桥梁结构损伤识别的应变模态方法研究

【作者】 杜思义；

【导师】 陈淮；

【作者基本信息】 郑州大学 ， 结构工程， 2002， 硕士

【摘要】 交通是社会的经济命脉，桥梁是交通畅通的咽喉，交通的不畅会制约社会经济发展。所以保障桥梁的功能性，尤其是安全性至关重要，这就需要经常对桥梁进行安全性检测和监测，以确保桥梁的正常使用。我国桥梁目前现状是桥梁数量极大，一方面，许多既有桥梁已接近设计寿命，桥梁的老化、损坏现象比较严重，另一方面，又有许多新的、大型桥梁结构陆续建成，为保证这些桥梁安全运行、避免严重事故发生，需要对新建桥梁进行健康监测、对既有桥梁进行损伤识别和可靠性鉴定。传统的桥梁静力检测方法不能快速确定桥梁损伤位置和剩余寿命，而且工作面大，加载时间长，通常要中断交通。因此研究一种简便、快捷的桥梁损伤识别的方法具有重要的现实意义。本文研究的目的就是探索一种合适的识别桥梁损伤的方法。 利用结构动力学原理和现代检测技术相结合对桥梁的健康状态进行识别的方法研究已成为相关科技工作者关注的热点。结构模态参数(振动频率、振型和模态阻尼等)是结构物理特性参数(质量、刚度、阻尼)的函数，结构损伤必然导致结构物理特性的变化，即结构参数发生改变，利用现代的测试技术准确地测出这些参数变化，就可对桥梁损伤状况进行评估，应变模态方法识别桥梁损伤就是基于这种理论提出的，本文所做的主要工作为： 1．论文通过对国内外桥梁损伤检测方面的文献资料研究，探讨了识别桥梁损伤的基本理论，比较了多种结构损伤敏感参数识别桥梁损伤的优缺点，最后确定用应变模态参数识别桥梁结构损伤较为合适，应变模态是对损伤敏感的参数，满足四个基本条件：①对局部损伤敏感，且为结构损伤的单调函数；②具有明确的位置坐标；③在损伤位置，应变模态差曲线出现明显的峰值变化；④在非损伤位置，应变模态差曲线的变化幅度小于预先设定的阈值。在结构损伤识别问题上应变类型的损伤识别指标优于位移、固有频率等类型的损伤识别指标。 2．论文综合结构动力学、材料力学、弹性力学等知识推导出桥梁结构应变响应模态模型的数学公式，指出了该方法的适用范围，基于FORTRAN POWER STATION 4.0计算机工作平台，用Fortran语言编制了 能H算桥梁结构特征值及特征向帛羽小于变模态的＊哭小m［序。程序人计 讣应变模态时采川州邻单元的模态位移，卅抑桥梁介动载作川十人勺应变 棋忐公式，从一定程度＿卜解决了应变模态方法应川：J“结构损伤检测受到 传统应变测量手段制约的难题。论义具体通过应变模态差曲线识别桥梁 ＿结构的损伤位置和程度。。3．论文中分别对简支梁桥、预应力混涨十连续梁桥＊ 架桥的损伤 以别进行了数值仿真计算。计算中桥梁损伤采用。V元抗弯刚度M的降 低壮模拟，不同损伤程度用抗弯1训度折减的百分比1〕表示。每fi。桥梁 的损伤识别都采用多种工况模拟，具体＿＿Ich况为：－－个单元的不同损伤私1 度、多个单元同时有相冈损伤、多个单元口时有损伤但损伤程度不同。 桥梁划分不同的有限单元等。 本文通过数值仿真分析，得出采用应变模态艺lH线识别桥梁结构损 伤的结论如下：①采用应变模态方法能准确识别（【5桥梁结构的损伤位 皆。②桥梁损伤位置不一定正对应变模态差曲线的跳跃峰值，有时会相 针卜－个单元。③简支梁桥中有一个单元或两个单元的损伤程度大于＊％ 时，其损伤位置都能通过应变模态差曲线进行识别；简支梁中一个单元 损伤对应的应变模态差曲线仅有一个单元跳跃峰，虽然反映简支梁损伤 的应变模态差阶数不固定，但每个损伤在梁的低阶应变模态差曲线中都 能得到反映；简支梁应变模态差曲线中对应损伤的单元跳跃幅值随单元 姊伤程度的增加而加大，且同一损伤程度单元跳跃幅值一般随模态阶数 的增加而加大。④对于连续梁桥，在一命V损伤工况下，并非每阶模态都 能反映出损伤存在，但总存在某阶模态能反映出损伤的存在：应变模态 差峰值虽随损伤程度的增加而增大，但并非每阶模态对损伤都有反映， 故仅用一阶模态不能反映损伤发生的程度，需用多阶模态对比分析才能 判别损伤的程度。⑤对于刚架桥的损伤识别，识别能力随损伤单元的增 加而降低，多单元损伤会降低应变模态差对损伤的敏感程度；应变模态 差峰值随损伤程度的增加而增大；山于刚架桥振动模态中有以桥墩横向 振动为主的模态，而桥梁主梁损伤识别要用桥梁主梁的以竖向振动为主 的模态，所以对于刚架桥的损伤检测，应检测主梁以竖向振动为主的多 个低阶模态，这样才能讹确识别刚架桥的损伤。③采用应变模态方法可 A 以丫性地确定出桥梁结构的损更多还原

【Abstract】 Traffic is a social economic blood, and a bridge is a traffic throal. The development of social economy will be limited if the traffic docsn’t move to and from, So it is very important to make sure every bridge’ s function and safety. To use every bridge normally as demands to test or moni tor to bridges’ safety from now and then. At, present there are a large quantity of bridges in our country, one hand, many old bridges have approached their design lifetime, their components have aged and be damaged, on the other hand, a number of new and large-scale bridges will be built. To assure these bridges’ safety and to avoid accidents, we should get on monitor on-line to new bridges, and detect damage and identify reliability to old bridges. The traditional testing approaches can’ t make sure a bridge’ s damage positions and rest lifetime, and it will take plenty of time and interrupt traffic. So it has an important realistic significance to explore a simple rapid approach to detect bridges damage . the paper’ s objectives is to quest a proper approach to detect bridges damage.The research of approach to monitor bridge health state has become a hot spot which social and technologic people have explored through the theory of, dynamics of structures and the lest technology. Structure mode parameters(vibration frequency, mode of vibration and damping)are the functions of physical property parameters(mass, rigidity, damping). The damage of structures certainly leads to the transformation of physical property parameters. The damage state of a bridge can be identified through the transformation. The parameters of strain mode do so. The paper’ s main contribution is followed beiow.l.The paper studies the theory to detect damage of bridges, and compares many sensitive parameters to detect bridge damage through correlative literature all over the world, finally concludes it suitable that bridge damage is detected by strain mode parameters. The strain mode parameters satisfy four foundstiona.l conditions as follows: ㏕hey are sensitive to sectional damage and they are monotone function of structure damage. @They have determinate location coordinate. (3)0n the damage location, the curves of difference of strain mode have evident peaks. @0n no damage location, the variety amplitudes of the peaks of difference of strain mode are less than posited threshold value in advance. The strain type parameters compare favorably with the nature frequency and thedisplacement parameters on detecting structure damage.2. The paper derived the formulae for the strain response mode with the knowledge of dynamics of structures, of materiaJ mechanics, of elastic mechanics, and pointed out their use range. A computer program is worked out with FORTRAN POWER STATIONS 4.0, It can compute the characteristic value, the characteristic vector and the strain mode for a bridge structure, and it is verified correct. The program used near elements’ vibration displacement to predicate a bridge’ s strain when it computed the strain mode of a bridge. To some extent, as solved measuring means to detect structure damage with strain mode approach.. The program’ s computing result certified that bridge damage’ s location and degree could be delected not by the approach of strain mode, but by the curve difference ol’ strain mode.3.In the paper, some of numerical simulation were respectively done on damage detection of bridges of simply supported beam, continuous beam, and rigid-jointed frame. Bridges’ damage degree was simulated with the percentage of reduction of bending r igidi ty . Every bridge’ s damage modes were divided by following types:( I ) A unit was damaged in different degree. (II)Al the same time ,several units were damaged in the same degree. (III) Several units were damaged in different degree. (FV) A bridge was divided by different finite elements. Through some of numerical simulation, some conclusions were drawn out as following:The damage positions of bridges can be accurately identified by the approach of strain mode.The dam更多还原