Abstract
The Resilient—Friction Base Isolator (R—FBI) is a device which can be incorporated into the foundations of new and existing structures to protect them from damaging earthquake ground motions. The device consists of a short column composed of a set of identical flat rings with an elastic core (reinforced rubber plug). The elastic core is positioned such that it carries no axial load and distributes the lateral displacement uniformly across the clear height of the column. In this paper, considering an R—FBI bearing as a short column, an approximate analytical model for the analysis of its stability is presented. Assuming no negative pressure at the interfaces of the flat rings, the values of the critical lateral displacement and the critical vertical load are defined and calculated in terms of the system's parameters. The upper limit of the safe lateral displacement, the lateral displacement beyond which the lateral load carrying capacity of the isolator deteriorates, is also defined. To validate the analysis method, a single bearing was fabricated and tested under various normal loads. The test results strongly confirm the analytical predictions.
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