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4 HEAVY TIMBER FRAME CONSTRUCTION History • Simple timberframed structures appear with the oldest known civilizations. • The traditional braced frame structure first appears in the middle ages. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. HISTORY Contemporary • Contemporary timber frame construction may be used for both residential and nonresidential structures. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. 4 HEAVY TIMBER FRAME CONSTRUCTION FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Resistance to Fire of Large Timbers • Large wood members have greater resistance to fire than unprotected steel. • Steel, due to its high thermal conductivity, quickly heats up and loses strength during fires. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Resistance to Fire of Large Timbers • Large timbers are slow to absorb heat, slow to catch fire, and slow to burn. • The charred outer layer of a partially-burned timber insulates and protects the inner undamaged portion of the timber which retains the capacity to carry some load. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Heavy Timber Construction • Fire-resistive, traditional Mill Construction consists of heavy timber framing within brick masonry exterior walls. • In the contemporary building code, Type IV Heavy Timber construction requires heavy timber framing within noncombustible—masonry, steel, or concrete—exterior walls. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Heavy Timber Construction • Timbers must meet minimum size requirements to qualify as Type IV-HT construction in the building code. • Members with lesser dimensions are classified as wood light frame (Type V) construction. Supporting Floor Loads Supporting Roof and Ceiling Loads Only Columns 8 x 8 (184 x 184 mm) 6 x 8 (140 x 184 mm) Beams and Girders 6 x 10 (140 x 235 mm) 4 x 6 (89 x 140 mm) Trusses 8 x 8 (184 x 184 mm) 4 x 6 (89 x 140 mm) Decking 3 decking plus 1" finish (64 mm decking plus 19 mm finish) 2" decking, or 1 1/8" plywood (38 mm decking, or 29 mm plywood) Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Heavy Timber Construction In IBC, note how allowable heights and areas of Heavy Timber (Type IV-HT) buildings exceed those for unprotected steel (Type III-B). Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Heavy Timber Construction Allowable heights and areas of Heavy Timber buildings also exceed those of light wood frame (Type V) structures. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Wood Shrinkage • Wood column/beam connections are designed to minimize the effects of cross-grain shrinkage that can lead to differential settling between interior framing and exterior walls made of materials that are not prone to shrinkage. • Right: Traditional cast iron pintle column base. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Wood Shrinkage • Right: Contemporary beam/column connection with bearing blocks, split rings, steel straps. • Note how beam ends are not supported on cross-grain material. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Beam Anchorage • Fire cut beam ends (right): Collapse of beam must not topple supporting wall. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Beam Anchorage • A ventilating air space around the beam end prevents moisture in the masonry wall from seeping into the beam. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Beam Anchorage • Upper clip restrains beam from side-to-side movement while allowing rotation due to structural deflection or beam collapse in a fire. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION Floor and Roof Decks • Decking comes in depths of 2" to 8", capable of spanning roughly from 5' to more than 20'. • To achieve the required fire-resistance, floor decking must be covered with tongue-and-groove boards or plywood. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. HEAVY TIMBER CONSTRUCTION Floor and Roof Decks • Fire-resistive heavy timber floors and roofs must be constructed without concealed cavities where fire could develop undetected. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LATERAL BRACING Bracing Heavy Timber Structures • HT structures may be braced against lateral forces with diagonal framing members, shear walls of masonry or concrete, or rigid panels attached to the building frame. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LATERAL BRACING Bracing Heavy Timber Structures • To meet contemporary standards, historical structures may require insertion of new steel or reinforced concrete bracing elements. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LATERAL BRACING Bracing Heavy Timber Structures • Floor and roof diaphragms must also be securely tied to the supporting structure. • Right: New OSB, metal straps, and structural angles tie the floor structure of an historic mill building to its masonry walls. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. HEAVY TIMBER CONSTRUCTION Building Services • When floor and roof systems cannot have concealed spaces, services such as lighting, ductwork, sprinkler piping, electrical wiring must be routed in the open. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. 4 HEAVY TIMBER FRAME CONSTRUCTION CONNECTIONS Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. CONNECTIONS • Knee bracing with traditional, pegged mortise and tenon joinery Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. CONNECTIONS • Proprietary fastening system with self-drilling steel dowels and concealed steel plates Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. CONNECTIONS • Fabricated steel seat, concealed plates, and exposed through-bolts Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. CONNECTIONS • Steel plate gusset with tie rod and through-bolts Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. CONNECTIONS • Copper sheet metal flashing to protect against moisture absorption at vulnerable ends of large timbers exposed to the weather Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. 4 HEAVY TIMBER FRAME CONSTRUCTION LONGER SPANS IN HEAVY TIMBER Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LONGGER SPANS IN HEAVY TIMBER Large Beams • Glulam beams can span over 80', and arches even further. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LONGGER SPANS IN HEAVY TIMBER Trusses • Heavy timber trusses can span beyond 200'. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved. LONGGER SPANS IN HEAVY TIMBER Domes • The Washington State Tacoma Dome spans 530'. Fundamentals of Building Construction, Materials & Methods, 5th Edition Copyright © 2009 J. Iano. All rights reserved.
