Seismic performance of a flexible integral abutment bridge with an EPS layer: shaking table tests and soil–structure interaction analysis

Integral abutment bridges (IAB) are one of the most popular bridges worldwide due to their greater durability and lower maintenance compared to conventional bridges. However, the seismic performance of IABs is significantly influenced by the interaction between the backfill soil, the pile foundation, and the abutment. In earth-retaining structures, elastic inclusions are often used to reduce the earth pressure and horizontal loads on the structure. This paper presents the application of Expanded Polystyrene (EPS) behind the flexible abutment of an IAB under seismic loadings. Shaking table tests were conducted on two 1/12.5 scaled bridge models using three ground motions for both lower and upper seismic hazard levels. The dynamic and seismic responses of the bridge models were analyzed to study the effectiveness of the EPS layer. The results indicate that the EPS layer changes the natural frequencies of the bridge for those modes with higher dynamic mass participation of the backfill soil. In addition, the EPS effectively reduces the acceleration and bending moment responses of the abutment and pile. In conclusion, the use of EPS behind the abutment proves to be a viable strategy for reducing seismic demand on the abutment and pile of IABs.