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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/47433


    Title: 應用希爾伯特黃轉換方法改進結構系統識別方法於橋梁振動訊號之研究;Using the Hilbert-Huang Transform to Improve Structural System Identification for Vibration Signal of Bridges
    Authors: 劉德俞;Te-Yu Liu
    Contributors: 土木工程研究所
    Keywords: 亞伯罕時間域法;隨機遞減技術;環境微振;頻率域函數方法;車橋互制;損傷偵測;撓度曲率變化;總體經驗模態分解法;flexibility difference curvature;damage detection;Frequency response function;ambient vibration;Random Decrement technique;Ibrahim Time Domain;Ensemble EMD
    Date: 2011-08-26
    Issue Date: 2012-01-05 11:10:57 (UTC+8)
    Abstract: 環境微振動試驗常被用來量測橋梁的反應,可將其應用在老舊橋梁檢測上。傳統上對於訊號處理的方法常使用傅立葉轉換來取得訊號在頻率域下的信息,近20年來小波分析被提出後大量被發展及應用。但小波基底同為傅立葉基底,本文應用希爾伯特黃轉換來分析橋梁微振動訊號並討論分析後的橋梁結構特性。 識別橋梁結構特性是重要的,得到自然頻率、阻尼比等結構動力參數是有意義的。在本文中,我們提出了一個新穎而有效的工具做為橋梁參數識別的前處理工具,使用數值模型輸出與橋樑現地微振動反應加以分析,可確定自然頻率和阻尼比。使用的方法有:總體經驗模態分解(EEMD)方法、隨機減量技術(RDT)、亞伯罕時間域(ITD)方法和頻率響應函數(FRF)方法。可僅利用一個加速度計即可得到多個模態參數,首先、將含白噪雜訊加速度訊號使用EEMD方法來確定各模態反應。然後,應用RDT方法得到自由振動模態反應。最後,應用ITD與FRF方法識別出自然頻率和阻尼比。根據模擬與現地訊號識別結果,該方法的準確性在確定固有頻率和阻尼比顯著成效。 本文最後對車橋互制行為做研究,應用車橋互制數值模型(微分方程模型與ANSYS有限元模型)來分析。確定ANSYS模型與微分方程模型輸出反應相同後,將損傷元素帶入ANSYS有限元模型模擬不同程度的橋梁損傷;輸出位移影線反應利用EEMD分解後,將固有模態函數(IMF)進行影響線曲率偵測法可偵測出撓度曲率變化定出損傷位置。 Most of the bridges in Taiwan are aging and may require repair or replacement. Ambient vibration tests are utilized to measure the response of old bridges, which are difficult to equip with accelerometers. The Fourier transform method is traditionally used to gain important information about ambient vibration records. However, the development of information technology over the last 20 years has meant that there are more kinds of signal management technologies, including the Hilbert–Huang transform (HHT) methods. In this paper we investigate the characteristics of aging bridges by comparison with their structural properties. We analyze their ambient vibration, and discuss the possible influence of the frequency function. For accurate prediction of the bridge response under external excitationon, information on the dynamic characteristics of the bridge, including the natural frequency and damping ratio is needed. In this paper, we propose a novel and effective tool for the parametric identification of bridges, which uses the output response of the numerical model and ambient vibration of the bridge to identify the natural frequencies and damping ratios. Our approach is based on the empirical mode decomposition (EEMD) method, the random decrement technique (RDT), the Ibrahim Time Domain (ITD) method and frequency response function (FRF) method. Only one acceleration sensor is required. First, the noise of the bridge acceleration is measured using the EEMD method to determine the response of each mode. Second, the free vibration modal response is obtained by RDT. Finally, the natural frequencies and damping ratios for the 3DOF model and the bridge can be identified using the ITD method and the frequency response function approach for each free vibration modal response. According to the simulation results, the accuracy of the proposed method in identifying natural frequencies and damping ratios is remarkable. In the last part of this thesis, the bridge- vehicle interaction (VBI) problem is studied by numerical methods (ODE method and ANSYS numerical software). These data together with the ODE method were used to calibrate the numerical simulation model of ANSYS software. Change the value of element parameters to simulate different damages of bridge. The output displacement of the damage bridge is decomposed by EEMD method. Through the second derivative of the displacement component (IMF) with respect to the axial variable along the beam, the damage position can be identified. By simulative damage detection to the ANSYS model, it proves the feasibility of the method of damage detection based on the flexibility difference curvature.
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