Stability of Laminated Elastomeric Bearings

Abstract

Steel‐laminated elastomeric bearings are widely used in bridges. In order to impose the smallest possible force on the substructure, the bearing should have the smallest plan dimensions and the greatest height possible. Both are controlled by stability. However, buckling of the bearing differs significantly from that of a conventional column in that it is strongly influenced by shear flexibility and axial deformations. Existing theories ignore the latter and become very conservative for bearings with the relatively low profiles typically used today. Extensions to the theory were developed to account for the influence of axial shortening as well, and experiments were conducted. The general form of the modified theory matches the pattern of the test results, and in particular they both show that bearings with a height‐to‐width ratio below a certain limit will never buckle. Perfect correlation could not be achieved because of difficulties in establishing reliable flexural stiffnesses for the bearings. Design equations are proposed based on the form of the theoretical equations, calibrated against the test results.