Viscoelastic stability model for elastomeric isolation bearings

Abstract

A viscoelastic model accounting for the stability effect is proposed for high-damping elastomeric bearings used in aseismic base isolation. This model is consistent with Haringx's theory, which takes into consideration the significant shear deformation of the elastomer. The method of mode superposition is used to obtain an alternative solution to the 'Haringx column', and this solution is readily generalized to include viscoelasticity. Each mode is an eigensolution of the corresponding stability problem. The rapid fourth-order convergence permits the use of only the first mode to give a very good approximation. The dynamic shear stiffness, damping characteristics, and height reduction of bearings are obtained by the first-mode consistent model. In particular, the phenomenon of increasing energy dissipation due to the axial load is explained by the model in a consistent way. The applicability of the model is then verified by experiments conducted on multilayer elastomeric isolation bearings with and without lead plugs.