Finite element analysis of unbonded square fiber-reinforced elastomeric isolators (FREIs) under lateral loading in different directions

Compared to conventional elastomeric bearings, fiber-reinforced elastomeric isolators (FREIs) are expected to cost much less and be easier to install, particularly when unbonded isolators are utilized. Due to the complex lateral response of unbonded FREIs, only a limited number of analytical studies are available in the literature. In addition, most of these analytical studies are based on a number of simplifying assumptions, applicable only to a few basic geometries. In this paper, three-dimensional finite element analysis (FEA) is carried out to investigate the lateral response of square FREIs, having aspect ratios of 1.9, 2.6 and 2.9, when loaded in different directions. Since square isolators are not axisymmetric, variations in lateral response can be expected to occur when subjected to different loading directions. The finite element (FE) models are validated using experimental test results for bearings loaded at 0° and are subsequently employed to analyze the lateral response characteristics of the bearings when loaded at 15°, 30° and 45°. The results show that in general, the effective lateral stiffness of the bearings increases as the loading direction changes from 0° to 45°. In addition, as the aspect ratio decreases, the sensitivity of the lateral response to the loading direction increases.