Performance of composite L-shaped CFST columns with inner I-shaped steel under axial compression

Abstract

To improve the behaviour of conventional L-shaped concrete-filled steel tubular (CFST) columns, experiments and numerical modelling of composite L-shaped CFST columns with inner I-shaped steel under axial compression were conducted. Experiments of thirty-two specimens, including 16 short columns and 16 middle long columns, were carried out with various steel tube confinement index (θ), built-in steel ratio (ρ) and slenderness ratio (λ). The load-average longitudinal strain curves, load-deflection curves and bearing capacity of the specimens were also investigated. The experimental results demonstrate that those specimens with higher values of θ and ρ, and lower value of λ, have higher ultimate bearing capacity. When the height of column remains constant, the strength and ductility can be improved by increasing θ and ρ. With the increase of λ, the local buckling failure is gradually transformed into a combination of local buckling and global buckling. A finite element analysis (FEA) model was developed to investigate the performance of composite L-shaped CFST columns with inner I-shaped steel under axial compression, and the feasibility of the FEA model was verified by the comparison against experiment results. Finally, the formulas were also proposed to estimate the ultimate bearing capacity of short and middle long composite columns and the estimated results match well with the experimental results.