A Comparison Between Linear and Nonlinear Modelling of a Wire Rope Seismic Isolator

This paper describes different modelling approaches to describe the shear restoring force of seismic isolators that are constituted by a wire rope spring coupled with a ball transfer unit. Two theoretical descriptions have been considered: the first one is based on the equivalent linear model while the second one is based on a modified version of the Bouc-Wen model. The calibration of the models has been performed comparing the theoretical hysteresis cycles with the experimental ones obtained with a seismic isolator test rig. The results clearly highlight the limit of the linear approach and at the same time show the capabilities of the proposed nonlinear model to reproduce the restoring force of the isolators.