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Based on the energy method, this article presents a theoretical study on the elastic local buckling of steel plates in rectangular concrete-filled steel tubular columns with binding bars subjected to eccentric compression. The formulas for elastic local buckling strength of the steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars are derived, assuming that the loaded edges are clamped and the unloaded edges of the steel plate are elastically restrained against rotation. Then, the experimental results are compared with these formulas, which exhibits good agreement. Subsequently, the formulas are used to study the elastic local buckling behavior of steel plates in rectangular concrete-filled steel tubular columns with binding bars under eccentric compression. It is found that the local buckling stress of steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars is significantly influenced by the stress gradient coefficient, width-to-thickness ratio, and the longitudinal spacing of binding bars. With the decrease of width–thickness ratios or the longitudinal spacing of binding bars or with the increase of the stress gradient coefficient, the local buckling stress increases. Furthermore, the influence of the longitudinal spacing of binding bar is more significant than the stress gradient coefficients. Finally, appropriate limitation for depth-to-thickness ratios (D / t), width-to-thickness ratios (B / t), and binding bar longitudinal spacing at various stress gradient coefficients (α 0) corresponding to different cross-sectional aspect ratios (D / B) are suggested for the design of rectangular concrete-filled steel tubular columns with binding bars under eccentric compression. [ABSTRACT FROM AUTHOR]

The axial compressive behaviour of an innovative type of square concrete filled steel tube (CFST) column to reinforced concrete (RC) beam joint was experimentally investigated in this paper. The innovative joint was designed such that (i) the steel tubes of the CFST columns were completely interrupted in the joint region, (ii) the longitudinal reinforcements from the RC beams could easily pass through the joint area and (iii) a reinforcement cage, including a series of reinforcement meshes and radial stirrups, was arranged in the joint area to strengthen the mechanical performance of the joint. A two-stage experimental study was conducted to investigate the behaviour of the innovative joint under axial compression loads, where the first stage of the tests included three full-scale innovative joint specimens subjected to axial compression to assess the feasibility of the joint detailing and propose measures to further improve its axial compressive behaviour, and the second stage of the tests involved 14 innovative joint specimens with the improved detailing to study the effect of the geometric size of the joint, concrete strength and volume ratio of the steel meshes on the bearing strengths of the joints. It was generally found from the experiments that (i) the innovative joint is capable of achieving the design criterion of the 'strong joint-weak member' with appropriate designs, and (ii) by decreasing the height factor and increasing the volume ratio of the steel meshes, the axial compressive strengths of the joints significantly increased, while the increase of the length factor is advantageous but limited to the resistances of the joint specimens. Because of the lack of existing design methods for the innovative joints, new design expressions were proposed to calculate the axial compression resistances of the innovative joints subjected to bearing loads, with the local compression effect, the confinement effect provided by the multi-layers of steel meshes and the height effect of concrete considered. It was found that the proposed design methods were capable of providing accurate and safe resistance predictions for the innovative joints. [ABSTRACT FROM AUTHOR]

This paper investigates the axial compressive behaviour of T-shaped concrete-filled steel tube (CFST) stub columns with blinding bars. In this column system, binding bars are applied cross-through the section and produce confinement effects. Eleven specimens with binding bars and five ones without binding bars were tested under axial compressive loading. The experimental results demonstrate that, by setting binding bars, the local buckling failure modes are changed and the occurrence of local buckling is delayed, and the global outward bulge of the steel tube at the concave corners can be effectively restrained. The ultimate strength and ductility of the columns with binding bars can achieve up to 1.53 and 7.5 times higher than those of the columns without binding bars, respectively. Taking into consideration the contribution of binding bars, the confinement effects of steel tube and the other sectional characteristics, a method for predicting the ultimate axial compressive strength of the columns with or without blinding bars is established. The accuracy of the method is validated through comparisons of the experimental results reported in this paper and in other available open literatures. [ABSTRACT FROM AUTHOR]