小波变换在简支梁桥和连续梁桥中的损伤识别应用研究

发布时间：2018-10-23 20:25

【摘要】：预应力钢筋混凝土简支梁桥和连续梁桥在我国市政公路桥梁中广泛使用,由于交通运输能力的要求不断提高,这些桥梁往往负荷过重,远远超出其设计承载能力,再加上这些桥梁结构已经服役多年,力学性能显著下降。桥梁结构损伤日积月累,成为交通运输发展的一个顽疾,轻则桥毁,重则人亡。因此,有必要对桥梁结构进行损伤识别,制定有效加固措施,避免安全事故发生。桥梁运营多年后会带有损伤,而损伤会使桥梁结构模态参数改变,进而影响力学响应,为检测结构损伤,须知道模态参数和力学响应的关系,从力学响应中寻找影响其突变的模态参数,对比损伤前后模态参数的改变,以此作为结构损伤特征,进行检测和识别。近年来,小波变换迅速发展,在时-频两域分析信号均可局部化,受到各个领域研究者的青睐。本文借助小波对结构响应进行小波变换,进行损伤识别,主要做了以下工作:1.阐述了本文研究的背景和意义、桥梁结构损伤识别常见方法及小波理论在桥梁结构损伤检测中的应用。2.简要介绍了小波理论(包括其发展过程),从傅立叶变换到小波变换过程及小波变换理论核心内容。3.阐述基于小波异常信号检测与识别原理,包括小波变换实质、奇异点位置识别和Lipschitz指数计算,并介绍了选择小波函数的原则和常用的几种小波函数。4.介绍了简支梁损伤力学模型,用有限元软件模拟一个简支梁,预设单损伤和多损伤,并且损伤程度不同,经过分析后,得到各阶位移模态振型,通过中心插值法得到各阶曲率模态,将各阶曲率模态看作信号,在Matlab小波工具箱中选取bior6.8小波,对其进行分析,得到多尺度下各阶小波变换系数,将损伤前后的小波系数作差,以此作为损伤指标,依据第3章小波异常信号检测与识别原理,计算Lipschitz指数,将其大小作为衡量结构损伤严重性的一个重要指标。5.连续梁桥损伤识别,用有限元软件模拟某座变截面连续梁桥,采用第4章的方法进行连续梁桥损伤识别,并确定其损伤位置和损伤程度。6.对本文工作了一个结论和展望。
[Abstract]:Prestressed reinforced concrete simply supported beam bridge and continuous beam bridge are widely used in municipal highway bridges in our country. Due to the increasing demand of traffic and transportation capacity, these bridges are often overloaded and far exceed their design bearing capacity. In addition, these bridge structures have been in service for many years, and their mechanical properties have declined significantly. The damage of bridge structure gradually becomes a stubborn disease of transportation development. Therefore, it is necessary to identify the damage of bridge structure and make effective reinforcement measures to avoid safety accidents. In order to detect the structural damage, it is necessary to know the relationship between the modal parameters and the mechanical response in order to detect the damage, which will cause damage after many years of operation, and the damage will change the modal parameters of the bridge structure, and then affect the mechanical response. The modal parameters which affect its mutation are found from the mechanical response, and the changes of modal parameters before and after damage are compared, which are regarded as structural damage characteristics to detect and identify. In recent years, wavelet transform has developed rapidly, and can be localized in both time and frequency domain, so it is favored by researchers in various fields. In this paper, the wavelet transform of structure response is used to identify the damage. The main work is as follows: 1. The background and significance of this paper, the common methods of damage identification of bridge structure and the application of wavelet theory in the damage detection of bridge structure are expounded. 2. This paper briefly introduces the wavelet theory (including its development process), from Fourier transform to wavelet transform and the core content of wavelet transform theory. The principle of detecting and recognizing abnormal signals based on wavelet is introduced, including the essence of wavelet transform, singular point position recognition and Lipschitz exponent calculation. The principle of selecting wavelet function and several kinds of wavelet functions are introduced. In this paper, the damage mechanics model of simply supported beam is introduced. A simple supported beam is simulated by finite element software. The single damage and multiple damage are preset and the degree of damage is different. After analysis, the modal modes of each order displacement are obtained. The curvature modes of each order are obtained by the central interpolation method. The curvature modes of each order are regarded as signals. The bior6.8 wavelet is selected in the Matlab wavelet toolbox, and the coefficients of each order wavelet transform are obtained by analyzing it. The wavelet coefficients before and after the damage are deviated. According to the principle of wavelet anomaly signal detection and recognition in Chapter 3, the Lipschitz exponent is calculated, and its size is regarded as an important index to evaluate the severity of structural damage. The damage identification of continuous beam bridge is simulated by finite element software. The method of chapter 4 is used to identify the damage of continuous beam bridge, and the damage location and damage degree are determined. A conclusion and prospect of this paper are given.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U446

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