隨著橋梁跨徑不斷的增加，工程師必須審慎評估橋梁在風力作用下之安全性及服務性。對於風力作用下所引起的橋梁主梁抖振反應，通常採用全橋風洞試驗或斷面模型風洞試驗配合數值分析進行評估。當以數值分析進行評估時，需要主梁的振態參數包括振態頻率、阻尼比與振形，及氣動力係數與顫振導數。振態參數一般是經由有限元素法模擬獲得，而氣動力係數與顫振導數則是藉由斷面模型風洞試驗來獲得。本文則是以所建立之複合識別方式識別實測反應歷時，以獲得主梁之振態參數，以隨機子空間法識別數值模擬之結果，求取主梁之顫振導數。
由於橋梁所量測得之微振速度歷時具有振態耦合之特性，本文提出一結合經驗模態分解法、隨機遞減法與希爾伯特轉換的分析方式，於時間域上進行橋梁振態參數之識別，可獲得較其他識別方式準確的結果。
在數值模擬部分，首先模擬流體流經方形、矩形與梯形斷面後產生之氣動行為，同時計算相關的氣動力係數；其次模擬矩形斷面之氣彈行為，其中氣彈行為之模擬採用任意拉格朗日-歐拉法，以斷面反應歷時求取顫振導數。由模擬的結果可觀察到與過去風洞試驗中相同之渦流及再接觸現象，所得之氣動力係數接近過去風洞試驗結果之平均值，而所得之顫振導數略為高估；在可接受之計算時間內，數值模擬結果可達到設定之準確度。根據對不同斷面流場數值模擬分析所累積之經驗，對一長跨距斜張橋斷面進行氣動與氣彈現象模擬；結果顯示氣動力係數與顫振導數略高於風洞試驗的結果。
本文利用一近似解析解，配合所得到之主梁振態參數及氣動力係數與顫振導數，求取主梁抖振位移均方根值，以作為橋梁安全性與服務性評估的依據。同時探討振態參數、氣動力係數與顫振導數對抖振反應的影響，結果顯示振態頻率與氣動力係數對抖振反應的影響較大。

As the main spans of bridges become longer, engineers have to assess the wind induced vibration of bridge decks for safety and serviceability. Generally, either the full bridge model wind tunnel test or section model wind tunnel test with analytical procedure is used to evaluate buffeting responses of bridges. Modal parameters, including modal frequencies and damping ratios, are usually obtained by finite element models; aerodynamic parameters, including aerodynamic coefficients and flutter derivatives, are obtained by section model wind tunnel test. In this research, modal and aerodynamic parameters are obtained by identifying filed measurement results and numerical simulations respectively.
This study proposes a method, combing empirical modal decomposition, random decrement technique with Hilbert transform, for identification of modal parameters in time domain from modally coupled response time histories.
Aerodynamic and aeroelastic phenomena of blunt sections are simulated by numerical simulations; the associated aerodynamic coefficients are evaluated; flutter derivatives are identified by stochastic subspace identification method. Vortex shedding and reattachment phenomena are observed in the simulated results. The obtained aerodynamic parameters are compared with those of the wind tunnel test in the literature, and indicated that aerodynamic coefficients approach to the average of wind tunnel test results, flutter derivatives are higher estimated slightly. Finally, numerical simulations are conducted for a bridge section; the interaction effect of fluid-bridge section is accounted by an arbitrary Lagrangian-Eulerian strategy.
Finally, the root mean square values of bridge buffeting responses are evaluated by an approximate analytic formula using the obtained parameters. These results can be used to assess safety and serviceability of the bridge. The effects of modal parameters, aerodynamic coefficient and flutter derivatives on buffeting responses are also investigated.

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