Time-Varying Seismic Fragility Analysis of ECC-RC Composite Bridge with High-Strength Steel Bars

An Engineered Cementitious Composites (ECC)-Reinforced Concrete (RC) composite pier with high-strength steel bars was developed to address various deterioration concerns in bridges, such as reinforcement bar corrosion, decreased concrete strength, and inadequate seismic performance of RC piers. This paper focuses on the seismic performance of the bridge with ECC-RC composite piers with high-strength steel bars. The nonlinear finite element models of bridges with common RC piers and ECC-RC composite piers with high-strength steel bars are established using OpenSees. Considering the effect of chloride erosion during bridge service and the damage and repair of concrete cover, time-varying fragility curves for bridge piers, bearings, and the bridge system were established based on the Incremental Dynamic Analysis (IDA) and the Capacity Demand Ratio (CDR) analysis method, followed by a comprehensive analysis. The results show that when ECC with high-strength steel bars is adopted in the plastic hinge area of bridge piers, the exceeding probability of ECC-RC composite piers with high-strength steel bars is significantly reduced. However, it has minimal impact on the seismic fragility of the bearings. When the bridge was in service for 100 years, the exceeding probability of the ECC-RC composite bridge system with high-strength steel bars was reduced by 18.79%, 51.33%, 49.38%, and 19.5%, respectively, under four different damage states.