Local finite element model updating with forced vibration measurements

Finite element (FE) model updating based on the method of selective sensitivity analysis is applied to a girder bridge. The response patterns are chosen in accordance with the selective sensitivity criteria and result in a set of four independent local girder bridge response patterns. The excitation of these patterns is conducted with a four-shaker system. This effectively reduces the degrees of freedom of the corresponding FE model from 486 to 7. Excitations and responses are measured at three nodes of each selective sensitive pattern. Local finite element model updating is conducted by minimising the influence of the rest of the structure and by maximising the relative sensitivities with the inclusion of the fourth shaker. This excitation is shown to be model independent; therefore, updating is separated from the measurement process. An independent verification shows the ability of the proposed method to identify submodel parameters. The sensitivities of the accelerometers used were very small, which impacted the data quality. Updating results are discussed considering these limits.     

Dynamic test and finite element model updating of bridge structures based on ambient vibration

The dynamic characteristics of bridge structures are the basis of structural dynamic response and seismic analysis, and are also an important target of health condition monitoring. In this paper, a three-dimensional finite-element model is first established for a highway bridge over a railroad on No.312 National Highway. Based on design drawings, the dynamic characteristics of the bridge are studied using finite element analysis and ambient vibration measurements. Thus, a set of data is selected based on sensitivity analysis and optimization theory; the finite element model of the bridge is updated. The numerical and experimental results show that the updated method is more simple and effective, the updated finite element model can reflect the dynamic characteristics of the bridge better, and it can be used to predict the dynamic response under complex external forces. It is also helpful for further damage identification and health condition monitoring. __________ Translated from Chinese Journal of Huazhong University of Science and Technology (Urban Science Edition), 2006, 23(4): 57–60 [译自: 华 中科技大学学报(城市科学版)]     

Effects of model updating on the estimation of stochastic seismic response of a concrete-filled steel tubular arch bridge

The objectives of this paper are to integrate the structural health monitoring (SHM) technique with the structural seismic analysis, and to make the SHM technique serve, benefit and promote the structural seismic analysis integrally. Therefore, considering a concrete-filled steel tubular arch bridge structure, the SHM technique is used to calibrate the finite element (FE) model through the model-updating scheme to minimise the structural response differences caused by FE model errors. Effects of model updating on structural seismic responses are investigated using the stochastic vibration analysis approach. It is observed that effects of model updating are significant on structural seismic responses, and these effects may become more evident in structural nonlinear dynamic analysis. Hence, it is of prime importance to calibrate the FE models through the SHM technique for seismic evaluations of some operational critical structures.     

Structural parameter identification and damage detection for a steel structure using a two-stage finite element model updating method

A two-stage eigensensitivity-based finite element (FE) model updating procedure is developed for structural parameter identification and damage detection for the IASC-ASCE structural health monitoring benchmark steel structure on the basis of ambient vibration measurements. In the first stage, both the weighted least squares and Bayesian estimation methods are adopted for the identification of the connection stiffness of beam-column joints and Young’s modulus of the structure; then the damage detection is conducted via the FE model updating procedure for detecting damaged braces with different damage patterns of the structure. Comparisons between the FE model updated results and the experimental data show that the eigensensitivity-based FE model updating procedure is an effective tool for structural parameter identification and damage detection for steel frame structures.     

结构有限元模型修正的灵敏度分析方法

文章简要介绍了结构有限元修正的灵敏度分析方法的基本原理、研究现状及现存的问题,并对若干改进算法和发展方向进行了展望。     

电机试验平台有限元模态分析

运用ANSYS建立某陀螺稳定平台的三维实体模型,进行合理简化后,建立该平台的有限元模型,采用有限元数值计算方法,计算得到该平台前六阶模态的频率及振型,各阶模态的频率均满足要求,并提出了改善该平台结构动态性能的措施。     

铁路桥变形吸收带有限元分析

对采动区受地表移动影响的铁路桥涵设置柔性材料进行了有限元分析，得到了在框架桥设置橡胶材料变形吸收带可以有效改善采动地表变形引起的附加作用的结论。     

拱桥施工过程的有限元分析

用有限元方法对某拱桥施工过程中的拱架承载力及拱架倒拆进行了分析计算,并根据计算结果提出了建议及改进方法,供类似工程参考借鉴。     

曲线梁桥温度梯度效应的有限元分析

在流动坐标系下，考虑到平面假定，利用能量原理将温度梯度效应转换成曲梁单元的等效节点力，提出了一种适用于有限元法的曲线粱温度梯度效应分析方法，通过算例证明了该方法具有满意的计算精度。     

Damage identification of a large-span concrete cable-stayed bridge based on genetic algorithm

The global stability of a structure, the stiffness of its main girder and concrete tower, and the variation of the forces of its stay cables are key issues to the safety assessment of an in-service cable-stayed bridge. The efficiency and rationality of local elaborate non-damage-identification could be enhanced by the primary damage identification of cable-stayed bridges on the basis of periodic detection of the cable force and strain monitor in key sections of the main girder. The genetic algorithms of damage identification for cable-stayed bridges were investigated in this paper on the basis of the monitor data of the cable force and strain in a key section of the main girder. A damage detection program for complex civil structure was generated to implement the identification of damage location and extent. The deterioration of the structure was calculated according to the variation of monitor data. It is demonstrated that the results of damage identification from the parametric finite element method are accurate. The method had been verified using a long-span concrete cable-stayed bridge in Ningbo, which has been in use for the past four years. Translated from China Civil Engineering Journal, 2006, 39(5): 85–89 [译自: 土木工程学报]     

人行斜拉桥结构有限元分析

通过对人行斜拉桥进行索力测试,并结合有限元模型对比索力变化情况下结构的响应情况,得出索力变化对结构静力及动力响应的影响,通过快速测定索力并进行有限元计算,进而判定桥梁运营状态。     

变截面钢箱梁人行天桥的有限元分析

应用大型通用有限元分析软件ABAQUS,采用壳单元对某变截面钢箱梁人行天桥进行了详细的模拟分析,准确地验算了主梁的强度、变形等,结果表明该分析方法效果较好,可为今后类似工程提供指导。     

遗传算法在钢结构截面优化设计中的应用

将遗传算法应用于钢结构截面优化设计问题的求解;并在此基础上建立了钢结构截面优化数学模型库,通过调用不同的钢结构截面数学模型,可方便地对各种钢结构截面进行优化设计.算例结果表明,该优化算法用于钢结构截面优化设计是有效可行的.     

超高耸钢结构的模态参数识别及模型修正

广州新电视塔(GNTVT)是一座高度为610 m的超高层柔性钢结构,很有必要对其进行健康监测。应用多参考点稳定图算法(M-NExT/ERA)、数据驱动随机子空间识别法(SSI/Data)和增强频域分解法(EFDD),依据GNTVT Benchmark提供的结构振动数据识别广州新电视塔的模态参数,以掌握其动态特性;利用ANSYS建立GNTVT的有限元模型,根据识别得到的实测模态参数,结合遗传算法对GNTVT初始有限元模型进行参数修正,使有限元模型得以正确反映真实结构的动态特性,以供后续健康监测研究之用。     

基于桥梁优化理论的有限元模型修正技术

针对桥梁的试验模态和有限元分析模型存在的误差,提出一套可靠的基准有限元模型,并利用基于优化理论的有限元模型修正技术,对一个短跨桥模型进行损伤识别,通过损伤刚度来定量的描述该短跨桥的损伤程度,并得出了一些有益的结论。     

CFRP/GFRP混杂加固混凝土梁胶层界面应力有限元分析

建立了CFRP/GFRP混杂纤维布加固混凝土梁有限元模型,采用数值方法研究了不同HFRP弹性模量、不同胶层厚度、不同胶层弹性模量下胶层的剪应力、正应力和混凝土梁底面的第一主应力变化情况.通过对比分析,研究这些参数对CFPR/GFRP混杂纤维布加固工程结构界面粘结力学性能的影响,揭示了胶层剪应力、正应力和界面混凝土第一主应力对纤维布剥离破坏的影响.     

Damage detection and rehabilitation on a curvilinear steel box girder bridge by multistage model updating

This paper presents an efficient model-updating method suitable for complex finite element model with shell and solid elements utilising static inspection data. Based on the standard parameter estimation procedure, a simplified parameterisation procedure based on engineering experience and static inspection was used. Moreover, the parameter estimation was conducted by stages according to the sensitivity level of parameters. To verify the effectiveness of the algorithm, a curvilinear steel box girder bridge is taken as a research case study. General damage detection and corresponding rehabilitation are conducted. It indicates that the parameterisation procedure can meet the practical engineering demands. The multistage model-updating method is more effective and efficient than direct model updating, especially when low sensitivity level parameters are removed from the parameter groups. The updated model can contribute to reveal the behaviour of the structure and can be used for related safety assessment and rehabilitation according to the case study. It is proved that the method shown in this paper works well for existing complex structures. It is sufficient for practical engineering demand and can provide useful reference for similar projects.     

大跨度连续刚构桥有限元建模与动力特性分析

本文采用有限元软件ANSYS建立某大跨连续刚构桥有限元模型,通过该模型的模态分析结果和实桥的环境振动测试结果的比较,得出一些有意义结论。     

Fuzzy logic control for a parallel hybrid hydraulic excavator using genetic algorithm

In this paper, fuzzy logic control is put forward in a parallel hybrid hydraulic excavator for the purposes of better energy distribution and higher fuel economy. A mathematical model of parallel hybrid hydraulic excavator is presented in detail, and the parameters of components and overall system are listed and analyzed. The fuzzy logic controller is then designed to cope with energy distribution and management. To achieve better equivalent fuel consumption, genetic algorithm is implemented to fine-tune the membership functions. The control effects are compared between different control strategies, e.g. rule-based control and fine-tuned fuzzy logic control. The results indicate that hybrids with the proposed strategy can improve fuel economy for the excavator without sacrificing any system performance.     

钢框架梁抗火分析有限元模型的建立

介绍了应用有限元法进行钢框架梁抗大设计研究时有限元模型的建立，简述了所研究问题的必要性，总结出将工字钢上下翼缘及中间腹板的实际温度加到模型中去的技巧。