不同模态振型在梁结构裂缝识别中的差异

本文采用Gaus2小波对多裂缝梁的不同模态振型进行小波变换,分析了不同模态振型在梁结构裂缝检测中的差别。同时,本文还采用最小二乘法将各裂缝处的Lipschitz指数算得,进而分析了各模态振型函数在裂缝处的奇异性程度。结论表明:梁结构裂缝识别的效果主要由裂缝处的小波系数的模的大小决定。     

利用基本模态振型对梁结构裂缝识别的小波方法研究

文章首先讨论了含裂缝梁结构的柔度矩阵的变化;其次,通过选择不同模态振型函数进行小波变换分析,总结了不同模态振型在梁结构裂缝检测中的不同规律;最后,文章以悬臂梁为例,选用Gaus2小波对悬臂梁基本振型进行小波变换,进而对悬臂梁中的裂缝进行识别,裂缝深度与Lipschitz指数进行拟合。     

基于小波分析的简支梁损伤识别数值分析

基于有限元建立简支梁模型,对存在损伤的简支梁振型曲线进行连续小波变换,变换后的小波系数出现模极大值,从而判定损伤的存在并锁定损伤位置。研究表明小波分析结果与损伤位置及振型阶数关系密切,分析宜选用使损伤位置处振幅较大的振型阶次。基于小波分析的简支梁损伤识别结果与实际损伤位置基本一致,该方法在梁结构损伤诊断中具有较高的应用价值。     

基于运行检测的小波模态参数识别

众所周知结构的运行条件和实验室测试条件明显不同,在实验室中结构的特性可以较为准确的模拟,结构激励是已知的.但是对于正常使用的结构来讲,激励往往是不可测量的,同时大部分情况下是非稳态的.因此基于运行模态的结构分析方法被提了出来,并将它作为传统模态分析的一个补充方法.提出基于运行检测的小波模态参数识别技术,基于小波的模态参数识别是将信号变换到时(频域),这有利于识别结构的动态特征参数频率、阻尼和振型.给出运行情况下结构振动响应数据的小波变换的振幅和相位与特征频率及阻尼之间的关系.提出小波谱分析方法,并用它来识别结构的振型.数值模拟的例子表明,采用小波的识别方法所识别的结果与频域的峰值法和时域的随机子空间方法所识别的相符.     

墩梁固结处模拟方式对连续刚构桥动力特性的影响

连续刚构桥墩梁固结处存在一个较大范围的刚域,其模拟方式对连续刚构桥动力特性有直接影响。拟采用4种(共节点、主从约束、刚性材料、实体单元)不同方式,来分析墩梁固结处的模拟方式对高墩大跨径连续刚构桥动力特性的影响,同时运用自然环境激励技术联合特征系统实现算法(NExT/ERA法),测试出实际桥梁结构的模态频率与振型,并与上述4种模拟方式比较。结果表明,采用NExT/ERA法能很好地识别出结构的模态参数,不同模拟方式对桥梁结构的动力特性有较大影响,实体单元有限元模型最为精确,刚性材料法也能够很好地模拟墩梁固结处的刚域,对高墩大跨径连续刚构桥这种存在较大范围刚域的结构必须要对刚域准确模拟才能够得出结构正确的动力特性。     

基于贝叶斯的钢筋混凝土梁模型修正方法

本文提出了一个基于贝叶斯原理的钢筋混凝土梁有限元模型修正方法。针对钢筋混凝土梁模型修正中的方程病态问题及模态测试中测点信息不完整和模态信息不完备的实际情况,建立了适用于有限测点的目标函数和似然函数,且在目标函数中同时考虑了频率和振型信息。采用延迟拒绝自适应算法(DRAM)对待修正参数的后验概率进行了计算。数值算例表明本方法在仅使用低阶测量模态信息和不完整振型信息的情况下,仍能准确修正结构参数;实验算例表明,修正后的钢筋混凝土梁有限元模型的动力特性和测量结果一致,修正后的模型参数值和梁的轻微裂缝的位置及大小基本对应,说明了本文方法的有效性。     

基于曲率模态的钢筋混凝土梁多点损伤位置识别

采用曲率模态对钢筋混凝土梁的多点损伤位置进行了识别研究。首先用有限元程序建立结构模型,并计算出位移模态振型,然后用差分法计算出曲率模态;同时对实际结构进行检测,得到结构的振型并计算出曲率模态。通过有限元模型和实际结构的曲率模态计算得到结构损伤因子,通过分析该损伤因子,可以判断实际结构的损伤位置。数值模拟算例分析表明,曲率模态对结构的损伤较敏感,用该方法识别结构的多点损伤位置是行之有效的。     

某游泳跳水馆钢屋盖结构自振特性和风振动力响应分析

通过对某游泳跳水馆屋盖结构体系的频率和模态分析发现 ,此类斜拉筒壳结构的自振频率密集 ,振型分布很有规律。根据不同模态对整个结构在脉动风作用下应变能的贡献多少来定义模态对结构风振响应的贡献 ,对此屋盖结构选取前 2 0阶振型进行风振响应分析 ,得到了各阶振型对系统能量的贡献 ,对此屋盖结构 ,考虑前 2 0阶振型的影响 ,可满足结构设计的需要 ,但必须考虑各振型之间的耦合。     

基于曲率模态差的隐框玻璃幕墙结构胶损伤识别研究

鉴于应用曲率模态的隐框玻璃幕墙结构胶损伤识别研究较少，提出以隐框玻璃幕墙面板单块试件为研究对象，针对四边不同脱胶损伤进行模态试验并获取模态参数，通过模态分析获取模态振型，采用中心差分法获得曲率模态差，并利用Matlab进行绘图，针对不同工况损伤进行了一阶曲率模态分析。分析结果表明，结构胶脱胶损伤处的玻璃面板模态振型相比未损失时振幅发生起伏，但很难直接用于判断损伤位置，但损伤处曲率模态差值变化显著，采用曲率模态差法可以对损伤位置进行准确判定。     

JQS30m-250t U型梁短尾式架桥机纵导梁模态分析

为解决架设轻轨桥梁的设备受环境条件影响的问题,设计了一种JQS30m-250t U型梁短尾式架桥机.纵导梁作为架桥机施工中承担吊装梁片的重要结构,采用有限元仿真软件ANSYS Workbench对架桥机无风工作时的纵导梁进行模态分析,分析得到纵导梁前10阶的模态频率与振型图,确定纵导梁的最大振幅位置.结果表明:纵导梁水...     

Pipe crack identification based on the energy method and committee of neural networks

A crack identification method using an equivalent bending stiffness for cracked beam and committee of neural networks is presented. The equivalent bending stiffness is constructed based on an energy method for a straight thin-walled pipe, which has a through-the-thickness crack, subjected to bending. Several numerical analysis for a steel cantilever pipe using the equivalent bending stiffness are carried out to extract the natural frequencies and mode shapes of the cracked beam. The extracted modal properties are used in constructing a training patterns of a neural network. The input to the neural network consists of the modal properties and the output is composed of the crack location and size. Multiple neural networks are constructed and each individual network is trained independently with the different initial synaptic weights. Then, the estimated crack locations and sizes from different neural networks are averaged. Crack detection is carried out for 16 damage cases using the proposed method, and the identified crack locations and sizes agree reasonably well with the exact values.     

基于振型参数的装配式桥梁损伤识别研究

利用结构动力特性的振型参数对桥梁进行快速损伤诊断和定位,可以提高结构性能评价与损伤诊断的效率。本文以装配式预应力混凝土T梁为算例,通过定义位移振型和曲率振型的桥梁损伤识别指标进行损伤识别,计算结果表明采用位移振型和曲率振型的方法进行损伤识别和定位效果较好。     

System identification using a standard finite element program

Frequently, experimental results for scale models or for prototypes of structural systems do not produce mode shapes and natural frequencies which concur with analytical results for the same structure. An algorithm for an iterative identification process for improving structural models is described, which relates structural parameters to changes in system response by application of the Bayesian technique of probability and statistics. Revision of the structural parameters is made using expansions of differences between experimental and analytical mode shapes and frequencies. Since the revision is based on modification of partial stiffness and mass matrices of beam, membrane, and shell elements in the element library of a commonly available finite element program, a method is developed to calculate those partial matrices with the matrix generating subprograms of the finite element program itself.     

Scalable Structural Modal Identification Using Dynamic Sensor Network Data with STRIDEX

This article uses the formulation of the structural identification using expectation maximization (STRIDE) algorithm for compatibility with the truncated physical model (TPM) to enable scalable, output‐only modal identification using dynamic sensor network (DSN) data. The DSN data class is an adaptable and efficient technique for storing measurements from a very large number of sensing nodes, which is the case in mobile sensor networks and BIGDATA problems. In this article, the STRIDEX output‐only identification algorithm is proposed for the stochastic TPM to estimate structural modal properties (frequencies, damping ratios, and mode shapes) directly from DSN data. The spatial information produced by this novel algorithm, called STRIDEX (“X” for extended), is scalable, as demonstrated in a strategy to construct high‐resolution mode shapes from a single DSN data set using a series of independent identification runs. The ability to extract detailed structural system information from DSN data in a computationally scalable framework is a step toward mobile infrastructure informatics in a large urban setting. The performance of the STRIDEX algorithm is demonstrated, using the simulated response of a 5,000 DOF structure, and experimentally, using measurements from two mobile sensor cars, which scanned about 8,000 points on a beam specimen in the laboratory. In the experimental results, a mobile sensor is shown to provide over 120 times more mode shape points than a fixed sensor.     

大型梁式渡槽竖向地震作用估计

应用流体势流理论与结构的振动理论 ,通过流 固耦合简化分析 ,导得了渡槽承重简支梁的湿频率及湿振型估算公式 ,导得了结构竖向地震响应的时程计算公式 ,应用反应谱法 ,导得了作用于结构的等效竖向地震荷载估算公式 ,做了几项数值算例 ,分析结果表明 :(1)由于附连水质量的影响 ,梁的湿频率比其干频率要低 ,但湿振型与其干振型完全相同 ;(2 )水质量在结构竖向地震响应中起着重要的作用 ,竖向响应的幅值随着不同的场地而发生改变 ,一般水越深 ,结构的响应越大 ;(3 )在 7度设防时应考虑竖向地震的作用。     

基于结构动力参数的RBF损伤辨识方法

本文研究了基于不同结构动力参数的径向基网络损伤辨识方法,并结合简支梁损伤辨识进行了应用.研究发现:(1)径向基网络的输入参数选择对结果有较大影响;(2)使用模态曲率变化作为输入参数的网络辨识效果优于采用频率变化率的辨识效果;(3)综合使用频率变化率和模态曲率变化的网络辨识效果优于单独使用频率变化率或模态曲率的效果.结果...     

某桥梁工程主梁裂缝鉴定处理及试验分析

根据工程特点,采用先鉴定、再加固、后试验的方法对某桥主梁进行结构安全性鉴定,详细介绍了该桥主梁裂缝的鉴定、处理及试验分析过程,为今后处理类似工程问题提供一定的参考依据。     

Vibration‐Based Damage Localization in Flexural Structures Using Normalized Modal Macrostrain Techniques from Limited Measurements

Abstract: This article presents damage locating indices based on normalized modal macrostrain (MMS) as improvement on the typical curvature‐dependent methods. Vulnerability to noise and the use of numerical differentiation procedures are the key factors for the poor performance of many curvature‐dependent methods using displacement mode shapes. Whereas dynamic distributed strain measurement data from long‐gauge FBG sensors have significantly improved the performance of many damage identification methods, the sensitivity to local damage diminishes as the gauge length increases. The proposed model‐free damage identification techniques based on normalized MMS vectors are successfully implemented to locate damage in beam‐like structures through numerical simulations and experimental verifications. The unique advantages of the techniques are their simplicity, robustness to noise, ability to precisely identify small damage extents, and localize single and multiple damage states using limited measurable modes from few sensors.