Numerical study on the end rotation effect of elastomeric bearing on their mechanical behavior in flexible bridges

The use of multilayer elastomeric bearings in bridges has showed that application of this bearings improved seismic behavior of this types of infrastructures during recent earthquakes. Applications of the elastomeric isolation bearings in long-spans or tall pier bridges can experience rotation due to flexure of the deck or the piers, that it can be effective on their seismic performance. In current study, a two-dimensional mechanical model of elastomeric bearings, under the simultaneous effect of pressure, shear and end rotation is investigated. This mechanical model consists of three layers of axial springs with nonlinear hysteresis behavior that play the role of bending and compressive deformation distribution. The model can take into account end rotations of the bearing, and the overall rotational stiffness includes the effect of the variation of vertical load on the bearing. Comparison of the results of nonlinear static bending tests of this model with the results of laboratory studies shows very well agreement. The results indicate that rotational stiffness increases with higher values of vertical pressure, however decreases with increasing shear deformation. As conclusion, end rotation does not affect the critical displacement appreciably, but it significantly influences on the critical shear force.