Axial Mechanical Properties of Timber Columns Subjected to Freeze-Thaw Cycles

The behaviour of timber columns subjected to freeze-thaw cycles under axial compression is presented in this paper.A total of forty specimens,including twenty circular timber columns and twenty square timber columns,were tested under axial compression.The failure modes,ultimate bearing capacity,ductility coefficient,load-displacement curves and load-strain curves were obtained and analyzed.The number of freeze-thaw cycles(from 0 to 80)and the specimens’height(from 225 mm to 360 mm)were considered as the main parameters.After freeze-thaw cycles,there was no obvious change on the surface of the timber columns.The test results showed that freeze-thaw cycles could reduce the ultimate bearing capacity of the timber columns,and the average reduction of the ultimate bearing capacity of the specimen reached 28%.The ductility coefficient of the square specimens subjected to freeze-thaw cycles almost remains constant compared with that of the square timber columns left untreated.While the ductility coefficient of the circular timber columns increases after freeze-thaw cycles.In addition,based on the extensive experimental analysis,a regression formula is derived to predict the ultimate bearing capacity of the timber columns after being subjected to freeze-thaw cycles,which is proved to be reasonable accurate.