The research on a reasonable seismic resistance system for urban rail transit bridges in high-intensity areas

Taking the standard simply supported beam of the Xi’an Metro Line 10 as an example, numerical analysis models were established using Midas /Civil software for both ductile seismic-resistant systems and seismic isolation systems. The study examined the rationality of two seismic-resistant systems for the elevated bridge of this project and compared the engineering economy of the substructure of simply supported beam bridges with different pier heights under the two seismic-resistant systems. The research results indicate the following: (1) From the perspective of stress system and the difficulty of post-earthquake repair, the ductile seismic-resistant system may exhibit plastic hinge formation at the bridge pier under E3 seismic conditions, with the foundation and bearings unable to maintain a completely elastic state, necessitating repairs or reconstruction of the pier and replacement or repositioning of the bearings post-earthquake; in contrast, under the seismic isolation system with E3 seismic forces, the shear pins of the bearings may break, maintaining the elasticity of the pier and foundation, with a clearer stress system that only requires the replacement of the shear pin devices post-earthquake. (2) From an economic perspective, compared to the ductile seismic-resistant system, while the engineering quantity of piers and the cost of bearings slightly increase when using friction pendulum seismic isolation bearings, the difference is minimal. Meanwhile, significant savings are observed in the pile foundation engineering quantity when employing the seismic isolation system, particularly when the pier height is lower. Therefore, this paper recommends prioritizing the adoption of seismic isolation systems in seismic design for urban rail transit bridges in high seismic intensity areas.