Experimental Investigation on Failure Mechanism and Hysteresis Behavior of RC Single- and Double-Column Piers

Reinforced concrete (RC) single-column piers (SCPs) and double-column piers (DCPs) are widely used in highway girder bridges. However, the seismic behavior of conventional RC DCPs has not received sufficient attention. This study aimed to investigate the seismic behavior of DCPs, especially the comparison of the failure mechanism, hysteretic behavior, and dynamic response between SCPs and DCPs. To this end, the critical performance parameters between SCPs and DCPs in the elastic phase were first calculated according to the simplified calculation formulas. Eight 1/3 scaled SCPs and DCPs were then fabricated and tested under quasi-static cyclic loading, and the effective height of the DCPs was twice that of the SCPs. The test results showed that the failure modes and damage mechanisms between the SCPs and DCPs are obviously different. In particular, the plastic damage states at the top and bottom of each column in the DCP were asymmetric, and this behavior was also observed on both sides of each plastic hinge region. Subsequently, the relationship between the performance parameters of SCP and DCP in the plastic phase differed from that of the elastic phase and was not proportional. Existing formulas for calculating the plastic hinge length of SCPs cannot effectively predict DCPs and may even underestimate it. Furthermore, numerical simulations were analyzed to investigate the effects of various design parameters and ground motions on the seismic behavior of the SCPs and DCPs.