Vibration Isolation Capabilities of a Low-Cost Seismic Isolation System Based on Elastomeric Rolling Spheres for Masonry Structures

In recent years, seismic isolation has been used as an effective retrofit technique to protect historical buildings and structures against earthquakes. However, for some isolation devices, man-induced low-amplitude vibrations (e.g., construction activities, vehicle, and rail traffic) can still be directly transmitted to the structure. These vibrations can cause damage and deteriorate structural elements if they persist during extended periods of time, especially on masonry or unreinforced structures. This paper explores the horizontal low-amplitude vibration isolation capabilities of a low-cost seismic isolation system based on elastomeric rolling spheres for low-rise structures. The isolation system consists of elastomeric spheres placed underneath the structure, providing lateral isolation through rolling and still providing vertical flexibility and damping through the deformability of the spheres. Experimental tests were performed to characterize the sphere’s rolling mechanical behavior under relatively small deformation amplitudes, calibrating a simple yet effective nonlinear model to perform further numerical analyses under other inputs that the shake table could not reproduce. The vibration isolation performance of the spheres was addressed through its transfer function. The results showed that the proposed isolation system based on rolling elastomeric spheres has the potential to serve as a dual isolation system, i.e., protect the structure against earthquake events and long-term ambient vibrations. Further experimental tests need to be performed to validate the conclusions presented herein and extend the applicability of such isolation system to industrial machinery or sensitive equipment where traditional vibration isolators are required but do not protect against earthquakes.