Behaviour of concrete-filled square steel tubular columns with stiffeners under concentric compression

Test results on concrete-filled square steel tubular stub columns with longitudinal inner and outer welded stiffeners under concentric compression are presented in this paper. A longitudinal stiffener was provided at each side of the tube. The main experimental parameters considered were the width-to-thickness ratio and stiffener rigidity. Moreover, empty tubes with or without stiffeners, as well as unstiffened concrete-filled square steel, tubes were also tested for comparison. Results from the study indicated that, compressive load of the composite stub columns was increased when stiffeners were provided. The stiffeners can effectively delay the local buckling of the tube, as well as improve the lateral confinement on concrete core.