因長跨徑的橋樑具有較大的柔度，所以其受風力而引發的不穩定現象的機率也大增，首重於橋樑的受風反應現象。施工中橋樑相較於施工完成的橋樑有更多不穩定的因素，進而產生了解未完成施工橋樑受風反應的想法。研究橋樑受風反應的方法主要藉由風洞試驗，風洞試驗分為斷面模型試驗和全橋模型試驗，利用模擬風場的特性來測量橋樑縮尺後的反應，再經由轉換來預測真實橋樑受風後的結構反應。 本文的研究方法主要為藉由斷面模型試驗，試驗內容為顫振導數測量、風力係數測量、抖振相似性反應測量，運用試驗結果得到的氣動力參數來建立數值模型，為了求證試驗結果的合理性以及正確性，分別用全橋模型試驗和數值模擬來做為比較以及驗證的依據。 研究結果得知，研究對象的橋樑產生顫振破壞的臨界風速實驗值和數值模擬的臨界風速相當吻合，可得知此橋樑應當是相當安全並且不會發生顫振破壞的行為。抖振相似性反應方面，紊流場8%的斷面模型試驗和全橋模型試驗的比較，在台北市50年回歸期設計風速下，發現到垂直反應約差了30%，而在扭轉向方面則是相當一致的。 Since long-span bridges have greater flexibilities, they are more susceptible to wind excitation. In general, the aerodynamic instability problems for the bridges in constructed stage need more attention than in completed stage. For this reason, the main objective of this thesis is to investigate the aerodynamic behavior of a bridge under construction through section model tests. The wind tunnel tests include the measurements of the static wind force coefficients and the flutter derivatives in smooth flow and buffeting responses in turbulent flow.
The critical flutter wind speed and the buffeting responses measured from the tests are compared with those measured from the full bridge model test which was conducted earlier. Also, a numerical model in conjunction with flutter derivatives and wind force coefficients, measured in the tests, is performed. The numerical results are also compared with the experimental results. The comparison show that the flutter wind speeds respectively obtained from section model test and calculated based on the flutter derivatives are in good agreement. For the buffeting responses at the design wind speed, the results obtained from section model tests, full bridge model tests and numerical analysis agree well to some extent. The discrepancies are in the range of 5-30%.
