共查询到19条相似文献，搜索用时 114 毫秒
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基于曲率模态和小波变换的结构损伤位置识别 总被引：12，自引：3，他引：9
小波变换具有在时域和频域内表征信号局部特性的能力,能够在不同尺度下对结构响应中的突变信号进行放大和识别.在结构曲率模态基础上,本文提出了一种基于小波变换的结构损伤检测和定位方法.利用双正交小波函数对损伤前后结构的曲率模态进行小波变换,用损伤前后小波变换系数残差建立了结构损伤指标,通过小波变换系数残差的分布统计情况判定损伤的存在并确定其位置.应用简支梁数值模拟结果对该方法进行了验证. 相似文献
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为提高梁式结构损伤诊断的效率,提出一种基于类柔度差曲率和频率摄动的结构损伤识别方法。首先根据结构振动理论,研究广义柔度矩阵计算公式;再利用模态柔度对结构损伤灵敏性高的优点,改进基于柔度差曲率的损伤定位指标,定义类柔度差曲率LCFC损伤指标,并初步识别损伤;最后基于矩阵摄动进行结构损伤识别结果确认。考虑多种损伤工况,对一简支梁结构进行损伤识别数值模拟验证。结果表明:仅使用一阶模态,建立的类柔度差曲率LCFC指标对梁式结构损伤定位具有良好的诊断效果,且计算工作量小;对于含边界损伤单元的多损伤工况,当损伤程度大于10%时,LCFC指标识别有效;当损伤程度不大于25%时,各工况二阶摄动识别结果精度较高,相对误差较一阶摄动结果明显降低,证明了该方法的实用性、有效性和精确性。 相似文献
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结构健康监测和结构状态评估的主要前提之一是结构损伤识别。基于曲率模态对结构局部损伤比较敏感和频率指标测试简单方便、精度高的特点,本文提出了一种以结构的曲率模态为基础,综合考虑频率的变化的改进的结构损伤识别方法。随机子空间方法是一种行之有效的基于环境激励的结构状态识别方法。该方法的主要优点是无需人工激励,不中断桥梁的运营。为此,论文提出了一种不中断桥梁运营的基于改进曲率模态的桥梁结构损伤识别方法。最后用一三跨连续梁的有限元模型对该改进方法进行了验证。结果表明,采用随机子空间结合改进的曲率模态方法可以在不中断桥梁运营的前提下有效地识别出桥梁的损伤状况。 相似文献
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针对网格结构中杆件数量众多，但节点数总是远远小于杆件数的特点，损伤识别中采用了基于BP神经网络技术和面向节点的损伤初步定位方法的网格结构损伤识别的三步法。对双层柱面网壳结构模型在不同杆件去掉时的四种损伤情况下的振动特性进行了实测，并以实测低阶模态的频率变化率和少数测点的振型分量作为神经网络输入参数，对模型的各种损伤情况进行了识别。结果表明，所用的方法可以精简神经网络的结构，并提高其模式识别的能力。该方法可用于对大型复杂结构的损伤识别。 相似文献
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基于模态曲率法的大跨度斜拉桥损伤识别 总被引：2，自引：0，他引：2
大跨度斜拉桥是重要的交通结构,研究其在主梁损伤条件下的损伤定位问题具有重要的工程价值。合理选择设计参数并对其进行敏感性分析,根据现场实测的桥梁动力特性数据,通过调整选定的设计参数对初始的有限元模型进行修正。在基准有限元模型的基础上,通过模拟不同位置和不同程度的主梁损伤,探讨了模态曲率法对结构损伤识别的有效性。结果表明,模态曲率法能够对大跨斜拉桥进行初步的损伤定位,确定主梁单处损伤和多处损伤的损伤位置;对于单处损伤,在噪声水平3%的情况下仍具有较好的适用性。从而为后期更为精确的桥梁结构损伤检测提供依据。 相似文献
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基于小波包分解和模糊聚类的网格结构损伤诊断方法 总被引：3，自引：1，他引：3
本文针对网格结构的特点,利用其在快速正弦扫频激励下的动力响应,基于小波包分解频带能量分析和模糊聚类法,提出了一种适合于网格结构的损伤诊断方法。利用两个传感器损伤信息的联合诊断,有效地解决了使用一个传感器无法检测出对称损伤的难题。利用有限元模拟,应用上述方法对一单层球面网壳结构进行了损伤诊断。结果表明,对网壳杆件较小程度的损伤,子频带能量成分变化敏感,用其构造诊断向量和建立损伤样本库,并进行模糊聚类和目标识别,基本可以正确地识别出网壳杆件的损伤位置和程度。同时该方法测试时间短,使用设备少,有可靠的理论基础,具有一定的工程应用参考价值。 相似文献
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《地震工程与工程振动》2017,(6)
为了采用结构柔度矩阵进行损伤识别,由均匀荷载面曲率差指标推导出一种加权柔度矩阵指标构造方法,权值分别取振型、振型曲率和、振型曲率符号函数构造出三个新的损伤指标。基于结构损伤前后指标的相对变化及节点损伤程度和单元损伤程度的关系,提出了指标的结构损伤程度计算方法。采用一简支梁和一三跨连续梁算例,考虑多种损伤情况,与均匀荷载面曲率差指标进行了对比分析,表明振型曲率符号函数加权损伤指标仅需前几阶模态便能进行损伤检测,具有良好的损伤定位能力,并能准确识别损伤程度。 相似文献
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曲率模态在结构损伤识别中有很好的应用。针对模态分析中某几阶曲率模态曲线未能有效地反映损伤的情况,本文提出对曲线进行一次数值微分的处理方法,计算结果表明这种方法能进一步提高曲率模态对损伤的敏感性,是一种很好的辅助处理数据方法。 相似文献
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本文针对输电塔架结构的损伤特点,采用优化等效的方法,建立了具有螺栓松动损伤的输电塔结构的有限元模型,同时提出了此结构螺栓松动损伤诊断基于应变模态的改进的模糊模式识别方法。通过距离贴近度与相似贴近度的双重识别,可达到对输电塔架结构螺栓松动损伤的位置和程度的诊断。对湘江输电塔架结构的数值仿真分析,表明本文提出的损伤诊断方法的结果是令人满意的,具有实际工程应用价值。 相似文献
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Plate structures are employed as important structural components in many engineering applications. Hence, assessing the structural conditions of in-service plate structures is critical to monitoring global structural health. Modal curvature-based damage detection techniques have recently garnered considerable attention from the research community, and have become a promising vibration-based structural health monitoring solution. However, computing errors arise when calculating modal curvatures from lateral mode shapes, which result from unavoidable measurement errors in the mode shapes as identified from lateral vibration signals; this makes curvature-based algorithms that use a lateral measurement only theoretically feasible, but practically infeasible. Therefore, in this study, long-gauge fiber Bragg grating strain sensors are employed to obtain a modal curvature without a numerical differentiation procedure in order to circumvent the computing errors. Several damage indices based on modal curvatures that were developed to locate beam damage are employed. Both numerical and experimental studies are performed to validate the proposed approach. However, although previous studies have reported relative success with the application of these damage indices on a simple beam, only one damage index demonstrated the capability to locate damage when the stiffness of the local region changed near the sensor. 相似文献
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Vibration‐based damage assessment of steel structure using global and local response measurements 
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下载免费PDF全文 Damage assessment of a structure involves acquiring and identifying dynamic characteristics of the structure and using these characteristics to evaluate behavior and performance. In this study, an unsymmetrical three‐story steel structure (fabricated with one weak column in the first floor) was tested on shaking table and subjected to a series of earthquake excitations with increasing level of excitation back to back. Besides, white noise excitation was also applied in between the earthquake excitation to serve as the reference state. Both the traditional sensing system (accelerometer and linear variable differential transformer) and the local optical tracker system were implemented in the structure to collect the vibration‐based responses. For operational modal analysis, structural response from white noise excitation will be used in this study. First, the traditional system identification using global response data is used (multivariate autoregressive (AR)‐model) to extract system natural frequencies and mode shapes from all different set of white noise responses after earthquake excitation. The migration of AR‐coefficient ellipse error from each sensor response was used to identify the damage location. Second, blind source separation technique was used to identify the modal contribution of the structure from each test, which provide information to detect the damage severity. Finally, from the local optical tracker array data, the principal component analysis was applied to quantify the earthquake‐induce local stress of the structural member. Combine the result from damage detection using global measurement and the identified local element stress, one can locate and quantify the damage. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Aging bridges coupled with increasing traffic loads are producing a severe toll on the nation's infrastructure. This has made it necessary to take a closer look at the health of existing bridges and develop automated damage identification methods if possible. Recent works in the field of structural dynamics have shown that damage detection techniques utilizing parameters like mode shapes, modal frequencies and damping ratios can be used to identify damage in structural systems. It is, however, important to be able to establish a baseline model for the structure first, and then a model updating technique can be utilized to evaluate the condition of the structure from time to time. It is with this goal in mind that the authors have decided to establish the process for obtaining a baseline model for a long span bridge. Based on the actual design drawings of a bridge, finite element (FE) models of the bridge in question are developed using SDRC-IDEAS. Three models of the bridge are simulated using Normal Mode Dynamics solver in SDRC-IDEAS to obtain the modal parameters of interest, in this case the modal frequencies and the mode shapes. A modal assurance criteria (MAC) is utilized to compare the different simulated mode shapes and, finally, the modal frequencies that have been obtained from the FE analysis are compared to frequencies that have been obtained from some preliminary field tests. 相似文献
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Structural modal parameter identification and damage diagnosis based on Hilbert-Huang transform 总被引：1，自引：1，他引：0
Traditional modal parameter identifi cation methods have many disadvantages,especially when used for processing nonlinear and non-stationary signals.In addition,they are usually not able to accurately identify the damping ratio and damage.In this study,methods based on the Hilbert-Huang transform(HHT) are investigated for structural modal parameter identifi cation and damage diagnosis.First,mirror extension and prediction via a radial basis function(RBF) neural network are used to restrain the troublesome end-effect issue in empirical mode decomposition(EMD),which is a crucial part of HHT.Then,the approaches based on HHT combined with other techniques,such as the random decrement technique(RDT),natural excitation technique(NExT) and stochastic subspace identifi cation(SSI),are proposed to identify modal parameters of structures.Furthermore,a damage diagnosis method based on the HHT is also proposed.Time-varying instantaneous frequency and instantaneous energy are used to identify the damage evolution of the structure.The relative amplitude of the Hilbert marginal spectrum is used to identify the damage location of the structure.Finally,acceleration records at gauge points from shaking table testing of a 12-story reinforced concrete frame model are taken to validate the proposed approaches.The results show that the proposed approaches based on HHT for modal parameter identifi cation and damage diagnosis are reliable and practical. 相似文献
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选择美国加州大学圣地亚哥分校7层钢筋混凝土剪力墙足尺结构振动台实验,开展结构损伤识别研究,实验采用白噪声、环境振动和不同强度的地震动交替激发,记录地震动激发实验前后的结构反应。基于该记录计算和对比自振频率和振型曲率的变化、剪切波走时及其变化和结构层间位移角,分析发现一层和二层振型曲率较大,走时较长,走时变化也较大,现场检查发现一层和二层的破坏也较为严重,这些参数可用于识别结构损伤程度和定位损伤位置,而自振频率和层间位移角变化仅可反映出结构损伤程度,难以揭示结构损伤位置。 相似文献
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对于弯梁桥支座病害中普遍存在的刚度不足，甚至脱空现象，提出利用平面多阶模态及高斯曲率模态相关系数来识别弯梁桥支座的损伤情况。在理论推导的基础上，以某小半径弯梁桥为研究对象，建立了相关分析模型。分析结果表明:无论单支座损伤，还是多支座损伤，相应支座处的高斯曲率模态相关系数与其它支座位置处的差异明显，可实现支座损伤的准确定位；且支座损伤越严重，相关系数下降越多；支点预偏心和抗扭支承等因素对损伤定位没有影响，相邻控制点处相关系数有所降低，但不会影响支座损伤识别的有效性。 相似文献
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多层及高层框架结构地震损伤诊断的神经网络方法 总被引：12，自引：4，他引：12
本文提出了强震后多层及高层框架结构地震损伤诊断的神经网络方法。文中在提出有结点损伤的梁柱有限元刚度矩阵的基础上，建立了有结点损伤框架结构的有限元模型。通过完好结构和有损伤结构的有限元分析，获取二者应变模态差值作为损伤标识量，并输入径向基（RBF）神经网络进行训练，得到了框架结构结点损伤诊断的神经网络系统。数值仿真分析结果表明，此神经网络可以对多层及高层框架结构结点各种程度的损伤做出成功诊断。 相似文献
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A statistical method with combined uncertain frequency and mode shape data for structural damage identification is proposed. By comparing the measured vibration data before damage or analytical finite element model of the intact structure with those measured after damage, the finite element model is updated so that its vibration characteristic changes are equal to the changes in the measured data as closely as possible. The effects of uncertainties in both the measured vibration data and finite element model are considered as random variables in model updating. The statistical variations of the updated finite element model are derived with perturbation method and Monte Carlo technique. The probabilities of damage existence in the structural members are then defined. The proposed method is applied to a laboratory tested steel cantilever beam and frame structure. The results show that all the damages are identified correctly with high probabilities of damage existence. Discussions are also made on the applicability of the method when no measurement data of intact structure are available. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献