Hybrid Strategy to Achieve 3D Base Isolation of Structures

Some aspects, related to the 3D base isolation of structures to control the effects of both the horizontal and vertical components of ground motion, are presented in this paper. A massive structure (a Nuclear Power Plant building) equipped with a traditional horizontal base isolation system is numerically studied. The base isolation system uses rubber bearings (low and high damping) coupled with a tuned mass damper (TMD) in the vertical direction. Possible positive and negative aspects from the implementation of the proposed hybrid strategy are investigated. Numerical analyses show that the presence of the TMD mitigate the vertical effects of the three-dimensional ground motion coupled with the elastomeric bearings, reducing both the vertical and the horizontal absolute acceleration in the superstructure under certain conditions. Vertical acceleration in the superstructure appears related to the horizontal motion, due to the building’s centroid position that induces rocking.