Behavior of hexagonal concrete-filled double-skin steel short columns under the effect of axial compression

Concrete-filled double skin tubular (CFDST) columns involve a tube-‌in-‌tube arrangement, where the steel sections can be round, square or rectangular hollow sections, with the annulus between the hollow sections filled with concrete. To date there have been no significant applications of hexagonal concrete-filled double skin tubular columns (HCFDST) with inner circular tubes worldwide, partly due to the lack of design provisions. This paper addresses the compressive performance of these columns. To obtain the structural behavior of HCFDST columns, a finite element analysis was conducted. To indicate the accuracy and the reliability of the model, the proposed FEM model was verified by the available experimental data for HCFDST. Columns were employed to conduct parametric studies, the effects of various parameters on the load-displacement response of HCFDST short columns are studied by using the validated FE model. A new formula to determine ultimate load for regular HCFDST short columns in compression has been proposed in this study.