Cabinet and Shelter Vibration Isolation: Numerical and Experimental Investigation

Passive isolation systems are often adopted to reduce vibrating energy acting on a sensitive equipment due to external sources as machinery, road/rail traffic, earthquakes, etc. The paper describes a theoretical and experimental investigation conducted on a steel light structure, simulating a cabinet or a shelter containing sensitive equipment. It is isolated from the ground seismic acceleration by means of four isolators each consisting of a ball transfer unit (BTU) and a wire rope spring (WRS). This kind of isolator has hysteretic non-linear behaviour with damping caused by the dry friction due to the wires relative motion; the non-linear stiffness and damping is function of the wire rope configuration and on its diameter and length. Some experimental tests have been performed to characterize the isolator and to obtain an analytical description of its dynamic behaviour; then the steel light structure, supported by four WRS-BTU isolators, has been tested on a shake-table to evaluate the isolation efficiency. The experimental results have been compared with the theoretical ones obtained with a numerical model in which the isolator hysteretic behaviour has been modelled with the Bouc-Wen theory. The validated model has been then used to simulate the cabinet dynamic response due to recorded seismic ground motion.