Analytical vs numerical determination of the axial and lateral stiffness of fiber reinforced isolators

This paper presents the results of a numerical and experimental study aiming to define the vertical and horizontal stiffness of Fiber-Reinforced Elastomeric Isolators (FREIs). In FREIs, the conventional steel shims of laminated rubber bearings are replaced by flexible fiber reinforcements. The axial and lateral response of these bearings is influenced by the flexibility of these layers. This study describes results of an analytical model capable of providing an accurate estimation of the vertical and horizontal stiffness of the bearings under static and dynamic loads. Results of this analytical model are compared to output of finite element analysis (FEM) available in literature. The influence of the geometry of the isolator (i.e., strip and circular shape), its shape factor and type of reinforcement on the vertical and horizontal stiffness are discussed. Considerations are also given on the effects of the compressibility of the rubber on the axial and lateral response of the devices.