.4. The angles observedwith a surveyor compassin traversing the lines AB, BC, CD, DE and EF are as given below. Computethe included angles and show them in a neat sketch. Line Fore bearing AB N 55° 30 E BC S 63° 30 E CD N 70° 00 E DE S 45° 30 E EF N72° I5E Solution: Figure 13.6 showsthis traverse.First back bearingsof all lines are calculatedand noted in the table shown below: Line FB BB AB N 55° 30 E S 55° 30 W BC S 63° 30 E N 63° 30 W CD N 70° 00 E S 70° 00 W DE S 45° 30 E N 45° 30 W EF N 72° 15 E S 72° 15 W. Fig. 13.6 Referring to the figure, we nd AB = 55° 30 + 63° 30 = 119° 00 Ans. AC = 63° 30 + 70° 00 = 133° 30 Ans. AD = 70° 00 + 45° 30 = 115° 30 Ans. LE = 45° 30 + 72° 15 = 117° 45 Ans. I13.6 DECLINATION AND DIP The magneticmeridian and the true meridian may not coincide with eachother in a place.The horizontal angle betweenthese two meridians is known as magnetic declination. The magnetic north at a place may be towards eastor west of true north (Fig. 13.7). If it is towards east,it is known as easternor +ve declination. Western declination is known as ~ve declination. Eastern declination is to be added to observedmagnetic bearingsto get true meridian. To nd magnetic declination at a point true meridian should be establishedfrom astronomical observationsand magnetic meridian by a compass.Maps are made with respectto true meridian. True True meridian Magnetic meridian Magnetic meridian meridian GE 9W (a) +ve Declination (b) -ve Declination Fig. 13.7. Magnetic declination Magnetic declination varies from time to time and also from place to place. In the noon sun is exactly on the geographical meridian. In India, Survey of India department conducts astronomical survey and publishes Isogonic Charts from which magnetic declinations at any point can be found. The lines joining the points at which declination is the same at the given time are called Isogonic Lines. Lines joining points of zero declinationsare called Agonic Lines. The isogonic lines are quite irregular near geographicpoles. The isogonic charts show lines of equal annual changein declination. The following type of variations are observedin declination: (i) Secular variation, (ii) Annual variation, (iii) Daily variations, and (iv) Irregular variations. 1 3.6.1 Secular Variation The magnetic meridian swings like a pendulum to the left and to the right of true meridian. Its period of variation is approximately 250 years. 1 3.6.2 Annual Variation It is observedthat in a year declination varies from 1 to 2. 13.6.3 Daily Variation The daily variation of magnetic declination is as much as 10. This variation is also known as Dirunal Variation. The following factors inuence its magnitude: (a) It is more in day and less in night. (b) It is more in summer and less in winter. (c) The amount of variation changesfrom year to year. (d) It is more near magnetic poles and less near equator. 13.6.4 Irregular Variation Due to earthquakesand volcanic eruptions, magnetic storms occur, resulting into changesin magnetic meridian. Such changesare from 1° to 2°. Magnetic Dip A perfectly balanced, freely suspendedmagnetic needle dips towards its northern end in northern hemisphereand towards its southernend in southernhemisphere.If it is at north pole, the needletakes Vertical position. The Vertical angle between the horizontal and the direction shown by a perfectly balanced and freely suspendedneedle is known as the magnetic dip at that place. Its Value is 0° at equator and 90° at magnetic poles. To counteract the dip, a sliding rider (weight) is provided on the needle. I Example 13.5: True bearing of line AB is 357° and its magnetic bearing is 1° 30. Determine the declination. Also find the true bearing of AC which has magnetic bearing equal to 153° 30. Solution: [Ref. Fig. 13.8] Magnetic Declination = 1° 30 + (360° 357°) = 4° 30, west.Magneticbearingof AC = 153° 30. B MM TM 1° 30 153° 30 C Fig. 13.8 'I1'ue bearing of AC = 153° 30 = 149° 4° 30 Ans. I Example 13.6: In an old map line AB was drawn with a magnetic bearing of 136° 45 when the magnetic declination was 2° 30 east. To what magnetic bearing the line should be set now, if magnetic declination is 3° 30 west ? Solution: Referring to Fig. 13.9, it is clear that TM MM new 3° 30 MM old 2° 30 136° 45 Fig. 13.9 Present magnetic bearing of line AB = 3° 30 + 2° 30 + 136° 45 = 142° 45 Ans. I Example 13.7: Find the declination at a place, if the magnetic bearing to the sun at noon is (a) 185° (b) 358°. Solution: (a) Referring to Fig. 13.10 (a), since the magnetic bearing to the sun in the noon is 185°, it is to the geographicsouth pole. Hence, to the magnetic bearing to north pole is 5°, i.e., declination is 5°. Ans. MM TM TM MM 185° 358° (8) (b) Fig. 13.10 (b) Referring to Fig. 13.10 (b), Declination = 360° 358° = 2° East. l13.7 LOCALATTRACTION A freely suspendedand properly balanced magnetic needle is expectedto show magnetic meridian. However,local objectslike electric wires and objectsof steelattractmagneticneedletowardsthemselves. Thus, needle is forced to show slightly different direction. This disturbanceis called local attraction. The list of materials which cause local attraction are: (i) magnetic rock or iron ore, (ii) steel structures,iron poles, rails, electric poles and wires, (iii) key bunch, knife, iron buttons, steel rimmed spectacles,and (iv) chain, arrows, hammer,clearing axe etc. Surveyor is expectedto take care to avoid local attractions listed in (iii) and (iv) above. Detecting Local Attraction For detecting local attraction it is necessaryto take both fore bearing and back bearing for each line. If the difference is exactly 180°, the two stationsmay be consideredas not affected by local attraction. If difference is not 180°, better to go back to the previous station and check the fore bearing. If that reading is sameas earlier, it may be concludedthat there is local attraction at one or both stations. Correcting Observed Bearings If local attraction is detectedin a compasssurvey observedbearingsmay be correctedby any one of the following two methods: Method 1: It may be noted that the included angle is not inuenced by local attraction as both readingsare equally affected. Hence, first calculate included anglesat each station, commencing from the unaffected line and using included angles,the correctedbearingsof all lines may be calculated. Method II: In this method, errors due to local attraction at each of the affected station is found starting from the bearing of a unaffectedlocal attraction,the bearing of the successivelines are adjusted. These methodsare illustrated with the examplesbelow: I Example 13.8: In a closedtraverse,thefollowing bearings were observed,with a compass.Calculate their interior angles and then computethe corrected magnetic bearings. 46° 30 226° 30 BC 118° 30 300° 15' CD 210° 00 28° 00 DE 271°15 93° 15° EA 313° 45 132° 00 Solution: Figure 13.11 showsthe traverse.Difference betweenFB and BB of line AB is exactly 180°. Hence, stationsA and B are not affectedby local attractions.Hence,all the bearingstaken from stations A and B are correct magnetic bearings. Correct bearing of AB = 46° 30 Correct bearing of BA = 226° 30 From the figure, AA = 132° 00 46° 30 = 85° 30 AB = 226° 30 118° 30 = 108° 00 AC = 300° 15 210° 00 = 90°15 AD = (360° 271° 15) + 28° 00 = 116° 45 LE = (360° 00 Total Interior Angle 313° 45) + 93° 15 = 139° 30 = AA + AB + AC + AD + LE = 540° 00. Hence there is no observations error. [Note: In a pentagonsum of interior angles= (2n ~ 4) X 90 = (2 x 5 4) x 90 = 540°. If there is observationerror it is to be distributed equally to all interior angles]. Since, stationsA and B are not affected by local attraction, correct bearingsare: Bearing of AB = 46° 30 Bearing of BA = 46° 30 + 180° 00 = 226° 30 Bearing of BC = 226° 30 AB = 226° 30 ~ 108° 00 = 118° 30 Bearing of CB = 118° 30 + 180° 00 = 298° 30 Bearing of CD = 298° 30 - AC = 298° 30 Bearing of DC = 208° 15 180° 00 Bearing of DE = 28° 15 = = 28° 15 AD = 28° 15 89° 30 = 90° 15 = 208° 15 116°45 88° 30 + 360° 00 = 271° 30 Bearing of ED = 271° 30 ~ 180° 00 = 91° 30 Bearing of EA = 91° 30 LE = 90° 30 = 48° 00 + 360° Bearing ofAE 48° 00 = = 312° 00 180° 00 139° 30 = 312° 00 = 132° 00 [Checked.It should be equal to the observedbearing, since station E is not affected]. I Example 13.9: Solveproblem no. 13.8 by the method of correction to local attraction. Solution: [Ref. Fig. 13.11] 210° 00 \ mews 27w15 Hg.13J1 Since, the difference between FB and BB of line AB is exactly 180°, stationsA and B are not affected by local attraction. Hence, corrections to the observedbearingsat A and B are zero. Correct bearing CB = 118° 30' + 180° 00' = 298° 30' But observedbearing = 300° 15 Hence correction = 298° 30 at station C Correct bearing of CD 300° 15 = 1° 45 = 210° 00 - 1° 45' = 208° 15' Correct bearing DC = 208° 15' 180° 00' = 28° 15' Observedbearing of DC = 28° 00 Corrections required at D = 28° 15 Correct bearing of DE = 271° 15 + 0° 15 = 271° 30 Correct bearing of ED = 271° 30 28° 00 = 0° 15 180° 00 = 91° 30 But observedbearing of ED Correction = 93° 15' for observations = 91° 30 at E 93°15 1°45 Correct bearing of EA = 313° 45 Correct bearing of AE = 312° 00 - 180° 00 = 132° 00. [Checked] 1° 45 = 312° 00 The calculations may be carried out in tabular form as shown in Table 13.2. Table Station A B C D E 13.2 Line Observed Bearing AE 132° 00 AB 46° 30 BA 226° 30 BC 118° 30 CB 300° 15 CD 210° 00 DC 28° 00 DE 271° 15 ED 93° 15 EA 313° 45 Correction Correct Bearing 0 132° 00 46° 30 0 226° 30 118° 30 1° 45 298° 30 208° 15 0° 15 28° 15 271° 30 1° 45 91° 30 312° 00 [Note.°Correction = Correct reading Observedreading] I13.8 CHAINANDCOMPASS SURVEYING FIELDWORK In compasssurvey chain or tape is used for linear measurement.If the surveying startsfrom a station, goes round an area and ends at the starting station it is called closed traverse. If survey starts from a point, goes along a number of interconnectedlines and ends at some other point it is called as open traverse. Closed traverseis usedfor preparing plan of an areawhile open traverseis useful in the road, rail or canal projects. The following are required for chain and compasssurvey: (i) Compassand stand (ii) Chain and tape (iii) 10 arrows (iv) 5 to 6 ranging rods (v) Ranging poles (vi) Pegsand hammer (vii) Plumb bobs (viii) Line ranger, cross staff etc. Field Work Field work involves: (i) reconnaissancesurvey (ii) preparation of location sketchesof stations (iii) measurement of directions (iv) measurementof lengths and offsets, and (v) recording measurements. (i) ReconnaissanceSurvey: The entire areato be surveyedis inspectedto selectsurvey stations. Important points to be consideredin selecting stations are: (a) Adjacent stations should be intervisible. ([2) Lines to be chained should be free of obstacles. (c) Number of survey lines should be minimum. (d) Survey lines should run close to the important objects, so that offset lengths are small. An index map is prepared with pencil and stations are marked. If necessary,changesmay be made in survey lines and correspondingchangesin the index plan. Location Sketches Before commencingsurveying a line, the location sketchesof the stationsof that line shouldbe prepared. At the beginning of the field book few pagesshould be reservedfor drawing location sketches. Direction Measurement The following precautionsshould be taken in measuringthe direction of a survey line with compass. (a) Centre the compasson the station correctly. (b) Level the compassand ensureneedleis free to move. (c) Take the reading only after vibration of graduationcircle/needleis stopped.Use the knob, if necessary. (d) Gently tap the top of the glassof compassto remove sluggishnessof the needleand take the reading after vibration stops. (e) While taking reading parallax should be avoided. (f) Care should be taken to keep away steel and iron objects like key bunch, metal framed spectacles,iron buttons, chain, arrows etc. (g) If handkerchiefis used to clean top of glassof campass,the glass is chargedwith electricity. As a result of it local attraction is induced.To avoid this problem apply moist fingers to clean the glass. (It) If the compassis not in use, fold the prism and object vane on the top of glass plate, so that needleis lifted from the pivot to avoid unnecessarywear of the pivot. (i) For all survey lines fore bearings and back bearings should be taken. If any other survey station is visible, bearing should be taken to that station also, which helps in checking survey work. Measurementof Lengths and Offsets This is similar to the one usedin chain survey. However, it may be noted that for the objects of less importance one can measurethe bearing of the offset and its length. RecordingChain and Compass Measurements The type of field book used in chain survey is used in this surveyalso. Apart from recording linear measurementsin this survey the bearingstaken also should be recorded.Figure 13.12 shows a page of typical eld record. Bearing of BA 133° 30 Line AB Ends stn. B 52.5 38.2 1.9 32.6 2.2 A Stn.A Line ABstarts FB of AB 53° 30' Fig. 13.12 7 623°, 0c IQUESTIONS Explain with a neat sketch construction of a prismatic compass. Bring out the differences between prismatic compassand surveyors compass. Distinguish between (cl) Magnetic meridian and true meridian. (b) Whole circle bearing and quadrantalbearing. (c) Declination and dip. (d) Fore bearing and back bearing. (e) Isogonic and agonic lines. What is meant by magnetic declination? List the different types of its variations. .?S". What is local attractions? How it is detected in the eld? What are the precautions to be taken while taking bearing of a line with a compass. In traversing in anticlockwise direction, the following readings were observed: AB CD BC 105° 15 20° 00 316° 30 DE 187° 15 EA 122° 45 Draw a neat sketch of the traverse.Determine the interior angles of the traverse and apply check. 8. AA = 162° 30 AB = 94° 45 AC = 116° 30 AD = 50° 45 AB = 115° 30 29 = 540° Checked. Ans. The following bearings were taken in running a compasstraverse: Line FB BB AB 124° 30 304° 30 BC 68° 15 246° 00 CD 310° 30 135° 15 DA 200° 15 17° 45 At what stations do you suspectlocal attraction? Find the correct bearings of the lines and also compute the included angles. Ans. Stations C and D are affected by local attraction. Correct bearing of lines are as shown below: Line FB AB 124° 30 BC 68° 15 CD 312° 45 DA 197° 45 AA = 106° 45 AB = 123° 45 AC = 64° 30 BB AD = 65° 29 = 360° Checked. Pianeialile Surveying In this method of surveying a table top, similar to drawing board fitted on to a tripod is the main instrument. A drawing sheet is fixed on to the table top, the observations are made to the objects, distancesare scaleddown and the objects are plotted in the field itself. Sincethe plotting is madein the field itself, there is no chanceof omitting any necessarymeasurementin this surveying. However the accuracy achieved in this type of surveying is less. Hence this type of surveying is used for filling up details between the survey stationspreviously fixed by other methods. In this chapter,accessoriesrequired, working operationsand methods of plane table surveying are explained.At the end advantagesand limitations of this method are listed. 14.1 PLANE TABLE AND ITS ACCESSORIES The most commonly usedplane table is shown in Fig. 14.1. It consistsof a well seasonedwooden table top mounted on a tripod. The table top can rotate about vertical axis freely. Whenever necessarytable can be clamped in the desired orientation. The table can be levelled by adjusting tripod legs. Adjusting the tripod Fig. 14.1. Planetable with stand The following accessoriesare required to carry out plane table survey: 1. Alidade 2. Plumbing fork with plumb bob. 195 3. Spirit level 4. Trough compass 5. Drawing sheetsand accessoriesfor drawing. 1 4.1 .1 Alidade It is a straight edgeruler having someform of sighting device. One edge of the ruler is bevelled and is graduated.Always this edge is used for drawing line of sight. Depending on the type of line of sight there are two types of alidade: (a) Plain alidade (b) Telescopic alidade Plain Alidade: Figure 14.2 showsa typical plain adidate.A sight vane is provided at eachend of the ruler. The vane with narrow slit servesas eye vane and the other with wide slit and having a thin wire at its centre servesas object vane. The two vanesare provided with hinges at the ends of ruler so that when not in usethey can be folded on the ruler. Plain alidade is not suitable in surveying hilly areas as the inclination of line of sight in this caseis limited. Eye vane Object vane Fiducial edge/Bevelled edge Fig. 14.2. Planealidade TelescopicAlidade: It consistsof a telescopemountedon a column fixed to the ruler [Fig. 14.3]. The line of sight through the telescopeis kept parallel to the bevelled edgeof the ruler. The telescopeis provided with a level tube and vertical graduationarc. If horizontal sight is required bubble in the level tube is kept at the centre.If inclined sightsarerequired vertical graduationhelps in noting the inclination of the line of sight. By providing telescopethe range and the accuracyof line of sight is increased. Bubble tube Vertical circle Telescope Focussing screw Straight edge Fig. 14.3. Telescopicalidade 14.1.2 Plumbing Fork and Plumb Bob Figure 14.4 shows a typical plumbing fork with a plum bob. Plumbing fork is a Ushaped metal frame with a upper horizontal arm and a lower inclined arm. The upper arm is provided with a pointer at the end while the lower arm is provided with a hook to suspendplumb bob. When the plumbing fork is kept on the plane table the vertical line (line of plumb bob) passesthrough the pointed edge of upper arm. The plumb bob helps in transferring the ground point to the drawing sheetand vice versa also. Upper arm Fig. 14.4. PlumbingFork and plumb bob. 14.1.3 Spirit Level A at basedspirit level is usedto level the plane table during surveying (Fig. 14.5).To get perfect level, spirit level should show central position for bubble tube when checked with its positions in any two mutually perpendicular direction. Fig. 14.5. Spirit level 14.1.4 Trough Compass It consistsof a 80 to 150 mm long and 30 mm wide box carrying a freely suspendedneedleat its centre (Ref. Fig. 14.6). At the ends of the needle graduationsare marked on the box to indicate zero to five degreeson either side of the centre. The box is provided with glass top to prevent oscillation of the needleby wind. When needle is centred (reading 00), the line of needle is parallel to the edge of the box. Hence marking on the edgesin this stateindicates magnetic northsouth direction. Wooden box Graduations Pivot Magnetic needle Fig. 14.6. Trough compass 14.1.5 Drawing Sheetand Accessoriesfor Drawing A good quality, seasoneddrawing sheet should be used for plane table surveying. The drawing sheet may be rolled when not in use, but should never is folded. For important works fibre glass sheetsor paper backed with thin aluminium sheetsare used. Clips clamps, adhesivetapesmay be used for xing drawing sheetto the plane table. Sharphard pencil, good quality eraser,pencil cutter and sandpaper to keep pencil point sharpare other accessories required for the drawing work. If necessary,plastic sheetshould be carried to cover the drawing sheet from rain and dust. |14.2 WORKING OPERATIONS After xing the table top to the standand drawing sheetto the table, the following operationsare to be carried out before map making: 1. Centering 2. Levelling 3. Orientation. 14.2.1 Centering Centering is the processof setting the plane table on the point so that its plotted position is exactly over the position on the ground. This is achievedby moving the legs of the tripod and checking the position of the point on the ground and on the paper with the help of plumbing fork and plumb bob. 14.2.2 Levelling The level of the plane table should be ensuredin two positions of spirit level which are at right anglesto each other. The legs of tripod are moved radially or along the circumferenceto adjust the plane table and get levelled surface. 1 4.2.3 Orientation Orientation is the processof setting plane table over a station such that all the lines already plotted are parallel to correspondinglines on the ground. Accuracy of plane table survey mainly dependsupon the accuracyof orientation of planetable at eachstationpoint. It canbe achievedby any one of the following methods: (a) using trough compass (b) by back sighting (c) by solving two point or three point problems. The first two methodsare commonly usedwhile the third method is used occationally.The third method is explained under the article methodsof plane tabling by resection. (a) Orientation Using Trough Compass:When the survey work starts,the plane table is set on first station and the table is oriented by rough judgement suchthat the plotted position of the areafalls in the middle portion of the paper.Then the table is clampedand the north direction is marked on right hand side top corner of drawing sheet.Trough compassis usedto identify north direction. This orientation is to be maintainedat all subsequentstations.After centering and levelling the table trough compassis kept along the marked north direction and the table is rotated to get freely suspendedmagnetic needle centred. After achieving it the table is clamped. This method of orientation is consideredrough, since the local attraction to magnetic needle affects the orientation. This method is used as preliminary orientation and finer tuning is made by observing the already plotted points. (b) Orientation by Back Sighting: It is the commonly used method in plane table surveying. After completing surveying from plane table set at A, if table is to be shifted to next station B, a line is drawn from the plotted position of stationA towards station B. Then distanceAB is measured,scaleddown and plotted position of station B is obtained.Then table is shifted to station B, centred, levelled. Then keeping alidade along BA, station A is sighted and the table is clamped.Thus the orientation of the table is achievedby back sighting. Orientation may be checkedby observing already plotted objects. I14.3 METHODS OFPLANE TABLING The following four methodsare available for carrying out plane table survey: 1. Radiation 2. Intersection 3. Traversing 4. Resection. The first two methodsare employed for locating details while the other two methodsare usedfor locating position of plane table station on drawing sheet. 1 4.3.1 Radiation After setting the plane table on a station, say 0, it is required to find the plotted position of various objectsA, B, C, D . To get thesepositions, the rays OA, OB, OC are drawn with soft pencil (Ref. Fig. 14.7).Then the distancesOA, OB, OC aremeasuredscaleddown andthe positionsof A, B, C are found on the drawing sheets. This methodis suitablefor surveying small areasand is convenientif the distancesto be measured are small. For larger areas this method has wider scope, if telescopic alidade is used, in which the distancesare measuredtechnometrically. \ \\ Fig. 14.7. Radiation method of plane tabling 1 4.3.2 Intersection In this method the plotted position of an object is obtained by plotting rays to the object from two stations.The intersectiongives the plotted position. Thus it needsthe linear measurementsonly between the station points and do not need the measurementsto the objects. Figure 14.8 shows the method for locatingobjectsA andB from planetablepositions01 andO2. f,.B \ \ , Plane table at O1 / \ Plane table at 02 Fig. 14.8. Intersection method of plane tabling This method is commonly employed for locating: (a) details (b) the distant and inaccessiblepoints (c) the stations which may be used latter. 14.3.3 Traversing This is the method used for locating plane table survey stations. In this method, ray is drawn to next station before shifting the table and distance between the stations measured.The distance is scaled down and next station is located.After setting the plane table at new station orientation is achievedby back sighting. To ensureadditional checks,rays are taken to other stationsalso, wheneverit is possible. Figure 14.9 shows a schemeof plane table survey of closed area.This method can be used for open traverses also. Fig. 14.9. Planetable traversing 1 4.3.4 Resection This method is just opposite to the method of intersection. In the method of intersection, the plotted position of stations are known and the plotted position of objects are obtained by intersection. In this method the plotted position of objects are known and the plotted position of station is obtained. If a, b and c are the plotted positions of objects A, B and C respectively,to locate instrument station P on the paper, the orientation of table is achieved with the help of a, b, c and then resectorsAa, Bb, Cc are drawn to get the p , the plotted position of P. Hence in the resection method major work is to ensure suitable orientation by any one of the methods.The following methodsare employed in the method of resection: (a) by compass (b) by back sighting (c) by solving two point problem (d) by solving three point problem. (a) Resectionafter Orientation by Compass:Let a and b be the plotted positions of A and B of two well dened points in the field. Keeping the through compass along north direction marked on the drawing sheettable is oriented on station P, the position of which is to be found on paper. The resectorsAa and Bb [Fig. 14.10] are drawn to locate p the plotted position of station point P. This method gives satisfactory results, if the area is not inuenced by local attractions. It is used for small scale mapping only. \ /9 Q \\Q&S \&o /in /0 \ /' I K O Y9 I 12? I <2? \\\\ I .\ Q I,,z Station P Fig. 14.10. Resectionafter orientation with compass (b) Resectionafter Orientation by Back Sighting: Figure 14.11 shows the schemeof resection after orientation by back sighting. From stationA, the position of B is plotted as b and ray hasbeentakento station P as ap. Then plane table is set at P and oriented by back sighting A, line AP is not measuredbut the position of P is obtainedon the paperby taking resectionBb. 4- Back sight Stn A Stn P Fig. 14.11. Resectionafter back sighting .............. (c) Resectionafter Solving Two Point Problem: The problem of nding plotted position of the stationpoint occupiedby the plane table with the help of plotted positions of two well defined points is known as solving two point problem. Figure 14.12showsthe schemeof solving this. Let A and B be two well defined points like lightening conductor or spire of church, the plotted positions a and b already known. Now the problem is to orient the table at P so that by resection its plotted position p can be obtained.The following stepsmay be followed to solve this problems: (i) Select a suitable point Q near P such that the anglesPAQ and PBQ are not accute. (ii) Roughly orient the table at Q and draw the resectorsAa and Bb to get the point q. (iii) Drawtheray qp andlocatepl with estimateddistanceQP. (iv) Shift the plane table to P and orient the table by back sighting to Q. (v) Draw the resectorAa to get p. (vi) DrawtheraypB. Let it intersectline bq at bl. (vii) Thepointsb andb1arenot coincidingdueto theangularerrorin theorientationof table.The angle bab, is the angular error in orientation. To correct it, * Fix a ranging rod at R along ab, * Unclamp the table and rotate it till line ab sights ranging rod at R. Then clamp the table. This gives the correct orientation of the table which was used in plotting the points A and B. (viii) The resectorsAa and Bb are drawn to get the correct plotted position p of the station P (d) Resectionafter Solving ThreePoint Problem: Locating the plotted position of a station point using observationsto three well dened points whose plotted positions are known, is called solving three point problem. Let A, B, C be three well defined objects on the field whose plotted positions a, b and c are known. Now the problem is to locate plotted position of the station point P. Any one of the following methods can be used. (i) Mechanical (Tracing paper) method, (ii) Graphical method, or (iii) Trial and error method (Lehmans method). (i) Mechanical Method: This method is known as tracing paper method since it needsa tracing paper.The method involved the following steps [Ref. Fig. 14.13.] * Set the table over station P and by observationapproximately orient the table. * Fix the tracing paper on the plane table and select P approximately, say asp. From p, draw p A, p B andp C. Theselines may not passthrough the plotted positions a, b and c since the orientation is not exact. * Loosen the tracing paper and rotate it so that the rays passthrough respectivepoints a, b and c. Now prick the point p to get the plotted position p of the station P. * Keep the alidade along pa and sight A. Then clamp the table. This is correct orientation. Check the orientation by observing along pb and pc. (ii) Graphical Method: The following two graphical methods are available to solve three point problem: * Bessels solution * Method of perpendiculars. BesselsSolution: It involves the following steps: 1. Keep the bevelled edge of alidade along ba and sight object at A. Clamp the table and draw bc along the line bc [Fig. 14.14 (a)]. 2. Keep bevelled edge of alidade along ab, unclamp the table and sight B. Clamp the table. Draw line ac intersecting be at d [Fig. 14.14(b)]. 3. Keep the alidade along dc and bisect C. Clamp the table [Fig. 14.14(c)]. This gives the correct orientation. 4. Draw resectorsto get p. B B A./\ \\\ \\ . .I / C / / A///'\ I IC Ill I E@ Stn P / , B A \\\ C . StnP Stn P (3) (b) (C) (d) Fig. 14.14. Graphical solution (Besselsmethod) Method of Perpendiculars This is another graphical method. It involves the following steps [Ref. Fig. 14.15]. 1. Draw line ae perpendicularto ab. Keep alidade along ea and turn the table till A is sighted. Clamp the table and draw the ray Bb to intersect the ray Aac at e [Fig. 14.15(a)]. 2. Draw cf perpendicularto be and clamp the table when fcC are in a line. Draw Bb to intersect Ccfat F [Fig 14.15(b)]. (b) Fig. 14.15. Method of perpendicularsof solvethree point problem 3. Join cf drop bp perpendicularto ef to get the plotted position p. 4. Orient the table suchthat pbB are in a line. Clamp the table to place it in correct orientation. ResectionsAa and Cc may be used to check the orientation. Trial and Error Method This methodis alsoknown as triangle of error methodand LehmansMethod. It involves the following steps: 1.Set the table over point Pand orient the table approximately, just by observation. 2. Draw the rays aA, bB and cC [Fig. 14.16]. If the orientation was perfect,the three rays would have intersectedat a single point, i. e. at point p. Otherwise a triangle of error is formed. 3. To eliminate the triangle of error an approximateposition, ray p, is selectednearthe triangle of error. Then keeping alidade along pa object A is sighted and the table is clamped. Draw the resectors cC and bB to check the orientation. 4. Above step is repeatedtill triangle of error is eliminated. B Triangle of error Fig. 14.16 Lehman presented the following guidelines to select p so that triangle of error is eliminated quickly. Rule 1: The distanceof point sought p is in the sameproportion from the correspondingrays as the distanceof those from the plane table station. Rule 2: The point sought p is on the sameside of all the three resectors. Dening the triangle ABC on the field as great triangle and the circle passingthrough them as great circle, from the above two rules of Lehman, the following subrules may be drawn [Ref. Fig. 14.17]. Fig. 14.17 * If P lies within the greattriangle,thepoint p is within thetriangleof error(pl in theFig. 14.17). * If the plane table station P lies outside the great triangle the point sought p is outside the triangleof errors(p2). * If the P is on the greatcircle,the correctsolutionis impossible(p3andp * If P is outside the great circle, p is nearer to the intersection of rays to the nearesttwo points(P5). * If point P is outside the great circle and the two rays drawn are parallel to each other the point soughtis outsidetheparallellinesandon the samesideof thethreerays(P6). l14.4 ERRORS IN PLANE TABLESURVEYING The errors may be grouped into the instrumental and personalerrors. 1 4.4.1 Instrumental Errors 1. The surfaceof plane table not perfectly plane. 2. Bevelled edge of alidade not straight. 3. Sight vanesof alidade not perfectly perpendicularto the base. 4. Plane table clamp being loose. 5. Magnetic compassbeing sluggish. 6. Drawing sheetbeing of poor quality. 14.4.2 Personal Errors 1. Centering errors Levelling errors . Orientation errors .\.°.V.-tr-*9. Sighting errors Errors in measurement Plotting errors Errorsdue to instability of tripod. I14.5 ADVANTAGES AND LIMITATIONS OFPLANE TABLESURVEY Advantagesare 1. Possibility of omitting measurementis eliminated. The surveyor can comparethe plotted work in the field then and there only. Irregular objects are plotted more accurately,since they are seenwhile plotting. .°°\.°.U:&# Booking errorsare eliminated. Local attractions do not inuence the plotting. No great skill is required to produce satisfactory maps. . Method is fast. No costly instrumentsare required. Limitations are 1. Survey cannot be conductedin wet weather and rainy days. 2. Plane table is cumbersomeand heavy to carry. 3. It needsmany accessories. 4. It is less accurate. 5. Reproduction of map to different scale is difficult. IQUESTIONS What are the accessoriesrequired for plane table survey? . Briey explains setting and orienting plane table at first station. S"P.°N." Explain any two methodsof orienting plane table in subsequentstations. Describe any two methodsof drawing details in a plane table survey map. How do you nd the distancebetweentwo inaccessiblepoints by planetable surveying?Explain. 6. Explain the following terms used in plane table surveying: (i) radiation (ii) intersection (iii) resection. 7. Explain the two point problem and its solution. 8. Statethree point problem in plane table surveying and explain any one method to solve it. 9. List the Variouspossible errors in plane table surveying. 10. What are the advantagesand limitations of plane table surveying? .im: and leveIIing Elevation measurementsinvolve measurementsin vertical plane. It is also known as levelling. It may be dened as the art of determining the elevations of given points above or below a datum line or establishing given points of required heights above or below the datum line. I15.1 OBJECT ANDUSES OFLEVELLING As statedin the definition of levelling, the object is (i) to determinethe elevations of given points with respectto a datum (ii) to establishthe points of required height above or below the datum line. Uses of levelling are (i) to determine or to set the plinth level of a building. (ii) to decide or set the road, railway, canal or sewageline alignment. (iii) to determine or to set various levels of dams, towers, etc. (iv) to determine the capacity of a reservoir. |15.2 TERMSUSEDIN LEVELLING Before studying the art of levelling, it is necessaryto clearly understandthe following terms used in levelling: 1. Level Surface: A surfaceparallel to the mean spheroidof the earth is called a level surface and the line drawn on the level surfaceis known as a level line. Hence all points lying on a level surface are equidistant from the centre of the earth. Figure 15.1 shows a typical level surface. 209 Mean spheroid of earth \ I ' : Centre ofearth \ : I Fig. 15.1. A levelsurface 2. Horizontal Surface: A surfacetangentialto level surfaceat a given point is called horizontal surfaceat that point. Hence a horizontal line is at right anglesto the plumb line at that point [Ref. Fig. 15.2]. Centre of earth Fig. 15.2. Vertical and horizontal lines 3. Vertical Line: A vertical line at a point is the line connecting the point to the centre of the earth. It is the plumb line at that point. Vertical and horizontal lines at a point are at right anglesto each other [Fig. 15.2]. 4. Datum: The level of a point or the surface with respect to which levels of other points or planes are calculated,is called a datum or datum surface. 5. Mean Sea Level (MSL): MSL is the averageheight of the seafor all stagesof the tides. At any particular place MSL is establishedby finding the mean sea level (free of tides) after averaging tide heights over a long period of at least 19 years. In India MSL used is that establishedat Karachi, presently,in Pakistan.In all important surveysthis is used as datum. 6. Reduced Levels (RL): The level of a point taken asheight abovethe datum surfaceis known as RL of that point. 7. Benchmarks: A benchmarkis a relatively permanentreferencepoint, the elevation of which is known (assumedor known w.r.t. MSL). It is used as a starting point for levelling or as a point upon which to close for a check. The following are the different types of benchmarks used in surveying: (a) GTS benchmarks (b) Permanent benchmarks (c) Arbitrary benchmarksand (d) Temporary benchmarks. (a) GTS Benchmark: The long form of GTS benchmark is Great Trigonometrical Survey benchmark.Thesebenchmarksareestablishedby nationalagency.In India, the department of Survey of India is entrusted with such works. GTS benchmarksare establishedall over the country with highestprecision survey,the datumbeing meansealevel. Abronze plate provided on the top of a concretepedastalwith elevation engravedon it servesas benchmark.It is well protectedwith masonry structurebuilt around it so that its position is not disturbed by animals or by any unauthorised person. The position of GTS benchmarksare shown in the topo sheetspublished. (12)Permanent Benchmark: These are the benchmarks establishedby state government agencieslike PWD. They are establishedwith referenceto GTS benchmarks.They are usually on the corner of plinth of public buildings. (c) Arbitrary Benchmark: In many engineering projects the difference in elevations of neighbouring points is more important than their reducedlevel with respectto mean sea level. In such casesa relatively permanentpoint, like plinth of a building or corner of a culvert, are taken as benchmarks, their level assumed arbitrarily such as 100.0 In, 300.0 In, etc. (d) Temporary Benchmark: This type of benchmark is establishedat the end of the days work, so that the next day work may be continued from that point. Such point should be on a permanentobject so that next day it is easily identified. l15.3 LEVELLING INSTRUMENTS A level is an instrument giving horizontal line of sight and magnifying the reading at a far away distance. It consistsof the following parts: (i) A telescopeto provide a line of sight (ii) A level tube to make the line of sight horizontal and (iii) A levelling head to level the instrument. The following types of levels are available: (i) Dumpy level (iii) Cookes reversible level (v) Tilting level and (ii) Wye (or, Y) level (iv) Cushings level (vi) Auto level. 15.3.1 Dumpy Level It is a short and stout instrument with telescopetube rigidly connectedto the vertical spindle. Hencethe level tube cannot move in vertical plane. It cannot be removed from its support. Hence it is named as dumpy level. The telescoperotatesin horizontal plane in the socketof the levelling head.A bubble tube is attachedto the top of the telescope.Figure 15.3 shows a typical dumpy level. Plate 15.1 shows its photograph. Plate 15.1 Dumpy level 6 2at 4 m E'12 1. 2. 3. 4. 5. Telescope Eyepiece Shade Objective end Longitudinal bubble tube 6. Transverse bubble tube 7. 8. 9. 10. 11. Bubble tube adjusting screws Diaphragm adjusting screws Focusing screws Foot screws Upper parallel plate (tribrach) 12. Foot plate (Trivet stage) Fig. 15.3. Dumpy level Telescopeis a tube with object glassand eyepiece.Object glasscanbe adjustedusing the focussing screw before sighting the graduatedstaff held on the object. Eyepiececan be adjustedby rotating it to seethat parallel is removed and cross hairs appearsdistinctly. Eyepieceonce adjustedneedsno change as long as the sameperson takes the readings. Level tube is a glass tube with slightly curved shapeprovided over the level tube. The tube is filled with ether or alcohol leaving a little air gap, which takes the shapeof a bubble. The air bubble is always at the highest point. The level tube is fixed with its axis parallel to telescopetube, so that when bubble is centred,the telescopeis horizontal. The tube is graduatedon either side of its centreto estimate how much the bubble is out of centre. The glass tube is placed inside a brasstube which is open from top and on lower side it is xed to telescopetube by meansof capstonheadednuts. The bubble tube is adjustedwith thesenuts, if it is out of order. Levelling head consistsof two parallel plates with three foot screws.The upper plate is known as tribratch plate and the lower one as the trivet. The lower plate can be screwedon to the tripod stand. By adjusting the screwsthe instrument can be levelled to get perfect horizontal line of sight. Dumpy level is to be fitted to a tripod stand to use it in the eld. The tripod stand consists of three legs connectedto a headto which the lower plate of level can be tted. The lower side of the legs are provided with metal shoesto get good grip with ground. Plate 15.2 shows typical level stands. Plate 15.2 Levellingstands (adjustable and non-adjustable) 15.3.2 Wye or Y-Level In this type of level, the telescopeis supportedin two Yshapedsupportsand can be fixed with the help of curved clips. Clips can be openedand telescopecan be reversedend to end and fitted. The advantage of this level is someof the errors eliminated, if the readingsare taken in both the direction of telescope. 1 5.3.3 Cookes Reversible Level In this instrumentthe telescopeis supportedby two rigid socketsinto which telescopecanbe introduced from either end and then screwed.For taking the readings in the reversedposition of telescope,the screw is slackenedand then the telescopeis taken out and reversedend for end. Thus it combines the rigidity of dumpy level and reversibility of Ylevel. 15.3.4 Cushings Level In this reversing of telescopeend for end is achievedby interchanging the eyepieceand the objective piece since both collars are exactly the same. 15.3.5 Tilting Level In this, telescopecan be tilted through about four degreeswith the help of a tilting screw.Hencebubble can be easily centered.But it needscentering of the bubble before taking every reading. Hence it is useful, if at every setting of the instrument number of readingsto be taken are few. 1 5.3.6 Auto Level The autolevel or the automaticlevel is a self aligning level. VV1thina certain range of tilt automatic levelling is achievedby an inclination compensatingdevice. The operational comfort, high speedand precision are the advantagesof this instrument. I15.4 LEVELLING STAFF Along with a level, a levelling staff is also required for levelling. The levelling staff is a rectangularrod having graduations.The staff is provided with a metal shoesat its bottom to resist wear and tear. The foot of the shoerepresentszero reading. Levelling staff may be divided into two groups: (i) Self reading staff (ii) Target staff. (i) Self reading staff: This staff readingis directly readby the instrumentmanthrough telescope. In a metric system staff, one metre length is divided into 200 subdivisions, each of uniform thickness of 5 mm. All divisions are marked with black in a white background.Metres and decimetresare written in red colour [Fig 15.4 (a)]. The following three types of self reading staffs are available: (a) Solid sta: It is a single piece of 3 m. (b) Folding sta: A staff of two pieces eachof 2 m which can be folded one over the other. (c) Telescopicsta: A staff of 3 pieces with upper one solid and lower two hollow. The upper part can slide into the central one and the central part can go into the lower part. Each length can be pulled up and held in position by meansof brass spring. The total length may be 4 m or 5 m [Fig. 15.4 (b)]. lllllIIlllllllIIII E WK) _. (a) Self-readingstaff (b) Telescopicstaff (c) Target staff Fig. 15.4 (ii) Target staff: If the sighting distance is more, instrument man finds it difficult to read self reading staff. In such casea target staff shown in [Fig. 15.4 (c)] may be used.Target staff is similar to self reading staff, but provided with a movable target. Target is a circular or oval shape,painted red and white in alternatequadrant.It is fitted with a Vernierat the centre. The instrument man directs the person holding target staff to move the target, till its centreis in the horizontal line of sight. Then target man readsthe target and is recorded. l15.5 METHODS OF LEVELLING not accuratemethod since the atmosphericpressuredependsupon seasonand temperaturealso. It may be used in exploratory surveys. 15.5.2 Hypsometric Levelling This is based on the principle that boiling point of water decreaseswith the elevation of the place. Hence the elevation difference between two points may be found by noting the difference in boiling point of water in the two places.This method is also useful only for exploratory survey. 15.5.3 Direct Levelling It is common form of levelling in all engineeringprojects. In this method horizontal sight is taken on a graduatedstaff and the difference in the elevation of line of sight and ground at which staff is held are found. Knowing the height of line of sight from the instrument station the difference in the elevationsof instrument station and the ground on which staff is held can be found. This method is thoroughly explained in next article. 1 5.5.4 Indirect Methods In this method instruments are used to measurethe vertical angles. Distance between the instrument and staff is measuredby various methods.Then using trigonometric relations,the difference in elevation canbe computed.This is consideredbeyond the scopeof this book. One can find details of suchmethods in books on surveying and levelling. l15.6 TERMSUSEDIN DIRECT METHODOFLEVELLING The following terms are used in direct method of levelling: (i) Plane of Collimationz It is the reduced level of plane of sight with respect to the datum selected.It is also known as height of instrument. It should not be confused with the height of telescopefrom the ground where the instrument is set. (ii) Back Sight (BS): It is the sight taken on a level staff held on the point of known elevation with an intension of determining the plane of collimation. It is always the first reading after the instrument is set in a place. It is also known asplus sight, sincethis reading is to be added to RL of the point (Benchmark or changepoint) to get plane of collimation. (iii) Intermediate Sight (IS): Sights taken on staff after back sight (rst sight) and before the last sight (fore sight) areknown as intermediatesights.The intension of taking thesereadings is to find the reduced levels of the points where staff is held. These sights are known as minus sights since the IS reading is to be subtractedfrom plane of collimation to get RL of the point where staff is held. (iv) Fore Sight (FS): This is the last reading taken from the instrument station before shifting it or just before ending the work. This is also a minus sight. (v) Change Point (CP): This is also known as turning point (TP). This is a point on which both fore sights and back sights are taken. After taking fore sight on this point instrument is set at someother convenient point and back sight is taken on the staff held at the samepoint. The two readings help in establishing the new plane of collimation with respect to the earlier datum.Sincethereis time gapbetweentaking the two sightson the changepoint, it is advisable to select changepoint on a well defined point. l15.7 TEMPORARY ADJUSTMENTS OFA LEVEL The adjustmentsto be made at every setting of the instrument are called temporary adjustments.The following three adjustmentsare required for the instrument wheneverset over a new point before taking a reading: (1') Setting (ii) Levelling and (iii) Focussing. 15.7.1 Setting Tripod standis set on the ground firmly so that its top is at a convenient height. Then the level is fixed on its top. By turning tripod legs radially or circumferentially, the instrument is approximately levelled. Some instrumentsare provided with a less sensitive circular bubble on tribrach for this purpose. 15.7.2 Levelling The procedureof accuratelevelling with three levelling screw is as given below: (i) Loosen the clamp and turn the telescopeuntil the bubble axis is parallel to the line joining any two screws [Ref. Fig. 15.5 (a)]. C C (3) (b) Fig. 15.5 (ii) Turn the two screwsinward or outward equally and simultaneouslytill bubble is centred. (iii) Turn the telescopeby 90° so that it lies over the third screw [Fig. 15.4 (b)] and level the instrument by operating the third screw. (iv) Turn back the telescopeto its original position [Fig. 15.5 (a)] and check the bubble. Repeat steps(ii) to (iv) till bubble is centred for both positions of the telescope. (v) Rotate the instrument by 180°. Check the levelling. 15.7.3 Focussing Focussingis necessaryto eliminate parallax while taking reading on the staff. The following two steps are required in focussing: (i) Focussing the eyepiece:For this, hold a sheetof white paper in front of telescopeand rotate eyepiecein or out till the cross hairs are seensharpand distinct. (ii) Focussing the objective: For this telescopeis directed towards the staff and the focussing screw is turned till the reading appearsclear and sharp. I15.8 TYPES OF DIRECT LEVELLING The following are the different types of direct levelling: (i) Simple levelling (ii) Differential levelling (iii) Fly levelling (iv) Prole levelling (v) Cross sectioning and (vi) Reciprocal levelling. 15.8.1 Simple Levelling It is the method used for finding difference betweenthe levels of two nearby points. Figure 15.6 shows one such casein which level of A is assumed,say 200.00 m. RL of B is required. 200.00 A Fig. 15.6 RL ofA = 200.00 In Back sight on A = 2.7 m. Plane of collimation for setting at station = 200 + 2.7 = 202.7 m Fore sight on B = 0.80 m ' RL of B = 202.7 0.80 = 201.9 m It maybe notedthattheinstrumentstationL1neednot be alongtheline AB (in plan)andRL of L1 do not appearin the calculations. 15.8.2 Differential Levelling If the distancebetweentwo points A and B is large, it may not be possibleto take the readingson A and B from a single setting. In such situation differential levelling is used. In differential levelling the instrument is set at more than one position, eachshifting facilitated by a changepoint. Figure 15.7 showsa schemeof such setting. A(200.00) (a) Elevation A0 B. §_ , B . CP1. L2 (b) Plan Fig. 15.7 RL of A is 200.00m. Instrumentis setup at L1 andbacksighton A is 1.35m. Thefore sighton changepoint CP1is 1.65m. Theninstrumentis shiftedto L2 andbacksighton CPIis 1.40m. Foresight on CP2is 1.70m. After this instrumentis shiftedto L3 andbacksighton CP2is 1.3m. Thework ended with a fore sight of 1.85 m on B. The RL of B is to be found. RL ofA = 200.00 m Back sight on A = 1.35 m Planeof collimationat L1 = 200+ 1.35= 201.35m Foresighton CPI = 1.65in RL of CPI = 201.35-1.65 = 199.70In Backsightto CP1from L2 = 1.40 Planeof collimationat L2 = 199.70+ 1.40= 201.10In Foresightto CP2= 1.70m .. RLofCP2=201.10 1.70: 199.40m Backsightto CP2from L3 = 1.30m Planeof collimationat L3 = 199.40+ 1.30= 200.70m Fore sight to B = 1.85 m RL of B = 200.70 - 1.85 = 198.85 In Ans. If thereareintermediatesightto thepointsE1andE2,theRL of thosepointsmaybe obtainedby subtractingreadingsfor E1andE2from the corresponding planeof collimations. Booking and Reducingthe Levels The booking of readings and reducing the levels can be carried out systematically in the tabular form. There are two such methods: (i) Plane of collimation method (ii) Rise and fall method. For the aboveproblem,with intermediatesightsto E1= 0.80m andE2= 0.70m is illustrated below by the both methods. Table 15.1. Booking and reducing levels by plane of collimation method Station Reading BS A Plane of IS FS 1.35 201.35 B1 RL Remarks Collimation 0.80 200.00 Benchmark 200.55 Plinth of building CPI 1.40 1.65 E2 201.10 0.70 199.70 CP1 200.40 Plinth of building CP2 1.30 1.70 B 200.70 1.85 Check 2 BS = 4.05 2 FS = 5.20 199.40 CP2 198.85 B Diff in RL of A and B 2 BS - 2 FS = - 1.15 (Fall) = 198.85 - 200.00 = -1.15 In this method note the following: 1. Plane of collimation for first setting = RL of BM + BS 2. Subtract IS from plane of collimation to get RL of intermediatestation and subtractFS from plane of collimation to get RL of changepoint. 3. Add back sight to RL of changepoint to get new plane of collimation. 4. Check: 2 BS - 2 FS = RL of Last point - RL of first point. If it is -Ve, it is fall and if +Ve it is rise. Table 15.2. Booking and reducing level by rise and fall method Station A BS IS FS Rise Fall 1.35 0.80 1.40 0.55 1.65 0.70 1.30 2 BS = 4.05 Check: ZBS -ZFS 0.70 Remarks 200.00 Benchmark 200.55 E1 199.70 CP1 200.40 B2 CP2 1.70 1.00 199.40 1.85 0.55 198.85 2 FS = 5.20 = -1.15 0.85 RL 2Rise-2Fall 2 Rise = 1.25 = -1.15 B 2 Fall = 2.40 RLoflast point-RLof first point = -1.15 Note the following: 1. FromA to E1,difference= 1.35 0.80= 0.55,rise 2. FromE1to CPI, difference= 0.80~ 1.65= 0.85,fall 3. FromCPI to E2,difference= 1.40 0.70= 0.70,rise 4. FromE2to CP2,difference= 0.70- 1.70 = -1.00, fall 5. FromCP2to B, difference= 1.30 1.85 = 0.55,fall. 15.8.3 Fly Levelling If the work site is away from the benchmark,surveyor startsthe work with a back sight on the benchmark by setting instrument at a convenient point. Then he proceedstowards the site by taking fore sights and back sights on a number of changepoints till he establishesa temporary benchmark in the site. Rest of the levelling work is carried out in the site. At the end of the work again levelling is carried out by taking a set of convenient changepoints till the bench work is reached.This type of levelling in which only back sight and fore sights are taken, is called y levelling, the purposebeing to connect a benchmark with a temporary benchmark or vice versa. Thus the difference between y levelling and differential levelling is only in the purpose of levelling. 15.8.4 Prole Levelling This type of levelling is known as longitudinal sectioning. In high way, railway, canal or sewageline projects profile of the ground along selected routes are required. In such cases,along the route, at regular interval readings are taken and RL of various points are found. Then the section of the route is drawn to get the profile. Figure 15.8(a) showsthe plan view of the schemeof levelling and Fig. 15.8 (b) showsthe profile of the route. For drawing prole of the route, vertical scaleis usually larger compared to scalefor horizontal distances.It gives clear picture of the profile of the route. CP212 13 14 15 (b) Fig. 15.8 The typical pageof field book for this work will be having an additional column to note distances as shown in Table 15.3. Table 15.3. Pageof level book for prole levelling Station Distance BS IS FS Plane of RL Remark Collimation 15.8.5 Cross-Sectioning In many engineering projects, not only longitudinal profile but also the prole of crosssectionsat regular intervals are required.Theseproles help in calculating the earth works involved in the projects. Figure 15.9 showsthe schemeof such work in which longitudinal profile is found by taking readingsat 20 In interval along chain lines AB, BC and readingsare taken at an interval of 3 In on either side.The distanceson the crosssectionsare treatedas left or right of the lines as they are found while facing the forward station of survey.The crosssectional length dependsupon the nature of the project. Fig. 15.9 Table 15.4 shows a page of level book required for this type of levelling. Table 15.4. A typical page book for crosssectionlevelling Station Distance in m L C Readings R BM 0 L1 3 L2 6 L3 9 R1 3 R2 6 BS IS Plane of FS Collimation RL Remarks R3 9 20 L1 3 L3 6 L3 9 R1 3 R3 6 R3 9 Checked. 15.8.6 Reciprocal Levelling In levelling, it is better to keep distanceof back sight and fore sight equal. By doing so the following errors are eliminated: (i) Error due to nonparallelism of line of collimation and axis of bubble tube. (ii) Errors due to curvature and refraction. But in levelling acrossobstacleslike river andravine, it is not possibleto maintain equaldistances for fore sight and back sight. In such situations reciprocal levelling as describedbelow is used: Level line Line of sight Level line Fig. 15.10 (i) Referring to Fig. 15.10 (a). Since A is very close,errorin readingat A is negligible.Hencehais correct reading. Let errorin hbbe e, Thencorrectreadingat B = hb e Differencein elevations= H = ha (hb e) (i) (ii) Referringto Fig. 15.10(b), sinceB is very closeto instrument,hb,canbe takenas correct reading. Correctreadingat A = ha e Differencein elevationsH = (ha e) hb (ii) From equations(i) and (ii) we get, 2H=ha(hbe)+(hae)hb =(ha +ha) (hb +hb) H = (ha+ha)-(h,, +h,,) (15.1) 2 Thus, the true difference in the elevations of the two points is equal to the mean of the two apparentdifferences in the elevations. I Example 15.1: Thefollowing sta readings were observedsuccessivelywith a level. The instrument has been shifted after the second and fth reading. 0.675, 1.230, 0.750, 2.565, 2.225, 1.935, 1.835, 3.220. Therst reading was with sta held on benchmark of RL 100.000 m. Enter the readings in a page of level book and calculate the RL of all points. Apply arithmetic checks.Useplane of collimation method. Solution: It is carried out as shown in Table 15.5. Table Station BS IS FS 15.5 Plane of RL Remarks 100.675 100.00 BM of RL = 100.00 100.195 99.445 Collimation 0.675 0.750 1.230 2.565 97.630 1.935 2.225 99.905 1.835 97.970 CP2 98.070 3.220 2 BS = 3.360 CP1 2 FS = 6.675 2 BS -2 FS = « 3.315 (Fall) 96.685 Last RL = Last Point first RL 3.315 (Fall) I Example 15.2: Reducethe levels in example 15.] by rise andfall method. Solution: It is carried out as shown in Table 15.6 below: Checked Table Station BS IS 15.6 FS Rise Fall RL Remarks 100.00 BM 0.555 99.445 CP1 1.815 97.630 0.675 0.750 1.230 2.565 1.935 2.225 1.835 0.340 97.970 0.100 98.070 3.220 2 3.360 ZBSZFS = 1.385 6.675 3.315 0.440 ZRiseZFal1= 96.685 CP2 Last point 3.755 3.315 RLof1ast~RLofrst = point 3.315 Checked. I Example 15.3: Thefollowing consecutivereadings were taken with a level on a sloping ground at a commoninterval of 20 m. 0.600, 1.235, 1.860, 2.575, 0.235, 0.915, 1.935 and 2.870. The reducedlevel of therst point was 192.125m. Rule out a page of level book and enter the above readings. Calculate the reducedlevels of points. Apply the check. Solution: Table 15.7 shows entries in typical page of level book and method of reducing the levels. Table Distance Station L A 15.7 Readings C R 0.0 BS Plane of IS FS . RL Remarks 192.125 First point . Collimation 0.600 192.725 20.0 1.235 191.149 40.0 1.860 190.865 60.0 2.575 190.150 80.0 0.235 192.490 100.0 0.915 191.810 120.0 2.870 2 BS = 0.600 2 BS 2 IS = 189.855 2 FS = 2.870 Last point RL of last point 2.270 RL of first point = ~ 2.27 Checked I Example 15.4: Reciprocal levelling was conducted with a dumpy level and the following readings were recorded. Instrument near A Sta reading at A B 1.245 B 1.050 1.575 0. 700 Compute the RL 0fB, ifRL 0fA = 218.250 m. ha=1.245 In ha = 1.505m Solution: Difference 111,:1.575In lib = 0.700In in levels of A and B is _ (hah,>+ 2 _ (1.245-1.575) + (1.050 0.700) _ Plane of collimation 2 at A = 218.250 -1-1.245 = 219.495 Elevation of B = 219.495 = 219.485 = 0.01 In In 0.01 In Ans. IQUESTIONS 1. Dene the following terms used in levelling: (ii) Level line (i) Benchmark (iv) Mean sea level. (iii) Changepoint 2. Differentiate between: (i) GTS benchmark and Temporary benchmark (ii) Fore sight and back sight (iii) Plane of collimation and RL of a point (iv) Fly levelling and profile levelling. What are the temporary adjustmentsof dumpy level .7Explain how they are performed. Write short notes on Barometric levelling and Hypsometry. >.°E"PE* Explain differential levelling. Write short note on reciprocal levelling. The following staff readings were taken with a level, the instrument having been moved after third and sixth reading: 2.200 1.620 0.980 2.250 2.840 1.280 0.600 1.960 1.450 The RL of first point is 100.00In. Rule out a page of level book and enter the above readings. Calculate the RL of all points. Apply the checks. [Ansz RL of last point 101.34.] [Note. First, fourth and seventhreadingsare back sights.Third, sixth and last readingsare fore sights]. Tools atsurveying Theodolite is an instrument which replaced compassand level. It can measureboth horizontal and vertical angles.If telescopeis kept at zero reading of vertical angle it servesas an ordinary level. In this modern era of electronics equipmentshave come up to measurethe distancesto relieve surveyor from chaining long lines. Total station is another modern survey equipment which combinesthe featuresof theodolite and electromagneticdistance measurement(EDM) instruments. Global positioning system is an instrument, which establishesglobal position of the station making use at least 4 satellite stations. In this chapter all thesemodern tools of surveying are briefly explained. I16.1 THEODOLITE It is a commonly used instrument for measuringhorizontal and vertical angles.It is usedfor prolonging a line, levelling and even for measuringthe distancesindirectly (techeometry).Using verniers angles can be read accuratelyup to 20. Precisetheodolites are available which can read anglesup to even 1" accuracy.They use optical principle for more accurateinstruments.Now a days electronic theodolites are also available which display the angles. In this article construction and use of Verniertheodolite is explained. 1 6.1 .1 Parts of a Vernier Theodolite Figure 16.1 shows a sectional view of a typical Verniertheodolite and plate 16.1 shows photograph of such theodolite. Main parts of such a theodolite are: 1. Telescope:A telescopeis mounted on a horizontal axis (trunnian axis) henceit can rotate in vertical plane. Its length varies from 100 mm 175 mm and its diameteris 38 mm at objective end. Its functions is to provide a line of sight. 226 . Telescope . Trunnian axis Vernier frame Standards or A-Frame Upper plate Lower plate Vernier Plate level 10. 9°..°.°:".°°' 11. 12. 13. 14. Foot crews Levelling head Tripod head Tripod Plumb bob Altitude level Focussing screw 16. Vertical circle 15. Fig. 16.1. Sectionalview ofa transit theodolite 2. Vertical Circle: A vertical circle graduatedup to an accuracy of 20 is rigidly connectedto the telescopeand hencemoves with it when the telescopeis rotated in vertical plane. The graduationsare in quadrantalsystem,0-0 line being horizontal (Ref. Fig. 16.2). Fig. 16.2 3. Vernier Frame: It is a Tshapedframe (Fig. 16.3)consistingof a vertical arm and a horizontal arm. \V1ththe help of the climping screwsthe vertical frame and hencethe telescopecan be clamped at desired angle. Vertical frame is also known as T-frame or index frame. The Vernier arm is known as index arm. At the ends it carries verniers C and D so as to read graduationson vertical circle. They are provided with glass magniers. Altitude bubble tube is fitted over the horizontal arm. J-- Altitude bubble mr Trunnian axis Horizontal arm Vertical arm rciip screw » 0o 53¢ Fig. 16.3 4. Standards or A-Frame: The frames supporting telescopeare in the form of English letter A. This frame allows telescopeto rotate on its trunnian axis in vertical frame. The T-frame and the clamps are also fixed to this frame. 5. Upper Plate [Fig. 16.4]: Upper plate supportsstandardson its top surface.On lower side it is attachedto a inner spindle which rotates in the outer spindle of lower plate. Using upper clamp, upper plate can be clampedto lower plate. Using tangent screws,it is possibleto give slight relative motion betweenthe two plates,evenafter clamping.Two diametrically opposite verniers A and B fixed to upper plate help in reading horizontal circle graduations.They are provided with magnifying glasses. B s.\\\.\\\\\%/ Vernier _.=._ /IIIIII/// lnnerspindle . Outer spindl g\ §V w\///g.\\\\\\V Lowerclampf Fig. 16.4 . Lower Plate: The lower plate, attachedto the outer spindle carries a graduatedcircle at its bevelled edge. Graduationsare up to an accuracy of 20. It can be clamped at any desired position using lower clamps. If upper clamp is locked and the lower one is loosenedthe two plates rotate together. If the upper clamp is loosenedand lower clamp locked, upper plate alone rotates.This mechanismis utilised in measuringhorizontal angle. . Plate Level: One or two plate level tubes are mounted on the upper plate. If the two level tubes are provided they will be at right angles to each other one of them being parallel to trunnion axis. Theselevels help in making the vertical axis of the instrument truely vertical. . Levelling Head: It consistsof two parallel triangular plates known as tribratch plates. The upper tribratch plate is provided with three levelling screwseach one carried by a arm of tribratch plate. By operating screwsthe levelling of upper plate and hencetelescopecan be ensured.The lower tribratch can be fitted into a tripod head. . Tripod: Theodolite is always used by mounting it on a tripod. The legs of tripod may be solid or framed. At the lower end the legs are provided with steel shoesto get good grip with the ground. The top of tripod is provided with external screw to which the lower tribratch plate canbe screwed.When not in usetripod headmay be protectedwith a steelcap,provided for this purpose. 10. Plumb Bob: A hook is provided at the middle of lower tribratch plate from which a plumb bob can be suspended.It facilitates exact centering of the theodolite on a station. 11. Shifting Head: It is provided below the lower plate. In this, one plate slides over another over a small area of about 10 mm radius. The two plates can be tightened in the desired position. It facilitates exact centering of the instruments. 12. Magnetic Compass: In sometheodolites a magnetic compassis xed on one of the strands. It is useful if readingsare to be recorded with magnetic north as meridian. 1 6.1 .2 Use of Theodolite Theodolite is usedfor measuringhorizontal and vertical angles.For this the theodolite shouldbe centered on the desired station point, levelled and telescopeis focussed.This processof centering, levelling and focussing is called temporary adjustmentof the instrument. Measurementof Horizontal Angle P Q Fig. 16.5 The procedureis explained for measuringhorizontal angle 6 = PQR at station Q (Ref. Fig. 16.5) 1. Set the theodolite at Q with vertical circle to the left of the line of sight and complete all temporary adjustments. . Releaseboth upper and lower clamps and turn upper plate to get 0° on the main scale.Then clamp main screw and using tangent screw get exactly zero reading. At this stageVernierA reads 0° and Vernier B reads 180°. . Through telescopetake line of sight to signal at P and lock the lower clamp. Use tangent screw for exact bisection. . Releasethe upper clamp and swing telescopeto bisect signal at R. Lock upper clamp and use tangent screento get exact bisection of R. . Read VerniersA and B. The reading of Vernier A gives desired angle PQR directly, while 180° is to be subtractedfrom the reading of Vernier B to get the angle PQR. . Transit (move by 180° in vertical plane) the telescopeto make vertical circle to the right of telescope.Repeatsteps2 to 5 to get two more values for the angle. . The averageof 4 valuesfound for 6, give the horizontal angle.Two Valuesobtainedwith face left and two obtainedwith face right position of vertical circle are called one set of readings. . If more precision is required the angle may be measuredrepeatedly. i.e., after step 5, release lower clamp, sight signal at P, then lock lower clamp, releaseupper clamp and swing the telescopeto signal at Q. The reading of VernierA doubles.The angle measuredby VernierB is also doubled.Any number of repetitions may be madeand averagetaken. Similar readings are then taken with face right also. Finally averageangle is found and is taken as desired angle Q. This is called method of repetition. . Thereis anothermethodof gettingprecisehorizontal angles.It is called method of reiteration. If a number of angles are to be measuredfrom a station this technique is used (Fig. 16.6). VV1thzero reading of VernierA signal at P is sighted exactly and lower clamp and its tangent screware locked.Then 61 is measuredby sightingQ and noted.Then 02, 03 and 04 are measuredby unlocking upper clamp and bisecting signals at R, S and P. The angles are calculated and checked to see that sum is 360°. In each case both Verniers are read and similar processis carried out by changing the face (face left and face right). Fig. 16.6 Measurementof Vertical Angle Horizontal sight is taken as zero vertical angle.Angle of elevationsare noted as +ve anglesand angle of depressionas ve angles. To measurevertical angle the following proceduremay be followed: 1. Complete all temporary adjustmentat the required station. 2. Take up levelling of the instrument with respectto altitude level provided on the A frame. This levelling processis similar to that usedfor levelling dumpy level i.e., first altitude level is kept parallel to any two levelling screwsand operatingthosetwo screwsbubble is brought to centre. Then by rotating telescope,level tube is brought at right angles to the original position and is levelled with the third screw.The procedureis repeated till bubble is centred in both positions. 3. Then loosenthe vertical circle clamp, bisect P and lock the clamp. Readverniers C and D to get vertical angle. Take the averageas the actual vertical angle. I16.2 ELECTROMAGNETIC DISTANCE MEASURING INSTRUMENTS Sun light or artificially generatedelectromagneticwaves consists of waves of different lengths. The spectrumof an electromagneticwave is as shown below: Wavelength (m) Long waves Medium waves Among thesewavesmicrowaves,infrared wavesand visible light wavesareuseful for the distance measurement.In EDM instrumentsthese waves are generated,modulated and then propagated.They are reflected at the point up to which distanceis to be measuredfrom the instrument station and again received by the instrument. The time taken by the wave to travel this 2x distancemay be measuredand knowing the velocity of wave, the distancemay be calculated.However time is too short, measuringthe time taken is difficult. The improved techniquesuse phasedifference method in which the number of completedwave and incompletewave is measured.Knowing the length of wave, distancesarecalculated. Built up microprocessorsprovided in the instrument calculate the distancesand display it by liquid crystal display (LCD). EDM instruments may be classified into the following three types: 1. Micro wave instruments 2. Infrared wave instruments 3. Light wave instruments. 16.2.1 Micro Wave Instruments Theseinstrumentsmake use of micro waves. Such instrumentswere invented as early as 1950 in South Africa by Dr. T.L. Wadley and named them as Tellurometers.The instrument needsonly 12 to 24 V batteries.Hencethey are light and highly portable. Tellurometerscan be usedin day as well as in night. The range of these instrument is up to 100 km. It consists of two identical units. One unit is used as masterunit and the other as remote unit. Just by pressinga button, a masterunit can be convertedinto a remote unit and a remote unit into a master unit. It needstwo skilled personsto operate.A speech facility is provided to each operator to interact during measurements. 16.2.2 Infrared Wave Instruments In theseinstrument amplitude modulated infrared waves are used. Prism reflectors are used at the end of line to be measured.These instrumentsare light and economical and can be mounted on theodolite. With these instruments accuracy achievedis : 10 mm. The range of these instruments is up to 3 km. Theseinstrumentsare useful for most of the civil engineeringworks. Theseinstrumentsare available in the trade names DISTOMAT DI 1000 and DISTOMAT DI 55. 16.2.3 Light Wave Instruments These instruments rely on propagation of modulated light waves. This type of instrument was first developedin Swedenand was namadas Geodimeter.During night its range is up to 2.5 km while in day its range is up to 3 km. Accuracy of theseinstrumentsvaries from 0.5 mm to 5 mm/km distance.These instrumentsare also very useful for civil engineeringprojects. The advantageof using EDM instruments is the speedand accuracy in measurement.Several obstaclesto chaining are automatically overcome when theseinstrumentsare used. I 16.3 TOTALSTATION It is combination of EDM instrument and electronic theodolite. It is also integratedwith microprocessor, electronic data collector and storage system. The instrument can be used to measurehorizontal and vertical anglesas well as sloping distanceof object to the instrument.Microprocessorunit processesthe data collected to compute: 1. averageof multiple angles measured 2. averageof multiple distancemeasured 3. horizontal distance 4. distancebetween any two points 5. elevation of objects and 6. all the three coordinatesof the observedpoints. Data collected and processedmay be downloaded to computers for further processing.Total station is a compact instrument and weighs 50 to 55 N. A person can easily carry it to the field. Total stationswith different accuracies,in anglemeasurementand different rangeof measurements areavailable in the market. Figure 16.7 shows one such instrument manufactured by SOKKIA Co. Ltd. Tokyo, Japan. U1->0Dl\) 6 7 1. Handle 2. Handle securing screw 3. Data input/output terminal (Remove handle to view) 4. Instrument height mark 5. Battery cover 6. Operation panel 7. Tribrach clamp (SET300S/500$/600$: Shifting clamp) 8. Base plate 9. Levelling foot screw 10. Circular level adjusting screws 11. Circular level 12. Display 13. Objective lens 14. Tubular compass slot 15. Optical plummet focussing ring 16. 17. 18. . 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. Optical plummet reticle cover Optical plummet eyepiece Horizontal clamp Horizontal fine motion screw Data input/output connector (Besides the operation panel on SET600/600$) External power source connector (Not included on SET600/600$) Plate level Plate level adjusting screw Vertical clamp Vertical fine motion screw Telescope eyepiece Telescope focussing ring Peep sight Instrument center mark Fig. 16.7. Parts of total station Brief Descriptionof Important Operations DistanceMeasurement.Electronicdistancemeasuring(EDM) instrumentis a majorpartof total station.Its rangevariesfrom 2.8 km to 4.2 km. The accuracyof measurement variesfrom 5 mm to 10 mm per km measurement. They are usedwith automatictargetrecognisers. The distancemeasuredis alwaysslopingdistancefrom instrumentto the object. AngleMeasurements: The electronictheodolitepartof totalstationis usedfor measuringvertical and horizontalangle.For measurement of horizontalanglesany convenientdirectionmay be takenas referencedirection.For verticalanglemeasurement verticalupward(zenith)directionistakenasreference direction.The accuracyof anglemeasurement variesfrom 2 to 6 seconds. Data Processing : Thisinstrument isprovidedwith aninbuiltmicroprocessor. The microprocessor averagesmultiple observations.With the help of slopedistanceand vertical and horizontalangles measured,whenheightof axisof instrumentandtargetsare supplied,the microprocessor computesthe horizontaldistanceand X, Y, Z coordinates.The processoris capableof applyingtemperatureand pressurecorrections to the measurements, if atmospheric temperatureandpressures are supplied. Display:Electronicdisplayunit is capableof displayingvariousvalueswhenrespectivekeysare pressed. The systemis capableof displayinghorizontaldistance,verticaldistance,horizontalandvertical angles,differencein elevationsof two observedpointsand all the three coordinatesof the observed points. ElectronicBook: Eachpoint datacanbe storedin an electronicnotebook (like compactdisc). The capacityof electronicnotebookvariesfrom 2000 pointsto 4000 pointsdata.Surveyorcanunload the datastoredin notebookto computerandreusethe notebook. Use of Total Station The instrumentis mountedon a tripod and is levelledby operatinglevelling screws.Within a small rangeinstrumentis capableof adjustingitselfto thelevelposition.Thenverticalandhorizontalreference directionsare indexedusingonboardkeys.It is possibleto setrequiredunitsfor distance,temperature andpressure(FPS or SI). Surveyorcan selectmeasurement modelike fine, coarse,singleor repeated. When targetis sighted,horizontalandverticalanglesas well as slopingdistancesare measuredandby pressingappropriatekeysthey arerecordedalongwith pointnumber.Heightsof instrumentandtargets canbe keyedin after measuringthemwith tapes.Then processorcomputesvariousinformationabout the pointanddisplayson screen.This informationis alsostoredin the electronicnotebook.At the end of the day or wheneverelectronicnotebookis full, the informationstoredis downloadedto computers. The pointdatadownloaded to thecomputercanbeusedfor furtherprocessing. Therearesoftware like auto civil and autoplotterclubbedwith autocadwhich can be usedfor plottingcontoursat any specied intervaland for plottingcrosssectionalongany specifiedline. Advantagesof UsingTotal Stations The followingare someof the majoradvantages of usingtotal stationoverthe conventionalsurveying instruments: . Field work is carried out very fast. -{>.L»)[\)> . Accuracy of measurementis high. . Manual errors involved in reading and recording are eliminated. . Calculation of coordinatesis very fast and accurate.Even corrections for temperatureand pressureare automatically made. 5. Computerscanbe employedfor map making and plotting contour and crosssections.Contour intervals and scalescan be changedin no time. However, surveyor should check the working condition of the instrumentsbefore using. For this standardpoints may be located near survey office and before taking out instrument for eld work, its working is checkedby observing those standardpoints from the specified instrument station. I16.4 GLOBAL POSITIONING SYSTEM The station points usedin surveying are to be identified before executing any project: For this purpose, surveyors used permanentobjects as reference points and made reference sketchesof station points. Navigators used sun and stars as references. Sometimes when the project is taken up the so called parmanentobject (like building corner) may not exist when the execution of project work is taken up. For navigations weather conditions may obstruct the observations.Now a days this problem is overcome by using an instrument called Global Positioning System (GPS). This was developedby United States defence department and was called as Navigational System with Time and Ranging Global Positioning System (NAVSTAR) or which is now simply known as GPS. There are 24 geostationarysatellitespositioned around the earthby US air force. Thesesatellites areusedasreferencepoints to locateany point on the earth.Thesesatellitesareat an altitude of 20200 km above the earth. The 24 satellites are positioned such that from any point on the earth a minimum of 4 satellites are visible. Auser needsonly GPSreceiver.The receivermeasuresthe travel time of the signalsfrom satellites and calculateposition (latitude and longitude) and the elevation altitude of the station with referenceto a selecteddatum. The advantagesof using GPS are: 1. Can be used in day as well as in night. 2. Intervisibility of the two stationson the earth is not a requirement. 3. Time required to establishthe position of a point is much less. 4. Man power required is less. 5. Accuracy is high. Most expensiveGPS provide accuracieswithin 10 mm. Uses of GPS GPS is very useful in 1. Marine navigation 2. Airborne aviation 3. Surveying of land. 4. Sports such as yatching, hiking. 5. The sophisticationof GPShasimproved somuch that drivers of automobilescanget directions to their destinationseasily on the screen. IQUESTIONS . Explain how you measurehorizontal angle with a theodolite? :"E*!°" What is meant by face left and face right readingsin theodolite survey? What is meant by method of repetition and method of reiteration in theodolite survey? Write short notes on the following: (a) EDM instruments (c) Global positioning system. (b) Total station UNIT - IV MAPPING AND SENSING This page intentionally left blank CHAPTER As statedearlier the aim of surveying is to make plans and mapsto show various objects on the ground at their relative position to suitable scale.Various stepsinvolved in making the plans is explained in this chapter.Contouring is the technique of showing the levels of ground in a plan. This technique is also explained in this article. |17.1 MAPPING After completing field work in chain survey and compass survey lot of office work is involved to preparethe plan of the areasurveyed.In plane table survey office work is less.The office work involved consist of 1. Applying necessarycorrections to measurements . Drawing index plan . Selecting scale Selecting orientation \DOO\l_O Drawing network of survey lines Distributing closing error . Filling in the details . Colouring the map . Drawing graphical scale > G. Writing index. 17.1.1 Applying NecessaryCorrections to Measurements Necessarytape and chain corrections and corrections for local attraction in case of compasssurvey, should be applied to the survey lines measured. 239 17.1.2 Drawing Index Plan On a rough sheetindex plan also known askey plan is drawn. This neednot be to the scalebut distances and directions of network of survey lines should be approximately to a scale.This plan is necessaryto identify the shapeof the areato be plotted. 17.1.3 SelectingScale Depending upon the type of survey, scale should be selected.In general, scale selectedshould be as large as possible, if a range of scale is recommended.It dependsupon the size of the paper as well as largest linear measurementin the field. 17.1.4 SelectingOrientation Looking at index plan, orientation of map is to be decidedso that the map is placed in the middle of the drawing sheet with its larger dimension approximately along the length of paper. North direction is selected and marked. 17.1.5 Drawing Network of SurveyLines Studying index map and orientation of paper,first station point of survey is marked. Starting from here one by one survey line is drawn to the scalein its direction. After drawing all survey lines, it is clearly seen whether the selected scale and orientation appropriate. If necessarythey may be changed and network of survey lines is redrawn. 17.1.6 Distributing Closing Error Sometimesin closed traverse, the last point may not coincide with the plotted position of first point. The difference betweenthe plotted position is known as closing error. Before adjusting closing error it is necessarythat there are no plotting errors. If it is due to field work error and the error is reasonably small it can be adjustedin the office. If error is large, one hasto go back to the field and check doubtful measurements.In the office closing error is adjusteddistributing it suitably to all lines graphically or by mathematicalcalculation of correctedcoordinatesof stationpoints. After adjusting closing error network of survey lines are drawn as per the convention. 17.1.7 Filling in the Details Surveyor has to go through details of one by one survey lines. One by one point of object noted in the eld is marked on the drawing sheetby converting the changeand offsets to the scale.Main scaleand offset scales will be quite useful for this work. After marking the salient points of the objects like building, boundary lines, roads, culvert ends,trees, electric poles etc. the respectivelines are joined to mark the object. The field book will be useful in identifying the objects. If the object is building, the measurementsmay be only for salient points near the survey lines looking at overall dimensionsof the building and scaling down, complete building may be shown in the plan. Thus attending to the eld observationsof each survey lines all details may be shown. Standardconventions should be used in showing the objects. 17.1.8 Colouring the Map If coloured mapsare to be made,the recommendedlight washesof standardshadesas listed is IS 9621989 (Chapter 7) may be applied. 17.1.9 Drawing Graphical Scale As the drawing sheetmay shrink andthe measurementtakenfrom shrunksheetmay misleadthe distances betweenany two objectson the map, it is necessaryto draw a graphical scaleof 150to 270 mm long just over the spacefor indexing the drawing, which is right hand side lower corner of the sheet. 17.1.10 Writing Index Index is the details giving the description of the areaplotted, scaleused,name of leaderof survey party and the person drawing the plan/map. etc. It is normally written in the right hand side lower corner of the drawing sheet.North direction is shown neatly at the right hand side top corner. 17.2 CONTOURS A contour line is a imaginary line which connectspoints of equal elevation. Such lines are drawn on the plan of an area after establishing reduced levels of several points in the area. The contour lines in an areaare drawn keeping difference in elevation of betweentwo consecutivelines constant.For example, Fig. 17.1 shows contours in an areawith contour interval of 1 In. On contour lines the level of lines is also written. Fig. 17.1. Contours 1 7.2.1 Characteristics of Contours The contours have the following characteristics: 1. Contour lines must close, not necessarilyin the limits of the plan. 2. VV1delyspacedcontour indicates at surface. 3. Closely spacedcontour indicates steepground. 4. Equally spacedcontour indicates uniform slope. 5. Irregular contours indicate uneven surface. 6 . Approximately concentric closed contours with decreasingvaluestowards centre (Fig. 17.1) indicate a pond. 7. Approximately concentric closed contours with increasing values towards centre indicate hills. 8. Contour lines with Ushape with convexity towards lower ground indicate ridge (Fig. 17.2). Fig. 17.2 Fig. 17.3 9. Contour lines with Vshapedwith convexity towardshigher ground indicate valley (Fig. 17.3). 10. Contour lines generally do not meet or intersect each other. 11. If contour lines are meeting in someportion, it showsexistenceof a vertical cliff (Fig. 17.4). (a) Elevation 105 Vertical cliff ¢ (b) Plan view Fig. 17.4 12. If contour lines crosseachother,it showsexistenceof overhangingcliffs or a cave(Fig. 17.5). (a) Elevation (b) Plan Fig. 17.5 1 7.2.2 Uses of Contour Maps Contour maps are extremely useful for various engineering works: 1. A civil engineer studies the contours and finds out the nature of the ground to identify. Suitable site for the project works to be taken up. 2. By drawing the section in the plan, it is possible to find out profile of the ground along that line. It helps in finding out depth of cutting and filling, if formation level of road/railway is decided. 3. Intervisibility of any two points canbe found by drawing profile of the groundalongthat line. 4. The routes of the railway, road, canal or sewerlines can be decided so as to minimize and balance earthworks. 5. Catchment area and hence quantity of water ow at any point of nalla or river can be found. This study is very important in locating bunds, damsand also to nd out ood levels. 6. From the contours, it is possible to determinethe capacity of a reservoir. I17.3 METHODS OFCONTOURING Contouring needsthe determination of elevation of various points on the ground and at the samethe horizontal positions of thosepoints shouldbe fixed. To exercisevertical control levelling work is carried out and simultaneouslyto exercisehorizontal control chain surveyor compasssurveyor planetable survey is to be carried out. If the theodolite is used both horizontal and vertical controls can be achieved from the sameinstrument. Basedon the instrumentsused one can classify the contouring in different groups. However, broadly speakingthere are two methodsof surveying: 1. Direct methods 2. Indirect 17.3.1 Direct methods. Methods It consistsin finding vertical and horizontal controls of the points which lie on the selectedcontour line. For vertical control levelling instrument is commonly used. A level is set on a commanding position in the areaafter taking fly levels from the nearby bench mark. The plane of collimation/height of instrument is found and the required staff reading for a contour line is calculated. The instrument man asks staff man to move up and down in the areatill the required staff reading is found. A surveyor establishesthe horizontal control of that point using his instruments.After that instrument man directs the staff man to anotherpoint where the samestaff reading can be found. It is followed by establishing horizontal control. Thus severalpoints are establishedon a contour line on one or two contour lines and suitably noteddown. Planetable surveyis ideally suitedfor this work. After requiredpoints areestablished from the instrument setting, the instrument is shifted to anotherpoint to cover more area.The level and surveyinstrumentneednot be shifted at the sametime. It is better if both arenearbyso asto communicate easily.For getting speedin levelling sometimes hand level and Abney levels are also used.This method is slow, tedious but accurate. It is suitable for small areas. 17.3.2 Indirect Methods In this method, levels are taken at someselectedpoints and their levels are reduced.Thus in this method horizontal control is establishedfirst and then the levels of thosepoints found. After locating the points on the plan, reduced levels are marked and contour lines are interpolated betweenthe selectedpoints. For selectingpoints anyone of the following methodsmay be used: (a) Method of squares, (b) Method of crosssection, or (c) Radial line method. Method of Squares: In this method area is divided into a number of squaresand all grid points are marked (Ref. Fig. 17.6). Commonly used size of squarevaries from 5 m x 5 m to 102.8 102.6| 101.1 100.6 5102.3 WV101.3 100.4 y 101.6 101.3 I 100.4 3101.59 100.6 100.3v. 99.1 V 98.9 I 199 98.7 I .100.9 100.6 100.1 995i 21011 100.8 A 100.5 B 100.3 C 99.8 D Fig. 17.6 99.3 E 98.6 F 98.5 G 20 m x 20 m. Levels of all grid points are establishedby levelling. Then grid squareis plotted on the drawing sheet.Reducedlevels of grid points marked and contour lines are drawn by interpolion [Ref. Fig. 17.6]. T Fig. 17.7 Method of Cross-section: In this method crosssectionalpoints are taken at regular interval. By levelling the reduced level of all those points are established.The points are marked on the drawing sheets,their reduced levels (RL) are marked and contour lines interpolated. Figure 17.7 shows a typical planning of this work. The spacing of crosssection depends upon the nature of the ground, scale of the map and the contour interval required. It varies from 20 m to 100 m. Closer intervals are required if ground level varies abruptly. The crosssectional line need not be always be at right anglesto the main line. This method is ideally suited for road and railway projects. Radial Line Method: [Fig. 17.8]. In this method severalradial lines are taken from a point in the area.The direction of eachline is noted. On theselines at selecteddistancespoints are marked and levels determined.This method is ideally suited for hilly areas.In this survey theodolite with tacheometryfacility is commonly used. 108 For interpolating contour points between the two points any one of the following method may be used: (a) Estimation (b) Arithmetic calculation (c) Mechanical or graphical method. Mechanical or graphical method of interpolation consist in linearly interpolating contour points using tracing sheet: On a tracing sheetseveralparallel lines are drawn at regular interval. Every 10th or 5th line is madedarker for easycounting. If RL of A is 97.4 and that of B is 99.2 m. Assumethe bottom most dark line represents.97 m RL and every parallel line is at 0.2 m intervals. Then hold the secondparallel line on A. Rotatethe tracing sheetso that 100.2the parallel line passesthrough point B. Then the intersection of dark lines on AB representthe points on 98 m and 99 m contours [Ref. Fig. 17.9]. Similarly the contour points along any line connecting two neighbouring points may be obtained and the points pricked. This method maintains the accuracyof arithmetic calculations at the sametime it is fast. 8----------(100) B 2 (99) Points to be pricked 1 I (98) """""""""7""""""""""""""""""" A 0Am) Fig. 17.9 Drawing Contours After locating contour points smooth contour lines are drawn connecting correspondingpoints on a contour line. French curves may be used for drawing smooth lines. A surveyor should not lose the sight of the characteristicfeature on the ground. Every fifth contour line is madethicker for easyreadibility. On every contour line its elevation is written. If the map size is large, it is written at the ends also. IQUESTIONS in-eas and vuIumes The land is always bought and sold on the basisof cost per unit area.For road and railways land is to be acquired on the basis of area.In the design of bridges and bunds catchmentarea of river and nalla are required. Thus nding areasis the essentialpart of surveying. It may be noted that areato be found is the projected area.Units usedfor finding areasare squaremetres,hectareand squarekilometre. Relation among them are Hectare = 100 m X100 m =1x104 m2 Squarekilometer= 1000m X 1000m = 1 X 106m2 = 100 hectare Similarly volume of earth work involved in projects like road, rail and canal are to be found by surveying. Capacity of reservoir also needvolume calculations. In this chaptercalculation of areasand volumes basedon surveying are explained. 18.1 COMPUTATION OF AREAS FROM FIELD NOTES If the area is bound by straight edges, it can be subdivided in a set of convenient figures and area calculated.But in most of the casesthe boundary may have irregular shape.In such casesmajor areais subdivided into regular shape and area is found. The smaller area near the boundary is found from taking offset from a survey line [Ref Fig. 18.1]. ._.nIlllIIIIIIII-.- 18.1.1 Computation of Areas of Regular Figures The following expressionsfor calculating areasmay be noted: (a) Triangle: (i) If basewidth is b and height is h, A=%bh muan (ii) If a, b and c are the sidesof a triangle, A: where s(sa)(sb)(sc) a+b+c s=:-Z-- ...(18.2) (b) Rectangle: If b and d are the dimension of a rectangle, A=bd ...(18.3) (c) Trapezium: A=dk1 Eh? ,where disthe distance between two parallel sides and I21 and I22 lengths of parallel sides. ...(18.4) 18.1.2 Areas of Irregular Shapes For this purposefrom a survey line offsets are taken at regular intervals and areais calculatedfrom any one of the following methods: (a) Area by Trapezoidal rule (b) Area by Simpsonsrule. (a) Area by Trapezoidal Rule: If there are n + 1 ordinatesat n equal distancesd, then total length of line is L each segmentis calculated treating it as a trapezium. Referring to Fig. 18.2, Area of first segment= o0+o,d = nd, Area of By adding all such segmentalareas,we get total A TO2+O1d+L1+O2 d+-----+O 2+0 d 2 =[~%-+O1 +02 +---+O,,_1]d 0 +0 ___(13_5) (12)Area by Simps0ns Rule Fig. 13.3 In this method,the boundary line betweentwo segmentis assumedparabolic. Figure 18.3 shows the first two segmentsof Fig. 18.2, in which boundary betweenthe ordinatesis assumedparabolic. Area of the first two segments = Area of trapezium ACFD + Area of parabolaDEFH =9°:g32d+2-><2d><15+;x45><21+%(15+20)(6022)+§(13.8 1 1 +-2-x20(12060)+-2-X13.8 (1208.5) Area = 2840 m2 Ans. I Example 18.2: Theperpendicular osets taken at 10 m intervals from a survey line to an irregular boundary are 2.18 m, 3.2 m, 4.26 m, 6.2 m, 4.8 m, 7.20 m, 8.8 m, 8.2 m and 5.2 m. Determine the area enclosedbetweenthe boundary, survey line, therst (i) Trapezoidal rule and the last offsetsby (ii) Simpsons rule. Solution: d = 10 m, n = number of segments= 8 number of ordinates= 9. Length of survey line = 8 x 10 = 80 m. (i) Area by trapezoidal rule 0 +0 A=(9i+O1+O2+---+O7jd = +3.2 +4.26 +6.2 +4.8 +7.2 +8.8 +8.2]10 2 Area = 463.5 m2 Ans. (ii) Area by Simpsons method d :3 [(O0+O8)+4(O,+O3+O5+O7)+2(O2+O4+O6)] 10 = ? [2.18+ 5.2+ 4 (3.2+ 6.2+ 7.2+ 8.2)+ 2(4.26 + 4.8+ 8.8)] = 474.333 m2 Ans. I Example 18.3: Thefollowing osets were taken to a curved boundaryfrom a survey line: 0, 2.46, 3.78, 3.26, 4.40, 3.28, 4.24 and 5.20 m. Computethe area betweencurved boundary, survey line and end osets, if the osets were at a regular interval of 10 m, using Simpsons rule and trapezoidal rule. Comparethe results. Solution: Number Number of offsets = 8 of intervals = 7 00 = 0.0, 01 = 2.40,02 = 3.78,03 = 3.26,04 = 4.40,05 = 3.28, 06 = 4.27,07 = 5.20 d = 10.0 m (i) From trapezoidal 0 rule +0 A=["2l+O1+O2+O3+O4+O5+O6]d _P0+5.20 +2.46 +3.78 +3.26 +4.40 +3.28 +4.27]10 2 = 240.5 m2 Ans. (ii) Simpsons rule Number of intervals are odd (7). Hence for first six intervals Simpsonsrule can be applied and for the last interval, trapezoidal rule will be applied. a. d A=§[O0+O6+4(O1+O3+O5)+2(O2+O4)]+5(O6+O7) 10 10 *3[0 + 4.27+ 4(2.46 + 3.26+ 3.28) + 2(3.78 + 4.40)] + -2 (4.27 + 5.20) = 236.12 m2 Ans. Simpsonsrule gavelesserarea,the magnitudebeing240.5 236.12 = 3.38m2 Ans. I18.2 COMPUTING AREAS FROMMAPS If map of an areais available its area can be found by the following methods: (i) Approximate methods (ii) Using planimeter. 18.2.1 Approximate Methods The following three approximate methodsare available for calculating area from the map: (a) Give and take method (b) Subdivisions into squares (c) Subdivisions into rectangles. (a) Give and take method: In this method irregular boundary is approximated with straight lines suchthat areataken in is equalto the areagiven out. Accuracy dependsupon the judging capacity of the engineer.Then the area with straight edges is divided into a set of simple figures, like triangles and trapezoidsand the areaof map is found using standardexpressions. Figure 18.5 shows such a scheme. (b) Subdivisions into squares: Similar to a graph sheet, squaresare marked on a transparent tracing sheet,each squarerepresentinga known area. Full squaresare counted. Fractional squaresare countedby give and take approximation.Then the number of squaresmultiplied by area of each squaregives the area of the map Fig. 18.6 shows such a scheme.Finer the meshbetter is the accuracy. III!!!!!II Fig. 18.6 (c) Subdivisions into rectangles: In this method,a setof parallel lines aredrawn at equal spacing on a transparentpaper. Then that sheetis placed over the map and slightly rotated till two parallel lines touch the edgesof the tap. Then equalising perpendicularsare drawn between the consecutiveparallel line. Thus given areais convertedto equivalent set of rectanglesand then area is calculated (Ref. Fig. 18.7). Fig. 13.7 18.2.2 Computing Area Using Planimeter Planimeteris a mechanicalinstrument used for measuringareaof plan. The commonly usedplanimeter is known as Amsler planimeter (Fig. 18.8). Its construction and usesare explained in this article. Tangent screw Index Needle point Tracing arm HingeTracing point / V Fig. 18.8. Planimeter The essentialparts of a planimeter are: 1. Anchor: It is a heavyblock with a ne anchorpin at its base.It is usedto anchorthe instrument at a desiredpoint on the plan. 2. Anchor arm: It is a bar with one end attached to anchor block and the other connected to an integrating unit. Its arm length is generally fixed but some planimeters are provided with variable arms length also. 3. Tracing arm: It is a bar carrying a tracer point at one end connectedto the integrating unit at the other end. The anchor arm and tracer arms are connectedby a hinge. The length of this arm can be varied by meansof fixed screw and slow motion screw. 4. Tracing point: This is a needle point connectedto the end of tracer arm, which is to be moved over the out line of the area to be measured. 5. Integrating unit: It consistsof a hard steelroller and a disc. The axis of roller coincides with the axis of tracer arm henceit rolls only at right anglesto the tracer arm. The roller carries a concentric drum which has 100 divisions and is provided with a vernier to read tenth of roller division. A suitable gear system moves a pointer on disc by one division for every one revolution of the roller. Since the disc is provided with 10 such equal divisions, the reading on the integrating unit has four digits: (i) Unit read on the disc (ii) Tenth and hundredth of a unit read on the roller (iii) Thousandth read on the vernier. Thus if reading on disc is 2, reading on roller is 42 and vernier reads6, then the total reading F = 2.426 Method of Using Planimeter To find the area of a plan, anchor point may be placed either outside the plan or inside the plan. It is placed outsidethe plan, if the plan areais small. Then on the boundary of the plan a point is marked and tracer is set on it. The planimeter reading is taken. After this tracer is carefully moved over the outline of the plan in clockwise direction till the first point is reached.Then the reading is noted. Now the area of the plan may be found as Area=M(FI+10N+C) where ...(18.7) M = A multiplying constant F = Final reading I = Initial reading. N = The number of completedrevolutions of disc. Plus sign to be used if the zero mark of the dial passesindex mark in clockwise direction and minus sign if it passesin anticlockwise direction. C = Constantof the instrument, which when multiplied with M, gives the area of zero circle. The constant C is added only when the anchor point is inside the area. Multiplying constantM is equal to the areaof the plan (map) per revolution of the roller i. e., area correspondingto one division of disc. Multiplying constantM and C are normally written on the planimeter.The user can verify these values by (i) Measuring a known area (like that of a rectangle) keeping anchor point outside the area (ii) Again measuringa known areaby keeping anchor point inside a known area. The method is explained with example. The proof of equation 18.7is consideredas beyond the scopeof this book. Interestedreaderscan seethe book on surveying and levelling. I Example 18.4: To determinethe constantsof a planimeter a 20 cm X 20 cm area was measuredwith anchor point outside the plan area. Thezero mark of disc crossedthe index in clockwise direction once. The observed readings are Initial reading = 7.422 Final reading = 1.422 Determine the multiplying constant M. Solution: Area = M (F -1 + 10 N) Now Area = 20 X 20 = 400 cm2 F = 1.422, I = 7.422 400 = M (1.422 7.422 +10 x 1) M = 100 cm2 Ans. I Example 18.5: A planimeter was used to measure the area of a map once keeping anchor point outside thefigure and secondtime keeping it inside thegure. The observationsare asfollows. (i) When the anchor point was outside the gure: Initial reading = 1.486 Final reading = 7.058 The zero of the dial did not pass the index at all. (ii) When the anchor point was inside the map: Initial reading = 3.486 Final reading = 8.844 Zero mark of the dial passedthexed index mark twice in anticlockwise direction. Find the (i) area of the map (ii) area of the zero circle. Takemultiplier constantM = 100cm2. Solution: (i) When the anchor point was outside the plan I=1.486 F = 7.058 N =0 M = 100 cm2. A=M(FI+10N) =100 (7.058 1.486 +0) A = 557.2 cm2 Ans. (ii) When the anchor point was inside the plan I: 3.486 F = 8.844 N =~2 M =100 cm2. A=M(FI+10N+C) 557.2 = 100 (8.844 - 3.486 10 X 2 + C) C = 20.214 Ans. I18.3 COMPUTATION OFVOLUMES The following three methodsare available for computation of volumes: (i) From crosssections (ii) From spot levels and (iii) From contours. First methodis useful for computing earthwork involved in road/rail/canal/sewageworks. Second method is useful for nding earth Work in foundationsof large building and the last method is useful for nding capacity of reservoirs. 18.3.1 Computation of Volume from Cross-sections To compute earth Work, prole levelling is carried out along the centre line of the alignment of the project and crosssectional levels are taken at regular intervals. Then the volume of earth Work can be found, if the crosssections are determined. First the calculation of crosssectional (a) If section is level (Fig. 18.9) area is discussed. Let h be the depth at the centre line of the alignment and 1 : n be the side slopes.Then w = Z) + 2nh =%(w+b)h 1 =§(b+2nh+b)h = (b + nh) h ...(18.8) (b) If it is a multilevel section [Fig. 18.10] Fig. 13.10 Let the coordinatesof pointsbe (x1,y1),(x2,y2),..., (xn,yn),thenarrangethe coordinatesin the following order X1,X2,x3,X4, / // II V1 / // Y2 / / I Y3 / / // Y4 / . . . . . ./ / // / ,Xn51 // / yn / V1 Then area of the gure 1 = E [2 Product ofpairofcoordinates connected bycontinuous lines 2 Product ofcoordinates connectedby dotted lines] ...(18.9) The above formula can be easily proved by taking a simple example of a quadrilateral [Ref. Fig. 18.11].Let thecoordinates of A, B, C andD be (x1,y1),(x2,y2),(x3,y3)and(x4,y4).Thenareaof ABCD =AreaofaABb+AreaofbBCc+AreaofcCDdAreaofaADd. %(x1+ x2) (y2 "y1) +%(X2 +353) 073 'y2) +%(x3 +x4) (y4 "'y3)"'% (-x1+x4)(y4 'y1) Fig. 18.11 =.3["135 ""131 1' x232 "x231 1' x233 x232 1' x333 x332 "' x334 "x333 1' "434 x433 " x1341' "135" x434+ "4311 = ("132 1' "2331' "3341x4313"("231 + 35332 1x431"' 351343 [Note terms with samesubscript appearin pairs and cancell each other]. Hence equation 18.9 is proved. Calculation of Volumes Once crosssectional areas at various sections are known volume can be found from trapezoidal or prismoidal rule as given below: Trapezoidal Rule n+A1+A2+""+An_1:| V=d[>_+_°;_ wheren arenumberof segments at intervalof d, Areaat L = nd, beingAn. Prismoidal Rule d V: 3-[(A0+An)+4 (A1+A3 + +An_1) + 2 (A2+A4+ +An_2)] ...(18.11) Wheren is number of even segments. If number of segmentsare odd, (n is odd), for n 1 segmentsprismoidal rule may be applied and for the last one trapezoidal rule is applied. Or else for the last segmentarea at middle of last segment foundandprismoidalformulaappliedfor An_1,AmandAn. I Example 18.6: A railway embankmentof formation width 12 m is to be built with side slopes of 1 vertical to 1.5 horizontal. Theground is horizontal in the direction transverseto the centre line. Length of embankmentis 200 m. The centre height of embankmentat 25 m interval are as given below: 1.6, 2.4, 3.4, 3.8, 4.2, 3.6, 2.8, 2.2, 1.2 m. Calculate the volume of earthlling. Solution: Since the section is level, A: (b + nh) h Where n = 1.5 The area at different sections are: A0 = (12+ 1.5x 1.6)x 1.6: 23.04m[0 A1 = (12 +1.5 x 2.4) x 2.4 = 37.44mN A2 = (12 +1.5 x 3.4) x 3.4= 58.14ml\-) A3 = (12 +1.5 x 3.8) x 3.8= 67.26mI0 A4 = (12 +1.5 x 4.2) x 4.2 = 76.86m[0 A5 = (12 +1.5 x 3.6) x 3.6= 62.64mN A6 = (12 +1.5 x 2.8) x 2.8 = 45.36mK0 A7 = (12 +1.5 x 2.2) x 2.2 = 33.66ml\-) A8=(12+1.5 x 1.2)x 1.2: 16.56m2 Volume by Trapezoidal Formula A0+A8 V=d[ 2 +A1+A2+A3+A4+A5+A6+A7] =25 +37.44 +58.14 +67.26 +76.86 +62.64 +45.36 +33.66] 2 = 10029 m3 Ans. Volume by Prismoidal Formula Since the number of segmentsare even (8), prismoidal formula d V=3[A0+A8+4(A]+A3+A5+A7)+2(A2+A4+A6)] =33: [23.04 +16.56 +4(37.44 +67.26 +62.64 +33.66) +2(58. 14 +76.86 +45.36)] = 10036 m3 Ans. I Example 18.7: Thefollowing notes refer to a three level work in cutting. Station 1 3-_0_ 3: _4-§_ -7. 0 0 11.0 3.0 3.8 6.0 79.3 77 72.75 Theformation level is in cutting and is 12 m wide. The distance betweentwo points is 40 m. Calculate the volume of cutting betweenthe two stations by (i) Trapezoidalformula (ii) Prismoidal formula. Solution: The meaningof the notesfor station 1 is at centrepoint i. e., at x = 0, depth of cutting is 2.4 m, at the end points on left at x = 7 m, the depth of cutting is 2 m and at a point x = 11.0 m depth is 4.8 m as shown in Fig. 18.11.Similarly the meaning for station 2 is also indicated in the Fig. 18.12. Fig. 18.12 Hence the coordinatesof points (1) to (5) on first sections are: Point-> 1 x -6.0 y 0 2 3 4 5 1 -7.0 0 11.0 6.0 -6.0 2.3 4.8 0 2.0 0 Note: Coordinatesof first point are Written again at the end is the coordinatesmethod of area calculation. 1 A:-2*[{6><2.0+(-7.0x2.4)+0><4.8+11.0x0+6x0} {(0.0) (47.0) + 2 x 0 + 2.4 x 11.0 +4.8 x 6 + 0 x ( 6)}] -42.0 m2 = 42.0ml, sincethereis no meaningin ve sign. Similarly for section 2, 1 2 4 5 x Point 6.0 9.0 0 3 14 6.0 y 0 3.0 3.8 6.0 0 1 6 0 2A={6><3.09.0><3.8+0><6+14x0+6><0} {0x(9.0)+3.0><0+ 3.8x14+6x6.0><0x(6)} =_141.4 A = 70.7 m2 From Trapezoidal Rule 1 V=-2-X40(42.0 +70.7) =2254.0 m3 Prismoidal Ans. Rule To apply this Weneed crosssectionat middle of the two sections.Assuming uniform slope, it may be found as the points with averagecoordinates.Hence at mjdsection the coordinatesof the points are: Point x 1 m y 06 2 40 23 3 4 5 0 ms an 33 51 1 e o 00 2Am=(6><2.58><3.1+0x5.4+ {0><(8)+2.5><0+3.1x12.5+ =11o.95 Am=55.475m2 Now 40 at= -2-= 20In,between twoconsecutive sections. V=239 (42.0 +4x55.475 +70.7) V = 2230.67 m3 Ans. 18.3.2 Computation of Earth Work from Spot Levels This method is used to calculate volume of earth Work for the elevations of basements,large tanks and borrow pits. In this methodthe Wholeareais divided into a numberof rectanglesor triangles (Fig. 18.13). The levels are taken at corner points before and also after excavation.The depth of excavation at each corner point is measured.Then for each simple gure (rectangleor triangle). a2 Hg.18J3 V = Area of the figure X averagedepth. Thusfor a rectanglewith cornerdepthha,hb,hcandhd, V =Areaofrectangle x @+m+m+m 4 For a triangle, V = Area of triangle m+m+m 3 3 3 1 It may be noted that in Fig. 18.13 (a), in total Volumecalculations depth of somecornersappear once, some twice, some of them 3 times and some 4 times. If Zhl = someof depthsusedonce Zhg= sumof depthsusedtwice Zh3= sumof depthsusedthrice 2h4= sumof depthsusedfour times. Then A V = Z (Eh,+ 22h2 + 32113 + 4Z.h4) ...(18.12) Similarly in Fig. 18.13 (b), sum depths are used once, some 2 times, some 3 times and some others6 times.Defininghi sameasabove. A V = *3(Zh1+2Zh2+ 3Zh3 + 62h6) ...(18.13) I Example 18.8: A 60 m X 60 m plot is to be excavatedto a formation level of 80.0 m. Thepresent levels at 20 m X 20 m grid are as shown in Fig. 18.14. Calculate the volume of earth work. 84.5 84.8 85.2 85.4 Fig. 18.14 Solution: The number of times a particular corner depth is used in volume calculation is marked in circles. Formation level is 80.0 m. Zh1= 4.5 + 5.4+ 3.4 +1.5 = 14.8m Eh, = 4.8 + 5.2+ 3.4 + 4.6 + 2.2 + 3.8+ 2.4 + 2.8 = 29.2 m Zh3= 0 Zh4= 3.8 + 4.1+ 2.9 + 3.6= 14.4m Areaof eachgrid, A = 20 X 20 = 400 m2. 400 V=T(14.8><1+29.2x2+0><3+14.4x4) = 13080 m3. 18.3.3 Computation of Volume from Contours Figure 18.15 shows a dam with full water level of 100 m and contours on upstream side. Capacity of reservoir to be found is nothing but volume of fill with water level at 100 m. The whole area lying within a contour line is found by planimeter. It may be noted that area to be measuredis not between two consecutive contour lines. ___________/ 100.0 / 95.0 069 90 .0 80 .0 Fig. 18.15 Let A0,A1,A2, ...,A be areaof contoursandh be contourinterval.Thenfrom trapezoidalrule: A A V=h ["J25l+A1 +A2 +---+An_1] and byprismoidal rule: h =E [(A0+An) +4(A1+A3+ +An_1) +2(A2+A4 + +An_2) where there are n segmentsand n is even number. I Example 18.9: The area within the contour lines at the site of reservoir and along theface of the proposed dam are asfollows: Contour Area in m2 100 m 800 104 m 9600 I 08 in 11800 112 m 12400 116 m 14300 120 m 18400 124 m 20360 Assuming 100 m as the bottom level of the reservoir; and 124 m as full level, calculate the capacity of the reservoir using trapezoidal and prismoidal formula. Solution: (a) Prismoidal Formula: A A v=;, [9i-'!+A1 +A2 +.-.+A,_1] = [800 +20360 +9600 +11800 +12400 +14300 +18400] = 308320 m3 (b) Prismoidal Ans. Formula: h V=§ [A0+An+4(A1+A3+---+An_1)+2(A2+A4+---+An_2)] 4 = 3 [800+ 20360 +4 (9600 + 12400 + 18400) + 2(11800 + 14300)] = 313280 m3 Ans. IQUESTIONS 1. Find the areaof the eld from the following notes of cross staff survey, all measurementsbeing in metres. Stn. B 16.2 X 90.4 74.6 12.8 X " 17.4 64.0 42.0 x 15.6 323 x 14.4 22.4 8.6 [Anst 2419.76 m2] The following observationswere taken to a boundary from a chain line. Distance in m 0 10 20 30 40 50 60 70 Offset in m 2.4 3.6 4.2 4.8 4.4 3.8 2.8 1.2 Calculate the area enclosedbetween the chains line, the boundary line and the end offsets by (2') Trapezoidalrule (ii) Simpsonsrule Ans: (1') 254.0m2 (ii) 257.33m2 [Hint: Consider first six segment by Simpsons rule and to this add area of last segment found by Trapezoidal rule]. A plot of ground is in the form of a quadrilateral. To find the areathe following measurementswere taken: AB = 118.6 m BC = 220.4 m CD = 158.4 m DA = 340.0 m and AC = 322.0 m Find theareaof theplot. [Ans: 33384.5m2] [Hint: Divide quadrilateral into two triangles) Describe the planimeter and explain how it is used for finding the area of a given map. A planimeter was used to measurethe area of a map once keeping anchor point outside the figure and secondtime keeping it inside the gure. The observationsare as follows: (1') When anchor point was outside the figure: Initial reading = 7.364 Final reading = 3.234 The zero of dial passedthe index mark once in the clockwise direction. (ii) When anchor point was inside the figure: Initial reading = 2.384 Final reading = 4.443 The zeroof the dial passedthe indexmarktwice in the anticlockwisedirection.TakeM = 100cm2. [Ans: Area of zero circle = 2381.1 cmz] How do you determine the multiplying constant and area of zero circle of a planimeter experimentally ? The following are the cross-sectionalareasof an embankmentat 30 m interval Distance in m 0 30 60 90 120 150 180 Area in m2 122 432 612 720 718 1020 1040 Determine the volume of earth work by (2') trapezoidal formula (ii) prismoidal formula [Ans: Trapezoidalformula, V = 122490m3,Prismoidal Formula, V = 125100m3] The areaswithin the contour lines at the site of a reservoir and along the proposeddam site are as follows: Contour in m 100 105 110 115 120 125 130 Area in m2 1250 1420 17300 20200 25200 32400 36780 Assuming 100 m as bottom level of the reservoir and 130 m as full level, determine the capacity of the reservoir using trapezoidal and prismoidal rules. [Ans:Trapezoidal rule,V = 578675m3,Prismoidalrule, V2= 565850m3] CHAPTER emulesensing andItsApplications Remote sensingis a revolutionary changein surveying in which objects on the earth are sensedfrom remote placeslike aircrafts or satellitesand are used in map making. It always goes with Geographical Information System (GIS) which is a software tool used for the analysis of remotely senseddata with the help of the computers. In this chapterintroduction is given to remote sensingand GIS. Application of remote sensingis explained. l19.1 REMOTE SENSING Remote sensing may be defined as art and science of collecting informations about objects, area or phenomenonwithout having physical contact with it. Eye sight and photographsare common examples of remote sensingin which sunlight or articial light energyfrom electricity is madeto strike the object. Light energy consistsof electromagneticwaves of all length and intensity. When electromagneticwave falls on the object, it is partly 1. absorbed 2. scattered 3. transmitted 4. reected. Different objects have different properties of absorbing, scattering,transmitting and reecting the energy. By capturing reected waves with sensors,it is possible to identify the objects. However this remote sensing has its own limitations in terms of distance and coverage of area at a time. Photographic survey, in which photographstaken from aircrafts are used for map making, fall under this category of remote sensing.Using electronic equipments,this basic remote sensingtechnique is extendedto identifying and quantifying various objects on the earth by observing them from longer distancesfrom the space.For this purpose, geostationary satellites are launched in the space,which rotate around the earth at the samespeedas earth. Hence the relative velocity is zero and they appear stationary when observedfrom any point on the earth. Depending upon the property of the object, the electromagneticwaves sent from the satellite reected energy is different. The reected waves in the bandwidth of infrared, thermal infrared and micro wavesare picked up by sensorsmountedon satellite. Since eachfeature on the earth has different reection property, it is possibleto identify the featureson 266 the earth with satellite pictures. Data obtainedfrom satellitesare transferredto ground stationsthrough RADARS where user analysesto find out the type of object and the extent of it. This is called image processing.For quantifying the objects computers are used. India is having its own remote sensing satellites like IRSseries, INSAT series and PSLV series. Application of Remote Sensing Various applications of remote sensingmay be grouped into the following: 1. 3. Land use 5.Resourceexploration 2. Environmental study 4. Site investigation Archaeological investigation and 6. Natural hazardsstudy. 1. Resource Exploration: Geologistsuse remote sensingto study the formation of sedimentary rocks and identify deposits of various minerals, detect oil fields and identify underground storage of water. Remote sensing is used for identifying potential shing zone, coral reef mapping and to nd other wealth from ocean. . Environmental Study: Remote sensingis used to study cloud motion and predict rains. With satellitedatait is possibleto studywaterdischargefrom variousindustriesto nd out dispersion and harmful effects, if any, on living animals. Oil spillage and oil slicks can be studiedusing remote sensing. . Land Use: By remote sensing,mapping of larger areasis possible in short time. Forest area, agricultural area,residential and industrial areacan be measuredregularly and monitored. It is possible to find out areasof different crops. . SiteInvestigation: Remotesensingis usedextensivelyin site investigationsfor dams,bridges, pipelines. It can be used to locate construction materials like sand and gravel for the new projects. . Archaeological Investigation: Many structuresof old era are now buried under the ground and are not known. But by studying changesin moisture content and other characteristicsof the buried objects and upper new layer, remote sensorsare able to recognise the buried structuturesof archaeological importance. . Natural Hazard Study:Using remote sensingthe following natural hazardscan be predicted to some extent and hazards minimised: . Earthquake 2. Volcanoes . Landslides 4. Floods and . Hurricane and cyclones. I19.2 GEOGRAPHICAL INFORMATION SYSTEM (GIS) Maps are used as the languagesof simple geography.Importance of map making is recognisedlong ago. Surveyors went round the land and prepared maps. Data required for locating and calculating extent of a place/region is called spatial data. Physical propertiesand human activities related to a place/regionare storedin the form of tables, charts and texts. This information is called attribute data. Referring to maps/plans and then to attribute data stored in hard copies like books is time consuming updating and managingthe data is difficult. This problem is overcome by combining spatial data and attribute data of the location by appropriate data base managementin computers.The location information (spatial data) is digitised from available mapsand storedin computers.For this data structureused is either raster data or vector data format. In raster data structures pickcells are associatedwith the spatial information, while in vector data structurecoordinatesare associatedwith eachregion and subregions.Over the spatial data attribute data is overlayed and stored.Oncethis geographicalinformation systemis developed,the user can accessthe attribute data of any place by clicking over the spatial data of that place. The user can utilise the information for further analysis,planning or for the management.For example,if land records of a village is developedas GIS data,the user can click the statemap to pick up the district map and then accesstaluka map.Then he will accessit to pick up the village map. Then land record of that village can be obtained and property map of any owner can be checkedand printed. All this can be achievedin a very short time from any convenient place. Remote sensing and GIS go hand in hand, since lot of data for GIS is from remote sensing. Remote sensingneedsGIS for data analysis. Some of the areasof GIS application are: 1. drainage systems 2. streamsand river basins management 3. lakes 4. canals 5. roads 6. railways 7. land records 8. layout of residential areas 9. location of market, industrial, cultural and other utilities 10. land use of different crops etc. The above information helps in planning infrastructural developmentactivities suchas planning roads,rail routes, dams,canals,tunnels, etc. It helps in taking stepsto check hazardsof soil erosion and environmental pollution. Monitoring of crop pattern and condition helps in taking necessaryaction to the challengesin future. |QUEST|ONS 1. Write short notes on (a) Remote sensing ([2)Geographical Information System. 2. List various area of application of remote sensing. DISASTER RESISTANT BUILDING This page intentionally left blank CHAPTER Isaslerllesistant Builtlings Disaster meansoccurrenceof uncontrolled, painful and serious conditions. There are Various natural disasters like: Earthquakes Volcanic eruptions Cyclones Fire Landsliding Tsunami (a long high sea Wave generated by an earthquake) Flood. Earthquakes,cyclone and re needsspecial considerationsin building design and construction since they are more frequent, Widespreadand more disastrous.In this chapter this aspectof building design and constructionsare discussed. |20.1 EARTHQUAKES RESISTANT BUILDINGS An earthquakeis a sudden,rapid shaking of the earth surface causedby the breaking and shifting of rocks beneath.During earthquake,ground motion occurs in a random fashion in all directions radiating from a point Within earth crust, called epicentre. It causesVibrations of structuresand induce inertia forces on them. As a result structuremay collapseresulting into loss of property and lives. Earthquakes do not kill people, Vulnerablebuildings do so. Hence there is need of designing earthquakeresistant buildings, especially in the earthquakeprone areas. Natural Earthquakes Natural earthquakesmay be due to (1') active faults (ii) movement of tectonic plates or (iii) due to volcanic eruptions. In earths crust there are somefaults which are not yet settled.The displacementof rocks along faults causeearthquake. Tectonic meanslarge scaleprocessaffecting the structure of the earthcrust.This processcauses gradual movement of material Within the crust of earth. Sometimesit shakesthe earth crust. Volcano is a mountain or hill having a crater through which lava, rock fragments,hot vapour and gasare or havebeeneruptedfrom the earthscrust. Occasionallythe volcanoesbecomeactive and create earthquakenear the mountain crater. Earthquakes due to Induced Activities These are causedby vibrations induced by atomic explosions and collapse of ground due to faulty mining. I20.3 TERMINOLOGY 1. Focus: The point on the fault where slip starts is the focus. It is also known as hypocentre [Ref. Fig. 20.1]. 2. Epicentre: The point vertically above the focus on the surfaceof the earth is the epicentre. 3. Focal Depth: The depth of focus from the epicentreis called the focal depth. 4. Epicentral Distance:Distancefrom epicentreto any point of interest on the surfaceof earthis called epicentral distance. Fig. 20.1 l20.4 MAGNITUDE AND INTENSITY Magnitude is a quantitative measureof the actual size of the earthquake.Professor Charles Richter proposedthe scaleof magnitudethat goesfrom 0 to 9. It is a geometric scale.Now this scaleis known as Richter scale.It is obtained from the seismograph.It dependson waveform amplitude on epicentral distance.It is denotedby letter M followed by the number.An increasein magnitude by 1 implies 10 times higher waveform amplitude and about 31 times higher energy released.Thus energy releasedin M6 andM5 earthquake havethe ratio 31, andM8 to M5 havethe ratio 31 x 31 X 31.Thereareother magnitudescales,like the Body WaveMagnitude, SurfaceWaveMagnitude andWaveEnergyMagnitude. Intensity is a qualitative measureof the actual shaking at a location during an earthquake.Hence for the sameearthquake,it has different values at different places,highest value being at epicentre.This is a linear scale.It is assignedas Roman Capital Numbers from I to XII. Intensity dependsupon 1. Amount of sourceenergy released 2. Distance betweenthe sourceand the place of interest 3. Geographicalfeaturesof the media of travel and importantly on the type of structure. Modied Mercalli Intensity (MMI) scaleis commonly used to expressthe intensity. MMI scale is as given below: I. Very slight, felt only by instruments II. Felt by people resting III. Felt by passingtrafc IV. Furnitures and windows rattle V. Can be felt outdoors, clocks stop, doors swing VI. Furnitures move about, cracks appearin walls VII. People knocked over, masonry cracks and falls VIII. Chimneys and monumentsfall, buildings move on foundations IX. Heavy damageto buildings, large cracks open on ground X. Most buildings destroyed,landslides occur, water thrown out of lakes XI. Catastrophic,railway lines badly bent XII. Utter catastrophic,no building is left standing. Koyna, Great Assam, Bihar and Shillong, Kashmir earthquakeshad magnitude 8. Uttarakhand, Chamoli, Jabalpur,Latur, Gujarat approachedlevels 5.5 to 6.5. I20.5 SEISMOGRAPH Seismographis an instrument for measuringoscillation of earth during earthquakes.It has three major componentsthe sensor,the recorder and the timer. Figure 20.2 shows a typical seismograph.The pendulum mass, string, magnet and support together constitute the sensor.The drum, pen and chart paperconstitutethe recorder.The motor that rotatesthe drum at constantspeedforms the timer. The pen attachedto the tip of an oscillating simple pendulum marks on the chart paper.The magnetaround the string provides the required damping to control the amplitude of the oscillation. Magnet String Pendulum bob Fig. 20.2. Seismograph A pair of suchoscilloscopesare placed at right anglesto eachother on a horizontal platform. For measuring vertical oscillations, the string pendulum is replaced with a spring pendulum, oscillating about a fulcrum. Thus three oscilloscopes are installed at each station to measurethe oscillations in three mutually perpendicular directions. Now a days analoginstrumentsare giving way to digital instrumentsto record the ground motion and processit with microprocessors. I20.6 |.S:CODES ON EARTHQUAKE RESISTANT BUILDING DESIGN After observing Indian earthquakesfor severalyearsBureau of Indian Standardhas divided the country into five zonesdependingupon the severity of earthquake.IS 1893-1984showsthe various zones.The following IS codeswill be of great importancefor the design engineers: IS 1893-2002: Criteria for EarthquakeResistantDesign of Structures(5th revision). IS 49281993: Code of practice for EarthquakeResistantDesign and Construction of Buildings. (2nd revision). IS 13827-1992: Guidelines for Improving EarthquakeResistanceof Low Strength Masonary Building. IS: 13920-1997: Code of practice for Ductile Detailing of Reinforced Concrete Structures Subjectedto Seismic Forces. IS: 13935-1993: Guidelines for Repair and Seismic Strengtheningof Buildings. I20.7 IMPROVING EARTHQUAKE RESISTANCE OFSMALLBUILDINGS The earthquakeresistanceof small buildings may be increasedby taking someprecautionsand measures in site selections,building planning and constructionsas explained below: 1. Site Selection: The building constructions should be avoided on (a) Near unstable embankments (b) On sloping ground with columns of diferent heights (c) Flood affected areas (d) On subsoil with marked discontinuity like rock in someportion and soil in someportion. 2. Building Planning: Symmetric plans are safer compared to unsymmetric. Hence go for squareor rectangularplans rather than L, E, H, T shaped.Rectangularplans should not have length more than twice the width. 3. Foundations: \V1dthof foundation should not be lessthan 750 mm for single storeybuilding and not lessthan 900 mm for storeyedbuildings. Depth of foundation should not be lessthan 1.0 m for soft soil and 0.45 m for rocky ground. Before foundation is laid remove all loose materials including water from the trench and compact the bottom. After foundation is laid backfill the foundation properly and compact. 4. Masonry: In case of stonemasonry: 0 Place each stone at on its broadest face. 0 Placelength of stonesinto the thicknessof wall to ensureinterlocking inside and outside faces of the wall. 0 Fill the voids using small chips of the stoneswith minimum possible mortar. 0 Break the stoneto make it angular so that it has no rounded face. 0 At every 600 to 750 mm distanceuse through stones. In case of brick masonry. 0 Use properly burnt bricks only. 0 Place bricks with its groove mark facing up to ensurebetter bond with next course. In caseof concrete blocks: 0 Place rough faces towards top and bottom to get good bond. 0 Blocks should be strong. 0 Brush the top and bottom faces before laying. In general walls of more than 450 mm should be avoided. Length of wall should be restricted to 6 m. Cross walls make the masonry stronger. It is better to build partition walls along main walls interlinking the two. 5. Doors and Window Openings: 0 Walls with too many doors and windows close to each other collapse early. 0 Windows should be kept at samelevel. 1 0 Thetotalwidthofallopenings inwallshould notexceed grdthelength ofwall. 0 Doors should not be placed at the end of the wall. They shouldbe at least at 500 mm from the cross wall. 0 Clear width betweentwo openingsshould not be less than 600 mm. 6. 7. Roof: 0Insloping roofs with span greater than 6muse trusses instead ofrafters. 0 Building with 4 sided sloping roof is strongerthan the one with two sided sloping, since 8. 9. gable walls collapse early. Chejjas: 0 Restrict chejja or balcony projections to 0.9 m. For larger projections use beams and columns. 10. Parapet: Masonry parapetwall can collapse easily. It is better to build parapet with bricks up to 300 mm followed by iron railings. Concrete and Mortar: Use river sandfor making mortar and concrete.It should be sieved to remove pebbles.Silt should be removed by holding it againstwind. Coarseaggregatesof size more than 30 mm should not be used. Aggregates should be well graded and angular. Before adding water cement and aggregatesshould be dry mixed thoroughly. Bands: The following R.C. bands should be provided (a) Plinth band (12)Lintel band (c) Roof band (d) Gable band. 11. For making R.C. bandsminimum thicknessis 75 mm and at leasttwo bars of 8 mm diameters are required. They should be tied with steel limbs of 6 mm diameter at 150 mm spacing. If wall size is large, diagonal and vertical bands also may be provided. Retrofitting: Retrotting meanspreparinga structurein a scientific mannersothat all elements of a building act as an integral unit. It is generallythe most economicaland fastestway to achievesafetyof the building. The following are someof the methodsin retrofitting: Anchor roof truss to walls with brackets. Provide bracings at the level of purlins and bottom chord membersof trusses. Strengthengable wall by inserting sloping belt on gable wall. Strengthencorners with seismic belts. Anchor oor joists to walls with brackets. Improve storey connectionsby providing vertical reinforcement. Induce tensile strengthagainstvertical bending of walls by providing vertical reinforcement at all inside and outside corners. Encasewall openings with reinforcements. l20.8 IMPROVING EARTHQUAKE RESISTANCE OFTALLBUILDINGS Tall buildings are subjected to heavy horizontal forces due to inertia during earthquake.Hence they need shearwalls. A shearwall is a R.C.C. enclosurewithin the building built to take shearforces. It is usually built around lift room. These shearwalls must be provided evenly throughout the buildings in both directions asWell asfrom bottom to top. Apart from providing shearwalls, the following techniques are also used for making tall buildings earthquakeresistant: 1. Base Isolation 2. Using Seismic Dampers. 20.8.1 Base Isolation The idea behind base isolation is to detach (isolate) the building from the ground in such a Way that earthquakemotions are not transmittedup through the building, or at least greatly reduced.The concept of base isolation is explained through an example of building resting on roller [Fig. 20.3]. When the ground shakes,the roller freely roll but the building above does not move. If the gap between the building and the vertical Wall of foundation pit is small, the vertical Wall of the pit may hit the Wall. Fig. 20.3. Hypothetical building Hence 100% frictionless rollers are not provided in practice.The building is restedon exible padsthat offer resistanceagainst lateral movements [Fig. 20.4]. This reducessome effect of ground shaking to the building. The exible pads are called baseisolators,whereasthe structuresprotected by meansof thesedevices are called baseisolatedbuildings. Small movement ofbuilding .. Large " movement 3 in isolators Stainless steel plates isolator duringileartiiquake Fig. 20.4. Baseisolated building 20.8.2 SeismicDampers Another approachfor controlling seismic damagein buildings is by installing seismic dampersin place of structural elements, such as diagonal braces. When seismic energy is transmitted through them, dampersabsorbpart of it, and thus damp the motion of the building. Figure 20.4 shows the following types of seismic isolation bearings: (a) High density rubber bearings (12)Laminated rubber bearings and (c) Friction pendulum bearings. [72 if (a)Viscous damper Yield location of metal . \s= ~me..,..,_,,M vK (c)Yiéldiridampers Fig. 20.5. Seismicdampers I20.9 CYCLONE RESISTANT BUILDINGS A cyclone is a storm accompaniedby high speedwhistling and howling winds. It brings torrential rains. A cyclone storm develops over tropical ocean and blows at speedas high as 200-240 km/hour. It is usually accompaniedby lightning, thunder and continuous downpour of rain. Cyclones extend from 150 km to 1200km in lateral directions with forced winds spiralling around a central low pressurearea. The central region of light winds and low pressure,known as the eye of cyclone has an average diameter of 20 to 30 km. This central eye is surroundedby a ring of very strong winds extending up to 40 to 50 km beyond centre.This region is called wall cloud. In this region strongestwinds andtorrential rains occur. Beyond this region winds spiralling extend outwards to large distances,which goes on reducing with the distancefrom the centre of the cyclone. The following care should be taken in designing buildings in cyclone prone areas: 1. Foundations should be deeper 2. R.C.C. framed structuresare to be preferred over load bearing structures 3. Sloping roofs should be avoided. 4. Cantilever projections should be avoided. 5. Roof and parapetWall should be properly anchoredto the columns and Walls. 6. Height of the buildings should be restricted. 7. Suitable Wind load should be consideredin the building design. 8. Openingsin the Wall should be less. 9. Structure should not rest on loose soil. I20.10 FIRERESISTANT BUILDING It is reported that in USA fire kills more people each year than all other natural disasterscombined including oors, cyclones and earthquake.The re load in a building should be kept to the minimum possible. The term re load indicates the amount of heat liberated in kilo joules per square metre (kJ/m2)of oor areaof anycompartment by thecombustionof thecontentof thebuildingincludingits own combustible part. It is determinedby multiplying the Weightsof all combustible materialsby their respectivecalorific values and dividing that with oor area. A building may be made more re resistantby 1. Using suitable materials 2. Taking precautionsin building construction 3. By providing re alarm systemsand re extinguishers. 20.10.1 Using Suitable Materials The fire resisting material is having the following characters: (a) It should not disintegrateunder the effect of heat (b) It should not expand under heat so as to introduce unnecessarystressesin the building (c) The material should not catch fire easily (d) It should not lose its strength when subjectedto fire. Fire resisting charactersof some of the commonly used building materials are given below: Stone: It is a bad conductor of heat. Sand stones with fire grains can resist re moderately. Granite disintegrate under re. Lime stone crumbles easily. Most of the stones disintegrate during cooling period after heatedby fire. Brick: Bricks can resist heatup to 1200°C.At the time of construction,if good quality mortar is used, fire resistanceis extremely good. Timber: Any structuremadeof timbers is rapidly destroyedin fire. Timber enhancesthe intensity of fire. Use of heavy sectionsof timber in buildings is not desirable.To make timber more fire resistant the surface of timber is coated with chemicals such as ammonium phosphateand sulphate,boric acid and borax. Sometimesfire resistantpaint is applied to timber used in the building. Concrete: Concretehas got very good fire resistance.The actual behaviour of concretein case of fire dependsupon the quality of cement and aggregatesused. In case of reinforced concrete and prestressedconcrete,it also dependsupon the position of steel. Larger the concretecover, better is the re resistance of the member. There is no loss in strengthin concretewhen it is heatedup to 250°C. The reduction in strength startsif the temperaturegoesbeyond 250°C. Normally reinforced concretestructurescan resist fire for about one hour at a temperatureof l000°C. Hencecementconcreteis ideally usedre resistantmaterial. Steel: It is a good conductor of heat. Steelbars lose tensile strength.Steel yields at 600°C. They melt at l400°C. Steel columns becomeunsafe during re. Steel reinforcement weaken the reinforced concrete structures. Hence steel columns are usually protected with brick Works or by encasing in concrete.Reinforcementin concreteare protectedby concretecover. Steel grills and beamsare applied with fire resistant paints. Glass: It is a poor conductor of heat.It expandslittle during heating.After heating when it cools, cracks are formed in glass.Reinforced glass with steel Wire is more resistantto fire and during cooling process,even if it breaks, fractured glassesare in their original position. Aluminium: It is good conductor of heat. It has got higher resistanceto fire. Asbestos Cement: It is noncombustible material. It posseseshigh fire resistance. 20.10.2 Fire Protection by Taking Precautionsin Building Construction A building may be made more re resistant by minimizing use of combustible materials, protecting steel by fire resistant paints and providing stairs at suitable positions and protecting them from fire. Various membersof buildings can be made fire resistant as follows: Walls: Brick walls with cement plaster gives better fire resistance. Roof: R.C.C. at roofs have good fire resistance.Hence they should be preferred. Ceiling: Ceilings should be madeup of cement plaster, asbestoscement board or fibre boards. Floors: R.C.C. oor is very good re resisting oor. Doors and Window Openings: All these openings should be protected against fire by taking the following precautions: (a) The thickness of shutters should not be less than 40 mm. (b) Instead of wooden, aluminium or steel shuttersshould be preferred. (c) They should be provided With re proof paints. Stairs: Wood should be avoided in the stair cases. To minimize re hazard, stairs should be centrally placed in the buildings so that people can approachthem quickly. More than one stair caseis always preferable. Emergencyladder should be provided in the building. Structural Design: It should be such that under worst situation, even if part of the structure collapses,it should be localised and alternateroutes are available for escape. 20.10.3 Fire Alarm Systemand Fire Extinguishers All important buildings should be provided with fire alarm system.Alarm may be manual or automatic. Automatic alarm sense the smoke and activate bells. Fire extinguishers should be provided at all strategic points in the buildings. The common fire extinguishersare as follows: (a) Manual: Carbon dioxide type portable fire extinguishers are commonly used. Sometimes buckets of Water,sandand asbestosblankets are kept ready at all possible places where fire is likely to catch. (b) Internal Hydrant: The hydrant should be located in and around the buildings so that water is available easily for fire fighting. (c) Automatic Water Sprinkler: In the buildings vulnerable for re like textile mills, paper mills automatic Water sprinklers are installed. As the re takes place the sprinkling of Water is automatically activated from the piping systemcontaining Waterunder pressure. IQUESTIONS 1. What do you understandby the term earthquakes?What are its causes?State different types of earthquake. Dene and explain the following terms With a neat sketch: (a) Focus (b) Epicentre (c) Focal length and (d) Epicentral distanceof earthquake. Write short notes on (a) Magnitude (b) Intensity of earthquakeand (C) Seismograph. Describethe various provisions to be madeto make a medium sizebuilding earthquakeresistant. Explain the different bandsto be given in a building to make it earthquakeresistant. Write short notes on (a) Base isolators (b) Seismic dampers. What special caresare to be taken to make buildings cyclone resistant? Write short note on cyclones. 10. Describethe characteristicsof an ideal re proong material and discussfire resistantproperties of any four building materials. 11. How a building can be made re resistant?Describe in short. 12. Write short notes on (a) Fire alarm system (c) Fire load. ([2)Fire extinguishers CHAPTER Illsastermanagemenl antlrlannm Disaster is a natural calamity which may be in the form of 0 Drought 0 Flood 0 Cyclone 0 Forest fire 0 Landslide 0 Earthquake 0 Volcanic eruption etc. India is one of the most vulnerable developing countries becauseof the following reasons: 0 Unstable land form 0 High density of population 0 Poverty 0 Illiteracy and 0 Lack of adequateinfrastructure. In India about 60 per cent land massis prone to earthquake.Over 40 million hectareis prone to oods. 8 per cent is prone to cyclone and 68 per cent is susceptibleto drought. From 1990-2000 on an averageevery year 4344 people lost their lives and 30 million people were affected by disaster.Hence there is need to adopt a multidimensional approachinvolving diverse scientific, engineering,financial and social processes.Apart from devastatingimpact on humanlife it costson economyand environment. In this chapter disaster prevention strategy, early Warning system, disaster mitigation and protection, disaster rescue and relief, disaster resettlement,rehabilitation, reconstruction and disaster managementtechniqueshave been presented. 21.1 DISASTER PREVENTION STRATEGY Construction of dams can prevent ood havoc. Identify the rivers and construct dams to regulate ow of Waterduring heavy rainfalls. Floods in many areaslike Punjab, Gangesplateau,Assam and Bengal 282 j :,;DusAs¬r,egl havebeencontrolled to a great extent. Spreadingthe awarenessof building earthquake,cyclone and fire resistantstructurescan prevent disasters.Major and minor irrigation projects aim at controlling drought. l21.2 EARLY WARNING SYSTEM Space technology plays an important role in efficient mitigation of disaster. Indian Meteorological Departmenthasdevelopeda four stageWarningsystemfor a cyclone.The systemWorkson the observation of developmentof low pressuresin ocean48 hours prior to the time of expectedcyclone to hit land the alert Warning is given. 24 hours prior to the anticipated time of arrival of cyclone, Warning is given. Then 12 hours early cyclone arrival Warning is given. Warnings about storms, their intensity and the likely path on regularly given through radio and television until the storm passesover. I21.3 DISASTER PREPAREDNESS At all levels of civil administration committeesare establishedand responsibilitiesand urgently required nance entrusted.At national level Ministry of Home Affairs, Governmentof India, a national disaster managementdivision is established.It has preparedguidelines for disastermanagement.The national disastermanagementauthority is responsiblefor 0 Providing necessarysupport and assistanceto state Governments. 0 Coordinating and managing Governmentpolicies for disastermitigation. 0 Ensure adequatepreparednessat all levels. 0 Coordinating responseto a disasterwhen it strikes. 0 Assisting the provisional Governmentsin coordinating post disasterrelief and rehabilitation. 0 Monitor and introduce a culture of building a requisite features of disastermitigation in all developmentplan and programmes. In India all stateshave been askedto set up Disaster ManagementAuthorities. Chief Minister headsthis authority. He is assistedby senior officers from various departmentslike Water Resources, Agriculture, Water Supply, Environment, Forest, Urban and Rural development. At district level district magistrate/deputycommissionerheadsthe committee. He is assistedby the officers from variousdepartmentsin the district. At block levels also disastermanagementcommittees have been established.Every concerned person is informed about his duties and responsibilities in disastermanagement.The committeeshave major role in 0 Community involvement and awarenessgeneration. 0 Close interaction with the corporate sector, NonGovemmenta1Organisations (NGO) and the media. 0 Train the disastermanagers. Training the concerned people in facing national disaster is very important part of disorder preparedness.Training programmesare organisedin Administrative Training Institutions and at various places for different target groups. In CBSE curriculum also lessonsare addedon disastermitigation. The masons and engineers should be trained to build earthquake, cyclone and fire resistant buildings. Hospital staff should be trained to take the challanges of disaster management.Disaster prone areasare to be identified and at suitable places good hospitals should be built, communication facility provided including helicopter landings. Sufficient medicines should be stored. I21.4 DISASTER MITIGATION Disastermitigation meansminimizing the painfulnesswhich occur due to disaster.After the disasterthe people face the following problems: 1. Sheltersare completely or partially damaged 2. Food is not available when required 3. Drinking water shortageis felt. 4. Diseasesspread. 5. Communication systemsare affected. To mitigate the misery of the affected people the following stepsare to be taken: 1. Provide temporary accommodationwith water supply, sanitary and electricity facilities. 2. Extend manpower,material and financial assistanceto repair/build their houses. 3. During the expected period of cyclones and floods, store up at least seven day stock of essentialfood articles, medicines and water supply. 4. Continue to listen to warning bulleting and keep in touch with local officials. 5. Be ready to evacuatepeople to placesof safety when advised. 6. Removedamagedand decayedpartsof treesto makethem resist wind andreducethe potential for damage. 7. Before cyclone seasonstarts carry out all necessaryrepairs to the building. 8. Keep valuables and documentsin containerswhich cannot be damagedby water. 9. Talk to children and explain about cyclone/oor. Remain calm. 10. Fishermenare advised not to venture into the seaduring cyclone warning period. 11. Avoid taking shelter near old and damagedbuilding or near trees. 12. Do not touch power lines. l21.S DISASTER RESCUE AND RELIEF MEASURES Disaster rescueand relief meanstaking stepsto face the distress situation after the disasterhas taken place. Volunteer groups, police force or military teams are organisedto 0 Rescuethe people trapped. 0 Rendering first aid to wounded 0 Donating blood 0 Organizing clearing up so that normalcy returns. 0 Locating places where dead bodies can be kept until they are disposedoff. The groups should know that victims are demoralized, anxious and depressed.The volunteers have to win the confidence of victims and carry out rescueoperations. The officers carrying out rescueand relief measuresshould have good leadershipqualities and quick decision taking abilities. Emergency announcementsshould be made. Required rescue teams should be formed and guided. Higher authorities informed about the situation continuously. Mobilize national resources,if necessary.They should undertake steps for compensationand maintenanceof rescue operations. l21.6 DISASTER RESETTLEMENT, REHABILITATION AND RECONSTRUCTION Disasterresettlement,rehabilitation and reconstruction meanstaking stepsto mitigate the problems of victims after the disasterdisappears. Victims needhelp and assistanceto return to their homesafter disasterperiod is over. They may be helped to build their damagedhouses.If it is ood prone area, they may be provided sites at new settlement areaswhich are safe. Financial assistancemay be mobilized for constructing houses.The new area should be developedby providing approachroads, water supply and electricity. Loss of lives and crop should be compensated.New settlementshould have school and hospital facilities. All efforts should be made to get normalcy restored. IQUESTIONS 1. Define the term disaster. Name various disasters.List various factors contributing to disaster managementproblems. 2. Write short notes on (a) Early disasterwarning systems ([2)Disaster preparedness (c) Disaster mitigation (d) Disaster rescueand relief methods (e) Disaster resettlement, rehabilitation and reconstruction. CHAPTER Imlianstandard canes All major countrieslike India, USA, UK, Australia are having their own standardsfor material standards, testing standards,design proceduresand for finished products. Before independence,India followed British standards,but after independenceit was felt there is need to preparethe standardsto meet the Indian environment. Hence Indian Standard Institution was established, which is now known as Bureau of Indian Standards.It haspreparedmore than 4000 standardsand now and then new standardcodesare brought out. In this chapter some of the important IS codes for building design and constructions are listed and briey explained. I22.1 ISCODES FORBUILDING DESIGN The following codeshelp engineersto design buildings: 1. IS 456-2000. It is code of practice for the designof plain and reinforced concrete.It was rst brought out in 1953. It was revised in 1957, 1984 and the latest revision is in the year 2000. It gives specifications or specifies the other codes for the requirement of various materials used in making concrete.It classies concreteinto various gradesbasedon 28 days concrete cubestrength.It specifiesthe methodsandcareto be takenin transporting,placing, compacting and using of concrete. It gives general design considerations,special design requirements and gives design procedure for various structural elementsby limit state method approach. Both strength and serviceability requirementsare to be satised in the design. IS 800-2007: It titled as General Construction in steelc0deand practice. To achieve efficient and optimum standardsfor structural steelproducts, Indian StandardInstitution initiated action in 1950 and was able to bring out a code in 1956.The code was revised in 1962, 1984 and the latest revision is in the year 2007. It gives guidelines for various classof steel, loads to be consideredin the design and the method of designing steelmembersby limit statemethod. It gives the serviceability requirementsto be fulfilled in the design. IS 875-1984: It is the Indian Code of practice for Design Loads for Building and Structures.It is available in ve parts. Specificationsare available for taking loads such as deadloads, live loads, wind loads, snow loads, craneloads etc. Dead load dependsupon the type of structuresand also on the part of 286 structure.Wind loads and snow loads dependupon the region, location of site, slopesof building roof, height of building etc. The code gives the guidelines for determining theseloads on the building to be designed.Code also gives the combination of loads to be consideredin the building design. IS 1343-1980: It is the code of practice for prestressedconcrete.It gives guidelines for selecting materials, species workmanship, inspection and testing. General design requirementsand limit state method for structural design are presented.Requirementsfor durability are also specified. IS 1893-2002: It gives criteria for EarthquakeResistantDesign of Structures.IS 4928-1993 is the code of practice for EarthquakeResistant Design and Construction of Buildings. IS 13827-1992 gives guidelines for Improving EarthquakeResistanceof Low Cost StrengthMasonry Buildings. IS 13920-1997: It is the code of practice for Ductile Detailing of Reinforced concretestructures subjectedto Seismic Forces. IS 13935-1993 gives guidelines for Repair and Seismic Strengtheningof Buildings. I22.2 ISCODES FORBUILDING MATERIALS ANDCONSTRUCTION The following is the list of someof the IS code giving requirementsfor building materials: IS 269-1989. Specification for ordinary portland cement. IS 455-1989. Specication for portland slag cement. IS 516-1959. Method of tests for strength of concrete. IS 1123-1975. Method of identification of natural building stones. IS 383-1970. Specications for coarseand ne aggregates. IS 432-1982. Specication for mild steel. IS 3495-1976. Gives specifications for building bricks. IS 287-1973. Gives maximum permissible moisture content in timber for different zone and for different uses. lQUEST|ONS 1. What is IS code .7Discusstheir importance. 2. Write the namesof any four IS codesusedfor building design and construction.Briey describe them.