Abstract:Tests were conducted on six concretefilled Tshaped steel tube (CFTST) stubs to investigate the characters of the deformation, failure modes and the bearing capacity of this kind of composite columns. The parameters taken into consideration in the test included the depth to thickness ratio of steel plates, the cross sectional depth to width ratio of the specimens. Experiment indicated that the bearing capacities of CFLST columns were not improved effectively, but the ductility were increased considerably, due to the fact that the local buckling mode of steel tubes were altered by the core concrete. It was also observed that the outward corners of steel tubes gave the greater confinement to concrete, and the inner corners almost failed to confine the core concrete due to the separation between the steel plate and the core concrete; hence CFTST stub columns failed in the local buckling of the wider steel plate and the crushing of concrete in the region of local buckling and inner corner. Test results showed that the decrease of the depth to thickness ratio of the flange plates of the steel tubes could postpone the occurrence of the initial local bucking in the wider steel plate, strengthen the confinement effects of steel tubes on concrete, and enhance the bearing capacity and ductility of the CFTST columns. Finally, the applicability of the methods in current specifications or codes, national and abroad, for calculating the bearing capacity of specimens was discussed.
