Vertical and Lateral Behavior of Unbonded Fiber-Reinforced Elastomeric Isolators

Fiber-reinforced elastomeric isolators (FREIs) are relatively lightweight, can be cut to the required size from larger pads, and can be placed unbonded (i.e., unfastened) between the supports. The two major geometric parameters that influence the vertical and lateral response of unbonded fiber-reinforced elastomeric isolators (U-FREIs) are the shape factor and the aspect ratio. The vertical response is strongly influenced by the shape factor, while the aspect ratio is the controlling parameter for the stable response of U-FREIs under lateral displacement. This paper describes an experimental study on the vertical and lateral response of U-FREIs under different loading conditions in both the lateral and vertical directions. Three U-FREIs, with different aspect ratios and shape factors, were tested using a multiload test apparatus. Results from vertical tests indicate that, in addition to the shape factor, the vertical stiffness is influenced by the vertical rate of loading. Furthermore, it was found that the static lateral offset did not significantly affect the vertical stiffness of the isolators considered. These observations are in part attributed to the composite action of the fiber reinforcement and the elastomer.