Seismic isolation of lightweight structures through Wire Rope devices: Preliminary experimental results and simulation

The work presents some preliminary results of experimental tests performed on a Helical Wire Rope Isolator (HWRI), to the aim of describing the dynamic behavior of the metal isolation device, without pre-load and under the effect of a vertical pre-load, for different displacement amplitudes. During the dynamic tests, the testing machine allows to apply a vertical displacement or load history to the tested device, subjected to a constant vertical pre-load. The dynamic behavior of the tested device depends on the applied displacement amplitude: the HWRI displays an asymmetric behaviour, i.e. a different response when it is subjected to compression or tension; in the latter case, it shows an hardening effect for larger displacements. Moreover, the experimental tests make clear that the application of a vertical pre-load determines a different behaviour in Compression vs. Tension, with slightly variable damping properties. In order to simulate the dynamic behavior of the HWRIs in Compression-Tension direction, a nonlinear model is proposed, that is validated by comparing the experimental hysteresis loops obtained during cyclic tests with those predicted analytically.