A Study Of Relative Displacement Between Deck-Elastomeric Bearing And Pier Top Under Earthquake Load

Most previous researches have demonstrated that, the seismic impacts on piers and foundations of the simply-supported-girder bridge, can be ignored. However, a transverse relative displacement exists between the slab and bent cap of the bridge. Structure failure, e.g. girder falling, may happen in a sudden if the transverse relative displacement is beyond a reasonable value. Current study is mainly focused on the application of seismic isolation bearing in bridge engineering, however, research on the relationship between sliding displacements and ground motion parameters is still lack of.In order to investigate the transverse relative displacement between the slab and bent cap of the bridge under seismic condition, the numerical software OpenSees is adopted as a platform to set up 40 representative numerical bridge models.1394 seismic records consisting of both horizontal and vertical components are applied at the bottom of the pier. The numerical results of the transverse relative displacement is obtained and analyzed. Three empirical models are developed by fitting the data obtained from the numerical results. The bridge period, span, seismic magnitude, distance from the seismic source, field period and peak acceleration is applied to estimate the maximum relative displacement in Model 1. The peak acceleration is not concerned with in Model 2, whilst the seismic magnitude and distance from the seismic source is not considered in Model 3. Residual analysis is used to validate the three proposed models. Given the practice in engineering, Model 1 and Model 2 are aimed for regional bridge design, while Model 3 is used to estimate the deck’s maximum relative displacement for each intensity zone.The results show that Model 1 is more capable of prediction of observed behavior, however, more parameters are involved at the same time. Once the remaining parameters in empirical formulations have been known, the transverse relative displacement increases with an increases in the seismic magnitude, field period and bridge period; nevertheless, a decrease in distance from the seismic source and in the friction coefficient. In addition, the maximum relative displacement is negligibly influenced by the vertical ground motion, however, tends to be more randomly.The proposed three empirical models are capable of analyzing the reliability of bridges if the exceeding probability is given. This study provides a fundamental theory and investigation method for further calculation of the overlap length of the simply supported girder bridge, based on the displacement spectrum. It is meaningful with respect to the design of bridges.