Seismic Performance and Confinement Reinforcement Design of High-Strength Concrete Columns Confined with High-Strength Stirrups

This paper aims at analyzing the failure process, failure modes, characteristics of hysteresis loop and the ductility of 10 high-strength concrete (HSC) columns confined by high-strength complex stirrups under cyclic lateral force and a higher constant axial loading. It is indicated that the hysteresis loop of this type of columns still show plump spindle-shaped at higher axial compression ratio, which shows better ductility, energy dissipation and anti-collapse performance. Therefore, it is an effective measure of setting high-strength stirrups to ensure the good ductility of HSC columns under high axial compression ratio and to increase the limit value of axial compression ratio. The stress of transverse reinforcement is evaluated, which shows that high-strength stirrups have yielded when most of the specimens are destroyed, and the strength of stirrups can be fully developed to provide a better effect of restraint. Based on a large number of experimental data, the relationships between the limit drift, the ductility coefficient of HSC columns and axial compression ratio, stirrup characteristic values, covering layer as well as longitudinal reinforcement ratio are established; the calculation formula of minimum stirrups characteristic value of HSC columns at different seismic levels considering of axial compression ratio is presented.