【作者】 范哲；

【导师】 周晶； 冯新；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2013， 博士

【摘要】 大跨桥梁的结构健康监测已成为当今土木工程界研究的热点问题。桥梁结构由于受到车辆、风、地震等荷载作用以及环境影响或突发事件(温度、湿度、撞击等)因素会在运营期间发生不同程度的损伤。桥梁结构一旦发生损伤,将对桥梁安全造成巨大威胁并严重危害人民的生命财产和安全。一些严重的突发事故诸如桥梁倾覆倒塌等还会给国家和社会带来巨大的灾难。利用桥梁结构的响应监测数据,通过模型修正与损伤识别揭示结构状态退化,据此评估结构安全与预测剩余寿命,对于桥梁运行维护与灾害预防具有重要意义。本文提出了一种大跨斜拉桥模型修正的方法,并且在实验室建立了一座缩尺比例为1：150的斜拉桥模型,通过理论研究与物理模拟较为系统地研究了斜拉桥模型修正中的一些关键问题：为了克服基于傅里叶变换的动力损伤识别方法的局限性,发展了基于小波变换的振动传递性的概念,建立了更加有效的斜拉桥结构损伤识别算法；针对结构损伤的空间位置的任意性,提出了一种斜拉桥损伤的分布式探测方法,并且利用物理模型试验验证了该方法的可行性。主要研究工作和结论如下：绪论部分首先阐述了桥梁健康监测和损伤识别的研究意义,接着回顾和总结了近几十年来桥梁健康监测的发展情况,介绍了健康监测系统的概念、组成、发展历史以及在工程中的实际应用情况。根据国内外近些年来对斜拉桥损伤识别方法的研究,详细地介绍了适用于大跨斜拉桥结构损伤识别方法的理论以及各类损伤识别方法的适用条件范围和优缺点。最后针对在桥梁健康监测和损伤识别中的问题给出了本文的主要研究内容和研究思路。以山东黄河胜利大桥为工程背景,基于模型相似理论建立比尺为1：150的斜拉桥模型,并通过开展斜拉桥模型试验获得斜拉桥的静动力响应数据。首先阐述了模型实验的目的与意义,相似理论在模型实验中的应用。然后详细介绍了模型的设计制作的整个过程,包括模型材料的选择、各物理量相似常数的推导、结构各构件的尺寸设计和边界条件的模拟等内容。在斜拉桥模型静力加载试验通过百分表测试桥面的挠度,自制FBG光纤传感器监测斜拉索的索力变化。通过模态分析试验获得了斜拉桥的前三阶竖向弯曲振动频率和相应的振型。最后通过模型试验研究了斜拉索损伤对桥梁位移和索力变化的影响,讨论了关键索索力变化对整个桥梁安全状况的影响。该模型桥为本文的研究基准模型,为斜拉桥健康监测与损伤识别的研究做铺垫。第三章提出了一种对大跨斜拉桥有限元模型进行分步修正的策略。首先回顾了斜拉桥有限元模型建立的各种方法,并采用ANSYS通用软件建立了模型斜拉桥的三维有限元模型。然后,利用斜拉桥模型试验获得的实测响应数据,构建包括频率响应残差、振型响应残差以及位移响应残差的多响应目标函数。对有限元模型进行优化,使得修正后的有限元模型全面准确地反映模型斜拉桥的静动力学行为。基于ANSYS参数化设计语言(APDL)进行二次开发,编制模型优化程序,采用一阶优化方法和子问题方法开展有限元模型修正。不同于以往的斜拉桥模型修正策略,仅仅关注于结构的动力或静力响应与原型的一致性,本文提出的有限元模型分步修正策略兼顾了正确反映模型桥的静动力响应。通过灵敏度分析选择合适的修正参数先对频率残差项进行优化,使第一次修正后的有限元模型计算频率与实测频率相近。然后选择其它修正参数对位移项和振型项进行修正,使第二次修正后的有限元模型在静力响应方面也与模型桥的实测响应一致。同时,还将修正后的有限元模型物理参数与实际估算值作比较,二者的一致性验证了模型修正程序的有效性。最后,利用修正后的有限元模型预测模型斜拉桥及其原型桥的响应,又进一步验证了该有限元模型的正确性。为寻找对损伤敏感的损伤指标,在第四章中提出了基于小波变换的传递性函数损伤识别方法。介绍了响应自由度之间的传递性函数的概念及其在土木工程领域的特点和应用,总结和归纳了利用传递性函数构造损伤识别指标进而对结构的损伤进行探测的方法。然后推导了通过小波变换构造结构传递性函数的损伤识别指标,并结合统计学中的离群值分析方法对损伤进行探测,同时给出了损伤识别的具体步骤。通过数值模型试验与实验室斜拉桥模型试验加以验证。在数值模型试验与斜拉桥模型试验中将本文所提出的方法与传统的传递性函数进行对比,结果表明本文所提出的方法对结构出现的损伤十分敏感,能够识别结构的早期微小损伤。结构损伤具有典型的局部性质,通常表现为局部应变的异常。结构应变的分布式监测与损伤敏感特征分析,是实现大跨桥梁损伤探测与定位的理想途径之一。第五章提出了基于分布式应变监测的大跨度斜拉桥结构损伤探测方法,通过小波变换对分布式光纤测试的斜拉桥桥面应变分布进行多尺度分析,克服了分布式光纤应变监测信号受观测噪声和空间分辨率平均效应的不利影响,准确地确定了空间域信号奇异点在桥面的位置。介绍了分布式光纤的特点、BOTDA(布里渊光时域分析技术)的测试原理以及其在桥梁健康监测中的广泛应用。在模型试验中通过布设不同形式的分布式光纤进行试验研究。通过斜拉桥数值模型与物理模型试验结果进行分析和比较验证所提出方法的有效性。数值试验和模型试验均表明,采用所提出的方法可以对桥梁多处位置发生的损伤进行有效地识别,该损伤识别方法具有对噪声的鲁棒性和对损伤的敏感性。最后,对全文的研究工作进行归纳和总结,并对大跨斜拉桥健康监测和损伤识别的发展方向进行了展望。更多还原

【Abstract】 Nowadays, the study of structural health monitoring and damage identification for the long span bridges has become hot issues in civil engineering. Damages of different level appear on the bridge due to the traffic loads, wind load, earthquake and other environmental effects (temperature, humidity and strike, etc.) in operation, which will greatly threaten the safety of bridges and may cause great loss to human life and property. Some serious accidents such as the collapse of the bridge will cause great disaster to our country and society. Therefore, in order to secure the safety of the bridge structures and prevent the case of disaster, one need to identify and alert the damage of the bridge structures in time, which is of great significance in saving the economic loss and protecting the human life and property. A great number of researchers and engineers expect to make use of the characteristics of the bridge, especially its dynamic property to investigate the damage identification algorithm and apply the structural health monitoring system to detect and alert the damage by constructing the damage index which is sensitive to the damage of the bridge. The study is carried out under this background.In order to better study the structural health monitoring and damage identification of the cable-stayed bridge, a cable-stayed bridge model with the scale ratio1:150was built in the laboratory. Based on this physical model, three issues including finite element model updating method, wavelet-based transmissibility function and the structural health monitoring of the cable-stayed bridge on the basis of measuring the distributed strain are studied by carrying out the model test and numerical simulation. The main work and research scheme are stated as follows.First of all, the significance of structural health monitoring and damage identification for the bridge structures is stressed in the introduction part. Secondly, the development of structural health monitoring for the bridge structures in recent decades is briefly introduced. Then the concept, composition, history and application of the structural health monitoring system are also presented. According to the recent study on the damage identification methods for the cable-stayed bridge, different kinds of damage identification methods adopted in bridge engineering are presented, and their application fields and advantages as well as disadvantages are also evaluated. Finally, the outline and the idea of this research are provided at the end of the introduction based on the issues and problems occurred in the structural health monitoring and damage identification areas for the cable-stayed bridges.Based on the engineering background of Yellow River Shengli Bridge in Shandong province, a small scale cable-stayed bridge model with the scale ratio1:150was built according to the similarity theory and the model tests were carried out to obtain both of the static and dynamic experimental data. The goal and significance of the model test are explained at first, and then the application of the similarity theory in model test is introduced. The whole process of the design and fabrication of the model bridge is presented, including model material selection, derivation of physical quantities, design of the structural components as well as boundary simulation, etc. The dial test indicators are used to measure the displacement of the bridge deck, and self-made FBG optical sensors are used to monitor the cable force change during the model tests. Modal test was also performed to obtain the first three vertical bending frequencies and mode shapes. Finally, the study on the effects of bridge displacement and cable force change caused by the damage of the cable is carried out, and the influence of the cable force change on the bridge health status is discussed. This physical model was used as a baseline model for the study of cable-stayed bridge of structural health monitoring and damage identification.A two-step FE model updating strategy for long span cable-stayed bridge is proposed in the Chapter3. The various methods of FE model updating for cable-stayed bridge were reviewed in the first time, then a three dimensional cable-stayed bridge model was established using ANSYS software. Based on the experimental data from the model test, a multi-objective function was formulated including frequency, mode shape and displacement differences. The FE model was updated to improve the accuracy of estimating both of the static and dynamic responses. An optimization program was developed using first order and sub-problem method to update the FE model based on APDL (ANSYS Parametric Design Language). The two-step FE model updating strategy proposed in this study takes consideration of both static and dynamic responses of the bridge model, and is different from the conventional FE updating methods, which only take account of either dynamic or static responses of prototype. The frequency difference was first minimized by selecting the appropriate parameter with sensitivity analysis, which makes the computed frequency as close as the measures one. Then other parameters were selected to minimize the mode shape and displacement differences, which makes the static responses predicted by the FE model agrees with the experimental results after the second step of model updating. Meanwhile, the updated parameters were used to compare with the actual ones of the model bridge. The agreement of them verifies the effectiveness of the updating program. At last, using the updated FE model to predict the responses of the model bridge and prototype bridge to further validate the accuracy of the FE model.In order to search the damage index which is sensitive to the damage, a wavelet-based transmissibility function method is proposed to detect the damage. The concept of transmissibility function between the responses between the degrees of freedom (DOF) is introduced and its features and applications are also presented. The damage identification methods using the transmissibility function are summarized. Then, a new damage index using wavelet-based transmissibility is derived and constructed. A statistical method named outlier analysis is adopted in the study to detect the damage in the structure and the concrete damage detection procedure is also presented. Numerical simulation and experiment were also carried out to verify the effectiveness of the proposed method. Also, a comparison study was carried out by using the conventional transmissibility method. The results show that the damage detection method proposed in this study is very sensitive to the damage, which highlight the strength of the method to detect the slight damage in the early stage of the structure.Structural damage is a typical local phenomenon, which commonly leads to the abnormality in the local strain. Monitoring the structural damage in a distributed manner, as well as extracting the damage-sensitive feature, is an effective way to detect the damages in the long-span bridges. A damage detection method for the long span bridge is proposed by using the distributed optical sensor. The strain signals of the deck, which are measured by distributed optical fiber sensor, are decomposed into multiple levels using wavelet transform. The proposed method has alleviated the noise effects on the strain signals and averaging effect caused by the spatial resolution of BOTDA (Brillouin Optical Time Domain Analysis), thus determines the exact location of the singular point of the spatial signal accurately and conveniently. The features of the distributed optical sensor, the principle of BOTDA, and its application are presented. The damage index is constructed using wavelet transform to detect the singularity of the distributed signal of the bridge structure. Different types of the optical sensors were used in the study. Both of the numerical simulation and model tests were carried out on the cable-stayed bridge model to testify the effectiveness of the proposed method. The results show that the proposed damage detection method can detect multi damage locations of the bridge structure and it is also sensitive to the damage and robust to the environmental noise.Finally, the summary is given at the end of the research, and the prospect for the structural health monitoring and damage identification of the cable-stayed bridge is also proposed.更多还原