Comparison Study of Time-varying Seismic Fragility of Precast Segmental and Cast-in-place Bridge Columns in High-speed Railway Bridges

Anxiety about the long-term seismic performance of precast segmental bridge columns (PSBCs) limits their wide application in harsh environments and high intensities. However, railway route selection inevitably occurs in offshore areas, and it is urgent to study the seismic performance of the PSBC considering environmental erosion and seismic effects. In order to To study the application of precast segmental bridge columns (PSBCs) in offshore high intensity areas, this paper comprehensively compares the time-varying seismic fragility of precast segmental and cast-in-place bridge columns (CPBCs) in high-speed railway bridges. Based on an offshore high-speed railway column, finite element models of representative PSBCs and CPBCs are established and verified by experiments. Then, the verified finite models are utilized to implement the time-varying fragility analysis by considering chloride ion erosion under four damage states. The main conclusions are as follows: the exceeding probabilities of PSBC and CPBC are close in intact bridges under different damage states and seismic intensities. With the prolongation of bridge service time, the exceeding probabilities of PSBC increase more rapidly than those of CPBC due to the discontinuity of PSBC segments, which leads to the acceleration of corrosion of steel bars. When the columns reach the design working life, the exceeding probability and PGA median of PSBC are higher than those of CPBC columns under four damage states. Taking the medium damage state as an example, the maximum exceeding probability of PSBC and CPBC was 97.2% and 89.1% at the medium damage state, and the PGA median of PSBC was 24% lower than that of CPBC at 100 years. This work provides a theoretical foundation for the better application of PSBC in offshore high intensity areas.