Seat-type bridge abutments consisting of expansion gaps and sacrificial shear keys significantly affect the response of bridge during strong earthquakes. Seismic pounding between the bridge deck and the abutment backwall caused by expansion gap closure may alter the dynamic characteristics consequently affecting the demands on various bridge components. Additionally, the loss of sacrificial abutment shear keys changes the support boundary condition and may significantly increase the demands on the bridge piers. A small scale parameter study investigates the influence of ground motion and bridge curvature on the performance of seat-type bridge abutments. Straight and highly curved configurations of a benchmark bridge are subjected to two suites of motions, on set with and the other without large velocity pulses. The vulnerability of the bridge configurations are compared using component fragility analysis. It is shown that bridges are more vulnerable to ground motions with large velocity pulses and that curved bridges are more likely to experience column damage and abutment unseating compared to straight bridges.
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