Axial compressive behavior of stiffened and multi-cell cross-shaped CFST stub columns

Abstract

Cross-shaped concrete-filled steel tube (CFST) can avoid the structural column protruding from walls and save the room space, but the steel tube is prone to local buckling under compression. The use of stiffeners and multi-cell form can effectively improve its mechanical performance. However, limited research studies were conducted on these column forms previously. In this paper, six stub columns were tested under axial compression varying the parameters of cross-section form and concrete strength grade. The failure pattern, ultimate strength, load-strain curve, compressive stiffness and ductility were obtained. The test results show that using longitudinal stiffeners or multi-cell form can improve the axial compressive strength, stiffness and ductility of cross-shaped CFST, and the mechanical performance of multi-cell form is superior. The axial compressive strength of stiffened and multi-cell columns can be enhanced by 4.9%–25.2% and 21.8%–28.4%, respectively, compared with unstiffened columns. The corresponding stiffness can be increased by 14.2%–27.4% and 25.2%–43.2%, respectively, and the corresponding ductility can be increased by about 9% and 120%, respectively. Finite element (FE) models were established for the cross-shaped CFST stub columns and the FE simulation results were in good agreement with the experimental results. 134 stiffened and 134 multi-cell stub column models with different parameters were calculated, and the design methods were suggested for axial compressive strength and stiffness of stiffened and multi-cell cross-shaped CFST stub columns.