Seismic protection of low- to moderate-mass buildings using RNC isolator

The general objective of base isolation is to increase the natural period of vibration of the structures out of the typical earthquake dominant periods through increasing their flexibility. This objective is particularly important for light- to moderate-weight structures as low masses imply lower natural periods. This paper presents the application of a new roll-n-cage (RNC) base isolator to mitigate the seismic response of this class of structures. From a functional point of view, RNC is essentially an isolation bearing, while it offers a significant resistance to wind and minor vibrations. Rolling is the basic mechanical principle adopted to offer a great range of horizontal flexibility, which is complemented with an energy dissipation mechanism. The device is designed to have several practical controls to ensure buffer, re-centering and no uplift during motion. In this paper, the principles of operation and force–displacement relationships of the novel RNC isolator are presented, along with its implementation and performance evaluation considering a wide range of structural, isolator and ground motion characteristics. The numerical results show that the proposed bearing is a useful tool for isolating light- to moderate-mass systems, and it can mitigate the seismic response under a variety of ground motion excitations while exhibiting the robust performance for a wide range of structures. Copyright © 2010 John Wiley & Sons, Ltd.