Hysteretic behavior of concrete filled thin-walled steel tubular columns

The flexural load-displacement hysteretic behavior of concrete filled thin-walled steel tubular columns was experimentally investigated. The parameters in the study included the axial load level and steel tubular section type. Nine concrete filled thin-walled steel tubular columns, including six columns with a longitudinal stiffener on each inner face of the steel tube and three columns with a longitudinal stiffener on the two opposite inner face of the steel tube were tested under constant axial loading and cyclically increasing lateral loading. The effect of axial load level on the hysteretic behavior was studied. The experimental results indicated that these columns under axial load level below 0.5 have plump hysteretic loops with slight pinching effect, better ductility and energy dissipation capacity. The displacement ductility decreased significantly with an increase in the axial load level. The ductility of specimens with a longitudinal stiffener on each inner face of the steel tube is better than that of columns with two opposite stiffeners.