Theoretical prediction of the dynamic behavior of rolling-ball rubber-layer isolation systems

This paper presents the results of a theoretical study carried out to characterize the dynamic behavior of a seismic isolation system consisting of steel-rolling balls on rubber layers. This type of device reduces seismic hazard during earthquakes by decoupling the superstructure from the ground motion and by dissipating the energy in damping, thanks to the viscous-elastic properties of the rubber. The behavior of the rolling balls on rubber layers isolation system is described by achieving suitable expressions for the resultant normal and shear forces acting in the device. In particular, it is shown how the resultant shear force is highly affected by the correct definition of the slip and stick regions, which develop at the steel-rubber contact area. The analysis allows to identify the main parameters characterizing this type of device, furnishing a valid tool in order to correctly calculate some response quantities significantly influenced by the isolation system. Copyright © 2016 John Wiley & Sons, Ltd.