HYBRID APPROACH FOR 3D BASE ISOLATION OF LOW DAMPED STRUCTURES

Some aspects related to the 3-D base isolation of structures are presented in this paper through a numerical approach. A traditional horizontal base isolation system with the use of rubber bearings and metallic springs is coupled with a tuned mass damper in the vertical di-rection. Both lightweight (e.g. artworks or special equipment) and massive structures (a nu-clear power plant building) have been considered and possible positive and negative aspects from the implementation of the proposed hybrid control strategy are investigated. It is found that the tuned mass damper is able to provide a reliable source of energy dissipa-tion, and to control the vertical motion of the structure, only when this has a low value of damping. For damping values that approximately exceed the 5% limit, the positive effects of TMD are negligible, if not slightly worsening.