Soil-dependent optimum design of a new passive vibration control system combining seismic base isolation with tuned inerter damper

The papers addresses a novel passive vibration control system combining seismic base isolation with a tuned inerter damper (TID) system. The latter, by analogy with the tuned mass damper (TMD), is a dynamic vibration absorber in which the physical mass of the TMD is partly or entirely replaced by an apparent mass, also called inertance, created by a particular arrangement of mechanical gearings-the inerter. By attaching a TID to the isolation floor, not only the displacement demand of base-isolated structures can be significantly reduced, but also the superstructure response (e.g. interstory drift, base shear) is effectively controlled. Optimum parameters of this system are found based on a simplified three degree-of-freedom model that reflects the dynamic properties of both the isolation system and the TID while accounting for the flexibility of the base-isolated superstructure. Within a probabilistic framework, the influence of soil conditions is investigated by modeling the seismic ground motion as a filtered Gaussian random process. Different filter parameters are considered that may be associated with firm, medium or soft soil conditions depending on the frequency content of the power spectral density function. A wide parametric study is performed in order to detect the optimal TID parameters depending on the soil conditions for a variety of isolation ratios, mass ratios and damping ratios of both the superstructure and the isolation system. Finally, a multi-story building equipped with the proposed passive vibration control system is examined. Effectiveness of the proposed system is assessed via the evaluation of the structural response in the time domain. Detuning effects are investigated via a sensitivity analysis. Comparison with alternative passive vibration control systems proposed in the literature and based on different arrangements of TMD and inerter-based device is discussed.