Effects of Axial Load on Elastomeric Isolation Bearings

摘要

The report studies the viscoelastic behavior of elastomeric isolation bearings with the effects of axial load taken into consideration. First, two series solutions are presented for computing the compression stiffness of bonded square layers accounting for compressibility. For typical square rubber layers, these solutions justify a simplified approach. The latter is then extended to obtain the effective bending stiffness. Then with this effective stiffness of elastomeric bearings, two viscoelastic axial load models are proposed. The first model is consistent with Haringx's theory, utilizing the eigenvalue solutions of the corresponding buckling problem. The convergence of the series involved is very rapid, leading to the first-mode consistent model. The second model is a simplified physical model dealing with only two springs to reproduce the essential features of the previous model. The reduction of the dynamic shear stiffness, the increased damping and the height reduction of bearings due to the axial load effect are obtained. The corresponding experimental program was carried out and both models are shown to give good correlations.