Behavior and Modeling of Glulam Beams with Bolted Connections Subjected to Shock Tube–Simulated Blast Loads

Abstract

An experimental program investigating the behavior of glued laminated timber (glulam) assemblies with various bolted connections subjected to simulated blast loading was undertaken. A total of 14 full-scale tests on 137×267-mm glulam members with idealized and realistic boundary conditions were carried out using a shock tube apparatus capable of simulating the effects of far-field blast explosions. Full-scale glulam specimens with bolted connections designed to yield in bolt bending performed better than those that were overdesigned. Proper detailing of the bolt group geometry was found to be sufficient to achieve the desired failure sequence. Reinforcement with self-tapping screws changed the failure mode from that of splitting to a combination of bolt yielding and wood crushing and provided additional ductility in the assembly. A two-degree-of-freedom blast analysis was found to adequately capture the system response with reasonable accuracy. An investigation of the current Canadian blast design provisions showed that the design approach does not allow for energy dissipation in the assembly. An approach is proposed that requires more stringent provisions for the design of brittle failure modes in connections and ensures that ultimate failure will occur in load-bearing timber elements.