Method to design fiber-reinforced elastomeric isolators (U-FREIs) and application

This paper proposes a method to design unbounded fiber-reinforced elastomeric isolators (U-FREIs) which, on the basis of the building mass, loads and target isolation period, allows the designer to determine the isolator geometrical dimensions and stiffness characteristics. Many studies in the literature demonstrate that U-FREIs are a viable alternative to Steel Reinforced Elastomeric Isolators (SREIs), making it feasible to employ seismic isolation in residential buildings, even in developing countries. However, currently there are only few references in the literature which give precise directions on how to design U-FREIs to take account of their peculiarities and differences with respect to SREIs. The method proposed herein imposes the fulfillment of three conditions, which take account of U-FREIs peculiar behavior. A step by step procedure developed for square shaped isolators is provided as guide to the application of the proposed design method. A case study is presented, both utilizing the proposed U-FREIs and equivalent SREIs. The differences in the performance of the building, obtained with the two different devices, are discussed.