Influence of parameters on the strength and behavior of concrete filled steel tube specimens subjected to axial compression and cyclic loading

Abstract

The strength and behavior of Concrete Filled Steel Tube (CFST) columns subjected to uni-axial compression and cyclic loading are presented from the available literatures. Based on the experimental test results of 230 circular, 163 rectangular and 113 square specimens subjected to axial loading and 33 circular, 18 rectangular and 23 square specimens subjected to cyclic loading, the parameters affecting the strength and behavior of CFST columns are outlined. The effect of relative slenderness ratio (λ), confinement (ξ), Length to Diameter (L/D), Length to Breadth (L/B), Diameter to thickness (D/t), Breadth to thickness (B/t) on the axial capacity of columns are examined. The effect on ductility ratio (μ) due to axial load level (n), steel ratio (α) and member slenderness (ƛ) are also presented. The ultimate axial loads (Ne) of the columns are compared with the design values (Nc) predicted using various codes namely, Eurocode-4 (EC4), Australian standards (AS5100), Chinese code (DBJ13-51) and American code (AISC 360–10). Results showed that relative slenderness ratio and Length to Diameter of circular CFST specimens showed direct effect on the strength and behavior of the column. Circular sections with high steel ratio reflected high ductility compared to rectangular and square sections. Steel ratio and member slenderness show significant changes in ductility ratio as the values are increasing for all three types of sections. Axial load predictions of EC4 agrees well with the experimental test results and are conservative. While, results predicted by AS5100, DBJ13-51 and AISC 360 – 10 are unconservative.