Seismic design of bridges with the participation of seat-type abutments

Abutments are not only earth-retaining systems as they also participate to the earthquake resisting system (ERS) of the bridge, under certain design considerations. Current research mainly focuses on the assessment of the performance of integral abutment bridges, while only a few studies dealt with the design of bridges with seat-type abutments accounting for their seismic contribution. Along these lines, a comparative study on seat-type abutment bridges was performed. The scope of the study was to identify possible differences in their seismic response affecting significant design parameters that are the displacements of the deck and the bending moments of the piers. The study employed three real bridges of variable total lengths, openings at the expansion joints, backfill models and moderate to strong earthquake excitations. Non-linear dynamic time history analysis was performed. The study showed that the strong participation of the abutment and the backfill soil can reduce effectively the seismic demand of bridges. However, attention should be given in bridges with tall piers, whose seismic forces can be increased under certain design conditions.