Industrial heat treatment technology for wood has been under development since the 1970s. The technology consists in heating wood to temperatures of from 150°C to 240°C while preventing it from burning. This is achieved by heating the wood in either an inert atmosphere or saturated vapour environment. Heating the wood over 200°C changes the chemical structure of the wood and results in a reduction in its hydrophilic behaviour. After heat treatment when wood colour has changed to brown, an improvement in dimensional stability and biological durability should be observed. However, some mechanical properties of the wood may have decreased. This enhanced dimensional stability and biological durability make heat treatment an interesting option for the protection of wood used in exterior applications. The objectives of this study are to assess the performance of heat treatment technologies and to determine the properties of jack pine and balsam fir after heat treatment, as regards to exterior applications. Owing to difficulties in the start-up period that significantly delayed the project, no experimental work had been conducted by the end of March 2003. The lumber has however been sent to two companies for treatment and the physical and mechanical tests will be conducted under a new project entitled “Quality Control and Certification of Thermally Modified Wood.” A final report will be issued at the end of March 2004.
The basic wood properties of 45-year-old second-growth sitka spruce were examined to determine if rapid growth produces poor wood quality. Five dominant and codominant trees were sampled from each of four stands with stocking densities of 520, 640, 1080, and 1520 stems/ha. Stem size, extent of live crown, yearly wood relative density trends, and longitudinal shrinkage were measured.
Higher bearing strength values for Hem-Fir, where justified, will allow designers to realise the full strength potential of the lumber. Machine stress rated (MSR) lumber would benefit the most from an increase in the Hem-Fir bearing strength. Although there are few Hem-Fir MSR lumber producers, it is anticipated that given the recent or planned increase in installed kiln capacity on the west coast, more mills will be considering producing MSR lumber. Acceptance of Hem-Fir MSR lumber in the marketplace will depend on the design values assigned to Hem-Fir MSR lumber. The objective of this project is to establish characteristic bearing strength values for the Hem-Fir species group in CSA O86.1 and progress to date is described.
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 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.
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
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.