CE 479: DESIGN OF BUILDING COMPONENTS AND SYSTEMS FALL 2012 – J. LIU Wood Beams: Additional Components

 Lumber Roof and Floor Decking  Fabricated Wood Components  Structural Composite Lumber (SCL) Laminated veneer lumber (LVL) Parallel strand lumber (PSL)  Prefabricated wood I-joists  Light-frame wood trusses

Lumber Roof and Floor Decking  Lumber sheathing (1” nominal thickness) used to span between closely spaced roof / floor beams  Typically plywood and other panel products  To be discussed later  Timber decking used for longer spans  Solid decking  Laminated decking

Solid Decking Common sizes are 2 x 6, 3 x 6, 4 x 6 nominal Tongue-and- Groove (T&G) edges most common

Glued Laminated Decking  Fabricated from three or more individual laminations  Laminated decking also has T&G edge patterns  Variety of face finishes available

Solid / Laminated Decking  Essentially a series of parallel beams that span between floor or roof framing  Bending stresses / deflection criteria govern maximum loads  Spans range from 3 to 20 ft and more

Layup of Decking

 Timber Construction Manual (TCM) gives bending and deflection coefficients for various types of layups  Used to calculate required thickness of decking  Also have allowable spans and load tables (IBC and TCM (by AITC))

Fabricated Wood Components  Includes glulam, plywood, etc.  Here, some fabricated wood elements used as beams in roof or floor systems  Many are proprietary products  Design criteria and material properties vary from manufacturer to manufacturer

Structural Composite Lumber (SCL)  Engineered lumber that is produced in a manufacturing plant  Usually a reconstituted wood product from much smaller pieces of wood (than used for glulam)  Thin pieces of wood (dried to low moisture content) glued together  Includes laminated veneer lumber (LVL) and parallel strand lumber (PSL)  Some requirements in NDS Section 8 (SCL)

Structural Composite Lumber (SCL) Front to back, Laminated Veneer Lumber, Laminated Strand Lumber, and Parallel Strand Lumber.

Typical Structural Composite Lumber Properties E (x10 6 psi) F b (psi)F v (psi)Dimensions (in) LVL to 3.5 thick Up to 24 deep PSL to 7 thick Up to 18 deep LSL to 3.5 thick 3.5 to 16 deep

Laminated Veneer Lumber (LVL)  Fabricated from veneer ranging between 1/10 and 1/6 inches  All veneers are laid up with wood fibers running in one direction, resulting in high reference design values  General fabrication process similar to that of glulam

Laminated Veneer Lumber (LVL)  Produced in boards or billets ranging from ¾ to 3- 1/2 in thickness  May be 4 ft wide and 80 ft long (depends on manufacturer)  Billets then sawn into sizes as required for specific applications

Laminated Veneer Lumber (LVL)  Uses include beams, joists, headers, scaffold planking, tension laminations of glulams, flanges for prefabricated I-joists

Parallel Strand Lumber (PSL) and Laminated Strand Lumber (LSL)  PSL starts with sheet of veneer, which is clipped into narrow strands that are approximately ½ in wide and up to 8 ft long  LSL made from small-diameter trees; flaking machines are used to produce wood flakes approx. ½ in wide, 0.03 in thick, and 1 ft long

Parallel Strand Lumber (PSL) and Laminated Strand Lumber (LSL)  Both types glued and bonded together under pressure and heat  Billets of PSL are similar to those of LVL, but can be somewhat larger for PSL (e.g. 12 in wide, 17 in deep, 60 ft long)  Uses similar to that of LVL

article.aspx?articleID=800 Parallel Strand Lumber (PSL)

Prefabricated Wood I-Joists  Initially constructed with solid sawn lumber flanges and plywood webs  More recently use LVL for flanges and oriented strand board (OSB) for webs  Some requirements in NDS Section 7 Prefabricated Wood I-Joists

Prefabricated Wood I-Joists  Make efficient use of materials (like steel I-beams)  Relatively stiff  Can be used to span up to 40 or 50 ft, but most uses are for shorter spans  Relatively lightweight and easy to handle on site  Deep and slender, so follow manufacturer’s recommendations for bracing and blocking  Prefabricated metal hardware available for connections

Light-Frame Wood Trusses

Trusses

Light-Frame Wood Trusses  Majority of residential wood structures, and some commercial/industrial buildings, use some form of light wood trusses  Common spans range up to 75 ft  Spacing is on order of 16 to 24 in o.c. for floors and up to 8 ft o.c. for roof systems  Information on proper handling, bracing during construction, etc., from individual truss manufacturers

Light-Frame Wood Trusses From Canadian Wood Council

Roof Truss Layout

Trusses M04 – Mono Truss M03 – Mono Truss C01 – Common Truss

Truss Specifications