The effect of EPS geofoam backfill on the seismic performance of integral abutment bridge

This study was performed to investigate the seismic response of Integral Abutment Bridges (IABs) with Expanded Polystyrene (EPS) geofoam backfill in comparison to IABs with compacted backfill as well as typical jointed bridges. Three-dimensional Finite Element (FE) models of an existing bridge were developed and analyzed using the 1000-year seismic event according to the American Association of State Highway Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD). Results from existing information were used to determine soil characteristics and site class at the bridge location. Frame elements were utilized to model the piles, girders and diaphragms. Abutments and deck sections were modeled using shell elements to capture the effect of the connection to the girders. Nonlinear soil springs were used to model soil elements according to the Federal Highway Administration Seismic Retrofitting manual. The study shows that the use of EPS has major effects on the seismic performance of IABs. These effects include increasing the fundamental period of the bridge and reducing the forces in the superstructure as well as the integral abutments.;This combination of EPS geofoam backfill and integral abutments provides the benefits of reduced number of joints and bearings, which is highly desirable as it provides reduced maintenance and inspection costs as well as reduced repair costs. It also provides a potential for reduced initial construction costs over integral abutments with compacted backfill as the design forces in the abutments are lower; therefore smaller sections and less reinforcement would be required, although the material and installation costs of EPS geofoam can offset that cost savings.