高屏溪斜張橋受風之實場量測與理論分析的比較研究

Comparative Study of Aerodynamic Responses of Kao-Ping-Hsi Cable-Stayed Bridge between field measurements and buffeting analysis

鄭詩穎(Shih-Ying Cheng)

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(2008年)

https://doi.org/10.6846/TKU.2008.00185

摘要

高屏溪橋為國內最長之斜張橋，由於其跨徑長，因而受風影響甚大，因此橋梁受風之實場量測與理論分析的研究是一門重要的課題。因此本文以國內高屏溪斜張橋為標的，於其主跨二分之一處裝置三維風速計與速度計，主跨三分之二處裝設速度計，用以量測颱風經過時橋體周遭之風場特性，以及橋體受風之振動反應，來研究橋梁受風之效應。
本文利用2007年所紀錄到之柯羅莎颱風經過時所紀錄到的資料進行研究。柯羅莎颱風垂直橋軸10分鐘平均風速最大可達16m/s，因此本文以柯羅莎颱風為主軸來探討其風場特性分析以及結構分析，結構反應分別使用FDD法與多自由度RD法分析其結構動力相關特性。最後將分析得之風場特性與結構動力特性代入數值方法中，配合抖振理論模擬橋梁反應，並與實場量測及風洞實驗的結果作比較。
為與實場量測數值作比較，因此以實場量測之風速頻譜、紊流強度、以及實場量測之振動反應所識別之自然頻率與阻尼比配合抖振理論做數值分析。分析結果與實場量測反應比較顯示，垂直向相當吻合，而扭轉向約有30%的誤差,而水平向的誤差較大,再分析數值約為實場量測之1/4。顯示修改數值模型的各相關條件，使之更加接近現地的風場狀況對於橋體受風的反應可以更加接近真實性。斷面風洞模型試驗雖和實場的風場條件有些許的不同，但仍和數值再分析相似,與實場量測反應曲線有一樣的趨勢也很接近實場數值。而全橋風洞試驗由於是為了求得顫振臨界風速所設定的試驗，因而使用的是無因次化風速，實場量測風速與之相比過小，因而在低風速下受雜訊影響，與實場相比顯得較不準確。

關鍵字

斜張橋 ； 實場量測 ； 頻率域分解法 ； 隨機遞減法 ； 抖振效應

並列摘要

Since Kao-Ping-Hsi Cable-Stayed Bridge has the longest span length in Taiwan, it is more sensitive to wind The study to monitor this bridge and compare the field measurements with buffeting theoretical results becomes an important task. Therefore, this bridge was chosen as the target for monitoring. Two 3D anemometers were installed at the middle point of the longer span to measure wind characteristics. Two sets of velocity censors, respectively installed at the middle point and on third point of the longer span, were used to measure the dynamic responses of the bridge.
The aerodynamic behavior of the Kao-Ping-Hsi Cable-Stayed Bridge was analyzed based on the measured data obtained from the field measurements. The data were collected as several typhoons were attacking Taiwan during 2006-2007. Among these typhoons, Typhoon Krosa was the strongest and its maximum 10 min. mean wind speed was as high as 16 m/s. The effects of this typhoon on the bridge are the main concern in this study. The modal frequencies and damping ratios of the bridge were identified by the methods of FDD and MRD, respectively. These identified parameters along with the fitted wind spectrum were substituted into a numerical model to evaluate the buffeting responses of the targeted bridge. The results obtained from the re-analysis, the field measurements, the section model test and the full model test were compared.
The comparative study indicates that the differences between the results obtained from the re-analysis and the results measured from the field measurements are 10% in the vertical direction and 30% in the torsional direction. The drag response obtained from re-analysis is only 25% of that measured from the field measurements. The possible reason for this large discrepancy results from high noise in the field measurements. Since turbulent intensities and damping ratios used in the section model tests and the full model tests were different from those identified from the field measurements. The results obtained from the section model tests are still consistent with those from on-site measurements. However, the results obtained from the full model test are much larger than the other results. This is because the reduced wind velocity in the tests is low and the high noise affected the results..

並列關鍵字

cable-stayed bridge ； field measurements ； frequency decomposition ； random decrement ； buffeting analysis

參考文獻

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