A design method for seismic isolation systems considering the dual-objective seismic performance coordination of high-speed railway track-bridge system under near-fault earthquakes

Near-fault earthquakes pose a serious threat to high-speed railway (HSR) bridges because of their strong velocity pulses, large displacement demands, and the need to maintain post-earthquake traffic functionality. Traditional seismic isolation systems often fail to simultaneously control track residual deformation, restrain bearing displacement, and optimize pier seismic performance under different levels of seismic intensity. To address this issue, this study proposes a seismic isolation design method that considers the dual-objective performance coordination of the HSR track-bridge system. First, the dynamic interaction and functional requirements of the track-bearing-pier system under near-fault earthquakes are systematically integrated, and a design framework targeting the coordination of structural safety and traffic safety is established. Then, using a combined system consisting of bearing, restraining, energy-dissipation, and self-centering devices as the implementation platform, a parametric design method is developed to account for the performance demands of individual isolation components under different earthquake levels. A typical HSR simply supported bridge is selected as a case study, and nonlinear dynamic time-history analyses under near-fault ground motions are conducted. The effectiveness of the proposed method is verified through comparisons with two conventional seismic isolation schemes. The results show that the proposed performance-coordinated isolation scheme (PCIS) can significantly reduce track residual deformation and the risk of girder unseating, while fully utilizing the seismic capacity of the pier and improving the adaptability of the system across different seismic intensity levels.