Theoretical study on concrete-filled steel tubes under static and variable repeated loadings

This paper presents an analytical study for modelling the behaviour of concrete-filled steel tubular (CFST) columns subjected to Static Loading (SL) and Variable Repeated Loading (VRL). The variables considered in this study are concrete strength and load eccentricity. Simple mathematical models are developed and used in the analysis. The analytical results show that the incremental collapse (IC) occurs in high load ranges in CFST columns under VRL and instability failure occurs under SL. The CFST columns with large end load eccentricity were found to fail at a low upper limit load level than that with small eccentricity of loading. The IC failure was found to be unaffected by the strength of concrete infill. The hollow steel tubular (HST) columns showed similar behaviour under SL and VRL protocols. The study showed that the theoretical analyses satisfactorily model the actual behaviour of the columns under SL and VRL protocols.