Seismic performance of a bridge with tall piers

This paper presents the study of seismic performance evaluation of a proposed railway bridge with tall piers. The study is mainly focused on the central span of bridges having 100-m high piers. The primary aim of the study is to examine the applicability of the response reduction factors, R, given in seismic design codes, for bridges with tall piers. The bridge is designed with increasing values of response reduction factors and its performance is evaluated considering different detailing practices. Moment curvature behaviour and shear resistance of hollow reinforced concrete piers is also discussed. The effect of foundation flexibility on seismic performance of the bridge is explored by performing a sensitivity study with varying modulus of subgrade reaction of the founding soil. It is observed that the response reduction factors prescribed in the Indian code also yield satisfactory performance for tall bridges. In contrast to buildings, currently, displacement is not considered as a design criterion for bridges; however, in most of the cases considered in the present study, the bridges behaved elastically or nearly elastically, with excessive displacement at the top. Foundation–soil flexibility has a significant effect on the displacement of tall bridges, and results in a change of seismic performance level of the considered bridge, in some cases.