Parametric Study on the Response of Stable Unbonded-Fiber Reinforced Elastomeric Isolators (SU-FREIs)

Tests on stable unbonded (SU) square carbon fiber-reinforced elastomeric isolator (FREI) bearings were conducted to investigate their lateral and vertical response. The bearings are intended for seismic isolation of low-rise buildings including those of ordinary importance. To simulate the in-place application of SU-FREI bearings, the contact surfaces of the bearings were not bonded to the platens of the test machine. This unbonded application permitted stable rollover deformation to occur which enhances the bearing's isolation efficiency. The bearings were shown to safely sustain large lateral displacements. When subjected to large lateral displacements, their originally vertical faces completely contacted the horizontal surfaces of the upper and lower platens, which created a stiffening response and ensured the stability of these very large displacements. The sensitivity of SU-FREI bearings to lateral displacement history and vertical pressure applied on the bearings were investigated. Regarding the latter parameter, it was found that the effect of variations in vertical pressure on the lateral response can be neglected when the SU-FREI bearings are subjected to relatively light vertical pressures such as considered for low-rise buildings.