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.