Axial compressive behaviour of RC columns with high-strength MTS transverse reinforcement

To improve the mechanical behaviour of reinforced concrete (RC) columns with square cross-section, an additional configuration of transverse reinforcement using high-strength multiple-tied spirals is proposed to achieve better lateral confinement to the concrete and to delay or avoid the buckling of longitudinal bars. In total, 12 specimens are designed for the axial compression test, including ten RC columns with high-strength multiple-tied-spiral transverse reinforcement (MTSTR) and two RC columns with conventional stirrups to provide a reference. The variables of specimens in the experiment are the spacing of circular spirals and rectangular hoops, the confined area of circular spirals and concrete strength. The experimental results indicate that the concrete and the longitudinal bars are effectively confined by the high-strength MTSTR, leading to considerable enhancements in both the load-carrying capacity and ductility of RC columns. On the basis of strain compatibility, an analytical approach to the axial behaviour of the RC column with high-strength MTSTR is proposed, and the analytical results using the model proposed by Bing and co-workers agree well with the experimental results.