Flutter Characteristics and Modes of Suspension Bridge with Open Steel-Concrete Composite Stiffening Girder
The bridge crossing the Dongting stream that flows into the Yuanshui River in Hunan Province,also known as the Dongtingxi Yuanshui River Bridge,is used as a case to study the flutter characteristics and multimode participation effects of the suspension bridge with stiffening girders composed of double open steel edge boxes and concrete panels.A scale-down sectional model of the stiffening girder was fabricated for the wind tunnel test to investigate the flutter performance of the original bridge structure as well as ways to improve the flutter critical wind velocity,including adjusting the structural damping ratios,optimizing the aerodynamic shapes of the stiffening girder and adding central buckle in the stiffening girder.The flutter modes and multimode participation effects of the stiffening girder with central buckles were three-dimensionally and two-dimensionally simulated.It is shown that the flutter critical wind velocity in the case bridge is high,and the flutter is registered mainly as the torsion-dominated torsional-vertical resonances,with big phase difference between torsion and vertical vibrations(about 180°).When the stiffening girder is fitted with central buckles,the symmetrical torsional modes with higher frequencies were observed before the occurrence of asymmetrical modes in the wind tunnel test,which was in agreement with the results of the wind tunnel test,and there was minimal difference between the 3D and 2D flutter analyses.
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