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鉴于频率变化平方比仅是与损伤位置有关的量,利用基于频率变化平方比损伤识别方法不能识别网架结构的损伤程度,本文提出了一种网架结构损伤识别模糊推理方法.该方法以网架结构的前6阶频率变化率作为输入变量,以杆件的损伤程度作为输出变量,通过合理的模糊推理规则使频率变化率与损伤程度建立唯一的联系.经过网架结构的数值模拟分析验证了该... 相似文献
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桥梁结构在运营过程中由于车辆荷载作用和自身存在损伤的情况下都将引起结构动力特性的变化。文章采用瑞利-里兹法,提出了多跨连续桥梁位移试函数的一般表达式,以契比雪夫多项式为级数函数,计算了结构三阶自振频率,通过与ANSYS有限元结果进行了详细的比较分析,检查了所提方法的准确性。从而推广计算了多跨连续梁桥在通行车辆下的有载频率,对车辆、损伤引起的结构频率变化分别进行了定量分析。模拟计算结果表明:连续梁桥在模拟的车载作用下,振动频率最大可以发生接近7%的变化,大于模拟损伤状况下因损伤引起的自振频率变化。 相似文献
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随着U型梁的应用越来越广泛,由于施工缺陷以及服役期间受到环境和荷载的影响,结构的敏感部位会发生不同程度的损伤。为了保障U型梁桥的运营通畅和降低维修成本,就需要对桥梁损伤部位进行准确迅速的识别定位。通过对实验室现有缩尺U形梁进行静力加载试验,同时对空载下的U形梁进行动测试验并采集信号得到损伤前后的模态参数。基于频率和振型这两个结构振动特性,以频率平方比和模态曲率差为指标对道床板损伤部位进行识别。结合有限元模拟与试验结果可知:从频率角度识别U型梁的结果不理想,但模态曲率差对其损伤位置及程度有一定识别能力。 相似文献
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在基于小波包节点能量相对变化量的基础上,采用节点能量平方比αij(n)作为损伤定位依据,对结构损伤进行无模型定位,并通过数值算例验证了该方法的损伤适用性和损伤敏感性。 相似文献
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《四川建筑科学研究》2016,(2)
桥梁损伤识别对于评定桥梁结构的服务状态极其重要。中性轴为中性层与横截面的交线,用来反映梁结构的受力状态与结构状况具有很高的敏感性。本文介绍了中性轴位置理论计算方法,并采用中性轴位置直接测量法对国内某市的桥梁的某一截面中性轴位置变化进行了研究,并进行了损伤分析。分析发现中性轴位置未发生明显的变化,截面未出现损伤。 相似文献
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针对结构损伤问题,采用损伤定位、定量的分阶段识别方法,即利用柔度曲率改变率指标来确定结构损伤的具体位置,然后以频率改变率为输入参数构建神经网络对损伤部位进行程度识别。通过对一个简支梁的仿真计算,表明上述方法能判别损伤位置和程度,且识别精度较高。 相似文献
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针对振型是判断建筑物动力特性的主要参数,采用振型平方差法对结构的损伤进行定位,并就结构损伤对频率及振型的影响进行分析,找出结构损伤与动力特性参数间的关系,从而为判断结构损伤位置提供了参考. 相似文献
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预应力空心方桩具有承载力高、施工方便等优点,在建筑桩基中应用较为广泛。但是由于预应力空心方桩破坏时呈脆性特征,其抗震性能有待进一步研究,为此,通过现场试验对预应力空心方桩和配置非预应力筋后的复合配筋空心方桩的抗震性能进行了研究,结果表明:预应力空心方桩在破坏时表现出脆性破坏的特征,配置非预应力筋后,其脆性破坏特征逐步改善,逐渐过渡到延性破坏;配置非预应力筋可使预应力空心方桩的水平承载力有小幅度的提高,且可以大幅度提高其桩身变形能力;预应力空心方桩存在一个最优的非预应力筋配筋率,该配筋率时其延性和耗能能力最好;可在桩身受力较大处一定范围内配置非预应力筋以提高其在水平地震作用下的抗震性能。 相似文献
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Hamed FATHNEJAT Behrouz AHMADI-NEDUSHAN 《Frontiers of Structural and Civil Engineering》2020,14(4):907
In this study, the performance of an efficient two-stage methodology which is applied in a damage detection system using a surrogate model of the structure has been investigated. In the first stage, in order to locate the damage accurately, the performance of the modal strain energy based index for using different numbers of natural mode shapes has been evaluated using the confusion matrix. In the second stage, to estimate the damage extent, the sensitivity of most used modal properties due to damage, such as natural frequency and flexibility matrix is compared with the mean normalized modal strain energy (MNMSE) of suspected damaged elements. Moreover, a modal property change vector is evaluated using the group method of data handling (GMDH) network as a surrogate model during damage extent estimation by optimization algorithm; in this part of methodology, the performance of the three popular optimization algorithms including particle swarm optimization (PSO), bat algorithm (BA), and colliding bodies optimization (CBO) is examined and in this regard, root mean square deviation (RMSD) based on the modal property change vector has been proposed as an objective function. Furthermore, the effect of noise in the measurement of structural responses by the sensors has also been studied. Finally, in order to achieve the most generalized neural network as a surrogate model, GMDH performance is compared with a properly trained cascade feed-forward neural network (CFNN) with log-sigmoid hidden layer transfer function. The results indicate that the accuracy of damage extent estimation is acceptable in the case of integration of PSO and MNMSE. Moreover, the GMDH model is also more efficient and mimics the behavior of the structure slightly better than CFNN model. 相似文献
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基于振型损伤的高层建筑结构地震破坏准则 总被引:1,自引:0,他引:1
汪梦甫 《工程抗震与加固改造》2008,30(6)
针对高层建筑结构在地震作用下的地震损伤现象,参考国内外房屋建筑结构的损伤分析模型,本文以地震作用下高层建筑结构各阶振型对应的损伤指数为基础,建立了新的高层建筑结构地震破坏准则,通过这些准则计算分析了国内21幢高层建筑结构模拟地震振动台试验模型,并结合振动台试验结果划定了按这些准则进行计算时各种结构破坏状态对应的破损指数范围。探讨了在基于性能的抗震设计中如何应用这些准则的原理与方法,并以日美联合足尺实验模型为例作了说明与论证。 相似文献
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《Structure and Infrastructure Engineering》2013,9(11):1369-1384
This paper presents a framework to assess the potential hurricane damage risks to residential construction. Studies show that hurricane wind, frequency and/or hurricane-induced surge may change as a result of climate change; therefore, hurricane risk assessments should be capable of accounting for the impacts climate change. The framework includes a hurricane wind field model, hurricane-induced surge height model and hurricane vulnerability models. Three case study locations (Miami-Dade County, FL; New Hanover County, NC and Galveston County, TX) are presented for two types of analyses: annual regional loss estimation and event-based regional loss estimation. Demographic information, such as median house value and changes in house numbers, and distribution of houses for different exposures, is used to estimate the time-dependent probability of damage with or without possible climate change-induced change in wind speed, frequency and/or surge height. Through both analyses, it was found that climate change may have a significant impact on regional hurricane damage losses. 相似文献
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Alireza Gharighoran Farhad Daneshjoo Naser Khaji 《Construction and Building Materials》2009,23(6):2167-2176
Damage-induced changes in modal characteristics can be detected using experimental modal analysis. In this article, based on changes in natural frequency, mode shapes, and damping ratios, a methodology for detecting damage location and severity is presented. The damage was induced by application of point load at half span location on the reinforced and post-tensioned concrete beams. The load was gradually increased to obtain different crack patterns to be used in simulation of damage scenarios. Experimental modal analysis was performed on the undamaged and damaged beams. The natural frequency and mode shapes were used to determine the location of damage. The approach is developed at an element level with a conventional finite element (FE) model by Ritz method, which is called Ritz damage detection method (RDDM). The mathematical model for both damped and undamped damaged structures have been established through the eigenvalue equations. The singular value decomposition (SVD) technique is used for determination of damage or sound index. These indexes are sensitive to the change of dynamic characteristics due to damages. This approach is applied to five simply supported post-tensioned concrete beams. The numerical results show that the exact location and severity of damage for different simulated damage scenarios could be efficiency found by the present methodology. 相似文献
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基于Hilbert-Huang变换的结构损伤识别及振动台试验验证 总被引:1,自引:0,他引:1
结构在强烈地震作用下,构件、节点会产生损伤,刚度、强度等力学性能会降低,结构的动力特性也会改变.分析与处理结构振动信号是结构健康监测和损伤识别的重要手段之一.利用Hilbert-Huang变换,提出利用具有时变规律的瞬时频率和瞬时能量识别结构的损伤演化过程,利用可以反映结构振动能量分布规律的Hilbert边际谱的相对幅... 相似文献
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为识别L形管道的局部损伤,根据局部结构的振型、刚度矩阵和固有频率,得到管道局部的模态应变能变化率指标,并利用有限元软件ABAQUS模拟不同参数模型,得到低阶模态数据以及管道各单元的模态应变能变化率。模拟结果表明:采用该损伤指标,能够较好地确定L形管道的损伤位置,并且直管单元比弯曲单元对该指标更敏感;对同一单元不同损伤程度的对比,可以反映其损伤程度的大小;对L形管道不同弯曲角度进行模拟,该指标对不同弯曲角度L形管道的损伤识别具有普遍性;对L形管道不同缺陷长度进行模拟,模态应变能变化率指标在缺陷取周向长度的1/32时达到极限。 相似文献