Seismic behavior of cross-shaped concrete-filled steel tubular columns

This paper experimentally investigated the behavior of a cross-shaped concrete-filled steel tubular (C-CFST) column subjected to a constant axial load and a low-cycle repeated loading. Nine C-CFST columns with different length-width ratio, width-thickness ratio and axial compression ratio were designed, and the failure mode, hysteresis curve, skeleton curve, ductility, stiffness degradation and energy dissipation capacity of each specimen were studied and analyzed. The results indicated that the cross-shaped steel tube had a strong restraining effect on the core concrete, and C-CFST columns of different sectional dimensions all exhibited favorable seismic behavior, which is suitable for middle-high residential buildings. An increase of length-width ratio enhanced the initial stiffness with a decrease of ductility, and more rapid stiffness degradation during loading. Specimens with smaller width-thickness ratios had higher ductility, stiffness, and energy dissipation capacity. A larger axial compression ratio could reduce the bearing capacity, and cause the stiffness to degrade faster. Moreover, a hysteretic model of C-CFST columns was also proposed based on an analysis of the test results.