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Engineered Wood Products. Paul Cooper Faculty of Forestry University of Toronto. Outline. What are engineered wood products? What are their advantages or benefits? Examples of EWP Some issues with EWP. Strands Oriented Strand Board Parallel strand lumber Parallam TM Veneer based
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Engineered Wood Products Paul Cooper Faculty of Forestry University of Toronto
Outline • What are engineered wood products? • What are their advantages or benefits? • Examples of EWP • Some issues with EWP
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 1. What are Engineered Wood Products? 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 _______________________________ • Biodegradable – vulnerable to decay • Combustible
Benefits or Advantages • Efficient use of wood through “engineering” e.g., placing stronger and more uniform components in areas of higher stress • Stable, uniform & consistent • “Reliable” • Flexible with respect to shape and size • Value added products • Composite products - Take advantage of best properties of different materials
Efficient use of wood, Stable Compression Tension Neutral axis – Shear only I-Beam is very efficient use of materials
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
More employment/m3 More value/m3 Generates value locally Smaller enterprises Lower or no tariffs/duties Value Added Benefits
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
OSB - uses Sheathing Rimboard I-Joists
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
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 Back Core
2. Laminated Veneer Lumber (LVL) – Poplar, Douglas-fir Southern pine etc.
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
4. Honey-comb, Sandwich productshttp://www.superhoneycomb.com/characteristics.htm
E. Fiber Based EWP • 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. .
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”