本論文的研究內容為比較和檢驗由簡化式所得之顫振臨界風速與抖振反應和精確理論式間之差異。選用三種不同斷面與跨徑的橋樑結構為例，檢驗簡化式與理論式所得結果之差異。計算顫振臨界風速時，選用中國規範、日本規範和奧地利規範所用之簡化式，再加上Selberg的理論作檢驗。利用參數影響分析改變垂直與扭轉的頻率，比較在不同頻率比下對於橋樑顫振臨界風速的影響。其結果顯示，各種簡化式的顫振臨界風速都比理論式來的保守，當中以日本的公式最為保守，Selberg的公式最接近用理論分析計算出的結果。 相較於顫振臨界風速的計算，抖振反應的計算就相當複雜與冗長，也因此只有極少數的簡化式被提出來過。中國規範提出的方法，仍然是一個相當複雜的設計方式。所以此方法計算的結果與理論式相近。由於此方法的簡化不多，再加上所使用之橋樑其結構耦合效應並不顯著，因此所得結果與抖振理論相近。因此簡化式只能適用於橋樑的初始設計，對於受風敏感的橋樑，還是須經由更精確的分析與風洞實驗來檢驗。 Some simplified formulae for the prediction of flutter critical wind speeds and buffeting responses were examined and compared to the precise theories in this study. Three bridge models, with different bridge decks and spans, were chosen as the examples. For the simplified flutter analysis, three formulae respectively used in the Chinese code, Japanese design manual and Austrian code and one proposed by Selberg were examined. The effects of vertical and torsional frequencies on the flutter critical wind speeds were also studied through a parametric analysis. The results show that all the flutter critical wind speeds calculated from the four simplified formulae are lower than those from flutter theory. Among them, the formula used in the Japanese manual is the most conservative and the Selberg formula is the closest to flutter theory.
Since the buffeting calculation is more complex and tedious than the calculation of flutter critical wind speed, there are few simplified formulae proposed. In the Chinese code, the proposed method is still complex for the engineers. The results obtained from the Chinese code are close to buffeting theory. It can be expected because there are few simplifications in this method and the structural coupling are not significant in the example bridges. It should be mentioned that the simplified analysis is better used for the preliminary design. If the bridge is sensitive to wind, more precise analysis should be performed.
