【作者】 任宜春；

【导师】 易伟建；

【作者基本信息】 湖南大学 ， 结构工程， 2004， 硕士

【摘要】 小波分析是近十几年国际上掀起热潮的一个前沿领域，它被认为是傅立叶分析方法的突破性发展，是一种新的时—频两维分析方法。结构的损伤诊断技术是当前结构工程学科十分活跃的研究领域并有广阔的工程应用前景，相关的理论和技术正在不断发展。本文着重对小波分析方法在结构损伤诊断中的应用进行了研究。主要研究内容有： 利用小波奇异性检测原理识别梁结构的损伤位置与损伤程度；对带裂缝梁结构的振型函数和移动荷载作用下梁跨中的位移响应用Mexican Hat小波进行连续小波变换，通过小波系数出现模极大值来判别裂缝的位置，通过模极大值处的小波系数计算Lipschitz指数，由Lipschitz指数的大小来识别裂缝的深度；研究了裂缝位置、振型的测点距离、荷载的移动速度、噪声等因素对识别的影响；对损伤引起的某一区段刚度下降，采用Gauss3小波对梁结构的振型函数和移动荷载作用下跨中的位移响应进行连续小波变换，通过小波系数出现一正一负成对的极大值来识别损伤的位置；数值算例证实了该方法的有效性。 基于小波包分解，得到对损伤敏感频段的能量值构成的特征向量，并采用该特征向量作为损伤因子进行损伤诊断。完成了一根钢筋混凝土简支梁在不同损伤情况下的振动测试。并基于梁在脉冲荷载作用下的响应信号测试数据，用小波包分解技术识别了梁的损伤程度。 对基于复小波变换的振动信号瞬态参数提取原理进行了研究。对粘滞阻尼线性系统和立方非线性系统的自由振动响应进行Morlet复小波变换，从脊线上的小波系数提取瞬态参数从而识别固有频率、模态阻尼和非线性系数。通过三个数值算例，对单自由度线性系统、多自由度线性系统以及立方非线性系统进行了参数识别。更多还原

【Abstract】 Wavelet analysis is a new time-frequency analysis method which has raised a research upsurge internationally in recent years. It is regarded as a breakthrough of Fourier Analysis. Damage diagnosis technique is an active research domain in cunent structure engineering and has strong engineering background. The correlative theory and technology are developing continuously. This thesis is concentrated on the research of the damage detection method by wavelet transform. The main subjects are summarized as follows:A wavelet-based approach is proposed for crack identification in beam structure by the singularity’s detection. The fundamental vibration mode of a cracked simple-supported beam and the displacement of the middle of the beam under mobile force are analyzed using continuous wavelet transform by Mexican Hat wavelet. The position of the crack is located by the maximum modulus of the wavelet coefficients. The Lipschitzs exponent estimated by the wavelet coefficients is used as a useful indicator of the crack depth, which decays with the increase of crack depth. The influence of the crack location, the sampling distance of the vibration mode and the velocity of moving load to lipschitzs exponent are discussed. It is testified that this method is also in effect to noisy data. The position of the stiffness decline caused by the damage is also detected by this method. The validity of the proposed method is investigated both by analysis and simulations.The component energy in different frequency bands gained by wavelet packet decomposing which is sensitive to damage is used as damage index. A series of vibration test on a reinforced concrete beam under different damage degree are finished. The damage degree is recognized by the wavelet packet decomposing of the response signal collected in vibration test.The transient parameters are distilled by the compound wavelet transform of the vibration signal. The impulse response of the linear and non-linear viscous damping system is analysed by Morlet wavelet. The transient frequencies and amplitude are obtained from the ridges of the wavelet transform. So the parameters of the system are identified. The method is illustrated by three simulated example.更多还原