Azzo Newsletter
The top 20 engineering achievements of the 20th century was published by the National Academy of Engineering (NAE) earlier this year. The ranking was based on the degree to which achievement contributed to quality of life within the past 100 years.
1. Electrification
2. Automobile
3. Airplane
4. Safe water treatment and supply
5. Electronics
6. Radio and television
7. Agricultural mechanization8. Computers
9. Telephone
10. Air conditioning 
and refrigeration		  11. Interstate highways
12. Space exploration
13. Internet
14. Imaging X-ray to film
15. Household appliances
16. Health technology
17. Petroleum and natural gas technology
18. Laser and fiber optics
19. Nuclear technology
20. High performance materials
Contents


Salvaged wood.
The leaky condos in Vancouver.
Single and multiple layer wood composite panels.
Value added wood products.
Plywood.
Salavged wood building material.
A recent study by the USDA Forest Products Lab. was performed on a large sample of timber collected from a military industrial building in St. Paul Minnesota. From a building that contained an extensive machinery but no evidence of excessive heat or moisture, 12-feet - (3.6m) long 8x8 Douglas-fir columns were collected 
for testing. Only 2 out of 60 columns (3.3%) tested were rejected after grading according to the West Coast Lumber Standard (WCLS). 
The 8x8 columns tested in the study used to support the mezzanine floor 
in the building. At least 40% of the columns have shown no checks, splits, knots, wane or damage, hence meeting the standards for the highest grade: select structural. More importantly for reuse as structural framing members in new construction, the compression strength of the tested columns was higher than it would be calculated using the current design methods. Otherwise, the columns could sustain in service loading.


The leaky condominium crisis in Vancouver, BC: the key issues. 
While Vancouver housing prices for 1999 ranked 7th in North America, according to a study by the Canada Mortgage and Housing Corporation (CMHC), the city and the province are still facing the aftermath of a crisis in the housing industry. A two year inquiry commission has tried to understand the causality of the problem. It remains however, the prospect of ~ $1 billion repair bill to be paid. The problem is pervasive and affecting not just wood frame buildings. In short, what caused the “leaky condo crisis” is faulty designs coupled with minimum code standards. Hence, with a strong influx of people to BC during the 80’s and 90’s,an over heated housing market leading to an increase of land prices, part of the intent was housing as many people as possible on as little land as possible. Consequently, in order to maximize square footage of entitlement, overhangs at roof-lines were also eliminated as often as possible using what was a highly appealing design, often referred to as California style, with corners and angles. As of July 1, 1999, new standards entered into effect meaning a greater policing of the building industry. Rainscreen technology using an air barrier is now a code requirement. 
Single layer and multiple layer wood composite panels: What is the difference?
The orientation and spatial arrangement of fibers and particles in composites govern the anisotropy of their physical and mechanical properties. Based on this principle, engineered wood products such as oriented strand boards (OSB) are manufactured with enhanced strength and stiffness in one direction to meet specific applications.The manufacturing process of OSB involves addition of resin to the wood particles, forming a loose mat and pressing it under heat. During mat forming, loose strands are arranged in multiple layers, with the principal strand direction in each layer oriented at right angles to one another. At times, the core layer may be of random orientation, thus increasing the shear and flexural properties of the panel. The choice of mat configuration could in principle be based on the end-use of the wood panel product. Based on a concept linking the manufacturing process to the performances of engineered wood products such as OSB, AZZO & Associates Consulting have conducted a recent comparative simulation study of single and three layer wood composite panels (to be published). It was observed that the within board variability for the physical (density) and mechanical (stiffness and strength) properties was much higher in the three layer composite panels. Aspen being the most widely species utilized in Canada for OSB, the study considered Asen 1x1m (4x4) wood composite panels with a target density of 600kg/m3 (36pcf), using a variable size of flakes within a 20% variability. The three layer composite panels with a 50/50% ratio face to core were designed such that the flakes or strands in the core and the faces were randomly oriented and aligned along the long direction of the panel, respectively.
  (a)

(b)
Structure configuration of the (a) single and (b) three layer wood composite panels.
From the light of this study, in order to achieve an average density of panel at least equal to the target density, the three layer composite panels required 25% more volume of raw material (Aspen flakes) than used for the single layer panels. Consequently, the stiffness for the latter panels was 22% and 72% lower in the directions x and y, respectivley. For the three layer composite panels, the significant increase of the stiffness in the perpendicular direction (y) to the alignement direction of the flakes (x) in the faces, is the direct result of a core layer using randomly oriented flakes.   The use of this concept and simulation is to provide the primary wood processing industry with very useful information and tool  in the optimization of the manufacturing process of engineered wood products such as OSB.

 
Value added wood products: preservative treatment of lumber.
Unlimited applications is one way of adding value to wood products. A list of commercial and industrial applications where treated wood is required includes utility poles, foundation piling, and highway applications. Marine treated wood is also ideal for typical applications such as docks, boathouses, boardwalks, and pole homes. Another application is the residential construction, where treated wood is used for permanent wood foundation. When left untreated in many outdoor applications wood becomes subject to degradation by a variety of natural causes. Wood species such as southern pine and douglas-fir possess little decay resistance and therefore need extra protection when they are exposed to adverse environments. Wood can be protected from the attack of decay fungi, harmful insects or marine borers by applying preservatives and specific treatments. Some preservatives and treatments are more adaptive to certain use requirements. Treatability also varies for each species as heartwood resists treatments more than sapwood. The two main methods for wood preserving are pressure and non-pressure processes. During pressure treatment method, common species of wood are loaded onto trams and pushed into a large horizontal treating cylinder where a vacuum is applied. A preservative solution is then pumped into the cylinder and forced under pressure into the wood. At the end of the process, excess treating solution is pumped out of the cylinder and back to a storage tank for later reuse. The treated wood is  then removed. Non-pressure treatment methods do serve useful purposes and add value when thorough treatments are impractical or exposure conditions are such that little preservative treatment is required. These methods consist of surface application treatment of wood where the preservatives are applied with a brush or by dipping. Cold soaking and steeping of seasoned and green wood provides more success on fence posts and timber. For example, pine posts treated for 2 days or longer in a low viscosity preservative oil, can have an average life of up to 20 years. The diffusion process, alike the steeping process, treats green or wet wood. Using waterborne preservatives, the diffusion process is a two step method that consists of steeping green wood in one chemical solution, then in another. Vacuum treatment of wood is used on millwork and lumber with water repellent and waterborne preservatives. This method provides optimized levels of retention and penetration for limited use of waterborne preservatives. In terms of new techniques for treating wood, the recent focus has been on different procedures of pressure treating wood. Pressure treatment is the most widely way used to treat wood. Hence, patents have been developed for single phase fixation of the preservatives, or the use of heat and or steam in the process. Also, there has been optimization of the pressure treatment with  multiple phase pressure process (MPP) reducing the total time of treatment with the delivery of ready to use treated wood. 
Oilborne and waterborne preservatives constitute the two general classes of wood preservatives. They are also classified in three categories according to their exposure levels with reference to  ground contact and decay hazard. Hence, waterborne preservatives are used in pressure treatment of wood destined for residential, commercial, marine, agricultural, recreational and industrial applications. Oilborne preservatives such as creosote and creosote/coal-tar mixtures are applied to railroad ties, pilings and utility poles. However, for most residential, commercial, and marine building applications, the waterborne preservatives are preferred. These chemical treatments are clean, odorless and paintable, plus they are registered for both interior and exterior use without a sealer.The most commonly used waterborne preservative is known as CCA, or Chromated  Copper Arsenate.With increasing environmental concerns, new preservatives have been developed within recent years. Current research trends emphasize the development of waterborne copper systems for pressure treatment including citrates, azotes and quartenary ammonium compounds. Hence, ACQ -  copper based and ammoniacal solution, has been developed as a substitute to CCA in pressure treatment especially when using accelerated fixation process (MPP). Another recently developed preservative to replace CCA is CC (chromated copper) with no content of the Arsenate component. The numerous new preservative solutions also include a low toxic soy protein solution combined with copper borate, and zinc chloride. As a substitute to creosote, pigment emulsified creosote (PEC) is currently used for better fixation especially in utility poles and railroad ties. Other research techniques related to CCA concern new adhesives and chemical solutions for the recycling and use of CCA treated wood in the manufacture of wood composites such as OSB, fiberboard and glulam.



 
 
 
 

Plywood: A traditional engineered wood panel product, still in service for the new millennium.
Since it was first developed in the early 20th century, plywood has changed little. Plywood is still widely used in construction and applications, as well as cabinet and furniture manufacturing. 
Softwood-veneer plywood mostly used in construction, are made with wood veneers of species such as pine, spruce, fir and hemlock. Hardwood-veneer plywood, on the other hand, use birch, oak, maple, ash, walnut and mahogany in the face and back plys, for applications in the cabinet and furniture manufacturing. Plywood panels are made by cross-laminating an odd number of wood veneers, each laid perpendicular to the ones above and below it, with the faces of the panels (front and back) always oriented so the grain is parallel with the panel long dimension. Plywood is graded by the quality of the veneer used on the face and back. The manufacturing process of plywood involves bonding wood veneers with adhesives under hot pressing. Panels are hence graded for exterior or interior use depending on the type of adhesive used. Plywood grades also describe the quality of the veneer. Plywood veneers are graded as  N, A, B, C, C-plugged and D. The highest quality N-grade or natural finish is free of defects. A-grade veneers have smooth, defect free surfaces with no more than 18 neatly made repairs parallel to the grain. B-grade has a solid surface with circular repair plugs and tight knots up to 1/2” diameter. C-grade plugged and regular allow synthetic repairs and knot holes up to 1/2” and 1-1/2” in diameter, respectively. The lowest quality D-grade veneers permit knots and knot holes  up to 2” and 1-1/2” in diameter, as well as synthetic and stitching repairs. Hardwood veneer plywood used in furniture and cabinet  applications can have softwood core plies and hardwood veneer on the panel faces. Another value added to plywood products consists of the highest quality lumbercore plywood with hardwood veneer faces laminated to a core of hardwood strips. 
Other specialty plywood panels include high density and medium density overlaid plywood (HDO and MDO), made with an inner plywood core covered with a resin-impregnated fiber.