Partially bonded fiber-reinforced elastomeric isolators (PB-FREIs)

Abstract

Summary Although stable unbonded fiber-reinforced elastomeric isolators (SU-FREIs) have desirable characteristics for seismic isolation, the unbonded application also introduces limitations in comparison with bonded elastomeric isolators. SU-FREIs are not capable of resisting tensile forces, making SU-FREIs unsuited for situations where overturning is of concern or where large vertical accelerations are anticipated. Furthermore, as SU-FREIs rely on friction to transfer horizontal forces, the isolator could potentially slip under certain loading conditions, resulting in permanent displacements. This paper proposes that concerns over the transfer of tensile forces and potential slip can be addressed by partially bonding the SU-FREI to the upper and lower supports. In this way, partially bonded FREIs (PB-FREIs) not only retain the beneficial characteristics of an unbonded FREI but also inherit characteristics of a bonded isolator; notably tensile and horizontal forces can be transferred through the partial bond. Experimental results from isolators tested unbonded and partially bonded under vertical compression are used to evaluate a finite element model. The experimental data and finite element analysis demonstrate that portions of a FREI can be bonded without substantially altering the rollover characteristics of the isolator within the range of average vertical compressive and tensile stresses considered. Despite an unconventional deformed shape under tensile vertical stress, the horizontal force–displacement relationship exhibits negligible deviation from a conventional unbonded SU-FREI under a compressive vertical stress. It is postulated that with further development, partially bonded FREIs can retain the beneficial characteristics of unbonded FREIs while addressing concerns over tensile forces and slip. Copyright © 2014 John Wiley & Sons, Ltd.