STUDY ON TIME-DEPENDENT SEISMIC RESILIENCE OF BRIDGE PIERS CORRODED DISCREPANTLY ALONG HEIGHT UPON COMBINED CAPACITY INDEXES

To investigate the seismic resilience of bridge piers corroded discrepantly along height during their life-cycles, a probability-based evaluation method was proposed upon the seismic response and post-earthquake function state. The method was implemented by defining the damage states firstly, and then followed by dividing the repairable levels. Based on seismic fragility analysis, the recoverability curves of bridge piers were established according to the combination of the maximum drift (MD) ratio and the residual drift (RD) ratio, and the calculation process was presented for the probabilities of multistage repairable degrees of bridge piers at various damage states. The finite element model of non-uniform corroded bridge piers was established according to the erosion characteristics of the marine environment, and Pushover analysis was performed to study the degradation law of its seismic performance in the whole service period. The seismic fragility analysis was carried out using incremental dynamic analysis (IDA) method. The MD ratio was captured to define the damage state of bridge piers, and the peak ground acceleration (PGA) was adopted as the intensity measure of ground motions. Regression analysis was performed to establish the relationship between the MD ratio and the PGA, and seismic fragility curves were then obtained. Multistage repairable degrees of bridge piers were classified for each damage state, and the corresponding recoverability curves were obtained to assess the probability of every repairable degree. The results indicate that the corrosion of reinforcements causes the constant degradation of seismic performance of bridge piers when the service time increases. Compared with the non-corroded condition, when the bridge pier serves 100 years, the load bearing capacity and lateral deformation capacity decrease by 20.22% and 75.30%, respectively. Meanwhile, the increase of service time also enhances the exceedance probabilities of various damage states, and the difficulty of repair also increases accordingly. When the PGA is equal to 0.6 g, the exceedance probability of severe damage state increases from 16.92% to 35.66% after the bridge pier serves 100 years, and the probability of easy repair increases from 14.17% to 26.49%. In addition, the condition that the bridge pier is hard to repair appears.