Coupled bending-shear-torsion bearing capacity of concrete filled steel tube short columns

Under coupled bending-shear-torsion (B-S-T) loading combinations, the ultimate bearing capacity of concrete filled steel tube (CFST) short columns has not been studied. In this paper, the test on eight CFST short columns was carried out. The load-deformation relations and failure modes of CFST short columns were obtained and analyzed. Based on experimental results, the failure mechanism of CFST short columns were obviously affected by the ratio of bending moment to torque, and CFST short columns under coupled B-S-T loading combinations had good ductility. The ultimate bending-shear bearing capacity of CFST short columns was significantly decreased by increasing torsion moment. Moreover, nonlinear finite element analysis was performed, which generated an accurate prediction of the ultimate capacity of concrete filled steel tube short columns under coupled B-S-T. As a conclusion, a simplified design equation for calculating the coupled B-S-T bearing capacity of CFST short columns was proposed according the regression results of the finite element parametric analysis.