Hysteretic behavior of square CFT columns with binding bars

Abstract

This paper presents the hysteretic behavior of square concrete-filled steel tubular (CFT) stub columns with binding bars. A total of ten square CFT stub columns including eight specimens with binding bars and two specimens without binding bars were tested under constant axial load and cyclic lateral loads. The effects of the axial load level and the spacing of binding bars on the hysteretic behavior were investigated carefully. Experimental results demonstrate that the specimens with binding bars show higher lateral bearing capacity, higher stiffness, higher ultimate deformation capacity and better energy-dissipation capacity compared with those without binding bars. In addition, the initial local buckling for specimens with binding bars is significantly delayed by the binding bars. Furthermore, the lateral bearing capacity, the ultimate deformation capacity, the energy-dissipation capacity and the stiffness of the specimens with binding bars are significantly improved with the spacing of binding bars decreasing. The ultimate deformation capacity decreases with an increase in axial load levels while the energy-dissipation capacity increases with an increase in axial load levels. Finally, the fiber element analysis for all specimens is carried out. The calculated envelope curves and the calculated hysteretic curves of the specimens by the fiber element analysis are in good agreement with the experimental results.