A simple mechanical model for elastomeric bearings used in base isolation

Abstract

The effect of weak shear rigidity is important in the analysis of elastomeric bearings used for base isolation of buildings. In particular, the buckling load is low and the P-Δ effect is significant, as compared to standard columns neglecting shear deformations. In this paper, a simple mechanical model accounting for both shear and flexural deformations is proposed to treat the P-Δ effect of elastomeric isolation bearings. With adequate choice of the model parameters, the simplified model agrees very well with an exact model in both static and dynamic cases. When applied to the experimental results for some natural rubber bearings, the model is found to describe with good accuracy the effects of axial load on the dynamic stiffness, the damping factor and the height reduction of bearings. A brief study of the post-buckling behaviour of elastomeric bearings using the simplified model is also presented. © 1988.