【摘要】：混凝土橋占橋梁總數(shù)的90%,絕大多數(shù)既有混凝土橋梁存在一定的損傷。既有混凝土橋的損傷是影響橋梁使用性能的重要因素。聲發(fā)射技術(shù)是檢測混凝土損傷的有效方法,聲發(fā)射檢測信號與混凝土內(nèi)部損傷對應(yīng)關(guān)系研究還不深入,本論文針對聲發(fā)射信號與混凝土損傷進行研究,具體工作如下:(1)對混凝土試件進行三分點加載彎曲試驗,監(jiān)測加載全過程混凝土應(yīng)變和聲發(fā)射特征參數(shù),分析試件不同受力階段聲發(fā)射特征參數(shù)與損傷關(guān)系�；炷猎嚰虞d初期,水泥砂漿和集料的界面存在的微裂縫等原始缺陷,就會產(chǎn)生低幅值、低能量的撞擊信號,隨著荷載的繼續(xù)加大,試件內(nèi)部不斷產(chǎn)生新的裂縫,聲發(fā)射信號活動增強,高幅值信號出現(xiàn)次數(shù)增多,同時伴隨著能量的多次突發(fā)釋放。(2)基于小波理論,分析研究了適用于混凝土試件的小波去噪?yún)?shù)選擇,當(dāng)選用db4小波、進行2層小波分解,在Heursure閾值準則下選用軟閾值函數(shù)進行數(shù)據(jù)去噪處理是效果最理想的。通過比對去噪前后信號波形圖,可以看出運用小波降噪,處理信號保留了原始信號的大部分主要特征,同時去除了一些噪聲信號,使采集到的信號更能表征聲發(fā)射源信號的特征。(3)在對采集到的信號進行小波降噪的基礎(chǔ)上,運用互相關(guān)分析法,計算出兩兩傳感器接收到聲發(fā)射信號的時間延遲,進而結(jié)合所測時間波速就可以定位出聲發(fā)射源位置,提高了聲發(fā)射損傷定位的精確性。
[Abstract]:Concrete bridges account for 90% of the total number of bridges, and most of the existing concrete bridges have certain damage. The damage of existing concrete bridge is an important factor affecting the performance of bridge. Acoustic emission technology is an effective method to detect concrete damage. The corresponding relationship between acoustic emission detection signal and concrete internal damage is not deeply studied. In this paper, the acoustic emission signal and concrete damage are studied. The specific work is as follows: (1) the three-point loading bending test of concrete specimens is carried out, the strain and acoustic emission characteristic parameters of concrete are monitored, and the relationship between acoustic emission characteristic parameters and damage in different stress stages is analyzed. At the beginning of loading, the original defects such as micro cracks in the interface between cement mortar and aggregate will produce low amplitude and low energy impact signals. with the continuous increase of load, new cracks will continue to occur in the specimen. The activity of acoustic emission signal is enhanced, the frequency of high amplitude signal is increased, and the sudden release of energy is accompanied by multiple bursts of energy. (2) based on wavelet theory, the selection of wavelet denoising parameters suitable for concrete specimens is analyzed and studied, and db4 wavelet is selected. The two-layer wavelet decomposition is carried out, and the soft threshold function is selected for data denoising under the Heursure threshold criterion. By comparing the signal waveform before and after denoising, we can see that by using wavelet denoising, the processed signal preserves most of the main characteristics of the original signal, and at the same time removes some noise signals. The collected signal can better represent the characteristics of the acoustic emission source signal. (3) on the basis of wavelet denoising of the collected signal, the time delay of receiving the acoustic emission signal by the pairwise sensor is calculated by using the cross-correlation analysis method. Combined with the measured time wave velocity, the position of acoustic emission source can be located, and the accuracy of acoustic emission damage location can be improved.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U441.4

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本文編號：2486848