CE 479: DESIGN OF BUILDING COMPONENTS AND SYSTEMSFALL 2012 – J. LIU
Wood Beams: Additional Components
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
http://www.lockdeck.com/
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
http://www.lockdeck.com/loadtables.html
Layup of Decking
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
http://www.canadawooduk.org/wood-products-structural.php
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)
http://www.structuremag.org/article.aspx?articleID=361
Front to back, Laminated Veneer Lumber, Laminated Strand Lumber, and Parallel Strand Lumber.
Typical Structural Composite Lumber Properties
http://www.structuremag.org/article.aspx?articleID=361
E (x106psi)
Fb (psi)
Fv (psi)
Dimensions (in)
LVL 1.8-2.0 2500-2850
285-290
1.75 to 3.5 thickUp to 24 deep
PSL 1.8-2.0 2400-2900
290 3.5 to 7 thickUp to 18 deep
LSL 1.3-1.7 1700-2600
310-400
1.125 to 3.5 thick3.5 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
http://en.wikipedia.org/wiki/File:Laminated_Veneer_Lumber.png
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
http://www.apawood.org/level_b.cfm?content=prd_lvl_main
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
http://www.structuremag.org/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
http://eeref.engr.oregonstate.edu/Sectors/Industrial/Wood_Product_Manufacturing
http://rooftrussblog.com/prefabricated-roof-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 TrussM03 – Mono Truss
C01 – Common Truss
Truss Specifications