Post-fire structural performance of glued-laminated timber columns subjected to real fires

This paper presents the results of an experimental test program conducted on fire-damaged glued-laminated timber (glulam) columns. The columns were part of the Mass Timber Demonstration Fire Test Program (MTDFTP) in Ottawa, Canada, during which a series of full-scale fire tests were performed on a two-storey mass timber structure. The structure was designed to represent the fourth and fifth storey of a hypothetical 12-storey mass timber building. The specimens were subjected to qualitative and quantitative post-fire structural assessments following the fire tests. The charred layer of each column specimen was removed by physical means and the residual cross-sections were measured and evaluated to determine the char depth. Full-scale axial compression tests were conducted to verify the post-fire structural demand of the columns. The findings indicated that the charring rates consistently exceed those prescribed in contemporary design standards. The column specimens were capable of withstanding expected post-fire axial loads, secondary effects caused by the fire damage need to be considered when predicting post-fire axial capacities. The research outcomes of this study are expected to support Canadian design and fire code provisions as they pertain to the use of mass timber in mid-rise structures, particularly in terms of conducting post-fire structural assessments.