| Budget Amount *help |
¥15,280,000 (Direct Cost: ¥13,900,000、Indirect Cost: ¥1,380,000)
Fiscal Year 2007: ¥5,980,000 (Direct Cost: ¥4,600,000、Indirect Cost: ¥1,380,000)
Fiscal Year 2006: ¥9,300,000 (Direct Cost: ¥9,300,000)
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| Research Abstract |
The objectives of this study are to discuss mechanisms of aerodynamic instabilities of stay-cables based on intensities of Karman vortex and to investigate the control methods and additional damping for mitigating the aerodynamic vibration. The obtained information in this study must be useful to consider the countenneasuresibr stay-cable deterioration.
In this study, all the factors for the aerodynamic instabilities of stay-cables, which are axial flow in the wake of inclined cable, water rivulet formed on the upper surface of the cable, critical Reynolds number effects and so on, are discussed as the effects of reduction of Karman vortex. For example, when the axial flow is weak in the wake of inclined cable, the intensity of Karman vortex increases and also, if the axial flow is intensive, the Karman vortex intensity becomes small. Then, it becomes clear that if the axial flow is unsteady, which means the Karman vortex intensity is also unsteady, unsteady galloping may occur. Also, the position of water rivulet controls the intensity of Karman vortex, and then, the aerodynamic instability occurs at the certain rivulet position. Therefore, the both rain-wind induced vibration and dry-state galloping must be generated by the combination of the above mentioned factors, and these mechanisms are explained by the reduction of Karman vortex.
The effects of Scruton number, which is a mass-damping parameter, on the galloping instability are sensitive to the galloping due to the critical Reynolds number, but less sensitive to the galloping generated by the axial flow. Furthermore, more field observation data of the dry-state galloping of the real stay-cables must be needed.
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