Blast and Post-Fire Behaviour of Glued-Laminated Timber Panels

Abstract

The increasing trend toward taller timber structures, built with mass timber panels, has made it essential to understand the multi-hazard response of these structural elements and how subsequent or simultaneous hazards affect their performance. Current design standards provide guidelines for individual hazards, such as fire, blast, seismic, and wind in isolation, and only conceptual holistic design frameworks have been proposed, focusing mainly on redundancy and stability under multiple hazards. Limitations in conducting research on structural elements subjected to multi-hazard scenarios are largely driven by the high cost and practical challenges associated with such experiments. An experimental program was developed that included twenty-three full-scale uncharred and charred glued-laminated timber panels tested under static and dynamic loading, with a focus on establishing their performance before and after exposure to a short-duration real fire. Simulated blast tests were conducted at the University of Ottawa Shock Tube facility, and the charred panels were extracted from the Mass Timber Demonstration Fire Test Program, a full-scale field fire test conducted in Ottawa, Canada, in 2022. In addition to the full-scale structural tests, twenty-five charred samples were examined using image analysis software. The experimental results showed that the theoretical dynamic zero-strength layer value exceeds the static value, suggesting rate-dependent effects. The findings also demonstrated that a single-degree-of-freedom model with the Reduced Cross-Section Method can be a reliable predictive tool with proper inputs to simulate the dynamic response of structural elements for fire followed by blast loading scenario; a methodology that can be extended to other timber structural elements. Based on the experimental results, recommendations for Canadian design provisions were highlighted and discussed, and a detailed design example was presented.