This study evaluated the effect of two different incisors followed by chromated copper arsenate pressure treatment on the bending strength and stiffness of No. 2 and better nominal 2 x 4 inch (38 x 89 mm) spruce-pine-fir and hem-fir lumber. The double-density incising method, developed at Forintek, allows SPF to meet the CSA O80 wood preservation standards. The high-speed incisor was developed by Forintek for operation immediately behind the planer in a sawmill to produce a treatable lumber product. The prototype tested here employed two solid rollers to lay down two superimposed patterns of incisions at a density of 17500/m2. Approximately 2900 specimens of SPF and 1200 specimens of hem-fir were sorted into nine and four matched groups, respectively, according to their average flatwise modulus of elasticity values tested in centre point bending. The matched groups were then given various combinations of drying, incising and pressure treatments. Bending strength properties were tested. It was found that kiln-dried SPF and green hem-fir commercial dimension lumber, treated by the above processes, can be safely used for all structural purposes for which preservative treatment is required.
This report summarizes the progress from Year 3 of the multi-year Lumber Properties project. All activities continue to conform to the guiding principles adopted by the Lumber Properties Steering Committee (LPSC) at the start of the program. This year the first steps were taken in preparing information for discussion with the new American Lumber Standard Committee (ALSC) Lumber Properties Task Group (TG). Work continues on the review of the Norway spruce testing program and the development of an on-going monitoring program.
The program has enabled the wider industry group represented by the LPSC, to be involved in monitoring progress on the program and providing strategic direction. The support has also enabled the program to retain the necessary statistical support from the University of British Columbia to not only address Canadian lumber property issues, but also contribute to technical discussions at the ALS Lumber Properties TG.
This report summarizes the progress from Year 4 of the multi-year Lumber Properties project. All activities continue to conform to the guiding principles adopted by the Lumber Properties Steering Committee (LPSC) at the start of the program. This year support was provided to statisticians from the University of British Columbia’s Department of Statistics to meet and work with researchers and statisticians from the US Forest Products Laboratory (USFPL) in Madison, WI. All physical testing under the ongoing monitoring pilot study was also completed, allowing the UBC statisticians to continue work refining their global lumber properties simulator. Work is continuing on the collection of secondary properties for Norway spruce and on the analysis of the data collected to-date.
No activities requiring significant resources were carried out under the Resource Assessment and the Special Products Initiative. Instead, these resources were redirected to cover shortfalls in the provincial funding under the Strategic Framework Initiative, so that the statistical work with the USFPL could continue.
The current Canadian Lumber Properties program was established to support multi-year research on topics judged by the industry to be critical to the safe and viable use of Canadian dimension lumber in structural applications. This program, in combination with the National Lumber Grades Authority’s grading rules and the accredited third party grading agencies form the backbone of the Canadian lumber quality system. This system enables Canadian lumber producers to grade and ship Canadian lumber for use in North American and overseas structural building applications.
When initiated in 2005, the program focussed on five areas. The effort is now focussed on three areas: 1) maintenance of existing lumber design values by means of an ongoing lumber properties monitoring program; 2) working with the US/Canada task group established to guide the development of standard procedures published in ASTM D1990 and used in the establishment of lumber design values; and 3) liaise with university-based research groups to leverage research suitable for addressing longer-term research needs in the area of lumber properties.
One of the planned activities for 2009-10 was the start-up of a trial on-going lumber properties monitoring program. The program, which is a longitudinal survey of lumber produced from mills across Canada, would have been modelled after the Pilot Ongoing Monitoring program that began in 2006 and ended in 2008. Because of the severe downturn in the industry starting in 2008, the proposed 2009-10 program needed to be postponed to accommodate the shortfall in industry funding. There were also concerns with the significant changes in production levels both within and between regions, and the potential disruptions to sampling because of unanticipated mill closures. Available resources were instead directed at establishing how best to respond to practical issues observed during the downturn, such as the closure of a mill that would have or had been providing samples. Following discussions during the year and consideration of possible alternatives, it is recommended that the sampling plan as used in the Pilot program be restarted. Additional details on the augmented mill list to account for mill closures are provided in the recommendations section of this report.
In the other major area of study, University of BC (UBC) and US Forest Products Laboratory (USFPL) statisticians met to discuss and evaluate alternatives to the ASTM D1990 procedures for developing design values for groups of wood species. Although the proposed alternative procedures would address one or more of the statistical anomalies identified in the ASTM D1990 procedure, the American Lumber Standard Committee (ALSC) Lumber Properties Task Group (LPTG) charged with reviewing the potential changes did not see any practical improvements to warrant changes to the procedures but suggested that the effort focus on establishing criteria for species grouping. Because of the potential inter-relationship between the species grouping procedures and other procedures used to assess in-grade lumber properties, it is recommended that efforts be maintained in this area and adjusted as required to respond to the needs of the LPTG.
Lastly, in late 2009, the UBC Dept. of Statistics and the Simon Fraser University Dept. of Statistics and Actuarial Science were awarded a research grant by the Natural Sciences and Engineering Research Council (NSERC) of Canada to establish the “Forest Products Stochastic Modeling Group”. FPInnovations is the industrial collaborator on this initiative. Several student projects targeting longer-term lumber properties research needs have been initiated, and a sample of suggested projects is included in the appendix of this report.
With the appropriate mainline attachment, chain chokers are a viable alternative to conventional wire rope chokers, particularly for small-scale operations. This report provides users of tractor-mounted winches and cable skidders with technical information on chain chokers. The report covers type of steels, chain specifications and grades, and how to inspect chains for wear elongation. The various components (e.g. sliding hooks, rings) used to assemble chain chokers are also discussed.
The major defining characteristic of lumber cut from trees that have been infected with the mountain pine beetle is the extent of fungal bluestain in the sapwood. To determine whether this bluestained lumber differs in its strength properties from non-stained lumber, small clear wood tests and a test on a truss connector were conducted.
Fourteen mills were approached and asked to provide an equal number of samples of bluestained and non-stained 2 x 4 in. lumber. Approximately 270 pieces each of bluestained and non-stained samples were collected and delivered to the Forintek Vancouver laboratory for conditioning and processing into test specimens. Small clear bending and toughness test specimens, meeting the general requirements of the standard test method ASTM D143, were prepared from an equal number of bluestained and non-stained lumber pieces. A subset of the bluestained and non-stained lumber sample was also selected and used to prepare metal plate-connected tension splice specimens. The three tests and the measured mechanical properties were judged to be sensitive indicators of any possible effects of bluestain on the structural performance of full-size lumber. For bluestain, an impact on the clear wood strength or the strength of the connector could be considered a precursor to a possible reduction in the structural performance of full-size lumber. Direct tests on full-size lumber tend to be confounded by the presence of strength-reducing growth characteristics such as knots or slope of grain, and are therefore more suited for quantifying a particular effect once it has been confirmed to exist.
The following results were found:
Wood with beetle-transmitted bluestain and non-stained wood have comparable clear wood bending properties and truss plate grip capacity.
The observed lower mean toughness of bluestained wood compared to non-stained wood was found to be only marginally significant (p = 0.05). There does not appear to be any difference at toughness levels below the lower quartile of the strength distribution.
The small differences that appear to be associated with bluestain (5% decrease in mean toughness, and 5% increase in mean truss plate connector grip capacity) are more likely to be masked by differences in the mechanical properties of the heartwood and sapwood, and, in the case of full-size lumber, by the presence of strength-reducing growth characteristics such as knots and slope of grain.
Insects - Attack on trees
Stains - Fungal
Pinus contorta Dougl. var. latifolia - Mechanical properties
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.
Changes to the Canadian timber engineering codes over the last 10 years have made it necessary for the wood truss industry to update the wood truss design procedures. The Truss Research Project was established to assist the truss industry to resolve some of the issues arising from the code changes. While most of the issues deal with the analysis of metal plate connected trusses and are therefore specific to the truss industry, some issues that deal with the fundamental strength properties of lumber apply to other engineered timber construction. One area that requires research is the strength of lumber under combined bending and axial loading conditions. A program to model the within-member strength variations of lumber is underway at the University of British Columbia. The purpose of this Forintek project is to develop equipment that can test lumber under combined bending and axial loads. This equipment will be used to validate the lumber strength model. The equipment to test lumber under bending and axial loading has been developed. This report presents a discussion of the equipment specifications and some of the limitations of the equipment identified to-date. The combined loading tester for lumber is currently undergoing verification and trial testing. It will be ready for use in the 1995/96 fiscal year.