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