Stochastic sensitivity and uncertainty of secondary systems in base-isolated structures

Abstract This work first investigates the sensitivity of secondary systems in a base-isolated structure to changes in the design parameters of the base isolation mechanism and of the ground motion model. In particular, a six-storey frame with secondary systems attached to the top floor and undergoing random ground motions is studied. It is noted that a scaled model of this structure was experimentally investigated on a shaking table in earlier work. The results of the sensitivity analysis are found to be in very good agreement with the finite difference method. Subsequently, root-mean-square acceleration spectra for secondary systems are constructed so that their sensitivity to the aforementioned design parameters can be assessed. Next, the sensitivity analysis methodology is extended to cover the case in which both the base isolator parameters and the ground motion filter parameters are uncertain. It is shown that, for the same example previously considered, the effect of uncertain system parameters on the response cannot be ignored. Successful base isolation designs using friction sliding bearings and restoring springs are possible, however, even in the face of uncertain system properties.

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