Simple mechanical models for the horizontal behavior of elastomeric bearings including the effect of support rotation

Past studies have shown that the lateral behavior of a laminated elastomeric bearing is affected by axial load, and various mechanical models that consider the effect of horizontal–vertical coupling have been proposed. Those studies have characterized the effect of vertical load on the lateral stiffness and the lateral stability limit under the assumption that the bearing’s top and bottom supports displace horizontally and vertically only, i.e., the supports do not rotate. In this study, the zero-rotation constraint is released, and the performance of different mechanical models in capturing the effect of support rotation on the lateral behavior of elastomeric bearings is evaluated. Three existing models are considered: the Nagarajaiah-Ferrell, Iizuka, and Han-Warn models. First, these three models are evaluated by comparing their predictions with results of Finite Element Analysis (FEA), assuming no rotation at the supports. The models are subsequently modified to incorporate support rotation. The modified models are evaluated using results from FEA under prescribed rotation values. In order to investigate the effect of bearing aspect ratio on the results, bearings with different second shape factors (2, 4 and 6) are considered. The results show that the modified models cannot accurately predict the lateral force at the instability (critical) point (defined as the displacement at which the tangent stiffness becomes zero). Depending on the axial load and rotation value, the modified models underestimate or overestimate the lateral force at the critical point. Nevertheless they predict the critical displacement with acceptable accuracy. It was found that in general the modified Han-Warn and modified Iizuka models provide more accurate predictions than the modified Nagarajaiah-Ferrell model. To improve upon these modified models, this paper proposes a new model capable of capturing the effect of rotation on the lateral response. This model is used to estimate the lateral stability limit and the results are compared against those from FEA. It is shown that the model can predict the lateral behavior of elastomeric bearings more accurately than the modified models.