基于简化模型的超高层结构传感器优化布置

对于自由度较多的超高层结构,传感器优化布置时应考虑多阶模态振型.由于存在空间耦合振动,根据振型质量参与系数难以准确选择出结构弱轴方向的高阶振型.基于等效刚度参数识别法,本文提出了一种将有限元模型沿弱轴方向先简化为等效串联多自由度体系,然后根据简化结构的物理参数来计算弱轴方向振型矩阵的方法,有效地解决了这一问题.以某超高层结构为例,根据计算得到的系统振型矩阵,首先由其转置的列主元QR分解得到传感器的初始布置方案,然后以模态置信度(MAC)矩阵的最大非对角元为目标函数,采用逐步累积算法逐步增加可降低此初始布置MAC非对角元的结构自由度,并考虑经济性因素,最终确定出了传感器的布置方案.     

基于有限测点信息的结构损伤识别柔度法

利用有限测点获得结构的模态参数,提出了基于有限测点的结构损伤识别的柔度法。该方法是通过仅考虑结构柔度的灵敏度分析,以结构各自由度的损伤信息为条件,选择对结构柔度变化敏感的自由度为测点,并利用有限测点的信息提出了结构完备模态振型的重建技术。在此基础上,对柔度矩阵做关于结构物理参数变化量的一阶泰勒展开,来确定结构单元的损伤因子对结构进行损伤识别。从而实现利用结构有限测点的模态信息来识别结构的损伤,解决了测试结构的模态振型的不完整给结构的损伤诊断带来的困难。通过数值算例说明了该方法的有效性。     

结构健康监测系统中传感器优化布置组合算法

在对结构健康监测中的传感器优化布置方法进行调研和总结的基础上,针对薄板、壳结构开展传感器优化布置的研究.提出了一种有效的传感器优化布置组合算法,由模态动能法、模态保证准则、遗传算法组合而成.该方法所得的传感器位置主要位于动态响应比较大区域,有利于提高信噪比;同时能够有效地保证模态振型的独立性,可以较完整地获得结构模态信息.针对这种组合算法的有效性采用简易机翼模型从数值计算和实验两方面进行了验证.     

时变环境与损伤耦合下桥梁结构频率及阻尼比的统计分析

对时变环境与损伤耦合下我国某斜拉桥的结构频率及阻尼比进行统计分析,以提高结构损伤识别的精度.首先,利用该桥的长期监测数据,采用环境激励技术结合特征系统实现算法识别该桥梁结构的频率及阻尼比;其次,利用人工神经网络算法建立该桥梁结构的环境温度与结构频率及阻尼比的关系模型;然后,通过统计分析,建立完好状态下该桥梁结构模态参数误差因子的概率分布模型;最后,通过分析不同时段与完好结构状态下该桥梁结构模态参数误差因子的相交概率比识别结构损伤,并利用该桥的实测结果验证所提算法的有效性.     

Exact solution of free vibration of adjacent buildings interconnected by visco-elastic dampers

With consideration of a high-rise coupled building system, a flexible beams-based analytical model is setup to characterize the dynamic behavior of the system. The general motion equation for the two beams interconnected by multiple viscous/visco-elastic dampers is rewritten into a non-dimensional form to identify the minimal set of parameters governing the dynamic characteristics. The corresponding exact solution suitable for arbitrary boundary conditions is presented. Furthermore, the methodology for computing the coefficients of the modal shape function is proposed. As an example, the explicit expression of the modal shape function is derived, provided only one damper is adopted to connect the adjacent buildings. Finally, to validate the proposed methodologies, three case studies are performed, in which the existence of the overdamping and the optimal damping coefficient are revealed. In the case of using one damper in connecting two similar buildings, the estimating equations for the first modal damping ratio are formulated.     

基于ABAQUS的超高层建筑动力弹塑性抗震分析Dynamic elasto-plastic seismic analysis for a super high-rise building based on ABAQUS

某国际金融中心超高层建筑共113层,结构高度423 m。首先,利用S A P2000软件建立结构的有限元模型,通过基于C＃语言开发的导航式接口程序TJU ．SAP2ABAQUS将SAP2000模型转换为 ABAQUS模型。然后,依据规范进行7°多遇、基本和罕遇地震作用下的弹塑性时程分析。最后,模拟了超大震作用下该超高层结构的破坏过程。结果表明,（1）不同强度地震作用下结构的层间位移角均能满足规范限值要求。（2）罕遇地震作用下,结构满足大震不倒的抗震设防要求且有较高的安全储备。（3）超大震作用下,结构竖向刚度变化位置是结构潜在的薄弱部位,在抗震设计时应给予重点关注。     

Virtual testing for modal and damping ratio identification of submerged structures using the PolyMAX algorithm with two-way fluid–structure Interactions

Based on the powerful Computational Structural Dynamics method coupled to a Computational Fluid Dynamics approach, the PolyMAX algorithm is used along with the simulation of two-way fluid–structure interactions, as a new virtual testing method for estimating the structural modal parameters and damping ratios of a vibrating structure in either air or some other fluid. The viscosity and motion of fluid are accounted for, as are the shape of the flow passage and a variety of boundary conditions. The method is shown to be able to simulate the vibration of a structure within a real operating environment in which the structure experiences a specified excitation load while the vibration responses of the structure are obtained through a two-way FSI model. Based on the PolyMAX method for estimating the modal parameters, these vibration responses are processed and analyzed. Finally, the dynamic parameters (i.e., the natural frequencies and the damping ratios) of the vibrating structure are identified. For validation, the natural frequencies and damping ratios of two simple submerged cantilever plates were simulated both in air and water and the simulated results were found to agree closely with experimental data.     

Identification of modal parameters for nonstationary mechanical systems

This paper presents two different approaches to the identification of modal model parameters for nonstationary mechanical systems. The problem is related to model-based structural health monitoring. Damage in this approach is detected by tracking modal parameters of the structure during operation. The detected parameter changes can be indicators of structural damage. The recursive method based on the autoregressive moving-average model of signals and wavelet-transform-based algorithms are presented. The methods are tested using simulated data. Case studies of airplane flutter detection are shown using both methods.     

Dynamics of cable truss via polynomial shape functions

A model for the in-plane dynamic behaviour of a biconcave cable structure, subject to large static deformations and potentially slack harnesses is proposed, based on polynomial shape functions, in line with the classical Ritz method. The model provides a semi-analytical approach to the calculation of natural frequencies and modal shapes of the structure. The proposed formulation leads to an eigenvalue problem, based on a reduced number of degrees of freedom compared with equivalent FEM solutions, providing the basis for fast and accurate sensitivity analysis. The behaviour of the deformed structure is analysed in detail to understand the non-linear effects of non-symmetric mass and load distribution and slack harnesses on natural frequencies and corresponding modal shapes. Results confirm the relevance of the non-linear effects, due to the statically loaded configuration, on the linear vibrations of the structure, in particular evidencing the influence of the slackening of harnesses on modal shapes. Results are compared to analytical models, where available (single sagged cable), and to FEM solutions (for cable trusses with non-uniform mass and load distribution and potentially slack harnesses), providing good agreement.

     

A strain-energy criterion for recognition of identified modes of continuous structural models

In structural modal analysis and modal testing, an important but difficult task is to match the identified natural frequencies and the corresponding modal deflections. This process is called the modal recognition in this paper. There were some treatments towards this problem for the lumped parameter structural models. For the distributed parameter models, however, little research has been reported on the modal recognition problem. In this paper, a strain-energy criterion for modal recognition has been developed. As an example, a distributed parameter model for a two-beam structural system has been formulated, which is expected to simulate the dynamics of a two-arm manipulating system fixed on a shuttle. Transfer matrix method has been used to set up the dynamic equation of the system. The natural frequencies are obtained from the solution of the characteristics equation. Consequently, the mode shape functions are found out analytically.

Strain energy can be viewed as a measure of the structural deformation. When performing modal analysis, we always assume that the structural system is vibrating at a particular natural frequency. The strain energy is, therefore, stored in the deflection caused by such a harmonic motion. The vibration at a particular natural frequency will not produce any strain energy in the other modal components. On the other hand, if a particular mode shape is contributed mostly by the deformation of a specific component of the global structural system, then the great percentage of the total strain energy will be stored in the deformation of that component. Based upon the calculation of the strain energy in the structural components we can find out which component is deformed most and in what motion it is deformed, thereby, the mode shape can be detected. The computer simulation demonstrated that the strain energy indicated an essentially perfect recognition of the identified natural frequencies with the corresponding mode shapes. The creation of the strain-energy criterion consummates the procedure of the distributed parameter modeling, modal identification and parameter estimation.     

On the Investigation of Some Parameter Identification and Experimental Modal Filtering Issues for Nonlinear Reduced Order Models

This paper discusses modal filtering of experimental data and the corresponding identification of linear and nonlinear parameters in reduced order space. Specifically, several experimental configurations will be discussed in order to provide insight into such identification issues as spatial discretization, observability, and the linear independence of the assumed filter or basis. The two experiments considered herein represent different measurement configurations of the same clamped–clamped beam. First, asymmetric inertial loading via asymmetric sensor location was considered, while the second scenario presents a symmetric sensor configuration. Several important conclusions can be drawn from the two experimental scenarios. First, by asymmetrically loading the beam, a corresponding asymmetric beam mode was excited yet not observable. In the second scenario, the symmetric distribution of sensors minimized the impact of the respective asymmetric mode. The resulting spatial information allowed for the proper filtering of the remnants of the asymmetric mode. Nonlinear parameters in modal space as well as the underlying linear parameters were successfully identified simultaneously in both experimental scenarios, although the usefulness of the asymmetrically loaded beam was limited. Finally, successful comparisons were made between the identified reduced order model and experimental response at the beam quarter point using the symmetric case and the beam midpoint using both experimental scenarios.     

有频率禁区的连续体结构拓扑优化

用ICM(独立连续映射)方法建立了以重量为目标、频率为约束的连续体结构拓扑优化模型,并转化为对偶模型利用序列二次规划求解.解决了“棋盘格”现象、网格依赖性、局部模态及模态交换等问题.以重量为目标建立的优化模型同截面及形状优化形成了统一模型,在处理多频率约束及解决模态交换问题上有优势.     

结构动力模型修正方法的比较研究及评估

在实际工程中,由结构动力模型得到的计算值与通过试验获得的测量值间往往存在偏差,为了能够精确预测结构的动力响应,依据测量信息修正存在的动力模型是非常必要的.对现有几种有效的用于结构动力模型修正的理论方法(包括基于敏感性分析的矩阵型法、基于神经网络算法的参数型法和基于遗传优化算法的方法)做了详细的综述;介绍了这些方法的步骤和研究进展;并分析了这些动力模型修正方法在工程运用中存在的一些实际问题,如不完整的模态测量值、模型修正的鲁棒性、模型修正的计算效率和收敛性等.最后,通过对一实际的五层钢框架的动力模型修正,比较了这几种方法的优缺点,提出了今后需要解决的问题.      

基于可靠度和功能的框架—剪力墙结构抗震优化设计

作为结构抗震设计的发展方向,近年来基于功能的结构抗震设计思想引起了地震工程界的广泛重视,并取得了迅速发展,其基本思想就是在充分考虑结构抗震设计中的不确定性的情况下,采用基于“投资－效益”准则和强调结构“个性”的设计,本文讨论了基于可靠度和功能的结构抗震优化设计思想,建立了钢筋混凝土呆－剪力墙结构 抗震优化设计模型,给出了结构可靠度的近似计算方法,最后计算了钢筋混凝土框架－剪力墙的算例。     

Identification of Damping and Dynamic Young’s Modulus of a Structural Adhesive Using Radial Basis Function Neural Networks and Modal Data

In this paper, the radial basis function neural networks (RBFNN) was applied to the problem of identifying dynamic Young’s modulus and damping characteristic of a structural adhesive, using modal data. To identify Young’s modulus from undamped model, an appropriate RBFNN using modal data (mode shape and natural frequency) in each mode is developed. Based on a previous work, in order to identify loss factor, two approaches adopted in the identification process. In the first one, a two stage RBFNN is developed. In stage I, Young’s modulus is identified from undamped model and in stage II using the results of stage I an appropriate RBFNN is developed in each mode for identification of loss factor by implementing real parts of eigenvalues of damped model. In the second approach, a one stage RBFNN is developed using real and imaginary parts of eigenvalues of damped model to identify Young’s moduli and loss factors simultaneously. The repeatability and consistency of the method is proved by repeating the identification process for several times. The validity of results is proved by comparing the results with those identified in a previous work.     

基于改进灰狼优化算法的结构损伤识别

结合模态柔度矩阵、广义模态柔度矩阵和振型三个识别精度较好的指标,构造新的目标函数求解损伤识别问题。通过Nelson方法求解得到的频率与振型的导数,得到对结构刚度发生变化时更具敏感性的位置,然后在这些位置布置传感器以提取结构信息。针对原有的灰狼算法虽然全局搜索能力强,但是存在局部搜索精度差的问题,本文从初始种群和收敛因子等方面着手,改善灰狼算法的局部搜索能力及收敛速度。最后利用提出的方法,通过识别梁模型及桁架模型中的损伤单元说明本文方法的有效性。     

利用Kriging方法进行结构模型修改

结构模型修改已经演化为一个多学科的研究课题，本文将该问题处理为确定从模态参数到模型参数之间的映射问题，并利用起源于地质统计学的Kriging技术实现该映射。对于一实际钢结构，通过实验测量得到了全部摸态数据，利用部分测量得到的模态数据进行了模型修改的实验研究，实验结果表明，利用修改后模型计算得到的全部摸态数据与测量结果吻合良好，表明该模型修改方法是可行的；同时该方法表现出了与基于神经网络的修改方法的互补特性。     

基于模态力谱的不同风谱风振效应差异分析

为明确风谱对顺风向风振效应的影响,选择工程常用的Davenport谱与Simiu谱,基于随机振动理论,对一座典型独柱式避雷针的风振效应进行了多种工况的频域计算,并提出采用模态力谱而非直接使用风谱判断风振响应的大小。研究表明:Davenport谱不随高度变化,而Simiu谱随高度变化,难以通过风谱的对比直接确定各自所得风振响应的大小,但模态力谱可综合考虑整个结构表面脉动风场的贡献,对于以单一模态为主的响应,可准确评价不同风谱所得风振响应的大小;在本文各种工况下,Davenport谱所得背景响应基本上略小于Simiu谱结果,但Davenport谱所得前2阶模态力谱在结构对应频率位置的谱值均大于Simiu谱所得模态力谱,故前者所得共振分量和总脉动响应均偏大。     

网壳结构健康监测中的传感器优化布置

针对网壳结构健康监测提出了一种以损伤可识别性与模态可观测性相协调为目标的传感器优化布置的方法.由于模态数目的选取对基于损伤灵敏度分析的传感器优化布置有很大的影响,因此本文建立了一种同时包含模态独立性信息和损伤灵敏度信息的Fisher信息矩阵,并选取合适的模态数目,然后发展了一种以信息矩阵最大和条件数最小为准则的多目标优化算法.空间网壳数值算例表明,本文提出的传感器优化方法能简单、有效地为空间结构传感器优化布置提供可行方案.     

Identification of inertia properties from the results of output-only modal analysis

Accurate knowledge of the rigid body properties of a structure including the mass, the location of mass center and the moments of inertia is important in machine design, vibration analysis, optimization and modeling of mechanical systems. However, estimation of these properties through theoretical methods is difficult when the structure has a complicated shape. In practice, the inertia properties can be estimated using the conventional modal testing methods by extracting the rigid body modes when the structure is tested in free-free boundary condition. However, all the rigid body modes are not always detectable, due to this fact that the structure is not excited at all degrees of freedom. In order to obtain all of the rigid body modes, many activities have been conducted for selecting the type and location of excitation without much success. In operational modal analysis (OMA), the structure can be excited at any arbitrary point and in different directions. In this paper, a new approach is introduced for estimation of the inertia properties from OMA. The data from OMA are adequate to extract all the rigid body modes of structure. A modal method is used for estimating the inertia properties from the rigid body modes extracted from OMA. The suggested approach is applied to a numerical model of a two-dimensional steel beam as well as a numerical model of a 3D frame and the accuracy of results is evaluated. It is shown that OMA can provide enough data to extract the inertia properties. A real beam is also tested in order to evaluate the performance of the method in practice, needless of a complicated procedure as for conventional methods.