Improving seismic behaviour of bridges with lead rubber bearing in Iran

Abstract

Construction of roads in Iran has received a considerable attention during these years. In this issue, the special geographic conditions of this country make bridge structures vital. Because of seismic location of Iran, attention to the reduction of risks is needed. Previous studies on seismic response of bridges prove the effective rules of isolators against the tremendous usage of elastomeric bearings in Iran. Lead rubber bearing (LRB) is one of the isolators that comprised of alternate layers of steel and vulcanized rubber with a central lead core. This paper describes the analytical study on seismic response of two concrete bridges with or without LRB based on a 3D time history nonlinear analysis using Sap2000 program. The models were subjected to strong seismic motions recorded near to the zone. Results show the beneficial effect of the isolation system in comparison with elastomeric bearing system on capability of energy dissipation. Not only, isolators reduce the base shear on bridges but also reduce shear force and bending moment of piers as well. According to this research deck displacement in isolated bridges reduces considerably whereas bent displacement is not effected practically in flexible bridges.