Modeling and Evaluation of Magnetorheological Dampers with Fluid Leakage for Cable Vibration Control

Magnetorheological (MR) dampers are common methods that are used to mitigate cable vibrations with high effectiveness. Under the long-term effect of external loads and harsh environment, MR dampers will probably suffer from various durability problems, especially fluid leakage. Hence, accurate modeling and evaluation of the effect of fluid leakage of MR dampers are of great significance for bridge maintenance. This paper will investigate the mechanical behavior of MR dampers with fluid leakage after long-term operation and will evaluate their residual performance for cable vibration control. First, three MR dampers with fluid leakage will be selected from a real bridge, followed by a laboratory test to illustrate their damping force characteristics. Based on the experimental results, a theoretical model will be proposed to predict the mechanical behavior of the leaked dampers. A parametric analysis will then be conducted to show the effect of fluid leakage on the damping capacity. Then, one full-scale cable will be idealized as a taut string and the equation of motion for the cable-leaked MR damper system will be formulated. Additional modal damping provided by the MR damper will be determined numerically. The results show that fluid leakage could cause considerable slipping in the damping force. This slipping could lead to a remarkable reduction of the achieved additional modal ratios for the cables. The results of this paper could be of practical significance for the assessment of cable dampers performance and their maintenance on real bridges.