Axial mechanical properties of small-diameter round timber short columns after exposure to elevated temperatures.

A total of forty-eight specimens were tested, including forty short timber columns at elevated temperatures and eight short timber columns left untreated at ambient temperature. The main parameters explored in the test include column heights (135, 180, 225 and 270 mm), elevated temperature duration (10, 20, 30, 40 and 50 min) and section form. It was found that two new failure modes were generated after the specimens exposed to the elevated temperatures: splitting failure and bottom crushing, and the ultimate bearing capacity of the specimens with bottom crushing is the lowest. The ductility of circular specimens increases with the increases of column height. When the elevated temperature duration reaches 50 min, the plasticity of the specimens basically subside. The ultimate bearing capacity of the timber columns decreases with the increase of the elevated temperature duration and the maximum reduction is about 60% percent.