3D base isolation of buildings

A 3-D base isolation system to control the structural effects of both the horizontal and vertical components of ground motion has been recently presented in literature and it is herein briefly summarized. A building model is used to test the 3D base isolation arrangement that consists of elastomeric bearings acting both in the horizontal and vertical directions, and an innovative negative stiffness devices acting only in the vertical direction. The elastomeric bearings horizontal reaction force is reproduced through the implementation of a linearized approach. The negative stiffness device in the vertical direction can be considered as an adaptive passive protection system, which can apparently change the stiffness of the structure. Numerical analyses show that the presence of the negative stiffness devices in the vertical direction coupled with the elastomeric bearings reduces both the vertical and the horizontal absolute acceleration in the structure. Nevertheless, accordingly with the passive control theory, the relative displacements increase. The adoption of supplemental damping from the implementation of high damping rubber bearings allows to mitigate such amplification effects without introducing specific dampers.