Abstract
A new self-powered magnetorheological (MR) damper control system was developed to mitigate cable vibration. The power source of the MR damper is directly harvested from vibration energy through a rotary permanent magnet direct current (DC) generator. The generator itself can also serve as an electromagnetic damper. The proposed smart passive system also incorporates a roller chain and sprocket, transforming the linear motion of the cable into the rotational motion of the DC generator. The vibration mitigation performance of the presented self-powered MR damper system was evaluated by model tests with a 21.6 m long cable. A series of free vibration tests of the cable with a passively operated MR damper with constant voltage, an electromagnetic damper alone, and a self-powered MR damper system were performed. Finally, the vibration control mechanisms of the self-powered MR damper system were investigated. The experimental results indicate that the supplemental modal damping ratios of the cable in the first four modes can be significantly enhanced by the self-powered MR damper system, demonstrating the feasibility and effectiveness of the new smart passive system. The results also show that both the self-powered MR damper and the generator are quite similar to a combination of a traditional linear viscous damper and a negative stiffness device, and the negative stiffness can enhance the mitigation efficiency against cable vibration.
Highlights
Due to high flexibility, low inherent damping, and relative small mass, long stay cables are often susceptible to excessive vibrations under various environmental excitations
Taking the second mode of the cable as an example, the entire time histories of accelerations at the observation point of the cable with a passively operated MR damper attached are shown in MR damper operated in passive-on mode (i.e., 1 V voltage) can only work well when the amplitude of the cable is relatively large
The feasibility and effectiveness of the new system for suppressing cable vibration was experimentally evaluated via a 21.6 m inclined cable model
Summary
Low inherent damping, and relative small mass, long stay cables are often susceptible to excessive vibrations under various environmental excitations. The performance of passive viscous dampers in mitigating cable vibration is greatly restricted by the small ratio of the distance from the cable anchorage to the damper over the length of the cable [1]. This may cause the supplemental damping induced by a passive damper to be insufficient to eliminate the problematic vibrations of long stay cables without significantly detracting from the aesthetics of the bridge
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