Study On LRB Design Parameters Influence Of Seismic Isolation And Pounding Effects For LRB Isolated Simple Supported Beam Bridges

The bridge isolation design is aimed to reduce the structural dynamic response by extending the structural period and consuming large amounts of seismic energy by isolation devices. Lead rubber bearings (LRB) have been widely used in the aseismic design of bridges because of its good mechanical properties and energy dissipation capability, but there are still many problems need to be solved.One of the most concerned problems of the bridge isolation design is how to determine the reasonable and effective bearing parameters to get a best isolation effect. This paper creates a single LRB isolation pier model for the LRB isolated simple supported beam bridge. By changing the parameters of the LRB, the influence laws of the structure dynamic response on the stimulation of the seismic waves are obtained. The results can make a reference for the LRB isolation design of the simple supported beam bridges.The LRB isolated single pier model ignores the possible pounding effects of the upper structures such as pounding between two adjacent beams or between the beam and abutment. In order to study the pounding impact on the bridge dynamic response, this paper build a two span simple supported beam bridge considering the pounding between two adjacent beams and pounding between the beam and abutment. Compare the pounding responses between the general designed bridge and LRB isolation designed bridge. Then at the cases of considering pounding or not, input a group of seismic waves with the same peak acceleration and make a nonlinear time history analysis for the LRB isolated simple supported beam bridge then get the bridge dynamic responds of these different cases. The result shows that the LRB isolation designed simple supported beam bridge is more likely to have poundings and the pounding times between two adjacent beams is more than the poundings between the beam and abutment but the pounding force is opposite.. Compare the LRB isolated simple supported beam bridges considering the pounding or not, poundings to some extent decrease the bearing deflection, reduces the risk of the beam falling. Meanwhile pounding has little impact on the pier shear and bending moment, so pounding effect can be ignored when considering the isolation effect. But pounding cause a tremendous impact force on the beams and abutments and make them damaged. At the same time pounding cause a large acceleration on the beam and it is danger for the traffic safety. So it needs to take some measure to avoid the pounding and reduce the pounding damage.