臺灣博碩士論文加值系統

　　現代的橋樑設計由於橋梁施工方法的進步及高強度材料的研發使得橋樑的跨徑逐漸增長，斷面亦趨於細長化，也因此大跨徑橋梁具更大的柔度、其受風力引發不穩定之機率也大為增加，因而在大跨度橋梁施加制振的機制來抑制這一現象是有必要的。
　　長跨徑橋梁受風之亂流效應所產生的振動位移反應，以垂直向及扭轉向最為顯著。然而傳統TMD只能有效控制某一方向之動力反應，因此本文乃提出一TMD模式，具垂直及扭轉頻率，來控制兩方向的動力反應。因此本文提出之2D. O. F. TMD 模型，其最大優點是可同時抑制垂直向及扭轉向之振動。由於本分析模式考慮氣動力耦合的效應，所以對氣動力耦合顯著的橋梁之制振效果，較能準確的預測，也因此無論對單自由度顫振或耦合顫振，均可提高其臨界風速增加結構之穩定性。
　　本文所建議之TMD模型，利用質量分佈之變化來改變垂直質量和扭轉慣性質量之質量比值，進而改變TMD垂直向及扭轉向頻率，來達到同時抑制兩個方向運動之目的。當將兩個方向之頻率都調整在結構垂直振態頻率或扭轉頻率時，其作用和雙TMD模型相同，且和傳統STMD一樣。
　　同時本文利用參數分析，對亂流效應振動反應的折減量及顫振風速的提高幅度均作一完整的探討，最後提出此TMD模式對氣動力耦合橋梁的設計建議。

　　The developments of bridge construction techniques and the improvements of high strengh materials have made the modern bridges designed and built towards longer spans with more slender sections. Because these types of bridges are more flexible than the other types of bridges, they are more susceptible to wind excitation. To strengthen the weakness of these types of bridges, some devices must be used to control the wind effects. Among these devices, tuned mass dampers have been installed in some existed bridges, and their performance is proven to be effective against wind-induced vibrations.
　　In the wind-induced buffeting problems of the long-span bridges, the vertical and torsional displacements are always the major concerns for the bridge engineers. However, the traditional tuned mass dampers are designed to reduce dynamic response in one direction only. To achieve the goal of suppressing both the vertical and torsional response, the 2 D. O. F. model, with two frequencies that are tuned at the effective frequencies of the first vertical and torsional modes of the bridge, is proposed. The aerodynamic coupling is taken into account for the formulation of the bridge-TMD system. Therefore, this model is specially applicable for those bridges in which mode coupling is significant. A parametric study is performed to investigate the buffeting response reduction and the increase of the flutter velocity. Based on this parametric analysis, the procedures of the TMD design for the wind-exeited bridges are then proposed. The influence of the aerodynamic coupling on the TMD design is also addressed. The results show that the propposed TMD is at least as effective as the usual TMD on suppressing buffeting respponse, and it appreciably raises the stability of the bridge either with the type of stalled or coupled flutter.