Use, Effectiveness and Long Term Reliability of MR Dampers for Seismic Protection of Framed Structures

The implementation, operation and efficacy of semi-active (SA) structural control systems based on the adoption of magnetorheological (MR) devices are still object of research. For a such system, generally a complex electronic equipment is required to acquire then elaborate then generate signals to properly command the smart devices in real time. Given this, the effectiveness of these control systems in reducing the seismic response of structures is often called into question. And one wonders about the performance of these systems in the long term, i.e. when called to respond to seismic actions after many years since their installation. Will the devices be ready to respond? Is their dissipative capacity still that exhibited before their installation? This work attempts to present a comprehensive description and offer suitable solutions for a number of specific aspects that characterize the implementation of SA control systems. Authors also highlight undesired and unavoidable effects and provide insights on the way to reduce their incidence. The performance of such system is then showed via a shaking table test of a full-scale steel structure. These tests allowed to measure the actual short-term effectiveness of this system. After 10 years of inactivity of those MR devices, these have been subjected characterization tests once again, in order to assess the evolution of their mechanical behaviour over time and the decay of performance. The long-term response in terms of readiness, dissipative capacity and reaction force was measured, leading to positive conclusions about the reliability of the control system after years of inactivity.