Experimental characterisation and verification of a base-isolation system including fluid viscous spring-dampers

An experimental investigation was carried out on an advanced seismic protection system incorporating base isolators and supplemental damping devices. This testing campaign was part of the Research Programme DISPASS (Dissipation and ISolation PAssive Systems Study), financed under the ECOLEADER contract within the Fifth Framework Program of the European Commission. The protection strategy considered herein consists in coupling stainless steel-Teflon bearings, operating as sliders, and silicone fluid viscous spring-dampers. The latter are connected to the base-floor of the isolated building to provide the desired passive control of superstructure response, as well as to guarantee its complete re-centring after termination of a seismic action. Two types of experiments were conducted: sinusoidal and random cyclic tests, and a pseudodynamic test in “substructured” configuration. The cyclic tests were aimed at characterising the hysteretic response of the spring-dampers, the frictional behaviour of the steel-Teflon bearings, and the combined response of their assembly. The pseudodynamic test simulated the installation of the protection system at the base of a three-story steel frame structure, physically tested in other tasks of the DISPASS Project in unprotected conditions, as well as by equipping it with different passive control technologies. The results of the performed tests, as well as of relevant mechanical interpretation and numerical simulation analyses, are presented in this report.