當橋體受氣動力效應時，會改變結構之有效阻尼和勁度，同時也會引起振態模 式耦合效應。本文目的是以斷面模型實驗所得之氣動力參數為根據，發展一數值分析模式 ，以探討振態模式耦合對橋梁動力反應的影響，分析方法是將氣動力阻尼和勁度融入結構 特性內，以複數特徵值法來解臨界風速，同時推導轉換函數以求解橋梁結構在各風速下之 位移反應。例題部分採用兩座橋梁進行風力動態反應分析，分別考慮振態模式耦合與無耦 合，其結果並與全模型風洞實驗資料作一比較，由分析結果顯示，振態模式耦合效應會隨 風速提高而遞增，若設計風速接近於臨界風速時此種效應不容忽視。
The aerodynamic forces can alter the effective damping and stiffness of the bridge and result in coupling of the natural modes of the structure. The purpose of this paper is to present an analytical model, based upon the flutter derivatives measured from the section model, to investigate the effects of mode coupling on the dynamic response of the structure. The set of coupled equations of motion is solved by the complex eigenvalue method for flutter determination. Buffeting response is calculated by the transfer function. Two examples are provided to examine the validity and applicability of the method and the results are compared with the full model test. The results show that the mode coupling greatly increases with the wind speed. Such an effect becomes significant when the wind velocity approaches to the critical velocity.
