Numerical study on the Behavior of High Strength Concrete Encased Steel (CES) Composite Stub Columns under Compressive Load

This paper evaluates numerically the compressive performance of axially-compressed high-strength concrete-encased steel (CES) high-strength steel composite stub columns. A three-dimensional (3D) finite element (FE) model was established using ABAQUS FE software, which was validated through comparison with existing experimental results of previous studies. A subsequent parametric analysis was performed to assess the influence of several parameters on the axial load-displacement curve, ultimate load-carrying capacity, and post-peak behavior of high-strength CES composite stub columns. Based on the predicted results, it was found that increasing the web and flange thickness of the steel section can enhance the ultimate capacity, post-buckling, and residual strengths with no pronounced improvement of the elastic and post-peak performance of high-strength CES composite stub columns under axial loading. Besides, increasing the compressive strength of concrete does not show any significant difference in the elastic response of specimens. However, using a higher strength grade of concrete showed a fast rate of decay in the post-peak performance of such columns. Additionally, it was demonstrated that high-strength steel sections can significantly improve the ultimate load, post-peak ductility, and residual strengths of short, compressively loaded, high-strength CES composite columns. It was also observed that increasing the transverse tie spacing does not show a significant effect on the elastic and post-peak response of high-strength CES composite columns while increasing the tie spacing results in a slight reduction in the ultimate strength and ductility of these columns. The FE-predicted results were used to evaluate the applicability of design codes in predicting the design compressive resistance of high-strength CES composite stub columns. It was indicated that EC4, JGJ, and CSA can accurately estimate the design compressive strength of CES composite columns, while NZS and ACI slightly exhibited conservative predictions of the design resistance of columns. It can be concluded that the findings of this study are expected to contribute to the available literature on the axial behavior of high-strength CES composite stub columns.