本文主要在探討如何僅利用環境振動下之結構響應資料來識別系統的模態參數。吾人利用定常響應訊號所組成的相關矩陣，使資料相關特徵系統實現法(ERA/DC)之理論能有效應用於定常白訊激勵之結構模態參數識別。另外，當環境激勵為符合乘積模型之非定常白訊時，藉由引進時調函數的分離擷取技術後，從而識別出系統之模態參數。此外，在適當的情況下，一般的非定常響應可近似表示為自然指數函數的組成，藉此應用引進擴充頻道技巧的Ibrahim 時域法進行模態參數識別，而不需將環境振動響應經由額外的數據處理為自由響應，因此可將ITD法推廣至處理更廣義的非定常環境振動系統識別問題。由數值模擬結果顯示，本文所提出的分析方法在實際的環境激勵下可得良好的模態參數識別結果，對於雜訊的影響亦有良好之強健性。

Innovative methods are proposed in this thesis for determination of the modal parameters of a structure from its ambient response data only. The eigensystem realization algorithm with data correlation (ERA/DC) is extended for modal-parameter identification of a structural system excited by stationary white. If the ambient excitation can be modeled as nonstationary white noise in the form of a product model, we can perform modal identification through the correlation method in conjunction with a technique of curve-fitting. Furthermore, by introducing a channel-expansion technique, Ibrahim time-domain method is extended for modal-parameter identification from general nonstationary ambient vibration data, which can be approximated directly as a linear composition of exponential functions under appropriate conditions. Numerical simulations, including some examples of using practical excitation data, are performed to confirm the validity and robustness of the proposed methods for identification of modal parameters from general ambient vibration data under noisy condition.

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