橋梁結構屬複合式結構體,產生非線性及非穩態的振動訊號,在傳統的土木分析中較常使用快速傅立葉轉換(FFT)之頻率域分析法,然振動訊號之變化極為複雜,FFT轉換無法準確地掌握橋梁的穩定性與安全性,而希爾伯特-黃轉換(HHT)能夠有效地將振動訊號進行解析,並區分出橋梁之梁、柱所屬的頻率,並由其HHT頻譜圖的成果檢視橋梁結構系統的完整性。 本研究將利用台3線東勢大橋現地24小時不間斷擷取量測的橋梁即時振動資料進行HHT解析,應用HHT分析方法探究橋梁之梁、柱的頻率變化。同時也以FFT分析對上述資料進行解析,比較傅立葉振幅譜與希爾伯特黃邊際頻譜二者對橋梁之梁、柱於振動訊號解析後的差異。再利用常時狀態下之SAP2000分析以東勢大橋五跨連續模型比對HHT振動解析成果,並驗證HHT振動解析法的準確性與可靠性。 根據研究成果顯示,FFT分析所得的頻譜會把低頻處能量密度稀釋而在高頻處放大能量密度,導致對訊號的誤判,而HHT分析除了能夠有效地區分出梁、柱所屬頻率,亦可識別出其弱化部位,而振動訊號的能量大小對其分析成果的特徵值有相當大的影響。 由SAP2000分析與HHT墩柱所得頻率顯示,HHT分析方法與SAP2000五跨連續模型分析結果應屬吻合,且橋墩之即時頻率震盪區間累積能量集中、穩定,研判東勢大橋橋梁結構、勁度皆良好,屬於穩定狀態。
Bridge structure, alike composite structure, resulting in nonlinear and non-stationary vibration signals. Traditional civil analyzes use Fast Fourier Transform (FFT) analysis of the frequency domain more frequently. The change of the vibration signal is extremely complex. FFT transform can not accurately assure the stability and security of the bridge while the Hilbert - Huang Transform (HHT) can effectively carry out the vibration signal analysis, distinguish beams, piers according to the frequency and view of the bridge structure system integrity by HHT spectrum result. This study is based on Dongshih Bridge situ 24 hours instant measurements bridge vibration data for HHT analysis, the application of HHT analytical methods to explore beams, piers frequency changes. Also, for the FFT analysis of the above data analysis, comparing the Fourier amplitude spectrum and Hilbert-Huang marginal spectrum both of the bridge beams, piers vibration signal resolved differences. Re-use SAP2000 analysis under the always state of the bridge five-span continuous results compared with HHT vibration analysis results, and verify the accuracy and reliability of the HHT vibration analytical method. According to the study results, FFT analysis the result of spectrum energy density at low frequency, which will be diluted and the energy density amplification at high frequencies, resulting in false signals, while the HHT analysis in addition to effectively distinguish beams, piers belongs frequency. Also, identify weakening of its position. The size of vibration signal energy of its value analyzed results has considerable influence. SAP2000 analysis and HHT piers analysis the resulting frequency display, HHT analysis methods and SAP2000 five-span continuous model analysis should be consistent, and the pier on the immediate frequency shock interval cumulative energy were concentration, stability, judged Dongshih Bridge structure, stiffness are good, belong to a stable state.