Behavior of concrete-filled round-end steel tubular stub columns under axial compression

A total of 17 tests of concrete-filled round-end steel tubular stub columns under axial compression were carried out with different sectional aspect ratios,steel ratios and the structural measures. The failure characteristics and the behavior of the composite column under axial compressive load were exhibited. It can be found from experiments that core concrete can be confined by the steel tube. The local buckling can be avoided by the longitudinal diaphragm or the binding bar. The longitudinal diaphragm or the binding bar can be used to improve the strength and ductility. For strength,the binding bar is better than the longitudinal diaphragm. But for ductility,the reverse is true.The finite element( FE) soft ABAQUS was used to analyze the behavior of concrete-filled round-end steel tubular stub columns. The FE results agree well with experimental ones. Based on existing simplified strength models of the concrete-filled rectangular steel tubular stub column under axial compression,a simplified strength model was proposed to predict the load carrying-capacity of concrete-filled round-end steel tubular stub columns with the longitudinal diaphragm under axial compression. In addition,the longitudinal diaphragm or the binding bar is suggested to be applied when the width to thickness ratio of the flat of the steel tube is more than 60.