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

Transcription

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

2 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

3 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

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

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

6 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

7 Layup of Decking

8 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))

9 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

10 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)

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

12 Typical Structural Composite Lumber Properties E (x10 6 psi) LVL PSL LSL F b (psi) F v (psi) Dimensions (in) 1.75 to 3.5 thick Up to 24 deep to 7 thick Up to 18 deep to 3.5 thick 3.5 to 16 deep

13 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

14 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

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

16 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

17 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

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

19 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

20 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

21 Light-Frame Wood Trusses

22 Trusses

23 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

24 Light-Frame Wood Trusses From Canadian Wood Council

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26 Roof Truss Layout

27 Trusses C01 Common Truss M03 Mono Truss M04 Mono Truss

28 Truss Specifications