In this work, the properties of aspen veneer from two mills (A and B) were compared. The comparisons between the incised veneer and non-incised veneer for mill A were made in terms of veneer thickness, ultrasonic propagation time (UPT), density and MOE. The aspen veneer was further characterized for LVL/plywood products by tailoring veneer grades to the requirements of final veneer products. In addition, MOE-based veneer stress grading and UPT-based veneer stress grading were compared for the aspen veneer. The advantages of MOE-based veneer stress grading over UPT-based veneer stress grading were identified in terms of veneer grade MOE and volume breakdown. The main results are summarized as follows:
1) Aspen veneer properties change from mill to mill. The differences in aspen veneer density and MOE between mill A and B are significant with mill A producing denser and stronger aspen veneer.
2) For aspen veneer in the mill A, the distribution shapes of veneer thickness, UPT, density and MOE between the non-incised and incised veneer are quite similar. Although the differences in veneer thickness, UPT and density between the non-incised veneer and incised veneer are identified as significant, the difference in veneer MOE is not significant due to the effect of both veneer UPT and density. The incised veneer has a slightly higher variation in thickness and is also slightly thicker compared to the non-incised veneer. This could due to the change of lathe settings or the property variation of aspen species as indicated with the veneer density variation.
3) Of the aspen veneer from mill A, using the optimum UPT thresholds, about 27.5 ~ 30.9% can be extracted through veneer stress grading to make 2.0 million psi LVL; about 43.4 ~ 59.9% can be sorted out for 1.8 million psi LVL; and the remaining 12.6 ~ 25.7% can be used for 1.5 million psi LVL or for plywood. It was also found that the incised aspen veneer generates 3.4% less of top stress grade G1 but 16.5% more of stress grade G2 compared to the non-incised aspen veneer if performing the optimum UPT-based stress grading.
4) The MOE-based veneer stress grading not only results in a smaller variation in MOE of each grade, but also higher volume percentages of stress grades G1 and G2 compared to the UPT-based veneer stress grading. This smaller variation in MOE of each stress grade will be very beneficial to the industry and structural applications since higher design stress can be assigned for the wood structural components. Also the higher percentages of stress grades G1 and G2 with the MOE-based veneer stress grading has significant economical implications and should be recognized by the industry.
5) To maximize mill profits, veneer sheets need to be periodically sampled and analyzed using the VGrader software. The optimum grading thresholds for the specific veneer can be established for on-line veneer stress grading based on the current market and requirements of final veneer products, providing a real solution to characterize and make best use of the specific veneer for LVL/plywood products.
Characterizing aspen veneer for LVL/plywood products. Part 2. LVL pressing strategies and strength properties|Manufacturing characteristics and strength properties of aspen LVL using stress graded veneer
In this study, aspen veneer sheets were sampled from a Forintek member mill. Their attributes and properties were measured. Using the optimum stress grading strategy, aspen veneer was segregated into 3 distinct stiffness groups (stress grades G1, G2 and G3) and conditioned to 3 different moisture levels. An experimental design for 3-level four factors comprising veneer moisture content, veneer stress grade, mat pressure and glue spread (or resin level) was adopted. Based on the experimental design, LVL panels with different combinations of four factors were pressed until the target core temperature reached 1050C to achieve full cure followed by a stepwise decompression cycle. The LVL panel final thickness, density, compression ratio and relevant strength properties were measured. After that the effect of aspen veneer moisture, stress grade, mat pressure and glue spread and their relative importance on LVL compression behavior, hot-pressing and strength properties were evaluated using a statistical analysis program. The relationship between LVL panel properties and veneer properties was examined. Finally a method to enhance LVL modulus of elasticity (MOE) to make high stiffness LVL was discussed. From this study, the following results were found:
Aspen veneer is capable of making LVL products meeting 1.8 and 2.0 million psi MOE requirements. Optimum veneer stress grading and proper pressing schedule are two important keys to the manufacture of high-stiffness aspen LVL products. Further, a possibility to make high-grade aspen LVL meeting 2.2 million psi MOE exists by proper veneer densification and optimum veneer stress grading.
The roles of four factors affecting LVL pressing behavior and strength properties are quite different. Glue spread and mat pressure, rather than stress grade and veneer moisture content, are two main factors affecting hot-pressing time taken for the core to reach 1050C. With incised veneer, the moisture from the glue in the glueline affects the rise of core temperature more pronouncedly than the moisture in the veneer, and is more critical to the cure of the glue. High glue spread (44 lbs/1000ft2) not only significantly increases the hot pressing time taken for the core to rise to 1050C, but overall also decreases most LVL strength properties with the pressing schedule used. High mat pressure does not necessarily result in high LVL panel compression due to the high gas pressure that occurs in the core.
Veneer stress grade and veneer moisture are the two predominant factors that mostly affect LVL strength properties. LVL panels assembled with high stress grade result in increases in both flatwise and edgewise MOE and MOR properties rather than shear strength either longitudinal or through-the-thickness. Further, using high stress grade veneer can help make more efficient structural systems in terms of both stiffness-to-weight and bending strength-to-weight ratios compared to using low stress grade veneer. High veneer moisture at 6% impairs all LVL strength properties except edgewise bending MOE.
LVL compression ratio can help link veneer MOE with LVL panel edgewise bending MOE. Overall, every increase of 1% in LVL compression ratio would result in 1% increase in LVL and veneer MOE ratio. With regard to aspen LVL MOE enhancement, using high veneer stress grade gains slightly less than using low veneer stress grade. On average, every increase of 1% in aspen LVL compression ratio results in 0.82%, 1.05% and 1.20% increase in aspen LVL and veneer MOE ratio assembled with stress grades G1, G2 and G3, respectively. In practice, those conversion factors for any specific veneer can be derived based on the correlation between veneer MOE and MOE of target LVL/plywood products made with proper pressing schedules, and be further used to derive requested veneer MOE for each stress grade to perform the optimum veneer stress grading.
Pressing schedules show significant effect on aspen LVL compression behavior and strength properties. Using a pressing schedule with step-wise decompression cycles following the core temperature to rise to 1050C, an excessive compression of LVL in the range of 13.5% to 27.6% is generated which results in high-stiffness LVL with an average MOE of approximate 2.0 million psi for all experiments. Although this pressing schedule has slightly longer pressing time and off-target LVL thickness than current commercial LVL pressing schedules, it helps enhance the strength properties of LVL.
It is recommended that further work should include the effect of different decompression cycles and mat pressure on LVL panel compression ratio and strength properties.
Ten varieties of hybrid poplars from 7 year-old to 30 year-old plantations were evaluated for OSB production. The clones were chosen for their similarity with aspen as well as their impressive growth. Static bending tests on small solid wood speciments indicate that all poplar hybrids have lower modulus of rupture (MOR) and modulus of elasticity (MOE) than aspen. Although the hybrid poplar varieties evaluated in this study generally had physical characteristics similar in aspen and the properties of the OSB panels made from them were good, manufacture of OSB using substantial quantities of hybrid poplar (i.e. 25% or more) will likely require adjustments to some processing steps.
This report summarises the work accomplished in this one-year project in which the fire performance of wood-frame buildings was to be documented. A detailed analysis of Canadian and American fire loss statistics for residential occupancies was undertaken in order to assess the impact of the choice of building materials and the nature of fire-safety provisions in building codes on the overall fire safety in buildings. It was expected that the knowledge gained would enable the wood industry to argue more effectively during deliberations of codes and standards committees.
This study demonstrated that buildings constructed in compliance with current North American building code requirements are among the safest in the world. It was found that the fire loss record of wood-frame houses is about the same as that of large apartment buildings of non-combustible construction. It was shown that the ignition of upholstered furniture or mattresses by smokers’ materials is far and away the leading cause of residential fires involving deaths. Most of these deaths occur before the structure of the building becomes damaged by or involved in fire. Enacting more stringent building code requirements is unlikely to pay a large dividend in terms of life safety. In fact, the statistics suggest that significant improvements in fire safety in buildings would be more easily achieved by limiting the flammability of upholstered furniture and mattresses.
Canada is one of the largest exporters of forest products in the world. To develop and transfer low environmental technology to eliminate wood infection is one of Forintek's program goals, and biotechnology is one of such technology. The application of biotechnology in forestry and wood protection has been explored to a limited extent worldwide. In order to allow the Canadian wood industry to take advantage of this enabling technology, this report summarizes various activities conducted by Forintek to stimulate the development and application of biotechnology for wood protection in Canada. The report also intends to review previously published researches on the use of biotechnology in wood protection. It will discuss the potential benefits and challenges to the applications of biotechnology in this area. It will cover the needs and opportunities of linking biotechnology and wood pest control. The future trends of the research and development will be discussed. In the last section, recommendations will be made to Forintek for devising a vision of the application of biotechnology in wood protection.
Wood is a renewable resource and plays an important role in the world economy; however, it is subject to attack from wood-degrading fungi and insects. In Canada, it is estimated that about 10 million m3 of softwood lumber is treated with anti-sapstain chemicals annually, and around 4% of the wood products are preservative treated against decay and termites. Biotechnology may help in developing more effective and low environmental impact technologies for wood pest control. In wood protection, biotechnology currently has applications in wood durability improvement, in genetic engineering for wood pest resistance, in biological protection of wood against insect, stain and decay damage, and in detection and diagnosis of wood sapstain and decay infection.
The future application of biotechnology to wood protection is likely to focus on the development of diagnostic kits for wood degrading fungi, commercialization of bio-pesticides against fungal degradation, wood surface modification by enzymes, and genetic engineering of trees for durability.
The key challenge faced by the Canadian biotechnology industry in the development and the use of biotechnology-derived products and processes of wood protection is the bio-product registration. Public attitude against the environmental release of genetically engineered organisms may also have a strong effect on the development of these bio-products.
It is recommended that Forintek take the following roles in the future development of biotechnology in wood protection: a) to provide the knowledge base and the technology to contribute to enhanced tree breeding processed for wood durability; b) to develop safe and effective deployment strategies for sapstain and decay control biotechnology-derived products; c) to provide the knowledge base and the technology for more energy efficient and environmentally friendly wood protection processes; and d) to foster the acceptance of forest biotechnology by the Canadian wood products manufacturing industry.
The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying process by comparison with conventional methods as applied to 4/4-inch red oak with respect to drying time, final product quality, efficiency and costs. The study was divided into two parts. In the first part, three loads of red oak were dried in Forintek’s eastern SS/V kiln to identify a suitable schedule with respect to time and quality. In the second part, comparative tests were conducted between the SS/V kiln and a conventional kiln of similar capacity. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including distortion, drying checks and splits, final moisture content (MC) gradient, shrinkage, and residual stress (prong test). Energy consumption was also measured for the SS/V and conventional kilns. Finally, drying costs were evaluated for the two systems in an industrial scenario.
We successfully developed a schedule to efficiently dry 4/4-inch red oak through the SS/V process. With this schedule, 4/4-inch red oak can be dried in approximately a third of the time required for a similar load in the conventional kiln. Our results from parallel measurements indicate that the final quality of the wood dried with the SS/V process is quite comparable to that obtained with conventional drying. In addition, quality results proved achievable without a conditioning phase at the end of the cycle. Parallel drying tests conducted on similar loads of 4/4 red oak indicated that total energy consumption was 15% lower with the SS/V kiln than with the conventional kiln. A comparison of drying costs for the two systems based on annual production of 10 million fbm suggested that capital and operating costs might be slightly lower with the SS/V kiln.
The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying process as applied to 8/4-inch red oak with respect to productivity, final product quality, efficiency and energy consumption. Another objective was to compare SS/V drying with conventional drying in terms of productivity and wood quality.
Two homogeneous test loads were prepared from a single lumber lot for the SS/V and conventional tests. Initial lumber moisture content in the two loads averaged 28%. The tests involved measuring drying time as well as wood quality before and after the drying operation, including: distortion, drying checks and splits, final moisture content gradient, dimensional shrinkage, and residual stresses (prong tests). In addition, the tests included measurements of energy consumption, both thermal and electrical, with meters. The schedule used for conventional drying was drawn from Boone et al. (1993) and that for SS/V drying was supplied by Iwotech, the equipment manufacturer. In both cases, the drying cycle was terminated when the all boards used for control had reached the 7 ± 1.5% moisture content range.
Drying was achieved in 7.6 days with the SS/V process, representing a significant reduction (by a factor of 2.2) relative to the time required with the conventional method; and wood quality after drying was comparable. The results obtained with respect to distortion, checking, moisture content gradients, and residual stresses attest to the quality of the drying operation with both processes. Total energy consumption for the SS/V process was 11,307 kJ/kg of evaporated water with 58% as thermal energy and 42% as electrical energy.
The objective of this project is to provide the information required by Canadian lumber producers to evaluate the superheated steam/vacuum (SS/V) drying technology as applied to 8/4-inch red oak with respect to drying time, final wood quality, and energy consumption. Two loads of red oak were dried in Forintek’s eastern SS/V kiln with the objective of identifying a suitable schedule with respect to time and quality. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including distortion, drying checks and splits, final moisture content gradient, shrinkage and residual stress (prong test). Energy consumption of the SS/V kiln was also measured.
We were able to develop a schedule to efficiently dry 8/4-inch red oak through the SS/V process. With this schedule, an industrial load of 8/4-inch red oak can be dried in a quarter of the time typically required in conventional kilns. Our results indicate that quality drying is achievable with the SS/V process if the set point temperature is kept relatively low and the relative humidity relatively high while the wood is above the fibre saturation point. 8/4-inch red oak dried by the SS/V process required no conditioning phase to equalize moisture contents at the end of the cycle. Energy consumption measurements indicate that the process used more electrical energy than thermal energy, this being due to the relatively long time required to dry 8/4-inch red oak.
The objective of this project was to provide the information required by Canadian lumber producers to evaluate the superheated-steam/vacuum (SS/V) drying technology as applied to 8/4-inch white oak with respect to productivity, wood quality, and energy consumption.
A drying test was conducted on a load consisting mostly of lumber in the Select&Better grade. Initial board moisture contents averaged 53.1%. The tests involved measurements of drying time as well as wood quality before and after the drying operation, including: distortion, drying checks and splits, final moisture content gradient, dimensional shrinkage, and residual stresses (prong tests). In addition, the tests included measurements of energy consumption, both thermal and electrical, with meters. A schedule that had been used successfully in SS/V drying tests with 8/4-inch red oak was used for this test.
A total of 21.6 days was required to reduce the lumber moisture content from 53% to 16%. In fact, this result underestimated actual drying time due to the cycle being interrupted prematurely and to relative humidity in the kiln at the beginning of the cycle being lower than set. As a result, a significant increase in surface and internal drying checks was observed. Relative humidity lower than the set point at the beginning of the cycle may account for such checking. The average final moisture content gradient of 12.3% was attributed to the cycle being interrupted when overage moisture content was still higher than target. Prong tests showed no indication of significant residual stresses, even though no conditioning had been performed. Total energy consumption was 18,602 kJ/kg of evaporated water with 48% as thermal energy and 52% as electrical energy.
Le volume moyen des arbres est passé de 170 dm³ dans les années 70’ à 123 dm³ aujourd’hui dans l’est du Canada. Au cours de cette période, le facteur de consommation des scieries est passé de 5,6 m³/Mpmp à 4,0 m³/Mpmp. Certaines scieries affichent toutefois des performances supérieures à la moyenne avec des rendements de près de 3,5 m³/Mpmp. Ce projet a été réalisé dans le but de générer des indicateurs de performance pour les scieries de l’est du Canada tout en évaluant les technologies de débitage les plus récentes. La ressource a été catégorisée par secteur géographique pour quantifier son impact sur les résultats, et le marché nord-américain a servi de référence pour analyser l’aspect économique. Le facteur de consommation et les revenus de transformation ont été retenus comme principaux indicateurs de performance, et le simulateur Optitek® a été utilisé pour réaliser les différents scénarios d’usine dont les tableaux suivants font l’objet. Il est à noter que les caractéristiques de la ressource ont beaucoup moins d’impact sur les résultats que la technologie de débitage ou la longueur des billes transformées. Les résultats sont similaires d’un secteur à l’autre, même si le volume des arbres varie.
Scieries de colombage
Description du scénario Facteurs de consommation
(m³/Mpmp) Revenus additionnels
Scierie de 8’ (4 faces/sciage courbe) 4,14 -
Scierie de 10’ (4 faces/sciage courbe) 4,28 2,0
Scierie de 8’ (4 faces + équarrisseuse-scies jumelées) 3,62 6,1
Scierie de 9’ (4 faces + équarrisseuse-scies jumelées) 3,73 1,0
Scierie de 10’ (4 faces + équarrisseuse-scies jumelées) 3,73 1,0
L’emploi d’une équarrisseuse-scies jumelées sur l’une des lignes de sciage est essentielle pour qu’une scierie de colombage atteigne des performances intéressantes. De plus les scieries de colombage ont intérêt à transformer des billes aussi longues que possible pour maximiser leur revenus.
Scieries de 16’
Description du scénario Facteurs de consommation
(m³/Mpmp) Revenus additionnels
Scierie non-optimisée (sciage droit) 4,32 -
Tronçonnage conventionnel (sciage droit) 3,74 18,9
Tronçonnage conventionnel (sciage courbe) 3,62 2,7
Tronçonnage optimisé (sciage droit) 3,52 0,4
Tronçonnage optimisé (sciage courbe) 3,46 2,4
L’optimisation au débitage primaire et secondaire apporte des revenus substantiels aux scieries de 16’ et réduit leur facteur de consommation de façon significative. Le sciage en courbe et le tronçonnage optimisé permettent d’accroître davantage les résultats. Ces deux technologies sont complémentaires puisque la première n’annule pas les gains de la seconde. Pour être efficace, le tronçonnage optimisé doit être jumelé à des lignes de sciage flexibles, capables de débiter des billes de toutes longueurs.
Average tree volume in Eastern Canada has shrunk from 170 dm³ in the 70s to 123 dm³ today. Over the same period, the wood consumption factor dropped from 5.6 m³/Mfbm to 4.0 m³/Mfbm. Some mills even do better than this and achieve factors approaching 3.5 m³/Mfbm. The objective of this project was to generate performance indicators for Eastern Canadian mills while assessing the most recent sawing optimization techniques. In order to quantify the effect of the resource on the results, we identified distinct geographic areas, and the North-American market served as a reference for economic analyses. Wood consumption factors and mill revenue were selected as principal performance indicators; and the Optitek® simulator was used to analyze the mill scenarios corresponding to the following tables. It should be noted that resource characteristics have far less impact on results than lumber manufacturing techniques or log lengths. Similar results were obtained in the various regions, even though tree diameters were different.
Description of scenario Wood consumption factors
(m³/Mfbm) Value uplift
8’ mill (integrated log processor/curve sawing) 4.14 -
10’ mill (integrated log processor/curve sawing) 4.28 2.0
8’ mill (integrated log processor + canter/twin) 3.62 6.1
9’ mill (integrated log processor + canter/twin) 3.73 1.0
10’ mill (integrated log processor + canter/twin) 3.73 1.0
A stud mill needs to have a canter/twin on one of its lines to achieve a satisfactory performance level. Stud mills should also process the longest logs possible to maximize revenue.
16’ dimension mills
Description of scenario Wood consumption factors
(m³/Mfbm) Value uplift
Non-optimized (straight sawing) 4.32 -
Conventional bucking (straight sawing) 3.74 18.9
Conventional bucking (curve sawing) 3.62 2.7
Optimized bucking (straight sawing) 3.52 0.4
Optimized bucking (curve sawing) 3.46 2.4
Optimization of primary and secondary breakdown operations significantly increases revenues in 16’ mills while greatly reducing wood consumption factors. Curve sawing and optimized bucking further improve such results; these two techniques are complementary as the former does not cancel out the benefits provided by the latter. To be effective, optimized bucking needs to be integrated into a flexible line that is capable of processing logs of all lengths.
Acoustic performance is one of the important issues that need to be addressed to help wood compete with other materials in the housing market, especially the multi-family housing market. The 1995 National Building Code of Canada (NBCC) increased the minimum sound transmission class (STC) ratings requirement from 45 to 50 between residential suites, and from 50 to 55 between suites and vertical shafts, against the 1990 NBCC. In a recent survey of prefabricated houses, sound performance was reported to be a key concern for increased acceptance of wood-frame buildings components in foreign markets, particularly Europe and Japan, where the code requirements for sound insulation are more stringent than in Canada. In view of this growing awareness of acoustic performance issues in Canada and elsewhere, and the corresponding evolution of building codes, the wood industry needs to demonstrate that wood-frame buildings can match or outperform buildings using other materials with respect to all major criteria, including acoustic performance.
This report identifies gaps in the sound-transmission research for wood-frame buildings. These gaps are either issues not completely addressed or understood, or they have been ignored by non-wood researchers or the current National Building Code of Canada. The issues identified include: 1) a lack of design information on Field Sound Transmission Class (FSTC) and Impact Insulation Class (FIIC) ratings for wood-frame construction; 2) conflicts between some construction solutions for sound insulation and other performance attributes; 3) a lack of design and construction guidelines for low frequency thumping noises induced by footsteps in wood-frame construction; 4) limited information on the design of wood-frame construction insulated against exterior noises. Forintek lacks the expertise to deal with noise insulation issues in wood-frame construction.
Four potential research projects are proposed to address these issues. It is recommended that Forintek should play an active role in sound insulation research in order to deal with occupant complaints about poor sound performance in wood-frame buildings.
Co-ordination with acoustics experts at the Institute for Research in Construction (IRC) and other institutes, the wood and building industries, and code regulators is necessary to the success of any research to be undertaken to fill these gaps, reinforce the performance attributes of Canadian wood-frame systems and increase their market acceptance.