Three-dimensional response of reinforced concrete bridges under spatially varying seismic excitation

A novel approach to study nonlinear seismic response behavior of three-dimensional (3-D) concrete bridges is presented in a six step methodology. The methodology rigorously considers spatial variability in the seismic excitation (SVSE) caused by wave passage and incoherence and local soil conditions, as well as the effects of far-field and near-field epicentral distance. Bridges are represented by 3-D finite element models with bidirectional plastic hinges at piers and soil-foundation interface elements that account for soil dynamic stiffness at each ground support. Results on pier rotational Ductility Demands (DD) in symmetric and asymmetric multi-span bridges considered in the study indicate that the magnitude of the DD depends on the type of soil, the pier location and the length of the bridge. Results also show that ignoring SVSE effects can cause severe underestimation of DD.