Experimental and numerical studies on the axial compression performance of hexagonal stiffened CFDST stub columns

In this paper, the authors conducted sixteen axial compressive tests on the hexagonal ultra-high performance concrete-filled steel tubular stub columns. The parameters studied in this research program included the cross-sections, section width, the steel tube thickness, and the hollow ratio. Based on the experimental results, the failure modes, axial load-shortening curves, composite strength, and ductility coefficient of the column were illustrated and discussed. The results indicated that stiffeners can significant delay the local bucking of steel tube and improve the interaction between the ultra-high performance concrete (UHPC) and the steel tubes. To simulate the mechanical response of these new types of columns, the authors developed a fiber-beam model (FBM) including the local buckling of steel tubes and the confinement effect. Then, the authors conducted a parametric study to discuss the influence of the hollow ratio, the steel tube thickness, and the strength of steel and concrete. Finally, the authors proposed a new method for predicting capacity and verified it against the test/numerical results. With the comparison of the design rules recommended by the current design codes, the new method proposed in this paper showed a good agreement with the test/numerical results. It can provide a reference for related engineering design.