Effect of lead rubber bearing on seismic performance of steel box girder bridge

Abstract

Rubber isolation bearings have been proven to be helpful in reducing bridge seismic damage. The response of bridges with rubber bearings are complex under seismic action due to the varying characteristics of isolation bearings. The effect of using rubber isolation bearings on seismic performance of continuous steel box girder bridges exposed to near-field and far-field ground vibrations is the focus of this paper. For this study a four-span continuous steel box girder bridge isolated with lead rubber bearings in Delhi, India is considered for numerical study. Nonlinear Response history analyses are carried out on the selected bridge to evaluate the sensitivity impact of hysteric energy of rubber bearing, bearing displacement limit, deck acceleration, and base shear. The influence of seismic ground motion and lead rubber bearing parameters on the behavior of seismically isolated bridge is investigated using a parametric study. The goal is to look at the impact of ground motion on the lead rubber bearing as well as the bridge. Due to bearing hysteric energy, the bridge with seismic isolation, such as lead rubber bearings (LRB), has roughly 20%-30% lower seismic reaction than non-isolated bridge. This indicates that the isolation bearings improve the seismic performance of the bridge. The results also reveal that when the frequency content of ground motion increases, it results in a substantial risk of damage of the bearing as well as bridge. The near-field earthquakes significantly alter the energy ratio dissipated to total input energy by the lead-rubber bearings in comparison to far-field earthquakes. Finally, recommendations are presented that will be valuable for bridge designers during the early bridge seismic isolation design with lead rubber isolators for varying features of ground motions.