Abstract：To investigate reinforcement effectiveness of timber columns strengthened with wrapped CFRP (carbon fiber reinforced polymer) strips and near-surface mounted steel bars, 54 strengthened timber columns with different cross section were tested under axial compression. Working performance of strengthened timber columns with different cross section was analyzed considering the number of mounted steel bars and the arrangement of CFRP strips. Experimental results indicated that the failure process of circular and square columns was almost the same. The CFRP strips of circular timber columns were prone to brittle fracture, while the square timber column showed the debonding failure of CFRP strips caused by local outward bugle of steel bars. Mounted steel bars are able to enhance the bearing capacity of both circular and square timber columns, and CFRP strips can significantly improve the ultimate load of circular timber columns. Stress-strain curves of test specimens show that peak stress and deformation capability of columns with different cross section go up with the increase in the number of mounted steel bars and wrapped CFRP strips. Due to effective confinement, CFRP strips and mounted steel bars can promote mutually and work together. And the effectiveness of composite reinforcement method for circular timber columns is better than that for square timber columns. According to fitting analysis of test data and related theories of concrete columns confined by FRP materials, a calculation model for load-bearing capacity of timber columns with composite reinforcement method was established. The reliability of proposed formula was verified through comparison between theoretical values and test results as well as added experimental research.
