Assessment of SSI on the longitudinal seismic response of short span bridges

Abstract Current practice usually neglects the effects of soil-structure interaction (SSI) in the seismic analysis and design of bridges. This work attempts to assess the significance of SSI on the seismic responses of short span bridges. The focus is placed on pier behaviour, since piers together with the abutments are the most critical elements in securing the integrity of bridge superstructures during earthquakes. The study is based on a simple representation of a soil-bridge pier system, yet one able to capture the effects of the most significant physical parameters. It has been found that SSI greatly affects the dynamic behaviour of bridge piers leading to more flexible systems, increased damping and larger total displacements. Besides a thorough investigation of the relative significance of various physical parameters on the system response, an easy-to-use approach that can be incorporated for a preliminary design of bridges concurrent with the AASHTO specifications is presented. The study concludes that safer and more economical bridge designs can be obtained by properly accounting for SSI.