A Preliminary Investigation of the Hanger Vibrations on the Great Belt East Bridge

On March 29, 2001, the Great Belt East Bridge exhibited large-amplitude hanger vibrations having elliptical orbits for wind speeds of between 16 - 17 m/s. Vibration amplitudes were in the order of 1.4m in the across-wind direction and 1.0m in the along-wind. In this paper, a preliminary investigation behind the causes of this relatively isolated hanger vibration event on the Great Belt East Bridge is undertaken. One of the main assumptions of the investigation is that coincidental icy conditions may have contributed in some way to large hanger response, by changing the cylindrical cross-sectional shape or partially changing the surface texture of the hangers. The change in shape or the surface texture has the effect of a change in the aerodynamic lift and drag coefficients in a certain Reynolds number range which in turn may lead to a form of “drag instability”. From the visual observations of the vibrations it is assumed that the aerodynamic moment coefficient is zero.