Stiffness analysis of fiber-reinforced rubber isolators under compressive loads: A finite element approach

Fiber reinforced elastomeric isolators (FREIs) can be effectively used for seismic mitigation of structures. In contrast to conventional steel reinforced elastomeric isolators (SREIs), FREIs are significantly lighter in weight, and can be fabricated in a cost-effective manner. Unlike SREIs, the reinforcement layers in FREIs are flexible in extension and have no bending rigidity. As a result, the response characteristics of FREIs are different, and in general more complex than those corresponding to SREIs. Due to the fiber flexibility, the theoretical approach employed in the stiffness analysis of SREIs cannot be directly extended to FREIs. Analytical closed-form techniques for stiffness solution of FREIs under vertical pressure have been presented in the literature. There is a need to compare these solutions with more rigorous numerical techniques. In this paper, a finite element approach has been employed to investigate the static response of a strip FREI under a compressive vertical load. A hyperelastic model has been used for the rubber material in the finite element code. Results of the finite element analysis, including compression stiffness and stress distributions in the elastomeric layers, have been compared with those predicted by the closed form analytical solution.