On the Vertical Response of Fiber Reinforced Elastomeric Isolators (Freis) Under Combined Vertical and Lateral Loading

Abstract

The vertical behavior of Fiber Reinforced Elastomeric Isolators (FREIs) is controlled by geometric and mechanical parameters, such as primary and secondary shape factors, shear modulus of the rubber and effective compressive modulus of the rubber-reinforcements compound. Several studies dealt with the vertical properties of the bearings, deriving analytical formulations in function of the bearing geometry and materials' properties. These relations have been derived under pure compression, considering the interaction between single rubber layers and flexible reinforcements. As of today, few works have been proposed on the influence of the horizontal displacement imposed on the bearing, i.e. no interaction between vertical pressure and horizontal displacement on the vertical stiffness and the compressive modulus has been accounted for. In this paper, a numerical study on the influence of the primary and secondary shape factor, the shear modulus of the rubber and the vertical pressure on the vertical properties of the FREIs is presented. In a first stage the behavior of square shaped FREIs under pure compression is examined and relative outcomes are presented. Then the influence of the horizontal displacement on the vertical response of the bearings is considered. Interesting results on the trend of the vertical stiffness and compressive modulus are obtained and useful considerations on the stability of FREIs are provided.

Vertical response of unbonded fiber reinforced elastomeric isolators (U-FREIs) under bidirectional shear loading

“…The area reduction due to rollover increase the vertical deformation of the bearing, thus reducing the vertical stiffness (Galano, 2021). Several research works studied the vertical response of U-FREIs under pure compression or under combined axial and mono-directional shear load (Angeli et al, 2013;Osgooei et al, 2016;Al-Anany et al, 2017;Calabrese et al, 2021;Losanno et al, 2022), highlighting the influence of different geometric parameters, among all the primary shape factor, defined as the ratio between loaded and free to bulge areas.…”