Nonlinear analysis of concrete-filled single and double skin steel tubular tapered columns under axial loading

In this study, the structural response of concrete-filled single and double skin steel tubular (CFST and CFDST) composite tapered columns was investigated through the finite element method (FEM). In the development of the FEM model, the concentric axial loading condition and circular section were adopted. Experimental results available in the literature were used to verify the proposed FEM model. In addition, a parametric study was performed to visualize the effectiveness of tapered angle and material strengths on the ultimate capacity of CFST and CFDST tapered columns. To this aim, a total of 60 tapered column samples (including 30 CFST and 30 CFDST columns) were modeled by taking into consideration five tapered angles, two steel tube yield strengths, and three concrete cube compressive strengths. The verification of the FEM model revealed that the developed model has a reliable and trustable assessment capability. It was noticed that the tapered angle was the most crucial parameter, influencing significantly the ultimate axial strength and stiffness of both CFST and CFDST composite tapered columns. As well, it was overtly beheld from the study that CFST composite tapered column specimens had better ultimate axial strength values than CFDST composite tapered column specimens with the same sectional and material properties.