Dynamic modeling of the lateral response of unbonded fiber-reinforced elastomeric isolators

Unbonded fiber-reinforced elastomeric isolators (FREIs) were proposed in the late 1990s as a low-cost alternative to traditional bonded steel-reinforced elastomeric isolators. The use of lightweight carbon-fiber reinforcement and the elimination of the attachment plates reduce the complexity of the manufacturing process, the weight of the device, and the overall material cost. However, the reduced manufacturing and installation cost come at the expense of a complex mechanical behavior. Therefore, FREIs under cyclic lateral deformation have typically been represented by uniaxial phenomenological models. These models accurately represent the isolator’s hysteretic behavior at maximum lateral displacement but deviate from experimental results at lower displacements, with a tendency to overpredict the energy dissipation and unloading stiffness. In this paper, a new model, called Pivot Bouc-Wen model, is proposed to address these shortcomings and obtain a better analytical prediction of the response over the whole range of motion. The model combines a nonlinear elastic spring with a traditional Bouc-Wen element with a stiffening pivot hysteresis rule to modify the lateral response prediction at different amplitudes. The paper initially compares the performance of non-iterative models in the literature to the Pivot Bouc-Wen model in predicting lateral hysteresis results from a previous experimental study. Later, the dynamic analysis of a simple structure subjected to different ground motion types and intensities is performed using the different models, and results are compared.