Test Research On Aerodynamic Characteristics Of A Long Span Bridge

With the development of modern construction technique and the application of new material, bridges which progress towards small rigidity, big flexility, long span and light weight are more sensitive to the action of winds. For researching on the wind induced vibration of the long span bridges, it is the foundation and essential approach to study the aerodynamic characteristics. 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 a sea-crossing bridge as background, on the basis of wind tunnel test, this paper focuses on the steady aerodynamic characteristic of the main girder, as well as the flutter characteristic of the main girder. Flutter derivatives of the main girder are identified also.The 1:60 scale section model tests of the main girder 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.Moreover, in the uniform flow, at -3°, 0°and +3°attack angles, using the same girder model as 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 parameters 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, this sea-crossing bridge possesses well aerodynamic stability. The main girder can well resist torsional flutter with critical flutter wind speed greater than 232.65m/s.