Abstract:A fiber element analysis method was proposed and verified according to the experimental results of 9 concretefilled Tshaped steel tube (CFTST) columns subjected to uniaxial eccentric loading or biaxial eccentric loading. The behavior of concretefilled Tshaped steel tube intermediate long columns subjected to axial loading was investigated. The parameters in the analysis included the yield strength of steel, the compressive strength of concrete, the depth to thickness ratio of steel plate, the cross sectional depth to width ratio, the slenderness ratio of the specimens, and the angle of the loading. The results of theoretical analysis show that the loadcarrying capacities of the CFTST columns under axial load were obviously influenced by the slenderness ratio of the specimens and to some extent the load ratio carried by core concrete and the load angle. A comparative study of the normalized slenderness ratio vs. stability reduction ratio curves of the CFTST columns (λnφ) predicted by the fiber element analysis method and Code for Design of Steel Structures in China shows that the curves with different section parameters wave in a larger range. Finally, based on the extensive parametric analyses, the simplified calculation method of normalized slenderness ratio vs. stability reduction ratio curves (λnφ) was proposed with a considerction of the effect of the slenderness ratio and the load ratio carried by core concrete. Good agreements between the values predicted by the simplified calculation method and the experiment results were achieved, and the simplified calculation method may be referred for practical engineering design.
