基于影像及小波变换的桥梁损伤识别

桥梁损伤定位和定量分析是桥梁健康监测的难点，为提高桥梁结构损伤位置识别的精度及准确性，利用位移模态对结构局部损伤的敏感特性，提出基于影像和小波变换的桥梁损伤识别新方法，通过工业相机获取悬臂梁振动形态，利用模版匹配方法提取结构动态位移响应及模态参数，对位移模态进行小波变换，建立小波系数平方差的损伤指标识别结构损伤位置。通过室内悬臂竖梁振动实验，对全域测点的振动衰减信号快速傅里叶变换成功获取了结构的模态振型，与数值模拟结果比较表明试验获得一阶固有频率最大误差为2.202%,二阶固有频率最大误差为3.182%,表明所提方法用于结构位移测量的可行性以及测量精度的可靠性；在此基础上利用小波系数平方差的明显突峰特性可准确识别结构单损伤、多损伤的存在，并能准确定位损伤位置。研究表明，所提方法可以准确识别不同位置、不同程度的单损伤和多损伤，具有远距离、非接触、高精度、高效快捷、可多点监测提升振型空间分辨率等优点，为桥梁结构全域损伤识别提供了一种新方法。

Research on Bridge damage Identification based on Image and Wavelet transform

Bridge damage location and quantitative analysis are difficulties in bridge health monitoring. in order to improve the accuracy of bridge structural damage location identification, this paper makes use of the sensitivity of displacement modes to local damage of bridge structure. a new method of bridge damage identification based on image and wavelet transform is proposed, the vibration shape of cantilever beam is obtained by industrial camera, and the dynamic displacement response and modal parameters of structure are extracted by template matching method. The displacement modes are transformed by wavelet transform, and the damage index of square variance of wavelet coefficients is established to identify the damage location of the structure. Through the indoor vibration experiment of the cantilever beam, the modal shape of the structure is successfully obtained by Fast Fourier Transform of the vibration attenuation signal of the global measuring point. compared with the numerical simulation results, the maximum error of the first-order frequency is 2.202%. The maximum error of second-order frequency is 3.182%, which shows the feasibility of this method for structural displacement measurement and the reliability of measurement accuracy. On this basis, the obvious sudden peak characteristic of the square variance of wavelet coefficients can be used to accurately identify the existence of single damage and multiple damage, and accurately locate the damage. The research shows that this method can accurately identify single damage and multiple damage in different locations and degrees, and has the advantages of long distance, non-contact, high precision, high efficiency, and can improve the spatial resolution of vibration modes by multi-point monitoring. it provides a new method for global damage identification of bridge structures.