Test Research On Aerodynamic Characteristics Of Long Span Arch Bridge

With the development of modern construction technique and the application of new material, arch bridges which progress towards small rigidity, big flexility, long span and light weight are more sensitive to the action of the winds. For researching on the wind induced vibration of the long span arch bridges, it is the foundation and essential approach to study the aerodynamic characteristics of girder and arch rib. Characteristic is a very extensive concept, consisting of two categories, ie, steady aerodynamic characteristic and nonsteady aerodynamic characteristic including researches on flutter characteristics, self-excited force, buffeting force, votex force and galloping force. With Chongqing Caiyuanba bridge as background, on the basis of wind tunnel test, this paper studies the steady aerodynamic characteristic of the girder and arch rib, as well as the flutter characteristic of the girder. Flutter derivatives of the girder are identified also. The 1:70scale section model tests of the girder and arch rib 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 varying with attack angle is analyzed. For the girder section, the effect of wind speed and light rail on three dimensional static component forces coefficient is discussed. Moreover, in the uniform flow, at -3°,0°and +3°attack angles, using the same girder model with static test, the vibration response as well as the natural frequency and displacement response of the girder are tested at any wind speed level by means of binary rigid section model hang through springs. In addition, the critical flutter wind speed of girder is measured. 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, using the same model and measuring device to identify the flutter derivatives of the girder. Basing on least-square method, eight derivatives are identified once. The test results indicate that, the girder and arch rib of Chongqing Caiyuanba bridge possess well aerodynamic stability. For arch rib, the drag is the primary static wind load, while the lift and lift moment are comparatively small; the girder can well resist torsional flutter with critical flutter wind speed big than 232.65m/s.