Engineered Wood Products

Paul CooperFaculty of Forestry

University of Toronto

Outline

1. What are engineered wood products?

2. What are their advantages or benefits?

3. Examples of EWP

4. Some issues with EWP

1. What are Engineered Wood Products?

Strands– Oriented Strand Board– Parallel strand lumber– ParallamTM

Veneer based– Plywood– Laminated veneer lumber

(LVL)– Veneer overlaid products

Lumber based– Glued laminated timbers– Trusses– Edge glued products

Combinations– I-Joists– Structurally Insulated

Panels

Fiber based– Fiber reinforcement

Wood based products (usually composites) designed to meet application-specific performance requirements and to take best advantage of the structural properties of the different components

EWP’s address some of wood’s disadvantages

• Natural variability of wood – strength unpredictable, unreliable

• Hygrosopicity and resulting dimensional instability

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• Biodegradable – vulnerable to decay

• Combustible

Benefits or Advantages

1. Efficient use of wood through “engineering” e.g., placing stronger and more uniform components in areas of higher stress

2. Stable, uniform & consistent 3. “Reliable”4. Flexible with respect to shape and size5. Value added products6. Composite products - Take advantage of

best properties of different materials

Efficient use of wood, Stable

I-Beam is very efficient use of materials

Neutral axis – Shear only

Compression

Tension

Strong and Consistent

Optimize strength through• Engineered design

– Put strongest components where stresses are highest

– Configure for efficient properties

• Randomization of defects to reduce variability or increase reliability

Reliable

Flexible with respect to shape and size, aesthetics

Value Added Benefits

• More employment/m3

• More value/m3

• Generates value locally

• Smaller enterprises

• Lower or no tariffs/duties

Take advantage of component properties

Fibre Reinforced Polymer reinforced wood beams

A. Strand Based EWP1. Oriented Strand Board (OSB)

• EWP since selected geometry of strands and orientation of layers of strands - Improvement over the original “waferboard”

• Special grades used for value-added engineered products such as I-joists and rim board

• Main deficiency is thickness swelling and Concentrated Static Load resistance

Reduced variability and increased reliability

OSB - uses

I-Joists

Sheathing

Rim board

2. Parallel strand lumber (PSL)

• Made from long narrow strands (from strander not veneer)

• E.g., Aspen• Used for window

joinery, headers…

Parallel strand products3. Parallam ™

• Strips of waste veneer (1/2” X 1-2’)

• Laid up in large molds• Phenol Formaldehyde

Resin – Microwave cure

• Mainly Douglas-fir and Southern pine

• Extremely strong and reliable

PARALLAM™

B. Veneer products 1. Plywood

• Flat panel built up of plies of veneer through bonding

• Cross-laminated for uniform transverse strength and high dimensional stability

Face

Cross-bands

CoreBack

Veneer

Plywood

2. Laminated Veneer Lumber (LVL) – Poplar, Douglas-fir Southern pine etc.

C. Lumber-based products1. Finger-joined lumber

2. Machine stress rated lumber (MSR)

3. Trusses

4. Glued laminated timbers

AGO

Combination Products1. Fibre Reinforced Polymer for Beams

• Failure is usually on tension face

• Reinforce glulam or solid timbers with small amounts (1% to 3% by volume) of FRP in tension

• Doubles beam bending strength or reduces beam size or allow longer span

• Can retrofit existing beams (e.g. in bridges)

2. I-JOISTS

• Light• Strong• Long Spans• Easy to put

wiring, plumbing etc. through the web

3. Structural Insulated Panels

4. Honey-comb, Sandwich productshttp://www.superhoneycomb.com/characteristics.htm

E. Fiber Based EWP

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• Fillers and reinforcement such as natural fibers embedded in or bonded to a matrix (polymer, cement etc.)

• Enhance properties while lowering cost

• Both matrix and fibers maintain their identity but

produce a combination of properties not achievable

by one component alone.

Wood particle/fiber cement composites

Some Issues• Perceived low durability (decay) • Issues with fire performance of some

composites• Potential new applications and new

developments– Design for tall wood buildings (6 story +)– “Massive components)– Earthquake stability, hurricane performance, fire,

durability, dimensional stability– Nano-composites, agri-fiber composites, biomass

based resins and adhesives

Market trend?

Tough time for all construction products

• New home construction ↓

• Renovation ↑ ↓?

• Commercial/residential ↑?

• Infrastructure ↑?

Thank you!

“Spruce Goose” – Resin impregnated and molded Birch “Microlam”