Strength of concrete-filled steel box columns with local buckling effects

Local buckling of steel plates with geometric imperfections and residual stresses significantly reduces the ultimate strength of concrete-filled thin-walled steel box columns. The effects of local buckling, however, have not been considered in advanced analysis programs that lead to the overestimate of the ultimate loads of composite columns and frames. This paper presents a nonlinear fiber element analysis method for predicting the ultimate strength and behavior of short concrete-filled thin-walled steel box columns with local buckling effects. The constitutive models in the method consider the stress-strain behavior of confined concrete and structural steel. Local buckling is incorporated in the fiber element analysis programs by adopting the effective width models, which account for the effects of geometric imperfections and residual stresses. The progressive local and post-local buckling is simulated by gradually redistributing the stresses within the steel box. The fiber element analysis technique developed can be employed in advanced analysis programs for the analysis of composite frames. The accuracy of the proposed fiber element analysis method for concrete-filled steel box columns is established by comparisons with existing experimental results.