On the performance of double rolling isolation systems

Abstract

Harvey and Gavin [1] previously proposed a double rolling isolation system (RIS) that possesses greater displacement capacity than that of its constituent subsystems alone. This study aims to quantify the performance gained by using the dual-layer system. The system's nonlinear equations of motion, adhering to the constraint of rolling without slipping, are derived for arbitrary rolling profiles. Linear equations are recovered when a circular rolling profile is assumed. The stochastic response of the double RIS under stationary white noise excitation is evaluated for relevant system parameters, namely mass ratio and tuning frequency. Both broadband and filtered (Kanai-Tajimi) white noise excitation are considered. The response variances of the double RIS are normalized by a baseline single RIS for a comparative study, from which parameter design maps are drawn. A deterministic analysis was also conducted to further evaluate the double RIS in the case of nonstationary excitation. The telecommunications equipment qualification waveform, VERTEQII, was used for these numerical simulations. Peak transient responses are compared to the single RIS responses, and optimal design regions are determined. General design guidelines based on the stochastic and deterministic analyses are given.