Experimental study on seismic behaviors of concrete columns confined by corroded stirrups and lateral strength prediction

To understand the seismic behaviors of concrete columns confined by corroded stirrups, low-reversed cyclic loading tests were carried out on eight corroded reinforced concrete columns to study their mechanical characteristics and failure mechanisms. The influence on seismic performance indicators such as bearing capacity, hysteresis characteristics, ductility, strength degradation, stiffness degradation, and energy dissipation was analyzed comparatively based on parameters such as stirrup diameter and stirrup-spacing changes. The experimental results showed that the restraint of concrete provided by corroded stirrups is reduced, which leads to a decline in seismic performance, and with increasing stirrup corrosion, the failure limit displacement of columns decreases. The pinch phenomenon of the hysteresis curve gradually increases, the attenuation degree of strength and stiffness increases, and the ductility and energy-dissipation capacity is reduced, while the accumulated energy increases under the same control displacement. A method for predicting the lateral strength of reinforced concrete columns confined by corroded stirrups is presented based on the axial-shear-flexure interaction approach for conventional concrete columns, with modifications to consider the effect of stirrup corrosion. There was good agreement is achieved between the test results and theoretical values.