The complexity of the current timber connection design process is one of the major reasons preventing the wider use of wood products in low-rise non-residential and innovative residential construction. Connections of members in structures, particularly in timber buildings, require the combination of both quantitative and qualitative aspects of design to produce a safe and aesthetically pleasing structure. Knowledge-based expert systems offer designers access to the full range of design methods, allowing the connection design task to be completed with ease and confidence. This study investigates the expert system approach by constructing a framework for such a design aid - a framework that incorporates techniques from artificial intelligence, architecture, and engineering. The design aid has potential for industrial application, and could be developed into an educational tool for timber and wood product design courses at the university level.
In response to a need for technical information to support the design of wood trusses in Canada, the Truss Research Program was established. Forintek's role in the Truss Research Program consisted of two projects: Truss Testing and Analysis, and Strength Variations in Trusses. The first project funded by the wood truss industry, focussed on establishing the structural reliability of residential pitched chord trusses and developing experimental data to verify truss analysis tools used by the truss industry. The second project, funded by the CFS, which is the topic of this report, provided the lumber properties information for the program. The combined loading equipment developed under this project has been used to test 2x4 S-P-F 1650f-1.5E MSR lumber under axial compression and bending loads. This data will now be used to verify a comprehensive stochastic finite element model that is currently under development at the University of British Columbia. A lumber design procedure comprised of a new interaction equation and factors to quantify load configuration effects for truss applications was developed under this project and at U.B.C. The design procedure was accepted in principle by the Technical committee on CSA-O86.
With the growing use of wood density as a design property, there is a need for a simple and rapid, but accurate, method of measuring wood density outside of a laboratory environment. In this report, a test apparatus developed at Forintek to accurately measure the relative density of small wood samples is presented. The apparatus was previously developed to measure the relative density of a large number of wood samples from an in-grade lumber testing program. Forintek's test set-up is an adaptation of the ASTM D2395 water immersion method. It consists of a micro-computer software and an electronic balance with a cage for submerging the test specimen. This apparatus may be used with waxed or unwaxed blocks. With this apparatus, test results from unwaxed (Forintek method) specimens may be calibrated to waxed (ASTM water immersion method)specimens provided the specimen size is maintained. In addition to the relative density, the oven-dry moisture content of the test specimen may also be determined using this apparatus. In this report, a comparison of the results from the Forintek method to the ASTM D2395 methods is presented. While not as accurate as the ASTM methods, ease of use, robustness, and level of accuracy make the Forintek method ideal for use in a mill environment, especially for ongoing quality control testing involving a small number of samples.
The bearing strength of Hem-Fir MSR lumber has increased from 11 to 38% over the previous bearing strength values. The upgraded design values will be published in the upcoming supplement to the Canadian Engineered Wood Design code, CSA-O96.1-M94. This code change was assisted in part by data developed in this project on the bearing strength of Hem-Fir. This code change, although it did not affect the bearing strength of visually grade Hem-Fir lumber, is significant to the utilisation of Hem-Fir MSR lumber in the Canadian market. Grades of MSR Hem-Fir lumber 1650f-1.5E or higher now have the same bearing strength values as S-P-F MSR lumber. This simplifies the design code when MSR lumber is specified and allows the full potential of MSR Hem-Fir lumber to be used in engineered wood applications such as trusses. Additional data are being collected on the performance of Hem-Fir lumber under constant loads. This data will create a data base on Hem-Fir lumber similar to that developed for S-P-F and D.Fir-L in 1993-1994.