Experimental parametric study and phenomenological modeling of a deformable rolling seismic isolator

This paper presents an extensive experimental study of a low-cost, high-performance seismic isolator comprising a deformable sphere rolling on concrete surfaces. Polyurethane spheres, with and without steel core, rolling on flat or spherical concrete plates, are investigated. Lateral cyclic tests under large displacements demonstrated a rolling friction coefficient between 3.7% and 7.1%. When tested in a shake table under 1170 ground motions, the isolators substantially reduced the acceleration transmitted to the superstructure (to less than 0.15 g) while maintaining reasonable peak and negligible residual displacements. A phenomenological model was calibrated on the lateral cyclic tests and predicted the shake table tests with reasonable accuracy.