Test Research On Aerodynamic Characteristics Of Long Span Cable-stayed Bridge

The long-span cable-stayed bridge with small rigidity is a flexible structure. The Structural Dynamic Response by the wind, which is wind-induced vibration, becomes the major concern for the wind–resistance design of the long-span bridge. Thus, study on the wind-induced vibration of long-span cable-stayed bridges become extraordinarily exigent.Aerodynamic characteristic of bridge is the foundation of studying wind-induced vibration. Aerodynamic characteristic is a very extensive concept, consisting of two categories, ie, steady aerodynamic characteristic and nonsteady aerodynamic characteristic. With someone coastal-span bridge as background, on the basis of wind tunnel test and the static test with sectional model, this thesis studies the steady aerodynamic characteristic of the main girder. On the basis of section model with dynamic test, it studies the flutter characteristic of the girder. Flutter derivatives of the girder are identified also.Accurate knowing the steady aerodynamic characteristic is very important in wind–resistance design of the bridge, it is the foundation of estimating the wind load of structure and studying the nonsteady aerodynamic characteristic. Three dimensional static component forces are a group of nondimensional parameters in description of static wind load. Four 1:60 scale section model tests of the girder include recommended scheme of No.1 bridge, the first alternative scheme of No.1 bridge, recommended scheme of No.2 bridge and alternative scheme of No.2 bridge, are carried out at FL-11wind tunnel which belongs to China Aerodynamics Research and Development Center. In the uniform flow, the regularity of three dimensional static component forces coefficient with varying attack angle is analyzed, and three dimensional static component forces is obtained.Flutter derivatives are the key parameter to depict the aerodynamic characteristic of bridges, which play an important role in analyzing the flutter and buffeting response. This paper makes use of free vibration method to identify the flutter derivatives of the girder. In the uniform flow, at -3°,0°and +3°attack angles, using the same girder model with static test, the vibration response are tested at any wind speed level by means of binary rigid section model hang through springs. Basing on least-square method, eight derivatives are identified once. In addition, the critical flutter wind speed of girder is measured.The test results indicate that, the girder of this coastal-span bridge possess well aerodynamic stability. The girder can well resist torsional flutter with critical flutter wind speed big than 118.5m/s,as well as the flutter inspection wind-load [Vcr] =97.5 m/s. The main girder of practical bridge will not happen to flutter under the local designed wind load.