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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. [ABSTRACT FROM AUTHOR]

Box concrete-encased, concrete-filled steel tube (CFST) piers have been used in bridges in high-earthquake-intensity regions in China in recent years. They are expected to have higher strength and better ductility than normal box reinforced concrete members owing to the contribution of CFSTs in the corners of the composite box section. However, studies on this type of composite piers are limited. This paper presents an experimental study on the behaviour of box concrete-encased CFST columns under eccentric compression. A total of 14 specimens, including 12 box concrete-encased CFST specimens and two reference box reinforced concrete specimens are tested. The main parameters in the test are height-to-width ratio and load eccentricity. A simplified method is proposed to predict the load capacity of the box concrete-encased CFST columns. [ABSTRACT FROM AUTHOR]