Effect of Variable Fluid Damper on the Response of Sliding Base Isolation System

To mitigate base displacement in seismic isolated structures under severe earthquake excitations, variable fluid damper (VFD) has been developed at Tohoku University. Sliding base isolation by utilizing friction mechanism has the benefit of controlling level of transmitted force into the superstructure, while large base displacement and residual slip may occur. Response of base isolated multistory structure is investigated through employing lumped-mass shear-building model subjected to horizontal component of near-field and far-field ground motions. In this paper, influence of implementing restoring device and damping within sliding isolation system is presented. A parametric study has been carried out to reduce base displacement with minimum counter effect on the superstructure. To decrease base displacement for severe earthquakes additional energy dissipation can be provided by nonlinear response of VFD. Results of analytical study demonstrate that VFD can improve performance and robustness of sliding isolation system by mitigating base displacement while shear and interstory displacement of superstructure are slightly increased.