Effect of deck and support stiffness on seismic response of slab-girder bridges

This paper investigates the effects of modeling assumptions for concrete decks of slab-girder single-span bridges subjected to earthquake forces. It is assumed that the bridges are elastically supported with elastomeric bearings in the longitudinal direction and end cross-frames in the transverse direction. The effects of varying support and deck stiffness on the translational periods of vibration and seismic responses are considered. AASHTOʹs (American Association of State Highway and Transportation Officials) recommended seismic forces for single-span bridges are discussed and compared with the El Centro time history analysis. It is concluded that rigid deck assumption simplifies seismic analysis and it is safe to use. It is also indicated that AASHTOʹs recommended design force for elastically supported single-span bridges could be unsafe in certain cases. An increase in the design force has been recommended for such cases.