Experimental research on seismic behavior of T-shaped concrete-filled steel tube columns with reinforcement stiffeners

Five T-shaped concrete-filled steel tube(CFST) column specimens including four stiffened columns and one non-stiffened column and one reinforced concrete (RC) column were fabricated and researched by quasi-static experiment under cyclic loading. Failure modes and hysteretic properties of specimens were investigated. The mechanism of reinforcement stiffeners and the constraining effect provided by T-shaped tube were also studied. Experimental results reveal that: compared with T-shaped RC columns, T-shaped CFST columns have positive effect on failure mode, initial stiffness, bearing capacity and energy dissipation capacity; the reinforcement stiffeners can effectively postpone steel tube's local buckling and restrain separation of steel tube and concrete at concave corners, to guarantee the interaction of steel tube and concrete; due to fully utilization of stiffeners' tension capacity, the tension reinforcement stiffeners' restricting function is more significant than that of serrated-shaped reinforcements; the CFST columns with larger steel ratio have high bearing capacity and better energy dissipation capacity; with the axial compressive ratio varying from 0.2 to 0.4, the bearing capacity of CFST specimens increases but the ductility decreases.