Expected seismic performance of irregular isolated bridges

Bridge structures are usually built on irregular topographical surfaces which create substructures with pier heights of different lengths. Three height irregularity types of typical RC medium length bridges are analyzed aimed at determining the best strength and stiffness parameters of an isolation system. The models were located in a high seismicity zone of Mexico. The isolation system is composed by lead rubber bearings (LRB) located on each pile and abutment. The bridge and isolation parameters conducted to the nonlinear time history analysis (NLTHA) of 169 models. Ten seismic records representative of the subduction zone in the Pacific Coast in Mexico were chosen to carry out the study. The maximum drift pier demands, bending moments and shear forces were analyzed to identify the best isolation properties for improving the bridges’ structural behavior, specially focused on looking for avoiding irregularity concentrations of shear forces on piers. Additionally, the seismic response of the bridges supported on traditional neoprene bearings was carried out.