COMPRESSIVE BEHAVIOUR OF A CIRCULAR UNBONDED FIBER-REINFORCED ELASTOMERIC ISOLATOR (UFREI)

Steel-reinforced elastomeric isolator (SREI) is the most used method of seismic isolation. It consists of several rubber pads interspersed with steel laminas for vertical reinforcement. Since these devices are generally too expensive due to the need to introduce thick connection steel plates and the high energy consumed for manufacturing, they are unsuitable for ordinary residential masonry buildings. Fiber-reinforced elastomeric isolator (FREI) is a new type of elastomeric device. Instead of steel lamina, thin fiber layers are used. Compared with SREIs, FREIs have considerably lower weight and can be manufactured through cold vulcanization. They can be applied to the structure in several ways: bonded (traditional), un-bonded, and partially bonded. In unbonded conditions (UFREI), the isolators can be installed between the upper structure and foundation without any bonding or fastening, reducing costs hugely. 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 into the compressive behavior of a circular UFREI. The device has been subjected to standard and cyclic compression tests considering different vertical pressures. Results, evaluated in terms of vertical stiffness and vertical frequency, provide insight into the UFREI potential for practical applications.