Viscoelastic frictional properties of rubber-layer roller bearings (RLRB) seismic isolators

This paper deals with the behavior of a rubber-layer roller bearing (RLRB) isolation system. This system consists of steel cylinders interposed between steel plates padded with high damping rubber layers. When the cylinders start to roll, a partial decoupling is achieved between the superstructure response and the ground motion. However, the presence of rubber layers in RLRB isolators aims at dissipating part of the seismic energy, thus reducing the relative motion between the base and the superstructure (building). To better understand this phenomenon, we proceeded to a mechanistic study of the viscoelastic contact interaction between the rolling cylinders and the rubber layers. The analysis is led in the framework of continuum mechanics and linear viscoelasticity by means of a numerical strategy, belonging to the class of boundary element methods, able to take into account the viscoelastic layer thickness. The results show that, depending on the design parameters, a strong reduction of the viscoelastic friction can be achieved, useful to uncouple the motion of the superstructure from the motion of the base and then of the ground, without negatively affecting the amount of energy dissipation per unit time. The simulations allow determining the optimal sizes and dimensions to the component parts of the isolator.