Lateral Behavior of a Circular High-Damping Unbonded Fiber-Reinforced Elastomeric Isolator (UFREI)

In recent years, several devastating earthquakes have occurred, highlighting the importance of effective seismic isolation systems in reducing seismic hazards to structures. One of the most popular isolation systems is the use of elastomeric bearings, such as steel-reinforced elastomeric isolators (SREIs). However, the high cost associated with the use of thick connection steel plates and high energy consumption during manufacturing has limited their applicability, particularly for ordinary residential buildings in developing countries. In this context, a new type of elastomeric device, a fiber-reinforced elastomeric isolator (FREI), has emerged as a promising alternative. It can be applied to the structure in several ways: bonded (traditional), unbonded, and partially bonded. In unbonded conditions (UFREI), the isolator can be installed between the upper structure and foundation without any bonding or fastening. This, combined with the use of thin fiber layers in place of steel laminations, results in a reduction in materials costs and makes UFREIs a more cost-effective and feasible option. Furthermore, the dissipation energy without steel supports improves thanks to the shear load transferred through the friction generated between the isolator and the structure surfaces. This study presents an experimental investigation of the lateral behavior of a circular high-damping UFREI. The device has been subjected to cyclic shear tests considering different vertical pressures, with the results evaluated in terms of horizontal stiffness and damping ratio. The objective was to determine the impact of the vertical pressure on the final horizontal behavior of the device.