Analytical behaviour of eccentrically loaded concrete-encased CFST box columns

This paper presents a theoretical study on the performance of concrete-encased concrete-filled steel tube (CFST) box columns subjected to eccentric axial loading. Finite-element analysis (FEA) was used to analyse the composite columns and experimental data reported recently by the authors was used to verify the FEA modelling. Analysis of the behaviour of the composite, including the full-range load versus lateral mid-height deflection, stress distributions, column failure modes and the interactions between steel and concrete, was carried out. The behaviour of the concrete-encased CFST box columns was compared with that of corresponding reinforced concrete columns and CFST built-up columns. Finally, a parametric study was carried out and the moment magnification approach adopted to propose design formulae for eccentrically loaded concrete-encased CFST box columns.