本文選題：健康監(jiān)測　切入點：小波變換　出處：《蘭州交通大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：小波分析被譽為“信號顯微鏡”,基于小波變換的多尺度分析和奇異點檢測以及小波包節(jié)點能量為處理實時監(jiān)測信號提供了方便又快捷的工具。本文從國內(nèi)外研究現(xiàn)狀入手,分析了橋梁健康監(jiān)測中存在的問題,并對研究背景的長期健康監(jiān)測系統(tǒng)做了簡單介紹;之后對小波分析理論進(jìn)行介紹,并在工程背景和數(shù)值模擬相結(jié)合的基礎(chǔ)上,系統(tǒng)地研究了小波法在橋梁長期健康監(jiān)測中的應(yīng)用,重點論述了基于小波變換的實測信號的多尺度分析和閾值去噪分析,以及小波包能量理論和小波奇異性檢測理論在獨塔鋼箱斜拉橋損傷識別和定位中的應(yīng)用;最后對理論研究成果應(yīng)用到工程實踐中存在的問題給出改進(jìn)意見。主要的研究內(nèi)容如下:1)將小波多尺度分析和閾值去噪相結(jié)合,利用真實信號和噪聲信號在小波變換不同尺度下的差異性表現(xiàn),實現(xiàn)監(jiān)測信號的閾值去噪。同時分別進(jìn)行了實測信號與去噪信號的幅值對比以及采用快速傅立葉變換后實測信號與去噪信號的幅值對比,并且對實測信號采用不同閾值規(guī)則時的表現(xiàn)效果進(jìn)行對比,討論了閾值規(guī)則選取的基本條件。利用小波理論進(jìn)行多尺度分析時,只需要對采集的加速度信號導(dǎo)入MATLAB軟件中,并編制相應(yīng)程序即能表達(dá)損傷特征,此時該位置在某個尺度時刻會出現(xiàn)尖點。2)將小波分解與小波包能量理論相結(jié)合,用來實現(xiàn)橋梁結(jié)構(gòu)損傷識別。通過Midas Civil軟件建立通海路斜拉橋有限元模型并進(jìn)行時程分析,分別提取單一損傷和多損傷時主梁節(jié)點的加速度信號,對該信號進(jìn)行小波包能量分析,得到未損和索力變化各種工況下小波包節(jié)點能量變化值。通過對比小波包頻段能量百分比可得出小波包能量變化對結(jié)構(gòu)微小索力變化有很高的靈敏度,由于只需要求損傷工況的時程加速度信號,故而十分有利于橋梁結(jié)構(gòu)的實時在線監(jiān)測,并且能夠?qū)Σ糠质軗p橋梁的及時修復(fù)提供重要的參考建議。3)將小波變換與曲率模態(tài)理論相結(jié)合,用于實現(xiàn)橋梁結(jié)構(gòu)損傷定位。通過Midas Civil軟件建立通海路斜拉橋有限元模型并進(jìn)行振型分析,提取主梁第一階和第二階位移模態(tài),然后利用中心差分法得到其曲率模態(tài),再對不同曲率模態(tài)曲線進(jìn)行小波變換。通過主梁剛度折減各工況的第一階和第二階曲率模態(tài)圖形可以很容易看出損傷發(fā)生位置,不但對主梁單元的細(xì)微損傷位置能夠得到很好的識別定位效果,而且對斜拉索的損傷也能夠通過主梁單元的曲率模態(tài)信號展現(xiàn)出來,這對于將小波奇異性理論應(yīng)用于各種不同類型橋梁的長期健康監(jiān)測中有極大地推動作用。
[Abstract]:Wavelet analysis is praised as "signal microscope". Multi-scale analysis based on wavelet transform, singular point detection and wavelet packet node energy provide a convenient and fast tool for processing real-time monitoring signal. The existing problems in bridge health monitoring are analyzed, and the long term health monitoring system based on the research background is briefly introduced. Then, the wavelet analysis theory is introduced, and based on the combination of engineering background and numerical simulation, The application of wavelet method in bridge long-term health monitoring is systematically studied, and the multi-scale analysis and threshold de-noising analysis of measured signals based on wavelet transform are emphasized. And the application of wavelet packet energy theory and wavelet singularity detection theory in the damage identification and location of single-tower cable-stayed bridge with steel box; Finally, the problems existing in the application of theoretical research results to engineering practice are improved. The main research contents are as follows: 1) combining wavelet multiscale analysis with threshold denoising. Using the difference of real signal and noise signal in different scales of wavelet transform, At the same time, the amplitude comparison between the measured signal and the de-noised signal and the amplitude comparison between the measured signal and the de-noised signal after fast Fourier transform are carried out. The performance of measured signals using different threshold rules is compared, and the basic conditions of threshold rule selection are discussed. When wavelet theory is used for multi-scale analysis, only the collected acceleration signals need to be imported into MATLAB software. The damage characteristics can be expressed by making a corresponding program. At this time, the cusp will appear at a certain scale. 2) the wavelet decomposition will be combined with the wavelet packet energy theory. The finite element model of the cable-stayed bridge along Tonghai Road is established by Midas Civil software and the time history analysis is carried out to extract the acceleration signal of the main beam node in the case of single damage and multiple damage respectively. The wavelet packet energy of the signal is analyzed. By comparing the energy percentage of wavelet packet frequency band, it can be concluded that the variation of wavelet packet energy has a high sensitivity to the change of minimal cable force of the structure. Because only the time-history acceleration signal of damage condition is needed, it is very helpful for the real-time on-line monitoring of bridge structure. And it can provide important reference suggestion for repairing some damaged bridges in time. 3) combine wavelet transform with curvature mode theory. The finite element model of the cable-stayed bridge along Tonghai Road is established by Midas Civil software, and the vibration mode of the cable-stayed bridge is analyzed. The first and second order displacement modes of the main beam are extracted, and the curvature mode of the bridge is obtained by using the central difference method. Then wavelet transform is carried out on different curvature mode curves. The damage location can be easily seen by the first and second order curvature mode patterns of the main beam stiffness reduction. Not only can the location of the minor damage of the main beam element be well identified, but also the damage to the stay cable can be displayed by the curvature mode signal of the main beam element. This will greatly promote the application of wavelet singularity theory to the long term health monitoring of different types of bridges.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U446

【參考文獻(xiàn)】

相關(guān)博士學(xué)位論文 前1條

1 郭健;基于小波分析的結(jié)構(gòu)損傷識別方法研究[D];浙江大學(xué);2004年

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本文編號：1588286