Static Soil-Structure Interaction Effects in Seismic-Isolated Bridges

In this paper, the effect of soil-structure interaction on the seismic performance of seismic-isolated bridges is studied. For this purpose, two typical seismically isolated bridges are selected. The selected bridges have distinct features to represent those bridges with: (1) Heavy superstructure and light substructure and (2) light superstructure and heavy substructure. Detailed structural models of both bridges excluding and including the soil-structure interaction effects are first constructed. Iterative multimode response spectrum analyses of the bridges are then conducted considering the nonlinear behavior of the isolation bearings. The analyses results have revealed that soil-structure interaction effects may be neglected in the seismic analysis of seismic-isolated bridges with heavy superstructure and light substructure constructed on stiff soil. However, the soil-structure interaction effects need to be considered for bridges with light superstructure and heavy substructures regardless of the stiffness of the foundation soil. In soft soil conditions, soil-structure interaction effects need to be considered regardless of the bridge type.