【作者】 李盛；

【导师】 姜德生；

【作者基本信息】 武汉理工大学 ， 结构工程， 2009， 博士

【摘要】 近些年来,由光纤光栅构成的传感网络已经应用于许多大型结构的安全监测。大跨桥梁结构健康监测是应用光纤光栅传感网络最活跃的领域。光纤光栅传感网络系统埋入结构中可形成智能结构。光纤光栅传感器的精度非常高,具有很好的动态响应特性,可用于应力、应变、温度、振动等多种参数的测量,是智能材料系统和结构中最具应用前景的光纤传感器之一。大跨桥梁结构中,斜拉索的索力监测一直是桥梁结构健康监测系统的重要组成部分;而广泛采用的预应力混凝土类桥梁结构中,目前还无法实现对预应力索受力的直接监测。了解结构施工、营运过程中缆索内部钢丝受力状况及预应力体系是否安全,可靠一直是设计、施工和科研部门所关注的课题。光纤Bragg光栅(FBG)传感器除具有普通光纤传感器重量轻,耐腐蚀,抗电磁干扰,使用安全可靠等优点外,还具有探头尺寸小,波长调制,抗干扰能力强,集传感与传输于一体,具有较强的复用能力,易于构成传感网络,测量对象广泛,易于实现多参数同步传感测量等独特优点。对于索力实时监测国内外虽然有诸多研究,但总的来说还没有解决其根本技术难点,少有实用报道,尤其对处于高应力工作状态下的桥梁预应力钢束,体外索及缆索钢丝应变均还无法开展直接监测。为进一步发挥FBG传感技术的优势特点,研究基于FBG传感原理(以下均将“基于FBG传感原理”简称为“基于FBG”)的缆索监测新技术,完成基于FBG的预应力损失监测,实现基于FBG的索内钢丝应力值及分布状态监测,寻找从连续采集的索力数据中有效分析提取有意义监测信息的数据处理方法,本文进行了如下几个方面的研究工作:(一)既有基于FBG的桥梁索力测试方法比较研究1.指出了以纤维增强材料为封装体的智能筋目前还缺乏工程实例支撑的应用现状。介绍了更为成熟的基于频率法,压力传感原理,差动传感原理的光纤光栅索力传感监测系统的技术特点,测试原理及在代表性工程实例中的应用情况。2.从工程应用的角度,就适用桥型、单点费用、测量方式、温度补偿、更换操作及测试信号几个指标对既有基于FBG传感原理的索力监测方法进行了归纳对比。基于提出的各类光纤光栅索力传感器比较指标,使用模糊一致矩阵,结合具体工程,提出了一种更为客观的传感器选型方法。(二)基于FBG的预应力损失监测研究1.分析了基于FBG的预应力损失监测技术难点,提出了高应力工作状态的监测策略,及适用于新建桥梁及既有旧桥加固时对于预应力索的监测思路。2.设计了适用于新建桥梁预应力监测用FBG传感器的原型,通过试验分析验证了设计思路的可行性,并指出了实际应用中还应深入考虑的相关问题。3.通过一具体桥梁体外索加固监测实例,给出了基于FBG对体外索施工及运营阶段预应力值可采取的监测方式。(三)基于FBG的智能斜拉索结构研究1.结合平行钢丝斜拉索的生产工艺流程及平行钢丝模型张拉试验得到的相关结论,设计了智能斜拉索结构的组成方案。2.针对斜拉索的高应力工作环境,分析了对于传感器可采取的FBG预松弛方法。开发了一种能良好传递受力,测试斜拉索钢丝应变的微型应变传感器。通过对高应力工作状态下应变传感器的工作条件进行模型等效,解决了其温度补偿问题。3.针对平行钢丝斜拉索的生产工艺特点,分析了智能斜拉索传感器的保护措施,可能引起失效的原因及避免对策。(四)基于FBG索力测试方法的索内断丝监测研究1.说明了斜拉索断丝的危害性,由某一数值算例分析了斜拉索不同断丝方式,断丝程度下结构线型,索力及应力的响应规律。比较了既有斜拉索内断丝监测的手段,方法及特点。2.提出了基于FBG索力测试方法的断丝监测策略。联合斜拉索的整体模型以及钢丝为单元的局部模型,构建了对应于部分断丝模式的以斜拉索索力值(平均应力),智能斜拉索采集钢丝应力值为输入参量的模式识别样本库。基于BP的模式识别方法验证了提出的监测策略能够实现断丝区域定位及2%断丝程度内的监测要求,且在小噪声干扰下识别方法仍能发挥一定作用。(五)基于EMD法的索力数据趋势提取研究指出了可利用EMD法对连续采集的索力监测数据进行基于IMF分量的平均趋势及高幅值脉冲信号的提取分离。更多还原

【Abstract】 In recent years, sensing networks based on fiber optical grating have been widely used in a great deal of large structures satety monitoring. Long span bridges health monitoring is one of the most active domains for the application of sensing networks based on fiber optical grating. Embedding sensing networks system that based on fiber optical grating in structures can form smart structures. The fiber optical grating sensor which can be used to measure stress, strain, temperature, vibration and other structural parameters has high test precision and good dynamic response and its application perspective is so flourishing in fiber optical sensors for smart material systems and structures. For long-span bridge structures, cable force monitoring is always the most important component of bridge structural health monitoring system. For the prestressed concrete bridge structures which have been widely used, the direct monitoring means for prestressed cable is still vacancy at present. Therefore, tearing the mechanical condition of steel wires inside the cable and the security of structural prestressing system usually become the common attention focus of design engineer, construction personnel and scientific research departments.In addition to some advantages possessed by common fiber optical sensor, namely, light weight, corrosion-resistant, anti-electromagnetic interference, safety and reliable in use and so on, fiber optical bragg grating (FBG) sensor has some unique advantages, namely, small probe size, wavelength modulation, good anti-interference ability, integration of sense and transmission, good multiplexed ability, easy to constitute a sensor network, wide range testing parameters and easy to implement many parameters simultaneous monitoring. Although a good many research work about cable force real-time monitoring have been carried out in the world at present, generally speaking, the radical technical difficulties about cable force testing haven’t been solved and the practical engineering application reports were also rare. For the structures which bear high stress, especially such as prestressed reinforcement, external cable in bridge and steel wires in bridge cable, the direct strain testing means is still a challenge. In order to further exert the advantages of FBG sensing technology, study new testing methods which based on FBG principle (in the following text , "FBG-based" was used as the abbreviation for "based on FBG principle") for cable, achieve the FBG-based prestressing loss monitoring, implement the FBG-based distributed condition monitoring for steel wires stress values and search an effective data processing method for extracting meaningful monitoring information from the continuous collecting cable force data, this paper carried out the following research work:(i) Contrast study on existing bridge cable force measure methods based on FBG1. The status application of smart tendon that encapsuled by FRP which lacked the real engineering support was pointed out. More matured cable force sensing monitoring systems based on fiber optical grating involving frequency measure principle, pressure sensing principle and differential sensing principle were introduced. Also the corresponding technology trait, structure form and engineering application effects were presented.2. From the angle of engineering application, some index relative to the aforementioned cable force testing methods, namely, adaptation object, unit price, measure manner, temperature compensation, alterability and testing signal, were summarized and compared. Aiming at a real engineering and proposed relatively index about existing cable force sensor based on fiber optical grating that mentioned in this paper and, a more objective method for type decision-making of sensor was elicited by using fuzzy consistent matrix.(ii) Study the prestressing loss monitoring method based on FBG1. According to the analysis about the technical difficulties of prestressing loss monitoring based on FBG, the high strain monitoring strategy and the FBG-based monitoring ideas for prestressed cables in newly-built bridges and exsiting old bridges strengthening were elicited.2. The FBG sensor prototype which can be applied for prestressing loss monitoring in newly-built bridges was designed. Experiment analysis results verified the validity of proposed design thought and related problems in practical application which should be further taken into accout were pointed out.3. Based on a concrete bridge external cable strengthen engineering example, the FBG-based monitoring means for prestressing value which was adapt to construction and operation stage was proposed.(iii) Study the smart stay cable structure based on FBG1. Combining the fabricating arts and crafts flow of parallel wires cable of cable-stayed bridges with several conclusions derived from the parallel wires model tension experiment, the configuration scheme of smart stay cable was designed.2. Aiming at the high stress work condition of stay cable, some FBG pre-relaxed methods for sensor were put forward. A new micro strain sensor was designed, which ensured the validity to transfer steel wire stress and its mensurability as stay cable force testing means. According to the equivalent simulation of strain sensor’s high stress work condition, temperature compensation of the strain sensor was solved.3. Based on the character of fabricating arts and crafts of parallel wire stay cable, protection measures, possible disabled reasons and avoidance strategies of sensor structure used in the smart stay cable were analyzed.(iv) Study the broken wires monitoring based on FBG cable force testing methods1. The fatalness of broken wires inside the stay cable was illuminated. By using a certain numerical model, structural deformation, displacement, cable force and stress distribution were analyzed under different cases which composed by various of broken wires number and damage extent. The character and monitoring means of different broken wires inspection methods were compared. 2. The strategy for broken wires monitoring which based on FBG cable force testing methods was proposed. Associating the whole model of stay cable with the local model based on steel wires, several broken wires samples were established, which using stay cable force (average cable stress), steel wires stress derived from smart stay cable as input parameters. Using the BP pattern recognition method, the mentioned monitoring strategy can recognize the broken wires location and meet the 2% degree requirement for monitoring broken wires, which still can exert its function under small noise disturbance.(v) Study the trend extraction of cable force data based on EMDThe function of extracting average trend and high amplitude pulse from the original continuous acquisition cable force data based on IMFs which were decomposed by using EMD method was elicited.更多还原