A procedure for the dynamic identification of the physical parameters of coupled base isolation systems is developed in the time domain. The isolation systems considered include high damping rubber bearings (HDRB) and low friction sliding bearings (LFSB). A bi-linear hysteretic model is used alone or in parallel with a viscous damper to describe the behavior of the HDRB system, while a constant Coulomb friction device is used to model the LFSB system. After deriving the analytical dynamical solution for the coupled system under an imposed initial displacement, this is used in combination with the least-squares method and an iterative procedure to identify the physical parameters of a given base isolation system belonging to the class described by the models considered. Performance and limitations of the proposed procedure are highlighted by numerical applications. The procedure is then applied to a real base isolation system using data from static and dynamic tests performed on a building at Solarino. The results of the proposed identification procedure have been compared to available laboratory data and the agreement is within ±10%. However, the need for improvement both in models and testing procedures also emerges from the numerical applications and results obtained. dynamic tests were performed on one of the two buildings. Some details of those tests as well as preliminary attempts at system identification have been reported in the literature [3][4][5][6][7]. The static test, up to the application of the design displacement, allowed for the identification of the static friction force and of the residual displacement after unloading [3]. Dynamic tests were performed in the form of free vibrations after applying an initial displacement as close as possible to the design displacement. The purpose of the present paper is to perform a dynamic identification of the isolated building with particular attention to the isolation system. The non-linear characteristics of the isolation system have called for the use of a special procedure for the separation of the isolation mode from the structural modes. Particular attention has been paid to this problem in References [4,5] where wavelet decomposition was used to separate the isolation mode from the structural modes. Furthermore, in References [6, 7], the problem of identifying the principal characteristics of the isolation system has been treated by system identification in the frequency domain. In those papers, the rubber isolators were considered as equivalent visco-elastic devices, while the sliding isolators were described as friction-regulated systems. The results show that the equivalent visco-elastic description is not adequate for the complete identification of the properties of the HDRB, because the non-linear behavior of these devices is not taken into account. LITERATURE REVIEWIn this section, a brief literature review of environmental and direct testing of base-isolated buildings will be presented, with the objective of providing the appropriate setting for...

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