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1.
基于频率响应的不同结构损伤识别方法研究   总被引:2,自引:1,他引:1  
为了解决结构损伤中的刚度和质量识别问题,将测量的响应位移应用于结构的损伤识别中,并提出了多频率激励损伤识别方法和改进的单频率激励损伤识别方法。对于多频率激励情况,首先分析了结构损伤的基本理论,然后推导了其刚度损伤指标和质量损伤指标的识别公式;对于单频率激励情况,则首先根据结构的刚度特性和质量特性确定结构损伤的简化定位方法,在此基础上提出了其相应的迭代改进策略,以提高识别的精度。数值仿真结果表明:对于刚度影响占主导地位的桁架结构,多频率激励法对于刚度损伤的识别效果较好,对于质量损伤的识别效果较差;而采用改进的单频率激励识别策略,则可以更好的识别出刚度和质量的损伤,其识别结果优于多频率识别法和简化单频率识别法。  相似文献   

2.
基于改进L-P小波的时变模态参数识别方法   总被引:2,自引:1,他引:1       下载免费PDF全文
研究了基于改进Littlewood-Paley(L-P)小波变换的结构时变模态参数识别方法.用改进的L-P小波对结构动力响应信号进行小波变换,由能量较大的频带所对应的尺度识别结构基本频率及其随时间的变化情况;由某时刻各自由度响应在各阶频率对应尺度上的小波系数的比值识别结构的各阶振型.针对剪切型框架结构,利用识别的频率变化判断结构是否发生损伤以及损伤发生的时间,通过识别损伤前后的一阶振型斜率变化判断损伤发生的位置.该方法不需要激励信息,且有较好的抗噪声能力.  相似文献   

3.
介绍了特征正交分解(Proper Orthogonal Decomposition, POD)的相关理论和一种基于特征正交分解的结构损伤识别方法的基本原理,并利用该识别方法对简支梁结构进行了损伤识别数值研究。研究结果发现:基于特征正交分解的结构损伤识别方法能较好地识别出梁结构的损伤位置,并具有一定的抗噪能力。  相似文献   

4.
改进模态应变能法在混凝土组合箱梁桥损伤诊断中的应用   总被引:4,自引:1,他引:3  
为提高结构损伤识别方法的准确性和对噪声的鲁棒性,将多源信息融合技术引入到结构损伤识别方法中。针对模态应变能法诊断结构损伤一般需要完备模态的特点,采用信息融合技术对各阶模态应变能进行融合,建立了基于信息融合的改进的模态应变能法。通过对一座预应力混凝土组合箱梁桥损伤识别数值算例的分析,可以看出该方法具有良好的损伤敏感性,仅需要较少的低阶模态就可识别结构的早期损伤;同时,该方法具有噪声鲁棒性,当加入噪声等于或小于10%时可以准确识别结构的早期损伤。因此该文提出的基于信息融合的改进的模态应变能法具有较好的工程实用性。  相似文献   

5.
摘要:本文提出了一种基于模型修正的钢管焊接结构焊缝损伤识别方法。利用从发射台骨架试验模型获取的模态参数,选择识别结果中精度较好的模态频率作为模型修正的基准频率。通过对待修正参数的灵敏度分析,运用ANSYS和MATLAB软件对有限元模型进行了修正。以实测模态和计算模态之间的误差建立一个带约束边界非线性最小二乘目标函数,将损伤识别问题转化为优化问题,并采用信赖域方法求解该优化问题。以有限元模型焊接结点单元组弹性模量的降低模拟焊缝损伤,并假定了两种损伤工况,通过对发射台骨架模型的数值仿真及试验研究,结果表明本文提出的损伤识别方法识别效果较为理想,为解决这种复杂焊接结构焊缝损伤识别问题提供了新的思路。  相似文献   

6.
黄民水  朱宏平 《振动与冲击》2012,31(21):168-174
提出了一种考虑噪声影响的基于改进损伤识别因子和遗传算法的结构损伤识别方法。首先,介绍了结构损伤识别的参数化思想,并提出了一种考虑不同模态信息和权重系数的损伤识别因子。然后,在选择算子、交叉算子、变异算子以及自适应交叉和变异等方面对遗传算法进行了改进,并在无噪声情况下,对一简支梁和连续梁进行了损伤识别,识别效果非常好,验证了方法的正确性和有效性。随后,分别考虑了随机噪声和高斯白噪声对简支梁进行损伤识别,发现该方法在噪声水平不是很高的情况下,识别效果很好。最后,在一钢框架基准有限元模型基础上,考虑了四种损伤工况进行了损伤识别,识别结果较好,该方法能够很好地应用于结构的损伤识别和健康监测。  相似文献   

7.
根据观测的结构频率变化,建立了基于人工神经网络的悬臂梁结构损伤识别方法.把结构固有频率的变化率作为BP神经网络的输入参数,对悬臂梁结构模型进行了损伤数值模拟计算.为了提高神经网络的泛化推广能力和收敛速度,将BFGS优化方法应用到神经网络的训练过程中.数值计算结果表明,所建立的结构损伤识别方法具有收敛速度快、识别精度高等特性.  相似文献   

8.
该研究针对空间拱结构损伤识别精度问题,提出了一种空间拱结构小损伤的动态识别方法。该方法在识别过程中考虑损伤区的质量变化的因素来提高了结构损伤识别的精度。在建立的空间拱结构损伤模型中,应用频率和振型的质量因子变化来表示损伤区质量的变化。应用Wittrick-Williams算法对损伤参数进行计算,根据计算结果来判定结构的损伤位置和程度。为了实现应用最少的测量模态和结构振动特性数据对结构损伤精确识别,建立了一个应用遗传算法的优化计算程序对损伤参数优化计算。在该优化程序中,应用初始的随机染色体群代表沿空间拱不同的损伤分布状况。通过对单一损伤、多个损伤区域和不同边界条件下空间拱进行损伤识别案例对所述方法进行验证,并分析解决了对称结构损伤定位唯一性的问题。结果表明,所提出的识别方法对空间拱结构的损伤具有较好的识别效果,所建立的损伤识别程序具有较高的识别精度。  相似文献   

9.
为了提高结构的多损伤识别效率,提出一种先利用归一化条件下的模态应变能变化进行结构损伤定位,然后再利用改进的频率变化法进行损伤定量的两阶段损伤识别方法。该方法首先对损伤前后的单元模态应变能进行归一化处理,提出基于归一化条件下的模态应变能变化率的损伤定位指标并对结构进行准确的损伤定位识别;其次,在确定损伤位置的基础上,建立了只跟损伤单元数目相关的基于比例损伤模型的损伤定量方程,并用最小二乘技术进行损伤程度的求解。为了验证所提方法的有效性,以一个单跨6节平面桁架结构为例进行数值模拟。仿真结果表明,所提方法不但可以准确地识别出结构的损伤位置和程度,而且对测量噪声具有较强的鲁棒性。  相似文献   

10.
以新沂河大桥为工程背景,提出了一种基于节点曲率和小波分析(NCWA)的梁式桥多尺度损伤识别方法。首先基于结构弯矩-曲率基本关系和结构微损伤对其应力重分布影响很小的假定,结合小波分析的消噪功能,采用奇异值分解(SVD)方法求解节点曲率损伤前后的线形矩阵方程,推导了基于节点曲率的损伤指标,并通过简支梁试验验证了该方法的理论可行性,最后新沂河大桥多尺度数值模型试验和动载试验验证了基于NCWA识别方法的损伤敏感性和抗噪性。结果表明:在不考虑噪声干扰作用下,基于节点曲率的损伤识别方法能较好实现结构不同尺度的损伤识别,但小尺度单元区域的识别效果普遍优于大尺度单元区域;在考虑噪声干扰作用下,基于NCWA的损伤识别方法基本能够实现结构小尺度下的损伤识别,小尺度单元区域的比大尺度单元区域的损伤识别抗噪性更好。提出的基于NCWA的多尺度损伤识别方法具有应用到实际工程健康监测中的潜力,可为梁式结构损伤及安全预后奠定必要的基础。  相似文献   

11.
Model reduction is a commonly used method for quickly computing the lower-order eigenvalues and eigenvectors of a structure. This article proposed a direct model reduction method without any iterations. Compared with the existing methods, the proposed technique has two main advantages. The first one is that the explicit expression of the transformation matrix can be directly obtained using a recurrence formula. The second one is that the calculation efficiency of the proposed method is very high because there is no need for iterative calculation. Three types of structure are used as examples to verify the proposed method. It is found that the lower-frequency eigenpairs calculated by the reduced model are very close to the exact ones obtained by the full model. Moreover, the calculation time of the proposed method is much less than that of the existing methods. It has been shown that the proposed method is reliable and effective.  相似文献   

12.
A simple method is proposed to search for all minimal cutsets (MCs ) for imperfect networks reliability subject to both arc and node failures under the condition that all of the MCs in the network with perfect nodes are given in advance. The proposed method does not require re-enumeration for all of the MCs for additional node failure consideration. All of the MC candidates found in the proposed algorithm are actual MCs without any need for further verification. This algorithm is more effective than the existing algorithm in which every MC candidate is not verified as a MC. No identical MCs are found using the proposed algorithm, which does not duplicate MCs and is more efficient than the existing methods. Only simple concepts are used to implement the proposed algorithm, which makes it easier to understand and implement. With considering unreliable nodes, the proposed method is also more realistic and valuable for reliability analysis in an existing network. The correctness of the proposed algorithm will be analyzed and proven. One example is used to illustrate how all MCs are generated in a network with arc and node failures solved using the proposed algorithm.  相似文献   

13.
Outliers are one of the main concerns in statistics. Parametric identification results of ordinary least squares are sensitive to outliers. Many robust estimators have been proposed to overcome this problem but there are still some drawbacks in existing methods. In this paper, a novel probabilistic method is proposed for robust parametric identification and outlier detection in linear regression problems. The crux of this method is to calculate the probability of outlier, which quantifies how probable it is that a data point is an outlier. There are several appealing features of the proposed method. First, not only the optimal values of the parameters and residuals but also the associated uncertainties are taken into account for outlier detection. Second, the size of the dataset is incorporated because it is one of the key variables to determine the probability of obtaining a large-residual data point. Third, the proposed method requires no information on the outlier distribution model. Fourth, the proposed approach provides the probability of outlier. In the illustrative examples, the proposed method is compared with three well-known methods. It turns out that the proposed method is substantially superior and it is capable of robust parametric identification and outlier detection even for very challenging situations.  相似文献   

14.
部分柱顶滑移钢筋混凝土框剪结构   总被引:1,自引:1,他引:0  
吴波  吕文龙  熊伟 《工程力学》2011,(4):82-88,95
从抗倒塌角度出发,提出了部分柱项滑移钢筋混凝士框剪结构的设想,并建议了具体的设计方法及步骤.通过弹塑性分析,初步比较了该类新型结构与常规框剪结构的经济性及弹塑性地震响应.研究结果表明:1)通过柱顶滑移释放部分框架柱的柱顶内力,可在造价略有增加的情况下,使结构具有更好的抗倒塌能力;2)与滑移柱顶相联的摩擦支座的摩擦系数在...  相似文献   

15.
The examination of product characteristics using a statistical tool is an important step in a manufacturing environment to ensure product quality. Several methods are employed for maintaining product quality assurance. Quality control charts, which utilize statistical methods, are normally used to detect special causes. Shewhart control charts are popular; their only limitation is that they are effective in handling only large shifts. For handling small shifts, the cumulative sum (CUSUM) and the exponential weighted moving average (EWMA) are more practical. For handling both small and large shifts, adaptive control charts are used. In this study, we proposed a new adaptive EWMA scheme. This scheme is based on CUSUM accumulation error for detection of wide range of shifts in the process location. The CUSUM features in the proposed scheme help with identification of prior shifts. The proposed scheme uses Huber and Tukey bisquare functions for an efficient shift detection. We have used average run length (ARL) as performance indicator for comparison, and our proposed scheme outperformed some of the existing schemes. An example that uses real‐life data is also provided to demonstrate the implementation of the proposed scheme.  相似文献   

16.
Hong J  Min SW  Lee B 《Applied optics》2012,51(18):4201-4209
Novel integral floating three-dimensional (3D) display methods are proposed for implementing an augmented reality (AR) system. The 3D display for AR requires a long-range focus depth and a see-though property. A system that adopts a concave lens instead of a convex lens is proposed for realizing the integral floating system with a long working distance using a reduced pixel pitch of the elemental image. An investigation that reveals that the location of the central depth plane is restricted by the pixel pitch of the display device is presented. An optical see-through system using a convex half mirror is also proposed for providing 3D images with a proper accommodation response. The concepts of the proposed methods are explained and the validity of system is proved by the experimental results.  相似文献   

17.
In this paper, the integrated production scheduling and vehicle routing problem is considered for a Make-to-Order manufacturer, who has a single machine for production and limited vehicles with capacity constraints for transportation. The objective is to determine production scheduling and vehicle routing, which are two interacted decisions, to minimise the maximum order delivery time. A property on optimal production sequence is proposed first, based on which backward and forward batching methods are developed and are embedded into a proposed genetic algorithm. The proposed genetic algorithm is capable of providing high-quality solutions by determining the two decisions simultaneously. For comparison purpose, a two-stage algorithm is developed, which decomposes the overall problem into two successively solved sub-problems. The experiments show that the proposed genetic algorithm can provide higher quality solutions than the proposed two-stage algorithm and two published algorithms studying related problems.  相似文献   

18.
The individuality of production devices should be taken into account when soft-sensors are designed for parallelized devices. Since it is expressed as differences of the correlation among measured variables, it is useful to cluster samples on the basis of the correlation among variables for adopting a multi-model approach. In addition, changes in process characteristics can be coped with in the same way. In the present work, a new clustering method, referred to as NC-spectral clustering, is proposed by integrating the nearest correlation (NC) method and spectral clustering. Spectral clustering is a graph partitioning method that can be used for sample classification when an affinity matrix of a weighted graph is given. The NC method can detect samples that are similar to the query from the viewpoint of the correlation without a teacher signal. In the proposed method, the NC method is used for constructing the weighted graph that expresses the correlation-based similarities between samples and the constructed graph is partitioned by using spectral clustering. In addition, a new soft-sensor design method is proposed on the basis of the proposed NC-spectral clustering. The usefulness of the proposed methods is demonstrated through a numerical example and a case study of parallelized batch processes. The performance of the proposed correlation-based method is better than that of the conventional distance-based methods.  相似文献   

19.
In the present paper, a solution scheme is proposed for frictionless contact problems of linear elastic bodies, which are discretized using the finite element method with lower order elements. An approach combining the interior‐point method and the semismooth Newton method is proposed. In this method, an initial active set for the semismooth Newton method is obtained from the approximate optimal solution by the interior‐point method. The simplest node‐to‐node contact model is considered in the present paper, that is, pairs of matching nodes exist on the contact surfaces. However, the discussions can be easily extended to a node‐to‐segment or segment‐to‐segment contact model. In order to evaluate the proposed method, a number of illustrative examples of the frictionless contact problem are shown. The proposed combined method is compared with the interior‐point method and the semismooth Newton method. Two numerical examples that are difficult to solve using the semismooth Newton method are solved effectively using the proposed combined method. It is shown that the proposed method converges within far fewer iterations than the semismooth Newton methods or the interior‐point method. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

20.
Li  Z. Sun  L. Ifeachor  E.C. 《Communications, IET》2007,1(5):970-976
Efficient mobility metrics are necessary for mobile ad hoc networks to measure the impact of node mobility on performance. Normally, measuring mobility requires the use of complex localisation systems. A new mobility metric for performance measurements, the intra-vicinity dependency, is proposed. Its main novelty is that it can fully capture the relative motions between a node and its vicinity in a 2D plane, in real-time, using simple triangulation. Variants of this metric are proposed for predicting the performance of networks that follow group and random mobility models (e.g. inter-group inter-meeting times and packet delivery rate). To make the proposed mobility metrics more robust in noisy environments, a calibration method is also proposed for improving accuracy. Experimental results show that, without the help of any localisation systems, the proposed metrics enable a more accurate approximation of the average relative speed between mobile nodes/groups than existing methods. It is also shown that the proposed metrics yield excellent performance when they are used to predict the inter-group inter-meeting times for networks that follow the Rereence point group mobility model and to estimate the packet delivery rate for those that follow the Random Way Point model.  相似文献   

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