A study on axial compressive behaviors of reinforced concrete filled tubular steel columns

It is clear from former researches on reinforced concrete filled tubular steel (RCFT) columns that RCFT columns have better performance than concrete filled steel tubular (CFT) columns. The enhancements may be mainly due to the improvements in performance of the concrete core because of the confinement pressure imposed by both steel tube and reinforcement. To clarify the effect of confinement on concrete core and propose evaluation equation for axial compressive strength of RCFT columns, numerical analyses of RCFT columns are conducted by matching the numerical results with experimental results via parametric study. According to the results of the analyses, effect of confinement on concrete and effect of stress state on steel tube of RCFT columns are discussed, as a result, a non-conventional method for evaluating the confinement effect which is concerned with load-sharing ratio of RCFT columns is proposed, and the evaluation equation for axial compressive strength of RCFT columns is obtained and validated through the experimental data.

► A method to define the multiaxial stress–strain law for concrete core is proposed.
► An evaluation method for confinement effect of concrete core is proposed.
► The strength reduction of steel tube can be neglected.
► The axial reinforcements are fully utilized without degradation in strength.
► An evaluation equation for axial compressive strength of RCFT columns is proposed.