悬索桥主塔结构的有限元模拟方法研究：2.模型修正与验证

本文在文献[1]建立的润扬悬索桥主塔的初始有限元模型基础上,采用基于灵敏度分析的模型参数修正方法,结合主塔动力特性的测试结果对主塔的初始有限元模型进行了动力修正。通过三种修正方案的比较,可以看出考虑梁柱节点刚域的影响以及修正参数的上、下限值约束的修正方案最可行。修正后的润扬悬索桥主塔模型能全面、正确地反映主塔结构的动力特性,可作为主塔结构健康监测与安全评估的基准有限元模型。     

Multi-scale damage analysis for a steel box girder of a long-span cable-stayed bridge

Accurate evaluation of the effect of possible damage in critical components on the dynamic characteristics of a structure is of critical importance in developing a robust structural damage identification scheme for a long-span cable-stayed bridge. The strategies of finite element (FE) modelling of a long-span cable-stayed bridge for multi-scale numerical analysis are first investigated. A multi-scale model of the Runyang cable-stayed bridge is then developed, which is essentially a multi-scale combination of a FE model for modal analysis of the entire bridge structure and FE sub-models for local stress analysis of the selected locations with respect to the substructuring method. The developed three-dimensional global-scale and local-scale FE models of Runyang cable-stayed bridge achieve a good correlation with the measured dynamic properties identified from field ambient vibration tests and stress distributions of a steel box girder measured from vehicle loading tests, on the basis of which the effectiveness of some damage location identification methods, including a modal curvature index, a modal strain energy index and a modal flexibility index, are evaluated. The analysis results show that the effect of the simulated damage in various components of the steel box girder on the dynamic characteristics of a long-span cable-stayed bridge should be properly considered in structural damage analyses using multi-scale numerical computation.     

Calibrating a high-fidelity finite element model of a highway bridge using a multi-variable sensitivity-based optimisation approach

This article presents the implementation of a calibration procedure for a finite element (FE) model of a state highway bridge using sensory data measured on the bridge. The objective is to modify the high-fidelity FE model of the bridge so that its dynamic behaviour matches, as closely as possible, that of the bridge under analysis. The bridge under investigation is a steel–concrete composite bridge that is instrumented with a wireless monitoring system to collect its vibration response under ambient vibrations. A detailed three-dimensional FE model of the bridge was developed to represent the bridge as realistically as possible. The detailed modelling can minimise the amount of uncertainty in the model and the number of parameters that require updating. A multi-variable sensitivity-based objective function is used to minimise the error between the experimentally measured and the FE-computed modal characteristics. An iterative optimisation approach has been undertaken to find the optimum structural parameters of the FE model that minimise the selected objective function. It is shown that developing a high-fidelity FE model may help simplify the model calibration process for a large structure, which is contrary to conventional thinking on the subject.     

桥梁损伤识别的实用模型修正方法研究

对面向损伤识别的桥梁结构模型修正实用方法进行了研究。提出了基于振动特性测量的三步模型修正策略和综合利用通用有限元程序ANSYS的优化功能进行模型修正的方法。为了缩减待修正的参数,根据计算目标函数对每个单元参数的敏感性,进行子结构划分,通过对子结构参数的修正进行结构损伤的大致定位,然后对确定为损伤的子结构的每个单元进行参数修正,进行结构的损伤定量识别和状态评估。修正算法的优化方法采用ANSYS一阶优化方法和随机搜索方法,敏感性分析和模型修正完全基于ANSYS软件进行,较适合于实际工程的应用。为了说明方法的可行性,以某一实际三跨预应力钢筋混凝土连续箱梁桥为仿真算例,以结构模型的单元刚度衰减来模拟损伤,进行损伤识别,达到了较好的效果。     

Uncertainty and Sensitivity Analysis of Damage Identification Results Obtained Using Finite Element Model Updating

Abstract: A full‐scale seven‐story reinforced concrete shear wall building structure was tested on the UCSD‐NEES shake table in the period October 2005–January 2006. The shake table tests were designed so as to damage the building progressively through several historical seismic motions reproduced on the shake table. A sensitivity‐based finite element (FE) model updating method was used to identify damage in the building. The estimation uncertainty in the damage identification results was observed to be significant, which motivated the authors to perform, through numerical simulation, an uncertainty analysis on a set of damage identification results. This study investigates systematically the performance of FE model updating for damage identification. The damaged structure is simulated numerically through a change in stiffness in selected regions of a FE model of the shear wall test structure. The uncertainty of the identified damage (location and extent) due to variability of five input factors is quantified through analysis‐of‐variance (ANOVA) and meta‐modeling. These five input factors are: (1–3) level of uncertainty in the (identified) modal parameters of each of the first three longitudinal modes, (4) spatial density of measurements (number of sensors), and (5) mesh size in the FE model used in the FE model updating procedure (a type of modeling error). A full factorial design of experiments is considered for these five input factors. In addition to ANOVA and meta‐modeling, this study investigates the one‐at‐a‐time sensitivity analysis of the identified damage to the level of uncertainty in the identified modal parameters of the first three longitudinal modes. The results of this investigation demonstrate that the level of confidence in the damage identification results obtained through FE model updating, is a function of not only the level of uncertainty in the identified modal parameters, but also choices made in the design of experiments (e.g., spatial density of measurements) and modeling errors (e.g., mesh size). Therefore, the experiments can be designed so that the more influential input factors (to the total uncertainty/variability of the damage identification results) are set at optimum levels so as to yield more accurate damage identification results.     

钢框架非比例损伤识别

提出能够鉴别损伤位置和截面损伤严重程度的钢框架非比例破坏监测方法。所提出的方法由两部分组成,一是损伤识别,二是损伤严重程度分析。损伤识别和严重程度分析均以结构动力性质的变化作为损伤的判据,以此来确定损伤位置和严重程度。所提方法中损伤判别的重要特点是能够在损伤严重程度分析之前,精确地区分不同的损伤区域。与整个结构尺寸相比,损伤区域相对较小,因此,确定损伤严重程度的计算量更小。检测方法的另一个特点是有些特征值或振型对噪声相对不敏感。采用所提检测方法对几个框架进行验证,结果表明,该方法能够成功地检测及量化截面的损伤。     

Theoretical and experimental modal analysis of the Guangzhou New TV Tower

The Guangzhou New TV Tower (GNTVT) in Guangzhou, China, is a supertall tube-in-tube structure with a total height of 600 m. A complicated structural health monitoring (SHM) system consisting of over 800 sensors has been implemented to the GNTVT for both in-construction and in-service real-time monitoring. By making use of this SHM system, the ambient vibration measurement is carried out in a continuous and long-term manner. This paper presents the analytical and experimental modal analysis of the tower and the field ambient vibration measurement at different construction stages and under different excitation conditions, particularly addressing the following issues: (1) a reduced-order FE model for the GNTVT; (2) field vibration measurement and modal parameter identification of the tower under construction and two environmental excitations (typhoon and earthquake); and (3) comparison of results under different excitation events in the time-frequency domain and correlation between natural frequencies and air temperature using linear regression analysis. The experimental dynamic characteristics of the tower can be used to update the finite element of the tower, so that the updated finite element model of the tower can be obtained, which will serve as the baseline model for future health monitoring and damage detection. They can also be used to verify the effectiveness of vibration control devices installed on the tower.     

采用静态和动态法改进有限元模型进行桥梁评估

通过有限元模型升级,将有限元分析与现场测量相结合,其潜力毋庸置疑。然而,简单化的初始模型和缺少测量可能导致升级的模型参数隐藏了不准确的模型假设,而不是提高实际结构参数的评估。因此,所提出方法的目标主要是在采用非线性优化对参数进行评估之前,借助手工模型的精度消除不精确的模型简化。此外,引进多级响应目标函数,结合不同类型的测量获得参数评估的坚实基础。所提方法被用于世界上最大的Svinesund单孔桥,研究表明采用非线性模型可对模型参数进行精确评估。     

Implications of subsoil-foundation modelling on the dynamic characteristics of a monitored bridge

Model updating based on system identification (SI) results is a well-established procedure to evaluate the reliability of a developed numerical model. In this inverse assessment problem, soil-foundation compliance is often not explicitly considered rigorously during design and/or purely numerical assessment. The present work aims to investigate the correlation between subsoil-foundation stiffness and modal characteristics of bridges, as a means to identify a threshold beyond which rigorous subsoil modelling is a prerequisite for reliable model updating. The second Kavala Ravine Bridge, in Greece, serves as the case study for this purpose for which a reasonably reliable finite element (FE) model is developed and updated based on ambient vibration measurements. Alternative soil profiles and subsequently redesigned foundation systems are then used to examine the effect that the correspondingly variable soil compliance would have on the natural frequencies of the bridge. It is shown that soil stiffness alone is not an adequate proxy to decide on the necessity for subsoil modelling, as the foundation stiffness (particularly in cases of softer soil profiles) tends to balance the dynamic properties of the holistic soil-foundation system. The soil-foundation stiffness is therefore the key parameter that dictates the need for refined modelling of soil–structure interaction in the framework of SI-based model updating.     

基于时-频域信息的结构系统识别方法研究

结构响应的时域、频域信息均可用来对结构模型进行修正。该文提出频域信息与时域信息相结合的方法,对结构参数以及荷载进行评估。首先,从结构测量加速度信息中提取结构的频域特性,对结构模型进行较为粗略的修正,优化结构模型的振型、频率,使其与测量信息一致。其次,利用时域信息,在状态空间对结构运动微分方程进行零阶离散化,采用正则化方法对模型进行荷载识别,同时基于约束优化方法对结构模型参数进行进一步修正。应用模型缩聚方法,保证计算精度的情况下减少结构模型参数修正和荷载识别的计算量。在数值仿真计算中,基于框架结构的不完备地震时程响应记录,对结构损伤状况进行评估。结果证明,即使在有噪声的情况下,该文提出的结构状态方法依然能够很好地识别结构损伤程度、位置。最后,通过14层加层隔震剪力墙结构的振动台试验进一步验证该文提出的结构参数与荷载识别方法。     

考虑局部细节特性的结构多尺度模拟方法研究

本文的目的是研究如何考虑局部细节特性如焊连接部位的应力集中影响来进行结构动力特性和静力响应模拟和分析。为此,采用子结构和约束方程的方法分别建立含局部焊接细节的桥梁结构钢箱梁纵向加劲桁架的不同尺度的有限元模型,并用此有限元模型进行该结构动力特性和静力响应分析,然后与传统有限元模型的分析结果及加劲桁架缩尺实验模型的实测结果进行对比。研究结果表明,采用子结构方法能有效地利用大型商用软件建立该类结构的有限元模型并进行非线性分析,对于大型复杂结构如一个主跨达到千米以上的大跨桥梁结构,如果采用本文提出的建模方法,在桥梁结构的局部焊接细节部分的模拟达到有限元单元特征尺寸为毫米级,则建立的有限元模型实际上已经是一个结构多尺度有限元模型。这样的模型就可用于不同尺度下的结构整体特性分析和局部热点应力分析。     

焊接结构响应的多目标模拟及模型修正敏感参数分析

本文主要研究复杂结构模拟和模型修正过程中的两个关键问题,即多级目标一致逼近模型的建立和模型修正的敏感参数分析.研究过程针对一个焊接结构钢桁架的缩尺试样进行,利用该钢桁架结构试验提供的多目标一致逼近建模和模型修正所需的结构细节和试验测试结果,研究这类焊接结构的多目标模拟过程,使建立的模型能够同时逼近三个测试目标,即钢桁架结构的整体动力特性、构件名义应力和焊接细节处的局部热点应力;并通过影响因素计算分析探讨该模型修正过程中需要考虑的主要敏感参数.研究结果表明,钢桁架结构的约束参数、焊接结构的焊缝厚度和焊缝弹性模量是模型修正中应该考虑的主要参数.以上分析结果为这类结构的多目标模型修正奠定了基础.     

粘钢加固对简支T型梁桥动力特性的影响

以福建安溪清溪大桥为工程背景,首先进行了粘钢加固前后的环境振动测试和刹车等强迫振动测试,并进行了实验模态分析;其次,分别建立了粘钢加固前后全桥的有限元模型,进行了模型参数修正,并比较了加固前后桥梁动力特性的变化;最后,基于修正后的模型,考察了粘贴钢板厚度和高度、T梁横向联结程度、桥面铺装厚度以及主梁腹板损伤程度等参数对粘钢维修加固桥梁动力特性的影响。结果表明:清溪大桥加固前后动力特性测试和分析结果基本吻合,粘钢加固改造能有效提高桥梁的振动频率和整体刚度。     

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.     

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.     

Dynamic investigation of a concrete footbridge using finite element modelling and modal analysis

In this article, the application of a manual updating method for finite element (FE) model updating of a concrete footbridge using modal analysis approach is described in detail. An FE model was developed using DIANA (FEM software package) to estimate the response of structure under free-vibration analysis. Afterwards, ambient vibration test (AVT) was conducted to extract the dynamic properties. The fundamental mode shapes of the structure were successfully identified applying ARTeMIS (modal analysis computer program). The mode shape pairs of initial FE model and a complete set of test results were employed for manual updating. A parametric study was carried out to specify the most sensitive parameters of the model. For this purpose, boundary conditions, mass density and Young's modulus of elasticity were examined as uncertain parameters. Attempts to calibrate the primary FE model revealed that the spring constants of supports were the most effective parameters for updating process. The FE model was calibrated considering three main criteria consisting of combination of natural frequencies/mode shapes and modal assurance criteria (MAC)/mode shapes. The calibration strategy performed in the present study, including parametric study on uncertain parameters of initial FE model, parameter and target response selection and MAC calculation based on modified formulation, has been discussed. The updated FE model and the measured mode shape counterparts exhibited very good correlation.     

Vision-aided three-dimensional damage quantification and finite element model geometric updating for reinforced concrete structures

This article presents a vision-aided framework to achieve three-dimensional (3D) concrete damage quantification and finite element (FE) model geometric updating for reinforced concrete structures. The framework can process images and point clouds to extract damage information and update it in an FE model. First, a mask region convolutional neural network was used to realize highly precise damage detection and segmentation based on images. Second, a 3D point cloud was adopted in conjunction with the processed images for 3D damage qualification. The model-updating method enables an FE model to delete concrete elements to update the variations in volume caused by structural damage. This framework supports interaction with mainstream FE software for further analysis. To demonstrate the efficiency of the proposed framework, it was used in an experiment on a reinforced-concrete shear wall.     

采用半主动摩擦阻尼器进行建筑结构综合振动控制和健康监测：第二部分——数值分析

在第一部分中提出的模型修正及采用半主动摩擦阻尼器进行建筑结构振动控制和损伤监测的综合程序的基础上，对所提程序的可行性和应用问题进行数值研究。首次在建筑案例中采用模型修正计划确定结构参数。对影响模型修正的噪声测量、不完全测量信息和阻尼器刚度进行评估。通过与具有相同局部反馈控制策略但没有Kalman过滤器以及具有全部反馈控制策略情况的对比，评估了带有Kalman过滤器，由局部反馈策略控制的半主动摩擦阻尼器建筑物地震响应的控制性能。确定适宜修正和振动控制模型的最优阻尼器刚度。最后，对不同损坏程度和有无噪声污染区域提出了两种破坏情形，以确保损伤监测方案的精确性。另外，对所提出的损伤监测方案与传统的敏感性方法进行对比，数值结果证明了综合程序的可行性。     

基于灵敏度分析和优化方法的异形钢结构烟囱模型修正

为了给异形钢结构烟囱的抗风、抗震计算及健康监测提供可靠的有限元计算模型,采用钢结构烟囱风洞试验模型的模态参数作为基准,将灵敏度分析和优化方法与大型有限元分析软件相结合修正烟囱结构模型的有限元模型。首先对烟囱结构参数化建模,然后通过灵敏度分析选择合适的优化变量,最后应用一阶优化方法修正烟囱结构的有限元模型。结构构件间连接的过分简化常会带来较大误差,因此烟囱结构的部分连接节点采用半刚性计算模型。结果表明,经过修正后的有限元模型动力计算结果与试验结果非常接近。