Model of the Shear Behavior of Unbonded Fiber-Reinforced Elastomeric Isolators

In this paper, an analytical model is developed and used to predict the horizontal behavior of unbonded fiber-reinforced elastomeric isolators (FREIs). An advantageous feature of unbonded FREIs is the ability to undergo rollover due to the lack of flexural rigidity of the reinforcement and the unbonded support conditions of the isolator. The rollover causes a characteristic softening, followed by stiffening, as the initially vertical faces of the isolator come into contact with the upper and lower supports—defined as full rollover. The force-displacement relationship is modeled by dividing the isolator into three sections: a central section, which experiences pure shear, and two rollover sections, which experiences combined shear and bending. The displacements of the rollover section are used to establish the curved deformed profile and predict full rollover. The model is evaluated with experimental data from four unbonded FREI designs. A parametric study is conducted to determine the influence of the aspect ratio and bending stiffness of the composite fiber reinforcement matrix on the horizontal force-displacement relationship.