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Wind and Structures
  Volume 30, Number 5, May 2020, pages 499-509
DOI: http://dx.doi.org/10.12989/was.2020.30.5.499
 


Effect of countermeasures on the galloping instability of a long-span suspension footbridge
Ruwei Ma, Qiang Zhou and Mingshui Li

 
Abstract
    The aeroelastic stability of a long-span suspension footbridge with a bluff deck (prototype section) was examined through static and dynamic wind tunnel tests using a 1:10 scale sectional model of the main girder, and the corresponding aerodynamic countermeasures were proposed in order to improve the stability. First, dynamic tests of the prototype sectional model in vertical and torsional motions were carried out at three attack angles (α= 3°, 0°, -3°). The results show that the galloping instability of the sectional model occurs at α = 3° and 0°, an observation that has never been made before. Then, the various aerodynamic countermeasures were examined through the dynamic model tests. It was found that the openings set on the vertical web of the prototype section (web-opening section) mitigate the galloping completely for all three attack angles. Finally, static tests of both the prototype and web-opening sectional models were performed to obtain the aerodynamic coefficients, which were further used to investigate the galloping mechanism by applying the Den Hartog criterion. The total damping of the prototype and web-opening models were obtained with consideration of the structural and aerodynamic damping. The total damping of the prototype model was negative for α = 0° to 7°, with the minimum value being -1.07%, suggesting the occurrence of galloping, while that of the web-opening model was positive for all investigated attack angles of α = -12° to 12°.
 
Key Words
    long-span suspension footbridge; galloping instability; web opening; Den Hartog criterion; damping
 
Address
Ruwei Ma, Qiang Zhou and Mingshui Li: Research Centre for Wind Engineering, Southwest Jiaotong University, Chengdu, China/
Key Laboratory for Wind Engineering of Sichuan Province, Chengdu, China
 

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