On the behavior of a roller bearing seismic isolator

In this paper, we focus on the behavior of an innovative seismic rolling isolator in light to provide a passive protection to light structures from earthquakes damages. The specific isolation system belongs to the class of Rubber Layer Rolling Bearings (RLRB), and consists of steel cylinders interposed between steel plates padded with viscoelastic layers (rubber). Due to the geometry of the RLRB system, a partial motion decoupling is introduced between the ground and the superstructure. Moreover, the high-damping viscoelastic material employed in the system partially dissipate the seismic energy, thus reducing the relative displacement between the base and the building. In this work, we provide a deep insight into the viscoelastic behavior of such an isolation system. We specifically address the contact problem between the rigid cylinders and the viscoelastic layers, exploiting specific contact mechanics techniques to correctly model the effect of the layers finite thickness on the results. The theoretical model provides useful guidelines for a design optimization aiming at producing high energy dissipation with low force transmissibility. Further, in view of an extension to the case of multi-layer rubber system, we investigate the effect of different boundary conditions on the viscoelastic layers involved in the RLRB isolator, such as: (i) a rigid constraint; (ii) a uniformly distributed pressure. These, represent the two limiting cases of a layered system in which the external layer stiffness is infinitely high and vanishing, respectively.