EFFECT OF RUBBER BEARING\u27S MODELING ON SEISMIC RESPONSE OF BASE ISOLATED HIGHWAY BRIDGE

The effects of modeling of isolation bearings on the seismic response of bridges are investigated. To this end, a nonlinear dynamic analysis of a viaduct with natural rubber bearings (RBs), lead rubber bearings (LRBs) and high damping rubber bearings (HDRBs) is carried out. Three analytical models of isolation bearings are considered for comparison: the equivalent linear model, the conventional bilinear model, and the rate-dependent rheology model developed by the authors. The proposed rheology model is able to reproduce the nonlinear viscosity and the elasto-plastic behavior along with strain hardening of bearings. A numerical algorithm for solving the first order governing differential equation of the rheology model has been developed to implement the proposed model into a nonlinear dynamic analysis software. Two level-2 earthquake ground motions, applied in the longitudinal direction, are used in the analysis. The dynamic responses of the isolation bearings and the rotation responses of the plastic hinge in concrete piers are compared for different modeling. Finally, a comparative assessment of the bridge responses shows the sensitivity of modeling of isolation bearings in evaluating seismic responses of the bridge