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    題名: 間接式強制振動於二維結構順風向氣彈效應之識別
    其他題名: Identification of along-wind aeroelasticity for 2-D structures using indirect forced vibration technique
    作者: 周泰安;Zhou, Tai-an
    貢獻者: 淡江大學土木工程學系碩士班
    吳重成;Wu, Jong-cheng
    關鍵詞: 圓柱斷面;顫振;氣動力阻尼;間接式強制振動;氣彈互制;基因演算法;Cylindrical cross-section;Flutter;Aerodynamic Damping;Force Vibration;aeroelasticity;Genetic Algorithm
    日期: 2009
    上傳時間: 2010-01-11 05:19:39 (UTC+8)
    摘要: 顫振(Flutter)現象為斷面結構受風載所產生一種氣彈互制行為氣彈互制行為。傳統上,結構顫振導數(Flutter Derivative)之識別採用自由振動方式,但其實驗結果常受周遭試驗環境影響,而且將自由振動頻率當成外力擾動頻率亦會造成結果上之誤差。為克服上述缺點,本研究使用間接式強制振動的實驗方式。首先由伺服馬達給予振動平台強制振動,透過彈簧擾動斷面結構模型,然後量測其在平滑流場下之氣彈互制反應。
    實驗架構分為不同的斷面模型(圓柱和橋面版),其圓柱大小分為直徑10公分和直徑5公分之圓柱,橋面版依其寬深比分為寬深比27和寬深比12.5兩種。
    實驗流程分為結構參數識別(質量、勁度、阻尼)和導數識別(非耦合顫振導數識別和耦合顫振導數識別,探討的方向是水平向與扭轉向),其中導數識別藉由氣彈互制反應之轉換函數實驗值與理論值比較,在頻率域以曲線擬合最佳化識別出理論式中最佳參數,最後得到斷面模型之顫振導數。其中於理論部分引用狀態空間方程式之觀念進行推導,而最佳化過程則引用基因演算法(Genetic Algorithm)求解,以確保得到全域最佳解。
    本論文以四種不同斷面模型為例,使用淡江大學土木系風洞實驗室進行上述識別實驗,結果可以得到圓柱斷面的非耦合振振導數與橋樑斷面的非耦合顫振導數和耦合顫振導數,其圓柱斷面之顫振導數和Scanlan的理論式進行比較,而趨勢接近,顯示間接式強制振動識別法能識別顫振導數,其中耦合項BD27斷面,在分析上尚須更精確,才能識別出更接近真實的顫振導數。
    Flutter is one of the aero-elastic behaviors in the wind-induced motion of cross-section structure. The conventional approach for identifying flutter derivatives of cross-section structure is to use the free vibration method which has disadvantages, such as lack of consistency due to high sensitivity of free vibration response to the test condition/environment, and the error inherited by treating free vibration frequency as excitation frequency. In order to overcome these shortcomings, In this study the use of indirect methods forced vibration test. First, given by the servo motor vibration platform for forced vibration, structural model cross-section through the spring disturbance, and then measured in a smooth flow in each system under the aero-elastic response.
    Experimental identification process is divided into structural parameters (mass, stiffness, damping) and the derivative identification (non-coupled flutter derivatives identified and coupled flutter derivatives to identify, explore the direction of the horizontal and reverse direction
    Which the derivative identified by the system aero-elastic response of the transfer function in each experimental value and theoretical value, in the frequency domain in order to curve fitting optimization to identify the best parameters of type theory, end up with cross-section model of the flutter derivatives . One reference in the theoretical part of the concept of the state-space equation to derive, and the best process by invoking the genetic algorithm to solve in order to secure the global optimal solution.
    In this paper, four different cross-section model as an example, the use of Tamkang University''s civil engineering laboratory wind-tunnel experiments the above-mentioned identification results can be cylindrical cross-section of non-derivative and coupled vibration vibration of non-coupled bridge deck flutter derivatives and coupled flutter derivatives, its cylindrical cross-section of the flutter derivatives and Scanlan to compare the theory of style, while the trend of close to show indirect forced vibration identification method to identify flutter derivatives. One coupling width / depth ratio of 27 sections, in the analysis yet to be more precise, in order to more accurately identify the flutter derivatives.
    顯示於類別:[土木工程學系暨研究所] 學位論文

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