Modelling of dimension lumber in axial compression at elevated temperatures

The design of wood-frame structural systems to withstand exposure to fire depends on knowledge of the fire endurance (time-to-failure) of the wood members used in the system. In fires, wood loses part of its load-carrying capacity due to charring and part due to strength degradation. This thesis examines the reduction in compression strength experienced by dimension lumber when exposed to elevated temperatures.; A program of experimental testing of nominal 2 x 4 Machine Stress Rated (MSR) lodgepole pine lumber concentrically loaded in compression and exposed to elevated temperature was undertaken by Forintek Canada Corp., Canada's wood products research institute. A computer program entitled HTExposure was written to simulate the experimental time-to-failure data gathered in Forintek's testing program. This computer program combines a modification of an existing heat-transfer model with various published compression-strength reduction models. This was done in order to determine which of those strength-reduction models could predict times-to-failure comparable to the observed values. As well, a new compression-strength reduction model was proposed. When predicted results were compared to the observed data, it was determined that the computer program predicted results closest to those observed when using the new compression-strength reduction model proposed in this study.