Cyclic and monotonic behaviour of steel-reinforced concrete-filled steel tubular columns

Steel-reinforced concrete-filled steel tubular (SRCFST) column, exhibits high strength and superior fire resistance, is a type of composite members developed by configuring the steel section in conventional concrete -filled steel tubular (CFST) column. In this paper, the cyclic behaviour of SRCFST columns was experimentally investigated. Twenty columns with cross and I-shaped steel sections under cyclic loading were tested. The effects of the axial load ratio and steel section type on the failure modes, lateral load-displacement curves, and seismic performance were investigated. The test results demonstrate that columns with circular cross-sections, which experience severe local buckling and fracture of the steel tube, exhibit superior cyclic performance compared with those with square cross-sections. The steel section type has a negligible influence on the seismic behaviour of the columns. As the axial load ratio increases, the ductility factor and ultimate load of the columns decrease moderately. A finite element (FE) model was developed to investigate the full-range behaviour of the columns under monotonic loading. Finally, design methods were proposed for calculating the lateral capacity of SRCFST columns with circular and square cross-sections.