曲線斜張橋之氣動力穩定研究

Study of Aerodynamic Stability of Curved Cable-Stayed Bridges

黃明慧(Ming-Hui Huang)

指導教授 ： 林堉溢

淡江大學/工學院/土木工程學系碩士班/碩士(2005年)

https://doi.org/10.6846/TKU.2005.00530

摘要

隨著橋梁工程的發展，現今纜索支撐橋梁的設計除了基本的實用性外，也考慮到外型上的美觀。因此，興建了一些強調外型上美觀的曲線斜張橋，例如，最近興建於台北的饒河街人行橋，人行橋的主梁呈S曲線造型，主梁與拱圈之間由傾斜的鋼索連接以提高勁度。本論文針對此類型橋梁研究其氣動力行為。
當曲線橋梁受風作用時，其風向角是沿著橋軸連續變化的。由於傳統上的顫振與抖振理論是由直線橋梁發展而來，因此無法直接應用在此類橋梁上。在過去經常使用餘弦法則(cosine rule)以及斜風理論(skew wind theory)等近似理論來處理有風向角下的橋梁顫振臨界風速以及抖振反應。但是，這些近似理論僅能適用於風向角較小的情況下。
本論文針對曲線橋梁的顫振臨界風速及抖振反應發展出一套更為精確的分析方法，並對此結果與近似方法分析所得的結果加以比較討論。另外為了證明此方法實際可行，額外再建立一個等值的直線數值橋梁來與曲線橋梁作比較，研究結果指出，曲線橋梁的顫振臨界風速高於等值直線橋梁，而抖振反應則因曲線橋梁結構振態耦合的關係而高於等值直線橋梁。

關鍵字

纜索支撐橋梁 ； 曲線斜張橋 ； 風向角 ； 餘弦法則 ； 斜風理論

並列摘要

Attributed to the developments of bridge engineering, modern cable-supported bridge design requires not only the basic functionality but also the aesthetical appearance. Therefore, some curved cable-stayed bridges emphasizing attractive appearance were built. The recent example is a pedestrian bridge which is under construction in Taipei. The geometry of this bridge is S-shape in the horizontal plane and linked with a vertical arch by the inclined cables to increase the bridge’s stiffness. The aerodynamic behavior of this type of bridges was investigated in this study.
As the curved bridge is subjected to wind excitation, the yaw angles along the bridge axis are continuously changing because of the curved nature. Traditional flutter and buffeting theories, developed for straight beams, cannot be directly applied for this type of bridges. In the past, for dealing with the buffeting responses and flutter critical wind speed in the case of the bridge subjected to yawed winds, the “cosine rule” and “skew wind theory” were often used. However, these approximate theories are only valid for the small yawed angles.
This study developed a more precise method for evaluating buffeting response and flutter critical wind speed for curved bridges. The results obtained from this approach and the approximate methods were also discussed. For practical use, an equivalent straight bridge structural model was also employed to compare with the curved bridge. The results show the flutter critical wind speed of the curved bridge is higher than that of the equivalent straight bridge. However, the buffeting responses of the curved bridge are larger for the contribution of the structural coupling.

並列關鍵字

cable-supported bridge ； curved cable-stayed bridge ； yaw angle ； cosine rule ； skew wind theory

參考文獻

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