長跨徑施工中之斜張橋受斜風作用下之氣動力反應

Aerodynamic Response of Cable-Stayed Bridge in Construction under Skew Wind

蔡爵宇(Chueh-Yu Tsai)

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(2013年)

https://doi.org/10.6846/TKU.2013.00836

摘要

由於斜張橋在施工中擁有較長的懸臂端，因此受風反應較完工後更為敏感。且有文獻指出在某些案例中，特定風向角下橋樑之氣動力反應會比零風向角時來得顯著。因此本文針對在不同風向角作用下對施工中斜張橋之影響進行探討。
本文研究對象為一全長180米之施工中斜張橋。透過斷面模型試驗，分別針對顫振導數、風力係數以及抖振相似性反應進行測量，並運用試驗結果得到的氣動力參數來配合數值模型，透過顫振與抖振理論分析出臨界顫振風速與抖振反應。最後將數值分析結果透過相似律轉換，分別與全橋模型實驗及斷面反應實驗進行比較，進而分析與探討橋樑在斜風作用下所受的影響。
由本文研究結果顯示，最低顫振臨界風速發生於無風向角且+3風攻角下。全橋實驗、數值分析以及斷面實驗其抖振反應皆隨著風向角的增加而下降，其顫振臨界風速無論是否有風攻角參與皆隨著風向角的增加而增加，與傳統上認知相符，顯示斜風對於本斷面影響較小。若採用餘弦法則推估顫振風速以及抖振反應，則於顫振風速會有高估的情況，於扭轉向抖振反應在30˚風向角則有低估的情況，因此若要取得較精確之結果仍需配合實驗結果進行分析。

關鍵字

斜張橋 ； 斜風 ； 顫振 ； 抖振效應 ； 長跨徑 ； 風洞實驗

並列摘要

In general, cable-stayed bridges in construction stage are more sensitive to wind than those in completed stage because of a long cantilever. Furthermore, some studies indicated that the aerodynamic responses of bridges under skew wind might be more significant than those under normal wind. Therefore, the study aims to investigate the aerodynamic behavior of a cable-stayed bridge in construction under skew wind.
The prototype bridge is a cable-stayed bridge with a longest cantilever of 180m. A series of section model tests were conducted both in smooth flow and in turbulent flow. The flutter wind speeds of the section model under different angles of wind attack and different yawed angles were measured in smooth flow. The buffeting responses of the section model under different yawed angles and zero angle of wind attack were measured in a turbulent flow. For use in the numerical analysis, the static wind force coefficients and the flutter derivatives under different yawed angles and zero angle of wind attack were also measured. A comparison among the numerical results, the experimental results obtained from section model tests and the experimental results obtained from full model section model tests was made.
The experimental results obtained from section model tests show that the lowest flutter wind speed is in the case of the zero yawed angle and the angle of wind attack of -3 degrees. In general, the flutter wind speeds increase with the yawed angles and the buffeting responses decrease with the increase of yawed angles. The numerical results including flutter wind speeds and the buffeting responses agree well with the experimental results measured from section model tests. For the buffeting responses, there are some discrepancies between the numerical results and the results measured from full bridge model tests. The reason is that the wind spectra used in the analysis differ from those in the full bridge model test. For comparison, the numerical results obtained from the decomposition method were also calculated. The comparison indicates that the results obtained from the decomposition method may not be applicable as the yawed angle increases.

並列關鍵字

bridge in construction ； flutter ； buffeting ； wind tunnel test ； skew wind

參考文獻

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