LORD Corporation Helps Solve Unique Vibration Problem on Chinese Bridge

Customer
Dong Ting Bridge in the People’s Republic of China. Located just outside of Changsha, the bridge, featuring soring, inverted “Y” towers and radiating steel support cables, spans Dong ting Lake.

Challenge
The cables that are central to the design of the cable-stayed Dong Ting Bridge tend to vibrate excessively, or “gallop,” from wind and/or rain excitation. While conventional tie cables and passive dampers can control vibration, they destroy the structure’s aesthetics. however, placing passive dampers only at the bottom of the structure in an attempt to preserve the visual lines of the bridge results in a damping force either so weak that it is virtually useless or so strong that it locks down the cable.

Solution
LORD Corporation’s proprietary magneto-rheological (MR) fluid was used to create semi-active dampers capable of providing rapidly changing force. When exposed to a magnetic field, the MR fluid can shift within milliseconds from a liquid to a semi-solid state, allowing the dampers to shift instantly between high damping and low damping states, removing unacceptable vibration and cable gallop.

Results
The Ding Tong Bridge is the first cable-stayed bridge in the world that uses this proprietary technology, developed in conjunction with DR. Y.A. Ni at Hong Kong Polytechnic University. The MR damping system was relatively inexpensive to develop, requires little maintenance and demands minimal amounts of power to operate.

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