Research On Behaviour Of Concrete-Filled Steel Tubes Subjected To Complicated Loading States

In the past, there were a large number of research studies on the behaviour of concrete-filled steel tubes (CFST) subjected to compression, bending or combined compression and bending, and there were a few research studies on the behaviour of CFST subjected to pure torsion, compression-torsion, bending-torsion, compression-bending-torsion and compression-bending- shearing. However, the behaviour of CFST members under complicated loading conditions still needs to be studied deeply.Based on ago study results, this paper has carried out the research on behaviour and simplified calculation methods of CFST members subjected to complicated loading conditions, the main achievements can be summarized as follows:(1) Experimental tests on thirty-eight high performance concrete filled steel tubular (HPCFST) beam-columns were carried out. The behaviour of high performance concrete filled steel tubular beam-columns was studied, and the simplified calculation method for bearing capacity of HPCFST beam-columns was discussed. Fifty concrete filled thin-walled steel tubular stub columns were axially tested, where diameter (width) to thickness ratio was selected as the main varied parameter. The behaviour of concrete filled thin-walled steel tubular stub column was analyzed, and the simplified calculation method of bearing capacity was discussed. Based on the current test results and those reported in the literature, the upper limits of D/t and B/t of CFST members were recommended.(2) Load versus deformation relationship curves of CFST subjected to compression (tension), bending, torsion, shear, and combined loading conditions were analyzed by finite element method. Comparisons between the predicted results and tested ones were carried out, and good agreements were achieved. Since verified by lots of tested results, it demonstrated that the numerical method is reliable in predicting the load versus deformation relationships.(3) Mechanisms of load versus deformation relationship curves of CFST subjected to compression (tension), bending, torsion, shear and combined loading conditions were analyzed based on the numerical method. The stress distributions in the steel tube and core concrete and the interaction between steel tube and core concrete throughout the loading process were investigated. The influences of loading paths on the behaviour of CFST members were also analyzed.(4) Based on a wide scope of parametric analysis, simplified calculation methods of bearing...