The effect of foundation-soil-foundation interaction on the response of continuous, multi-span railway bridges

This paper focuses on the effect of dynamic soil-structure interaction (SSI), including foundation-soil- foundation interaction (FSFI), on the dynamic response of multi-span railway bridges, which constitute an important part of high-speed rail networks around the world. We consider an infinitely long box girder bridge on piled foundations and use periodic structure theory to restrict the computational domain to a reference cell. The superstructure is modeled with finite elements, while a periodic finite element-boundary element (FE-BE) model is used to compute the dynamic stiffness of the piled foundation, taking into account FSFI. It is demonstrated that (1) the natural frequencies of the in-phase torsional and bending modes are significantly lowered due to the flexibility of the foundation-soil system; (2) the effect of FSFI on the bridge response is limited for typical span lengths and soil stiffness; and (3) the peak bridge deck acceleration is lower if SSI is taken into account, as is the resonant train speed.