傳統式顫振導數識別以自由振動法之風洞試驗為主，為改善其缺點，本文以強制驅動之擾動方式，針對非耦合項顫振導數，提出一套新的風洞試驗識別法。其中之擾動裝置為置於風洞下方之主動驅動台，以彈簧連接至橋面版斷面模型。藉由強制振動反應之量測，本研究將使用頻率反應函數與狀態空間表示式之轉換、頻率反應函數之曲線擬合、以及基因演算法之全域搜尋等相關技術進行非耦合項顫振導數識別。為與理想平板斷面之理論式比較，取寬深比27之橋面版斷面進行試驗量測，根據所提之識別法成功識別出該斷面之非耦合項顫振導數，同時以數值模擬之時間歷時反應與實驗進行比較，以驗證結果之正確性。本研究所提識別法之另一項優點為識別過程中之中間產物，亦即含氣彈效應之狀態空間表示式，將可直接用來進行爾後之抖振分析。 To resolve the shortcomings in the conventional approach, this paper presents a novel approach to identify the uncoupled flutter derivatives of bridge decks by incorporating white-noise forced actuation in wind tunnel tests. An actuation device was installed below the wind tunnel floor to actively drive the motion of the bridge section model through a serial connection of springs. By measuring such forced vibration responses, this approach involves the techniques in converting between frequency response functions and state space representations, curve-fitting on frequency response functions and genetic algorithm for global minimization. For demonstration of the identification scheme, the bridge deck of a chamfered plate with a width/depth ratio of 27, which is to model a stream-line thin plate, was used. Following this approach, the flutter derivatives were thus successfully obtained and compared with the theoretical values from the Theodorsen functions. Time history analysis was also simulated and comparison was made with the experimental data to further verify the validity of results. One supporting advantage in this approach is that the state space equation incorporating the aero-elasticity is obtained routinely during the process, which can facilitate the numerical time domain analysis for computing buffeting responses.
關聯:
中華民國第八屆結構工程研討會論文集=Proceedings of the 8th National Conference on Structural Engineering, 15p.
