The Canadian lumber industry has identified, as a high priority, the establishment of a multi-year Lumber Properties Program that pulls together a number of urgent initiatives currently underway to establish and/or maintain Canadian lumber design values. The desire is to have an overall program that emphasizes the proper development of a longer-term strategic plan and process to deal with current and future initiatives. Combining the current industry resources with Federal Government contributions through Natural Resources Canada (NRCan), the first step in the Program has been completed: to gather the various initiatives now underway and to begin the formal development of pan-Canadian policies to guide the development, implementation and on-going maintenance of such initiatives.
The key activities in 2006-07 were:
Launching of the pilot phase of the on-going monitoring program, and development of a simulation model to assist in determining what sort of trends can be reliably detected and which cannot;
Completion of the in-grade testing program on Canadian Norway spruce;
Analysis of the No.2 2x4 Hem-Fir (N) monitoring study and confirmation of the appropriateness of assigned design values;
Identification of an alternative species grouping procedure for further study;
Starting of a process under the ASTM Committee on Wood to address gaps in the Grade Quality Index provisions in ASTM Practice D1990, and
Establishing a forum for engaging the US in discussions on lumber properties issues.
Lumber properties issues crucial to maintaining the competitiveness of Canadian lumber continue to be the same as in previous years: tests and means to adjust for sample representativeness using the Grade Quality Index (GQI), species grouping and re-grouping procedures, and on-going lumber monitoring. As a result, discussion on a pan-Canadian strategy and supporting policies necessary to support Canadian lumber initiatives tend to focus on these three issues. The challenge is to ensure that these issues are dealt with in a way that balances both short and longer-term needs and provides a net overall benefit to the Canadian industry.
Western hemlock is a species that is highly susceptible to compression wood (CW) formation, an abnormal wood tissue that forms on the under side of leaning tree stems and branches. When lumber cut from logs containing CW is dried, the CW shrinks approximately 10 times normal in the parallel to grain direction, resulting in degrade, at times severe, due to warp in the form of crook and bow. In this project a technique using an ultrasonic materials evaluation system (UME) was tested for its ability to detect CW. Since stress wave velocity, in addition to being dependent on elastic properties and material density, is also a function of growth ring orientation, a slope of grain indicator was evaluated for its ability to measure growth ring orientation, to be used in conjuction with the UME.
There is interest in the lumber and truss industry to supply and use fingerjoined lumber for metal plate connected wood trusses. To support this, it is necessary to provide evidence that fingerjoined lumber meeting the requirements of a recognized fingerjoined lumber product standard can be used with the lumber design provision provided in the governing wood engineering design code.
In consultation with the truss and lumber industry, it was agreed that fingerjoined machine graded lumber meeting the requirements of the National Lumber Grades Authority (NLGA) Special Product Standard 4 (SPS 4) would be assessed for truss applications. The assessment would need to show no issues with applying the lumber design provisions in Clause 5.5.13 of CSA O86, the Canadian Engineering Design in Wood Code, to NLGA SPS 4 fingerjoined lumber. This is necessary because Clause 5.5.13 was originally developed for non-fingerjoined lumber and applies specifically to the design of lumber in truss applications.
The tests carried out under this program included bending test specimens with 1 to 4 joints per specimen tested to failure under three different bending moment configurations, and single fingerjoints tested to failure under pure axial tension or compression, and then under eccentrically applied axial tension or compression to induce bending in addition to the axial loading. All test specimens were prepared using a 2100f-1.8E grade spruce-pine-fir lumber and because the test to failure was typically less than 5 minutes, polyvinyl acetate (PVA) adhesive was used to bond the fingerjoints to facilitate joint fabrication.
Additional testing was also carried out to extend the testing protocol developed in 2008-09 for assessing fingerjoint adhesives under sustained tension loads. Samples bonded with a known performing adhesive, phenol resorcinol formaldehyde (PRF), were substituted with samples bonded with PVA, a known poor performer under sustained loads.
In the bending test, test span configuration and characteristic number of joints showed strong effects on the average bending capacity of the fingerjoints. While more joints in the region of maximum bending moment were expected to contribute to lower bending capacities, this was not as evident in this study. This is likely due to the small sample sizes and the tight control over the joint strength (i.e. low strength variability). Instead, having one or more fingerjoints in the maximum moment zone but near the load points appeared to have a stronger effect. The bending strength reductions were on the order of 5 to 10%.
In the combined loading test, loading eccentricity showed a strong effect on the capacity of the fingerjoints in both tension-bending and compression-bending. The tension-bending interaction should be noted for those evaluating online or offline tension test results. Both the tension-bending and compression-bending results are consistent with the assumptions in the CSA O86 design code.
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.
A study was conducted with the primary objective of examining the efficacy of a standard block shear test method to assess the bond quality of cross-laminated timber (CLT) products. The secondary objective was to examine the effect of pressure and adhesive type on the block shear properties of CLT panels. The wood material used for the CLT samples was Select grade nominal 25 x 152-mm (1 x 6-inch) Hem-Fir. Three adhesive types were evaluated under two test conditions: dry and vacuum-pressure-dry (VPD), the latter as described in CSA standard O112.10. Shear strength and wood failure were evaluated for each test condition.
Among the four properties evaluated (dry and VPD shear strength, and dry and VPD wood failure), only the VPD wood failure showed consistency in assessing the bond quality of the CLT panels in terms of the factors (pressure and adhesive type) evaluated. Adhesive type had a strong effect on VPD wood failure. The different performance levels of the three adhesives were useful in providing insights into how the VPD block shear wood failure test responds to significant changes in CLT manufacturing parameters. The pressure used in fabricating the CLT panels showed a strong effect on VPD wood failure as demonstrated for one of the adhesives. VPD wood failure decreased with decreasing pressure. Although dry shear wood failure was able to detect the effect of pressure, it failed to detect the effect of adhesive type on the bond quality of the CLT panels.
These results provide support as to the effectiveness of the VPD block shear wood failure test in assessing the bond quality of CLT panels. The VPD conditioning treatment was able to identify poor bondline manufacturing conditions by observed changes in the mode of failure, which is also considered an indication of wood-adhesive bond durability. These results corroborate those obtained from the delamination test conducted in a previous study (Casilla et al. 2011).
Along with the delamination test proposed in an earlier report, the VPD block shear wood failure can be used to assess the CLT bond quality. Although promising, more testing is needed to assess whether the VPD block shear wood failure can be used in lieu of the delamination test. The other properties studied (shear strength and dry wood failure), however, were not found to be useful in consistently assessing bond line manufacturing quality.
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.
The current Canadian Lumber Properties (LP) 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) liaison with university-based research groups to leverage research suitable for addressing longer-term research needs in the area of lumber properties.
In 2010/11, the ongoing monitoring program was initiated for SPF. This follows the 2-year pilot monitoring program, which was also carried out on SPF. Due to the late start, no testing was carried out this year. The start-up of the program was timely because in August 2010, the American Lumber Standard Committee (ALSC) directed the Lumber Properties Task Group (TG) to draft mandatory lumber monitoring procedures for implementation in ASTM D1990. Work done to date on the Pilot study and previous monitoring studies well positioned the FPInnovations, CWC and the NLGA to participate in the TG discussion.
Planned work with the TG and the US Forest Products Laboratory, Madison (USFPL) on new species grouping procedures for ASTM D1990 was suspended. The TG recommended that the work continue under ASTM as opposed to under the TG. Although next steps were discussed with the USFPL, these have been put on hold until the work on implementing lumber monitoring procedures in ASTM D1990 is substantially complete.
A new study to examine the application of machine grading to sawn timbers was initiated under this program. The study, if successful, will lead to a detailed study plan for developing new design values for timbers based on a hybrid “machine” and “output” controlled approach. The information would also be used as a basis for a new NLGA Special Products Standard.
Finally, funding for the second year of the NSERC Collaborative Research and Development (CRD) grant for the UBC/SFU Forest Products Stochastic Modelling Group was approved. This has permitted some of the longer term lumber properties issues to be presented as topics for Graduate Research Assistantships for the summer of 2011, leading potentially to MSc or PhD studies in the fall.
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