Seismic Isolation of Hospitals Through Fluid Viscous Dampers Combined with Isolators

The paper is focused on the recent trend of using fluid viscous dampers in seismic isolation system of hospitals or other strategic buildings. The effectiveness of high energy dissipation capacity of the seismic isolation system in reducing its displacement is well known. However, a high hysteretic/bilinear energy dissipation can increase the higher-mode response, and consequently is not optimal in strategic buildings. Conversely, energy dissipation provided by viscous dampers guarantees the best response both in the first modes and in higher modes. Furthermore, energy dissipation dependent on velocity guarantees the activation of the seismic isolation system at any level of earthquake. Some hospitals case studies are described, with fluid viscous dampers combined either with pendulum isolators or with elastomeric isolators. Some full scale test results on devices used in said hospitals are reported as well.