The design of multiple bolted connections in accordance with Appendix E of the National Design Specification for Wood Construction (NDS) has incorporated provisions for evaluating localized member failure modes of row and group tear-out when the connections are closely spaced. Originally based on structural glued laminated timber (glulam) members made with all L1 Douglas fir-Larch laminating lumber, the NDS provisions were confirmed by additional analysis, which indicates the applicability of the provisions to glulam with reduced design shear values. Due to the similarity to glulam in the grain orientation and layup strategy, laminated veneer lumber (LVL) is subject to similar failure modes. As a result, a study was initiated by APA – The Engineered Wood Association and the LVL industry, in collaboration with the Forest Products Laboratory (FPL) of the U.S. Department of Agriculture (USDA) to evaluate if a reduced design shear stress is necessary for LVL under similar multiple bolted connection configurations. This paper describes the test results obtained from the study, which indicate that an adequate load factor exists for LVL multiple bolted connections without a reduction in the LVL design shear stress when designed in accordance with Appendix E of the NDS.
This InfoNote summarizes recent research and work in progress. A significant amount of fire research has been conducted on mass timber over the last 10 years in Canada. This has supported the successful design and construction of numerous low-, mid-and even high-rise wood buildings. This has also fostered the introduction of new provisions into the National Building Code of Canada which has made wood and mass timber construction more accessible. However, the fire performance of these systems remains a concern for many potential occupants or owners of these buildings, not to mention building officials and fire departments. Research at FPInnovations continues to support designers and builders in the use of mass timber assemblies by ensuring fire safe designs.
The mechanical behaviour of timber structures is significantly influenced by the stiffness, load-carrying capacity and ductility of the joints. This study is focused on the stiffness of dowelled steel-to-timber joints, which were subjected to tensile loadings at different orientations with regard to the grain direction (0°, 30°, 45°, 60° and 90°). The values of the joint stiffness in service obtained from the tests were compared with predictive values from current design codes (Eurocode 5 and NDS). The current design codes showed their weak predictive ability. Besides timber density and fastener diameter, as well as clearance and friction between the joint members, orientation of load with respect to timber grain and dowel slenderness ratio are also the important factors that affect the stiffness of a joint. An empirical expression of stiffness for steel-to-timber joints with single dowel was proposed on the basis of the formula in Eurocode 5 and the Hankinson-type formula using non-linear fitting of the experiment results.