Modelling of the rubber relaxation effects on the small-deflections behaviour of the seismic isolation system RBRL

The Rolling-Ball Rubber-Layer (RBRL) isolation system for seismic isolation of lowmass structures, such as museum artefacts, is described. Finite strain linear viscoelasticity is used in Finite Element Analyses (FEA) to model the thin layers of unfilled rubber bonded to steel tracks. Results of experiments and FEA for load-indentation behaviour, recovery of the indentation “pits” formed in the rubber, and rolling resistance of steel balls loaded against the tracks are reported and compared. The FEA results agree qualitatively with the experimental rolling characteristics but the recovery of the indentation pits after removal of the ball are underpredicted and the peak roll-out force is overpredicted. The experimental observation of very different shapes of the residual indentation profile is remarkable.