Nonlinear pushover analysis of composite frames with concrete filled steel tube (CFST) columns

In this study, the nonlinear analysis and seismic performance of composite structures having concrete filled steel tube columns (CFSTs) were investigated. The case study composite frames were made of the columns surrounded by steel tube outside and filled with concrete, and also steel I beams. These frames were designed as 4, 6 and 8 storey with three equal bays. Then, the nonlinear pushover analysis was applied to examine the effect of variation in the width-thickness ratio, slenderness ratio, yield strength of the steel tube and compressive strength of the infilled concrete within the columns of the frames with each storey height. Thus, a total of 72 different composite frame models with CFST columns and steel beams were evaluated based on the structure response parameters such as the base shear vs. top displacement curves. The obtained results were discussed comparatively in terms of lateral load carrying capacity, initial stiffness, and plastic hinge formation. It was observed that the material and dimensional properties of the CFST columns influenced significantly the seismic behavior of the composite frames.