Short- Versus Long-Term Readiness and Dissipative Capability of MR Dampers for Structural Control

Abstract

The proposed work is based on an experimental activity aimed at comparing the long-term behavior of control devices based on the use of magneterheological (MR) fluids for seismic protection of framed structures. They have been tested three times in ten years: first in 2008, then in 2013 after five years of inactivity, and finally in 2017 after further four years of quiescence. The results of the three campaigns of passive and promptness experimental tests, in terms of force-displacement loops, electrical delay of the electromagnetic circuit, dissipated energy and maximum reacting force. The evolution of the response of such dampers due to inactivity over the time is assessed and discussed, aiming at recognize those phenomena are most probably responsible of a MR fluid deterioration (namely oxidation of iron particles, their sedimentation, fluid thickening, seal wearing), finally trying to give practical suggestions to the designers of smart control systems who should take this issues into account when dealing with the above kind of devices.