Building Construction Structural Systems 1. Load-bearing wall construction 2. Skeleton framing 3. Combination of the two Building Construction Factors governing type selection • Economics – not necessarily the one that requires the least structural materials • Architectural, mechanical, electrical, and other costs may be affected Building Construction Load-bearing walls serve as: • Facades • Enclosures • Separators • Fire barriers • Carry floor & roof loads to the foundation Building Construction Load-bearing wood walls • One to three story buildings (houses) • 2” x 4” or 2” x 6” construction • Studs on 16” to 24” centers • Top & bottom plates • Headers • Max. wall ht. (unsupported) = 15’ Balloon Framing Platform Framing Post & Plank Framing Building Construction Load-bearing masonry walls • 10 stories or more • Thickness of walls vary depending on height • Trapezoidal cross section • Lintels or arches at openings Building Construction Load-bearing reinforced concrete walls • Thinner than masonry • Solid or cavity Load-bearing walls are used for: • Exterior • Interior partitions • Wind bracing • Service core enclosure Building Construction Load-bearing partitions: • Short intervals • Carry floor/ceiling loads Load-bearing walls: • Can serve as shear walls = resists wind & earthquake (seismic) loads Building Construction Service core • Enclosing stairs or elevators • Service/mechanical rooms • Duct/pipe chase Building Construction Skeleton framing • Columns carry loads to foundation • Lateral forces resisted by columns and diagonal braces, or rigid frame Building Construction Horizontal structural slab or deck • Floor/ceiling/ducts • Flat-plate construction • Flat-slab reinforced concrete • Slab-band construction • Two way slabs Building Construction Beam-and-girder-construction • Wood joist or rafters on 16” to 24” centers w/lumber or plywood decking • Open web steel joist • Light, rolled-steel beams • Precast concrete planks Building Construction Heavier loads / longer spans • One-way ribbed concrete slabs • Two-way waffle slab • Prestressed concrete planks, tees, double tees, or girders • Laminated wood girders • Structural steel beams & girders Building Construction Lateral-force bracing • Low wood buildings • Rigid frames • Shear walls • Braced frames Building Construction Lateral-force bracing • Tall buildings – – – – – Hollow tube cantilever X – bracing Knee bracing between columns & girders Haunched-spandrels Moment-resistant connections between columns & girder Building Construction • Curtain Wall: non-load-bearing, exterior wall, supported on girts • Spandrel Wall: curtain wall at the level of the outside floor beams in multi-story buildings • Pilaster: bonded or keyed column of masonry, uniform thickness Building Construction • Buttress: bonded masonry column – integral part of wall – provides lateral stability – decreases in thickness from top to bottom • Curtain Walls: metal, plywood, stucco – stick systems – mullion-and-panel systems – panel systems • Glazing: various window systems Building Construction • Roof styles – steep sloped > 1½ “ in 12” – low-slope ≤ 1½ “ in 12” • Sloped roof types – gable – hip – gambrel – shed Building Construction • Sloped roof components – rafter/truss/purlins – sheathing – underlayment – fascia – soffet eaves – dripedge Building Construction • Sloped roof components – ridge or hip – valley – rake gable end – saddle – dormer – flashing Building Construction • Sloped roof materials – mineral fiber - cement shingles – asphalt (fiberglass) – wood shakes/shingles – slate shingles – clay (terra cotta) – concrete tile – metal roofing - corrugated or ribbed, aluminum, copper, or galvanized steel Building Construction • Low-sloped roof materials – built-up bituminous, roll-roofing, singleply membrane – components include: • substrate • underlayment • insulation • waterproof membrane • ballast Building Construction • Bitumens include asphalt & coal tar • Single-ply roofing – vulcanized elastomers (EPDM, neoprene) – non-vulcanized elastomers (CSPE, CPE, PIB) – thermoplastics – polymer-modified bitumens