Flutter Mechanisms of Long Spanned Bridge Sections Based on Structural and Aerodynamic Characteristics

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Flutter mechanisms and its stabilization for long spanned suspension bridges have been studied, and the results are as follows.・The flutter characteristics of new bridge sections, which models are rigidly combined with 2 or 4 rectangular cylinders, are examined using wind tunnel. 2-parallel rectangular section model becomes quite unstable with some wind angle of attack. However, 4-recgtangular model has rather stable flutter chracteristics mounting the each small section in the right place.・A windmill is mounted at the leading edge of the bridge section to control the flutter instabilities. The windmill can control the inner circulatory flow and then the flutter instabilities also can be reduced.・Open air ratio of grating between two separated box girders are changed and their flutter chracteristics are investigated. In the case of rhombus 2-box Girdersection with 40% open grating ratio, the flutter onset wind speed becomes twice higher than that of thin plate. Therefore, it is rather important chose the best open air ratio of the grating for each bridge sections.