Effect of high-strength spirals on eccentric compression behavior of square CFST columns

Abstract

In this study, the eccentric compressive performance of square CFST columns with high-strength internal spirals (HSS) was systematically investigated. First, an eccentric compression test was conducted on spiral-confined CFST columns with influential parameters of yield strength and pitch of the steel spiral and load eccentricity. It was found that the strength and ductility of square CFST columns were significantly improved by incorporating the contribution of the confined HSS. The improvements were more pronounced for columns with lower load eccentricity ratios. Subsequently, detailed finite element analyses were conducted to investigate the performance and mechanisms of the HSS-CFST columns, i.e., the distributions of axial stress and confining pressure of concrete, the interaction between concrete and steel tube, and load versus deformation responses. It was observed that the internal spirals could not only enhance the axial stress of the concrete they confined but also improve the interaction between the concrete and steel tube. Moreover, a parametric study was performed to investigate the influence of confined steel spiral layouts on the mechanical performance of HSS-CFST columns. Decreasing the steel spiral pitch improved the strength and ductility of square CFST columns more effectively than increasing the diameter of the steel spiral. Finally, design recommendations for eccentrically loaded spiral-confined square CFST columns are provided.