CE 479: DESIGN OF BUILDING

COMPONENTS AND SYSTEMS

FALL 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 thick

Up to 24 deep

PSL 1.8-2.0 2400-

2900

290 3.5 to 7 thick

Up to 18 deep

LSL 1.3-1.7 1700-

2600

310-

400

1.125 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

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 Truss M03 – Mono Truss

C01 – Common Truss

Truss Specifications