Horizontal Behaviour ofFiber-Reinforced Elastomeric Isolator (FREI) of Different Boundary Conditions

To achieve seismic isolation of a structure, a rubber device can be inserted between the foundation and the superstructure. This device extends the natural period of the structure. Elastomeric isolators, comprised of alternating layers of rubber pads and steel laminas, are widely used for this purpose. These isolators also feature thick steel plates at the top and bottom for connection to the superstructure and foundation. However, the high production costs and material requirements associated with these isolators render them unsuitable for ordinary residential buildings, particularly in developing countries. In response to these challenges, a promising alternative known as fiber-reinforced elastomeric isolator (FREI) has been proposed. FREIs offer significant advantages over traditional isolators, including lower costs, reduced weight, and the ability to be manufactured using cold vulcanization. Furthermore, they can be easily installed in unbonded applications (UFREIs). In UFREIs, the device is simply placed between the foundation and superstructure without the need for bonding or fastening. Notably, UFREIs exhibit superior seismic isolation performance compared to bonded isolators. This is attributed to the absence of bonding, which enhances damping performance and reduces horizontal stiffness through the rollover effect—an observed softening behavior during lateral deformation. However, this unbonded solution lacks vertical tension resistance. To address this limitation, a new application called partially-bonded application (PBFREI) has been introduced. In this approach, only specific sections of the device surfaces are bonded to the connection steel plates that link the foundation and superstructure. This combination enables the final device to benefit from both the unbonded deformation characteristics (rollover effect) and the vertical tension resistance of the bonded configuration. This study focuses on investigating the horizontal behavior of a circular high damping FREI, as proposed by the authors, in both unbonded and partially bonded applications for seismic isolation of low-rise masonry buildings. Additionally, a numerical model is proposed to accurately represent FREIs in future structural applications.