| Co-Investigator(Kenkyū-buntansha) |
BOONYAPINYO Vorote Dept.of Civil Engiineering, Research Associate, 工学部, 助手 (50251765)
KAZAMA Kohji Sumitomo Heavy Industries Ltd., Researcher, 総合技術研究所, 研究員
YAMADA Hitoshi Dept.of Civil Engiineering, Associate Professor, 工学部, 助教授 (00143735)
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| Research Abstract |
Considering the trend of longer span bridges in the future, the aerostatic and aerodynamic feature play a major role in their design. In the previous study with feasibility study model of 2,500m-4,000m span suspension bridge, the onset wind speed of flutter deteriorated a lot.
In this research, aeroelastic behavior and the effects of the structural countermeasures for flutter instability of super long span suspension bridges, featuring the Flutter Mode Shape Control, are discussed using a Direct FEM Flutter Analysis Method and its assessment technique of exciting/damping aerodynamic force distribution along the bridge axis.
Flutter analysis was performed for 2,500m-4,000m case study model under the assumption of flatter derivative of wing, the onset wind speed fell a lot. And the effect of simple increase of torsional rigidity of the girder proved to fall as span length.
The countermeasure which control the flutter mode shape was applied for 2,500m span model with moving its gravity-center of the girder with no increment of the materials. With the aerodynamic derivative of truss girder, the counter measure showed fair effect
Viewing its exciting/damping aerodynamic force along bridge axis and summed along bridge axis, the distribution of aerodynamic force change a lot. Moving its gravity center, mode shape was changed and even the identical flutter derivative applied, the distribution of exciting/damping aerodynamic force along bridge axis differed a lot. By moving the gravity center, flutter mode shape changed efficiently. As a result, exciting energy cause from vertical motion changed drastically.
In the aeroelastic design of super long bridges, using Direct FEM Flutter Analysis and its Assessment method of exciting and damping force from both point of view of economy and aeroelasticity, mode shape control proved very efficient especially on flexible structure.
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