Numerical simulation and analysis of seismic performance of swing T‐frame bridge based on the base isolation concept

Abstract To address the problems of limited isolation measures, a strong epicenter response, and insufficient ductility of pier‐girder consolidation swing bridges, this paper uses the overpass across the Beijing‐Guangzhou line on the Wuhan‐Dawu Expressway as its engineering background. Based on the concept of base isolation and the nonlinear time history analysis method, considering seven groups of seismic waves and designing three isolation schemes, the seismic performance of the swing T‐frame bridge is studied. The results demonstrate that the curved surface friction pendulum bearing concurrently satisfies the demands of swing construction and operational seismic isolation, indicating promising application prospects. Moreover, the base isolation system can significantly prolong the natural vibration period of the structure and reduce the seismic response. The bending moments at the bottom of the main pier are reduced by 44.6%–67.1% and 40.2%–64.0% in the longitudinal and transverse directions, respectively, while those at the bottom of the transition pier are reduced by 0.5%–18.6% and 1.1%–23.4% in the longitudinal and transverse directions, respectively. The peak displacement of the main beam is 121.5 mm, which meets the specification requirement; the fluid viscous damper can effectively control the lateral displacement of the main beam, and the reduction is 36.1%; the isolation performance of the curved friction pendulum bearing is controlled by the sliding friction coefficient μ d and the radius of curvature R . The internal force response increases with the increase of μ d and decreases with the increase of R , whereas displacement responses exhibit the opposite trend. Moreover, under load in the normal operational stage, the bridge displacements meet design specifications without any bearing uplift phenomenon, confirming the minimal influence of the base isolation system on operational safety and its favorable engineering applicability.