A Methodology for the Experimental Evaluation of Seismic Pounding at Seat-Type Abutments of Horizontally Curved Bridges

Seat-type supports are normally used at bridge ends to accommodate thermal expansion and eliminate the high stresses that would otherwise be present in the superstructure when the ends are rigidly held. However, during large seismic events, there is high possibility that the joint gap between the end of the bridge and abutment backwall would close and high acceleration impact would result. It is expected that this abutment backwall pounding would significantly affect the bridge response. Yet, limited experimental research has been conducted to investigate the extent, how, and what components are affected by such effect. As a part of a Federal Highway Administration funded project, a two-fifths scale curved bridge model was constructed at University of Nevada, Reno Large Scale Structures Laboratory for shake table testing. One of the six configurations of the bridge model was designed to experimentally study the seismic performance of seat-type abutments, abutment backwall pounding, and its effect on bridge response. An abutment setup was designed to facilitate the investigation of the abutment impact accounting for the nonlinearity of the backfill soil. A compression-only device with permanent deformation was developed to represent the soil passive resistance. This paper describes the experimental setup developed to evaluate the seismic performance of seat-type abutments and characterize the interaction between the bridge superstructure, abutment backwalls, and nonlinear soil backfill.