DYNAMICAL MODELING OF FIBER-REINFORCED ELASTOMERIC ISOLATORS AT MULTIPLE LATERAL DEFORMATION LEVELS

Unbonded fiber-reinforced elastomeric isolators (FREIs) exhibit a complex nonlinear mechanical behavior under dynamic lateral deformation, which has typically been represented by uniaxial phenomenological models. Existing models accurately represent the isolator’s hysteretic behavior at a target lateral displacement but deviate from experimental results at other displacement levels, with a tendency to overpredict the energy dissipation and unloading stiffness at small deformations and exhibit sudden increases in estimated load at large deformations. In this paper, a new model, called Pivot Bouc-Wen model, is presented with the objective of addressing these shortcomings by providing (a) improved interpretability of the model parameters, (b) adequate energy dissipation prediction at multiple deformation levels, and (c) stable response at large deformations. The model combines a nonlinear elastic spring and a Bouc-Wen element with a modified pivot hysteresis rule to capture the lateral response of the isolators at different amplitudes. The capabilities of the proposed model are compared to those of existing non-iterative models in predicting results of lateral cyclic tests from a previous experimental study. The proposed and existing numerical models are further compared via response history analyses of idealized base-isolated buildings subjected to ground motions at different intensity levels. The results highlight the importance of capturing the hysteretic response of the isolators at multiple deformation levels and not only at the maximum expected deformation level.