Cable-Stayed Bridges
Civil and architectural engineers are protecting bridges (and their occupants) with LORD MR technology. MR fluid dampers attached to cables provide a continuously controllable, cost-effective solution to wind-rain-induced cable “gallop.”
The Value LORD MR Provides
High dissipative force at low velocity. Unlike with variable orifice dampers, force is not wholly dependent upon velocity, enabling superior mitigation of a broader range of vibration.
Continual optimization. Unlike passive systems that are tuned once according to an inferred optimum setting, MR devices — continually optimize the rheology (stiffness) of their fluid up to 100 Hz. Further, this controllable re-tuning occurs more quickly with MR than with alternative semi-active solutions.
High dynamic range. The ratio of the maximum force to the minimum force that MR devices provide is much greater than that of any other controllable damper, particularly at low velocities. Unlike friction dampers, MR dampers experience comparatively very low levels of stiction.
Inherent stability and failure-safety. Unlike active dampers that require large power sources, semi-active MR dampers fail-safe to a passive damping mode.
Mechanical simplicity. MR damper valves have no moving parts, reducing maintenance concerns and potential expense.
Fast response-time. Because MR damper valves have no moving parts, their response time is significantly faster than that of variable-orifice dampers.
Small device size. MR technology enables smaller device sizes than with hydraulic or mechanical systems, leading to aesthetic and practical benefits.
Large temperature range. Importantly, MR materials can operate under the extreme conditions often associated with catastrophic events; MR dampers have an operating temperature range of 40° C to 130° C, with no significant variation in performance.
Stay cables are prone to vibration due to wind and rain effects. “Smart” dampers have the potential efficiency several times that of standard oil dampers. LORD MR dampers are being used on the Dongting Lake Bridge in China. Watch the videos linked below, which were filmed on the Dongting Bridge during an actual wind event. One cable that is not moving — thanks to the MR damper.