Seismic Response of Continuous Beam-Arch Bridge under Spatially Varying Ground Motions

In order to investigate the dynamic responses of a long-span continuous beam-arch bridge subjected to multi-support and multi-dimensional ground motions, a finite element model for a concrete-filled steel tubular arch bridge with a span of 139 m in South China was built using OpenSEES software. The spatially varying ground motions were artificially simulated to investigate the effects of the coherency loss, local site conditions, and wave-passage. The results show that the spatially varying ground motions have significant influence on the dynamic responses of bridge, and considering uniform excitations only might overestimate the responses. The influence of the local site effect on the seismic responses of the bridge is the most prominent. With softer site conditions at the support points, the inner forces and displacements responses of each part of the bridge are greatly increased. Weakly correlated ground motions can lead to larger arch inner forces and smaller arch peak displacements. Although the wave-passage effect has no obvious tendency, its influence is not negligible. Only considering the wave-passage effect may seriously underestimate the seismic responses of the bridge substructure. Therefore, the spatially varying ground motions should be considered in the seismic responses analysis of long-span bridges, and the effect of each factor should be accurately measured.