The progress in the second year of the 5 year research program entitled "Lateral Resistance of Engineered Wood Structures to Seismic Loads" is presented. Because of the international scope of the problem, the work is being carried out in cooperation with scientists from several universities and research institutes. A procedure for determining force modification factors for timber structures is presented using the experimental data collected on nailed shear walls.
In a previously completed study, lumber obtained from a 95-year old lodgepole pine sample representing a final stand density of 700 live stems/hectare (s/ha) was found to have relatively low modulus- of-rupture (MOR) and modulus of elasticity (MOE). It was determined that this resulted from lower than average basic wood density, and larger than average knot size particularly in large diameter trees. It was also determined that average MOR and MOE could be predicted to some extent (R2 > .60) on the basis of tree diameter-at-breast height (d.b.h.) and breast-height average basic wood density. Before accepting the above results as typical of lodgepole pine of similar age and final stand density, it was considered important to compare the relationships between d.b.h. and breast-height wood density observed in this 700 s/ha sample with that of trees in open-stand-densities in other regions. Average branch size added only marginally to explained variation in the predictive equation, but knot size is known to effect lumber strength. Thus a measure of branch size was included in the current study plan. Biogeoclimatic zones were chosen as the basis for regional comparisons. A minimum of 30 trees were selected from open-stand sites in each of the following five biogeoclimatic zones: Montane Spruce (MS), Engelmann Spruce-Subalpine Fir (ESSF), Interior Douglas-Fir (IDF), Interior Cedar-Hemlock (ICH) and Sub-Boreal Spruce (SBS). Sampling was systematic by d.b.h. to ensure representation of small, medium and large diameter trees. Stem counts were made in 1/200 ha plots around each sample tree to ensure that samples were indicative of a relatively open stand density. Average basic wood density at breast height was determined from two pith-to-bark increment cores obtained from each sample tree. The size and height of the largest branch in the first 5 m of tree height was measured and recorded. Average basic wood density values and estimates of branch size obtained for the five samples in this study were compared to the values and estimates obtained from the original 700 s/ha sample site. Basic wood density obtained from three of the sites was not significantly different from that of the 700 s/ha sample. It was significantly higher in one site (ICH) and significantly lower in another (ESSF). The higher wood density was possibly the result of a slower growth rate to 30 years combined with older average tree age. The significantly lower wood density was attributed to a younger average stand age (80 years). Basic wood density showed a consistent relationship with d.b.h. in all of the tree samples, tending down as d.b.h. increased. There was a less consistent relationship between knot size and d.b.h. but what relationship there was would serve to reinforce the effect of differences in wood density on lumber strength and stiffness. Average size of the largest knots was smallest in the tree sample where wood density was highest, and largest in the sample where wood density was lowest. Important lumber strength determining tree characteristics (wood density and knot size) that resulted in the low MOE and MOR at the original 700 s/ha sample site were found to be unexceptional when compared to trees of similar age and final stand densities in other biogeoclimatic zones. Although a slower than average growth rate to 30 years offers a plausible explanation for the higher than expected wood density in the ICH sample, further investigation is recommended.
This report describes the results of a mill test investigating the effect of a 15 degree alternate top bevel (ATB) tooth for bandsaws. The test involved comparing the sawing variation and surface roughness of Douglas-fir lumber cut by both ATB and standard saws. The test results showed no improvement in sawing accuracy with the ATB blades. In fact, as the blades became dull, the sawing accuracy of the ATB saws deteriorated faster than for the standard blades. Visual evaluation of surface roughness also indicated that the ATB saws produce slightly rougher lumber. However, this may be due to increased tooth bite associated with the ATB teeth. Further testing will be required to determine if the results of this test are truly representative of the performance of ATB bandsaws in general.
Tree and log characteristics, wood properties, visually graded lumber yields, and machine-stress-rated (MSR) lumber yields were determined for 95 year-old lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) trees on good sites in southeastern British Columbia. A total of 220 trees were selected stratified by diameter-at-breast height (d.b.h.). Based on measurements of stand density made for plots around each sample tree, three samples were obtained which represented end-of-rotation stand densities of 700, 1100 and 1900 live stems/hectare (s/ha). Logs were sawn to maximize the yield of wide dimension lumber. Lumber recovery factor increased with increasing tree d.b.h. class, but due to greater stem taper, it was generally lowest for a given d.b.h. class in the 700 s/ha stand density class. Due to decreasing knot size, yields of Select Structural lumber increased as stand density increased (45.6, 62.5 and 65.4% for the 700, 1100 and 1900 s/ha samples respectively) but knots were small enough that a high proportion of lumber (> 90%) was visually graded No.2 & Btr. in all three stand density classes. Wood basic relative density was significantly inversely related to d.b.h., but was not significantly related to crown persistence or stand density. Lumber modulus-of-rupture (MOR) and modulus-of-elasticity (MOE) decreased as tree d.b.h. increased. Wide dimension lumber from open-grown trees generally failed to meet in-grade specifications for MOR and MOE. Lower MOR and MOE values were reflected in reductions in MSR yields. The juvenile wood proportion of tree stems, defined either as 15 or 30 annual rings from the pith, was only weakly related to lumber MOR and MOE. Kiln drying degrade increased with stand density class and ranged from 3% of pieces in the 700 s/ha sample to 7% of pieces in the 1900 s/ha sample. Drying degrade was essentially unrelated to proportions of juvenile wood. Application of study results to theoretical tree size and volume distributions generated by a stand growth and yield model (TASS) produced stand yields which in terms of lumber recovery, and premium structural and appearance grades, would rank stand densities in the following descending order: 1100, 700 and 1900 s/ha. Study results indicate that, for lodgepole pine grown on good sites, stand managers will achieve the optimal combination of lumber yield and grade by targeting a medium final stand density. Further research is underway to determine if the inverse relationship between average basic wood density and large diameter trees recorded in this regional study persists in other biogeoclimatic zones. It is important to note that, because the tree samples were stratified by d.b.h. and stand density classes, the lumber strength and stiffness results obtained in this study are not representative of the current lodgepole pine resource in general.
In 1992, FERIC began a two-year operational evaluation of Binol Hydrap - a non-toxic, biodegradable, canola-based hydraulic oil - in a forestry application. The study monitored the use of Binol Hydrap in a Barko 145A log loader mounted on a Kenworth log truck working in the east Kootenay region of British Columbia. This report discusses the results of the evaluation, and the experience of converting a hydraulic system from mineral oil to a canola-based oil.
This paper presents the results of an analytical and experimental investigation into the effect of bandsaw roll-tensioning on blade stiffness and cutting accuracy. The results show that rolling in the centre 60% of the sawblade will increase blade stiffness while rolling outside this region will decrease it. The optimum rolling location was shown to be the blade centre-line. A modified roll-tensioning procedure coupled with an increase in bandmill strain was shown to increase blade stiffness and improve cutting accuracy over conventionally tensioned blades. This was accomplished without increasing sawblade stress levels. Benefits of the revised procedure are an estimated increase in lumber recovery of 0.5% coupled with reductions in sawblade maintenance requirements. Mill trials are in progress to determine the long term behaviour of saws with the modified tensioning.
Compression perpendicular-to-grain (C-Perp) is one of many structural design checks that must be made by the design engineer. Up until now, much of the effort in updating the Canadian timber design code, CSA-O86, has focused on the more prominent strength properties such as bending, tension and compression parallel-to-grain strength. With the increased use of machine stress rated (MSR) lumber in engineered wood products such as trusses, designers have encountered instances where design details must be revised in order to meet the compression perpendicular-to-grain requirements specified in the timber design code. Where design details cannot be revised, certain species of lumber cannot be used although these species are able to provide more than enough strength in bending, tension or compression parallel to the grain. Inconsistencies in C-Perp design resulting from code changes for the 1989 edition as well as developments in engineered wood products have made it necessary to review the design procedures for compression perpendicular-to-grain design. The aim of this project is to rationalise the design procedures and assist the CSA task group on C-Perp in updating design values for MSR S-P-F lumber. This task has been completed. The work has resulted in new design procedures and design values for compression perpendicular-to-grain in the 1994 edition of CSA-O86.1. A background paper on these changes was presented at the July 1994 meeting of CIB Working Commission (W18A) - Timber Structures in Sydney, Australia.
At the request of the Council of Forest Industries, a simplified (hand-calculation) design method has been proposed for estimating the ultimate shear capacity and load-deflection response of wood-framed and panel-sheathed diaphragms, by Forintek's Wood Engineering Department. In its current form, the simplified code design approach can predict ultimate shear capacity for a wide range of (blocked) diaphragm constructions, sheathed with panels ranging from 7.5 mm (3/8") to 18.5 mm (3/4") in thickness, with a 22% coefficient of variation. This is comparable to the 21% variability exhibited by the current Canadian diaphragm design method, and not alarmingly larger than the 16% shown by the more detailed APA design method. Indeed, for the three high-shear diaphragms sheathed by 18.5 mm (3/8") Douglas-fir plywood panels, the proposed simplified design method yielded shear prediction errors of only 0%, 1% and 6%. Furthermore, simplified functions were also able to provide good estimates of diaphragms failure mechanisms, and their load-deflection patterns, as measured in earlier verification tests. Predictions from the simplified model need to be experimentally verified for high shear capacity diaphragms sheathed in thick panels fastened to glulam frames by large diameter nails; before its possible introduction to the Canadian wood design code.
Six trials were conducted at the Department of Wood Science, UBC on the drying of "redry" and green SPF veneer using a 0.3 m3 laboratory Radio Frequency/Vacuum (RF/V) apparatus. A larger scale trial was conducted at Canfor's Eburne mill, on the drying of "redry" SPF veneer using a 60 m3 pilot plant apparatus. Results from all these trials showed there was a wide variation in the final moisture content (m.c.) of the veneers with many veneers showing low m.c. regions. This m.c. variation could pose problems for bonding with moisture tolerant phenolic adhesives. Results from the Eburne RF/V trial showed there was a species effect in drying rates and subalpine fir veneer dried at a faster rate than spruce veneer using radio frequency heating.
In the face of reducing fiber supply green trim ends represent a valuable resource base if they can be put to a better use than hog fuel or chips. If a technically and economically feasible method for drying these was available, they could be finger- jointed into higher value products. A search of forest products data bases was carried out to locate any literature on handling and drying short lengths. All appropriate articles were obtained and reviewed. Contact was made with companies with experience in drying short lumber. The reviews are compiled under common themes with respect to package construction, major drying methods, laboratory-scale studies, handling systems and industrial experience. It was concluded that technology is available for drying, but the need for manual stacking may make the economic gains questionable.
The global objective of the project is to investigate the feasibility of increasing bandmill production by proportionately increasing both the blade speed and the lumber feed speed. The objective of this phase of the project is to transfer the results of the laboratory experiments to the sawmill industry. The work described in this report covers the transfer of the technology to two sawmills. The first report has a more detailed introduction to the project and a review of the literature.
An investigation was made to determine the feasibility of electrostatically spraying adhesive on strands and veneer for the purpose of improving adhesive bonding efficiency. If electrostatic spray treatment could improve coverage uniformity on the composite product compared to conventional spray application, then theoretically bond strength should improve, allowing for adhesive quantities normally required for production to be reduced. Estimates for a 5% reduction in the annual adhesive requirement for an OSB mill producing 300 million square feet on a 3/8" basis amounts to a $300,000 saving. Tests carried out at Forintek examined the fundamental interactions between charged water spray and strands and veneer to determine whether coverage characteristics could be improved. Laboratory set-ups included fitting Forintek's lab blender with electrostatic spray equipment and a vertical tube assembly for investigating charged spray interaction with free-falling strands. Since most commercial applicators spray free-falling strands within a blender, our first objective was to investigate how strand coverage would be effected within such an environment. Test results showed that coverage on strands electrostatically treated within the blender was not significantly different than non-charged applications. This was probably due to the free-falling strands not being adequately grounded when treated. These results are consistent with theory which states that targets should be grounded for spray coverage improvement to occur. To further test this theory, using a vertical plastic tube apparatus, individual strands were tethered by a fine ground wire and then allowed to free-fall through a charged spray, resulting in dramatic increases in coverage compared to uncharged tests. Although grounding strands within a blender may at present be unpractical, methods for momentarily grounding the strands within the blender should be investigated. Also, alternatives for applying adhesives within a blender, that allow for proper strand grounding, should be considered. Following spray tests with OSB, tests were conducted to treat veneer with electrostatic spray. A 50/50 mixture of resin and water was electrostatically applied to veneers and results showed that although coverage was improved, both in uniformity and quantity, the size of drops was considerably smaller that what is recommended for optimum bonding. In theory, to apply a charged spray consisting of larger drops would significantly reduce the effects of electrostatic forces on droplet trajectory and therefore, further tests to apply resin to veneer were discontinued.
Solutions are required to the problem of CCA-treated wood waste disposal or reuse in Canada. This issue will become more important in the coming decades as the volumes of CCA- treated wood currently in use are taken out of service. Incorporation of wastes as furnish in composites is one option and there is already industrial interest in the use of wastes from the "urban forest" in such products. While markets for many of the existing "commodity" composites are buoyant with increases in future demand anticipated and a literature review has indicated considerable research activity in the field, the use of CCA-treated wastes in composites currently presents a lot of questions and not many clear cut answers. A literature review, in combination with information on treated wood waste quantities and a study of market feasibility/consumer acceptance issues, suggests that use of CCA-treated wastes in wood/cement composites might be feasible and could be compatible with existing exterior applications for these products. Apart from the need to understand the practical impact of such wastes on the wood/cement composite process and product, key questions concerning market acceptance and effect on process cost need to be addressed. A feasibility study in cooperation with industry would establish whether specific details of technical viability should be investigated as a next step.
The recognised method for measuring the relative density of wood in North America is described in the ASTM Standard D2395. Forintek has developed a procedure, which is a variation of one of the ASTM D2395 methods, to quickly and accurately determine the relative density of wood blocks cut from lumber samples. The procedure may be used as part of a quality control program in the production of MSR lumber. The objective is to compare the relative density results obtained following a simplified procedure developed at Forintek, to the ASTM D2395 Method A and Method B procedures. Progress to date is described.
A system which integrates architectural and structural design issues for timber connections will be developed for a limited number of connections and loading conditions which are dealt with in various national and international codes and standards. The scope of engineering issues relevant to connections will be expanded to include a wide range of timber connections and engineering solutions which are not covered by code procedures. This will include cases such as 3-dimensional loading configurations, dynamic analysis of connections and more rigorous analysis procedures. Progress on these objectives is described.
A series of plywood and laminated veneer lumber (LVL) panels were prepared using incised veneers in the second phase of this two year project. The primary purpose of the work was to evaluate the effects of steam injection on the pressing times. A secondary objective was to expand the study of warpage in three-ply and four-ply plywood which was begun in phase one. Thirteen-ply 40 mm (1 5/8 inch) thick panels were evaluated for press times and thin 9.5 mm (3/8 inch) and 12.5 mm (1/2 inch) panels were evaluated for cupping and bowing. Press temperatures of 150 degrees C, 175 degrees C and 204 degrees C were used with a commercial adhesive mix for the LVL study while normal plywood pressing conditions were used for the plywood. For the plywood warpage study, the effect of lathe check orientation and species mix were evaluated. The lathe check orientation had little effect while the surface veneer species had a pronounced effect on the warpage in the plywood. Steam used for injection was heated to 260 degrees C at 450 KPa (65 psi) with a super-heater. All panels were made with incised 3.2 mm (1/8 inch) SPF veneers. The project demonstrated that steam injection can shorten press times by fifty percent if incised veneers are used.
This paper describes observations made during a trip to Japan to study wood machining technology. Topics include highlights of the 12th International Wood Machining Seminar, the 32nd Nagoya International Woodworking Machinery Fair and several visits to Japanese companies. Wood machining technology in Japan (WP-OI 95.11) Copies available from Pacific Forest Centre, Canadian Forest Service, 506 West Burnside Road, Victoria, B.C. V8Z 1M5. Fax 604 363-0797.
Research into the cutting characteristics of bandsaws has shown that, in nearly every case studied, the average cutting path of the saw is biased to one side of the ideal cut path. This paper presents the results of a laboratory investigation into this off-centre cutting. The influences on the shape and cutting behaviour of bandsaws of such basic factors as bandmill strain, guides, guide alignment, and blade overhang, are measured. It is concluded that bandsaw blades are curved in the cutting region and angled slightly out of the cut. The curvature and angle of the blade are due to the interaction of the bandsaw with the bandmill wheels, in the presence of bandmill strain, overhang and wheel crown, and are relatively insensitive to bandmill strain or pressure guides. The curvature and angle of the blade in the cutting region are most likely the cause of the cutting bias.
This report looks at the Japanese laminating industry from the perspective of the technology and techniques used in manufacturing laminated products. Through contact sessions held with Canadian embassy officials, B.C. Trade officials and with members of the various Japanese laminating industry associations, information on the potential of laminated wood products in the Japanese market was made available. On completing the plant tours, a visit was made to the most prominent woodworking machinery trade fair in Japan, the Nagoya International Woodworking Machinery Fair. This fair provided a window on the latest developments in wood processing technology of Japanese origin. An examination of Japanese wood laminating technology (WP-OI 95.10) Copies available from Pacific Forestry Centre, Canadian Forest Service, 506 West Burnside Road, Victoria, B.C. V8Z 1M5.
In the Kootenay Lake and Arrow Forest Districts of southeastern British Columbia, harvest planning and selection of harvesting systems must be responsive to high recreation and tourist values and the visually sensitive slopes. In 1992-93, the Forest Engineering Research Institute of Canada (FERIC) monitored harvesting on small patch clearcuts, and the British Columbia Ministry of Forests conducted site-disturbance surveys. On one study site, both ground skidding and cable yarding were used, in summer and winter seasons; at the second site, on ground pressure skidders were used and only in summer.