Behavior of large SCFST column with different confinement effects under pseudo-static loading

Abstract

In this study, tests of twenty-four square concrete filled steel tubular (SCFST) columns with different structural sizes by the pseudo-static method were conducted to investigate the influence of the confinement effects. In addition, the structural size and the confinement effect are respectively represented by column width and width-to-thickness ratio. The experimental results, including the failure mode, the lateral load-displacement curves and the indices of the seismic performance were recorded and analyzed. The mode of failure is typical compressive flexure pattern. As the structural size increases or the confinement effect decreases, the nominal flexure strength of SCFST column decreases. Compared of the nominal flexural strength of small column, the influence of confinement effect is more significant on that of large column. The displacement ductility coefficient, the mean energy dissipation factor and the relative stiffness decrease with the increasing column width. Then enhanced confinement effect has no obvious influence on the displacement ductility coefficient of the SCFST column. When the confinement effect increases, the energy dissipation capacity of the SCFST column increases. Finally, the modified calculated method considering size effect is established, and this method is applicable to predict the bending moment of the SCFST column with different confinement effects and structural sizes.