The approach problem of an integral abutment bridge subjected to cyclic loading due to temperature changes

Integral abutment bridges (IABs) have been increasingly utilized in many countries due to the advantageous concept of eliminating the movement joints. Compared to conventional bridges, IABs require less maintenance and construction costs. However, the absence of movement joints will result in rotational movements of the bridge abutments against and away from the retained soil backfill in response to the fluctuation in the ambient temperature. Such movement may result in a soil settlement at the bridge approaches and increased lateral pressures on the abutment wall, due to the densification and strain ratcheting of the backfill behind the abutment. The soil settlement will develop troughs or humps at the bridge approaches and produce rideability problems. To gain the necessary insights required to rectify the approach problem, this paper presents finite element model developed to study an integral abutment wall subjected to cyclic perturbations using the ABAQUS software. The model was initially verified against centrifuge test results of an integral bridge abutment and found to replicate the wall and backfill responses well. It was also used to study potential solutions using expanded polystyrene (EPS) geofoam as a compressible inclusion to mitigate the soil settlement and to prevent the stress ratcheting at the interface between the backfill and the abutment. Results from this study are reported in this paper.