Retracted: Seismic Risk Probability Assessment of Offshore Bridge Based on the Material Degradation

Abstract

In order to analyze the effect of chloride corrosion on seismic performance of bridge structures, a methodology is proposed to evaluate the seismic risk probability of offshore bridges considering the material degradation in marine environment. The numerical model of a continuous concrete reinforcement bridge is established by finite element software of OpenSees. The random samples of longitudinal reinforcement diameter, yield strength, stirrups diameter and cover concrete compressive strength of corroded piers under different service time are obtained based on the probabilistic method. The set of samples combining ground motion and bridge is formed. The damage states capacity of bridge piers is analyzed by the Pushover analysis. The incremental dynamic analysis of bridge is carried out. The seismic vulnerability analysis is carried out for each component and the whole system of the bridge. According to the site type, the seismic hazard curves of bridge structures in different service time are obtained by the equal transcendental probability theory and the existing seismic hazard model. Monte Carlo method is used to generate random samples of ground motions in different service time. The seismic risk probability of the offshore bridge can be evaluated based on the seismic vulnerability analysis and the seismic hazard evaluation. The results showed that the performance of reinforced concrete degraded and became progressively worse with advancing service time. The corrosion of stirrup resulted in a significant decrease in shear capacity of the pier. The failure mode of corroded pier is changed. The influence of shear deformation should be considered when establishing the finite element model of corroded pier. Considering the degradation of material properties caused by chloride ion erosion, the seismic risk probability of longitudinal and transverse damage of bridge system decreases with the increase of service time. The risk probability is about 25% higher than the bridge without material degradation.