Vertical Accelerations in Rolling Isolation Systems: Experiments and Simulations

Rolling isolation systems (RISs) have been used extensively to protect bridges, buildings, and equipment from earthquake-induced ground and floor motions. RISs are attractive in a performance-based design context because horizontal acceleration design requirements may easily be met by adjusting the slope of the rolling surface. However, in the process of reducing horizontal accelerations, the isolator transmits vertical accelerations due to the pendulumlike motion. These vertical accelerations may exceed tolerable limits if left unchecked. In this study, the influence of the rolling surface profile on peak vertical accelerations is assessed through experiments and simulations. RISs with different radii of curvature are fabricated and then tested for a wide range of ground-motion frequencies and amplitudes. The experiments and simulations show that vertical accelerations are not negligible and should not be ignored in the design of RISs.