Post on 28-Mar-2015
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
History
• Simple timber-framed structures appear with the oldest known civilizations.
• The traditional braced frame structure first appears in the middle ages.
4 HEAVY TIMBER FRAME CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Contemporary
• Contemporary timber frame construction may be used for both residential and nonresidential structures.
HISTORY
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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)
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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).
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Heavy Timber Construction
Allowable heights and areas of Heavy Timber buildings also exceed those of light wood frame (Type V) structures.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Beam Anchorage
• Fire cut beam ends (right): Collapse of beam must not topple supporting wall.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Beam Anchorage
• A ventilating air space around the beam end prevents moisture in the masonry wall from seeping into the beam.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Beam Anchorage
• Upper clip restrains beam from side-to-side movement while allowing rotation due to structural deflection or beam collapse in a fire.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Floor and Roof Decks
• Fire-resistive heavy timber floors and roofs must be constructed without concealed cavities where fire could develop undetected.
HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
LATERAL BRACING
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Bracing Heavy Timber Structures
• To meet contemporary standards, historical structures may require insertion of new steel or reinforced concrete bracing elements.
LATERAL BRACING
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
LATERAL BRACING
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
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.
HEAVY TIMBER CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
CONNECTIONS
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
• Knee bracing with traditional, pegged mortise and tenon joinery
CONNECTIONS
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
• Proprietary fastening system with self-drilling steel dowels and concealed steel plates
CONNECTIONS
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Fabricated steel seat, concealed plates, and exposed through-bolts
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Steel plate gusset with tie rod and through-bolts
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 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, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
LONGER SPANS IN HEAVY TIMBER
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Large Beams
• Glulam beams can span over 80', and arches even further.
LONGGER SPANS IN HEAVY TIMBER
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Trusses
• Heavy timber trusses can span beyond 200'.
LONGGER SPANS IN HEAVY TIMBER
Fundamentals of Building Construction, Materials & Methods, 5 th EditionCopyright © 2009 J. Iano. All rights reserved.
Domes
• The Washington State Tacoma Dome spans 530'.
LONGGER SPANS IN HEAVY TIMBER