大跨度悬索桥索鞍无预偏索塔张拉锚跨索股纠偏施工控制

澜沧江悬索桥是国内首次采用索鞍无预偏索塔张拉锚跨索股纠偏方法施工的大跨度悬索桥.利用悬索桥结构理论和有限元非线性分析方法,分析结构在裸塔、主缆施工、主梁吊装到成桥不同阶段的控制参数,建立了张拉纠偏决策确定索塔纠偏量和主缆张拉量--参数测量、数值分析和有限元模型修正的非线性施工控制流程.有效地调整控制了桥梁内力和线型,确保桥梁施工安全和质量.     

基于虚实混合的齿轮箱模态分析研究

通过三维建模软件Pro/E对齿轮箱箱体进行模型的建立,将建立好的几何模型导入到有限元分析软件ANSYS中进行模态分析,可以得到齿轮箱体结构的固有频率和振型.为了验证此模型,通过在实验室搭建齿轮箱体的模态试验平台,在对箱体进行合理布点后,以力锤的敲击作为激励,最终获得齿轮箱体的模态试验结果.将有限元分析的结果与实验结果进行了对比分析,并进一步修正齿轮箱箱体模型参数后,发现两者的结果基本一致,从而验证了通过有限元分析与模态试验相结合的技术路线对箱体结构进行修正的可行性,因此,该方法对齿轮箱体结构及其他结构体的设计与优化有一定的指导意义.     

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。     

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.     

基于试验数据的吊拉组合模型桥梁有限元模型修正

为获得吊拉组合模型桥梁的基准状态,结合子结构与响应面有限元模型修正方法,建立一种新的桥梁结构有限元模型修正方法。依据构造及力学特点,划分子结构并选择待修正参数;基于方差分析,利用参数显著性检验确定待修正参数;用均匀设计方法生成待修正参数样本集,由有限元分析获得对应的响应信息后,建立每一待修正参数与目标值的响应面模型;建立自振频率和位移适应度函数线性组合的联合目标函数,利用模型桥梁的静动力试验数据,由遗传算法获得参数的修正量,实现测试结果与有限元计算结果间误差的最小化。试验结果表明:所提方法能在确保设计参数合理且具有明确物理意义的前提下,对桥梁结构有限元模型实现有效的修正。     

地震作用下结构振动保性能鲁棒H2/H∞控制

针对建筑结构振动控制模型的不确定性,研究了被控建筑结构模型参数不确定性时的保性能鲁棒混合H2/H∞控制问题.将结构模型参数不确定性引入到被控结构状态方程的摄动矩阵之中,基于线性矩阵不等式设计了多目标保性能鲁棒混合H2/H∞鲁棒控制器.该控制器在规定的模型参数变化范围内,使得闭环控制系统同时满足H∞干扰抑制和最优H2性能.最后,以一个缩尺的多层剪切型建筑结构模型为例,给出了保性能鲁棒混合H2/H∞控制问题的设计过程,验证所提控制方法的有效性.数值分析结果表明,所提出的保性能鲁棒混合H2/H∞控制方法的控制效果明显,能有效地减小结构的地震峰值响应,且控制系统对结构参数不确定性有很强的鲁棒性.     

基于静动力测试的混凝土T形梁有限元模型修正

为建立适用于混凝土T形梁的有限元模型,以钢筋混凝土T形简支梁为研究对象,利用联合静动力的有限元模型修正方法对混凝土T形叠合梁进行模型修正.首先利用ANSYS建立混凝土T形简支梁有限元模型,根据工程经验初选混凝土弹性模量等待修正参数.构造实测响应与相应响应差值的目标函数,通过灵敏度分析,筛选待修正参数并设定待修正参数取值区间,在区间内选取5组随机的参数值作为“试验”模型,利用联合静动力的修正方法对参数进行迭代修正,修正后模型的静动力响应计算值与“试验”值吻合较好.在简支梁的基础上,将此修正方法推广到三跨连续梁,修正结果良好,验证了该方法的适用性和准确性.     

A形井架动态特性研究

为研究A形井架的动态特性，对A形井架的自振频率与振型进行了分析．采用随机有限元方法，计算出单元多个结构参数随机摄动时的一、二阶灵敏度，并给出了A形井架随机特征值的具体表达式。     

低矮小开口剪力墙自由振动问题的半解析解

针对低矮小开口剪切型剪力墙,研究基于直接模态摄动法原理的结构动力特性的半解析分析方法。首先把低矮小开口剪力墙视为变截面的剪切型悬臂结构,依据连续系统动力分析原理建立剪切型剪力墙自由振动分析的变系数微分方程;然后利用等截面剪切型悬臂结构模态函数的解析解和直接模态摄动法原理,考虑剪力墙中小开口对系统特征值和主模态所带来的影响,并进行修正;最后应用Ritz变换,将低矮小开口剪力墙的自振特性分析问题转化为一组非线性代数方程的求解问题,进而求得该类剪力墙自振特性的近似半解析解。算例结果表明,该方法对以剪切变形影响为主的低矮小开口剪力墙动力分析简便有效。     

基于荷载试验的圬工拱桥力学分析修正模型研究

以有限元分析模型参数更新理论为基础,提出一种基于荷载试验的圬工拱桥结构力学分析参数的识别方法。该方法参数更新的目标是使试验实测结构各力学效应与有限元模型计算所得理论值最为接近,进而识别出结构体系的各参数;经实例验证,用所提出的方法建立的有限元修正模型可实现对圬工桥梁结构力学效应的分析,从而可为同类桥梁结构承载能力评价和加固改造提供可靠依据。     

在役T构桥梁的有限元模型修正

有限元模型修正是建立精确的基准有限元模型的基础。以在役T构桥梁——324国道乌龙江大桥为工程背景,利用ANSYS软件建立了全桥结构的三维有限元模型,进行了结构静、动力数值模拟分析,并与实测结果进行了比较;结果表明,未修正的有限元模型计算结果与实测结果存在较大误差。通过参数灵敏度分析,确定了对桥梁结构静、动力特性影响均较大的参数;采用零阶和一阶算法,基于自振频率与静力挠度组合的目标函数,对乌龙江大桥有限元模型进行了修正。修正后的有限元模型能较真实地反映结构的实际状态,可作为该桥梁长期健康监测与状态评估的基准有限元模型。     

Candidate model construction of a cable-stayed bridge using parameterised sensitivity-based finite element model updating

An efficient method for constructing multiple candidate finite element (FE) models which are consistent with the measured dynamic properties of a civil structure is presented. A parameterised sensitivity-based FE model updating method was developed to permit a feasible FE model set for the target structure to be produced. In this method, an aggregated multi-objective function, which is defined by the weighted sum of the error functions, is parameterised by its relative weighting factors. By introducing multiple parameter sets for the weighting factors, a number of optimal updated FE models are produced that permit both the natural frequency errors and mode shape errors to be simultaneously minimised. The effectiveness of the proposed method is illustrated by an example using an existing cable-stayed bridge. The findings show that error-minimised, well-distributed FE models can be obtained in terms of modal frequency errors and mode shape errors. The high quality of the candidate model sets is also verified by observations showing that the distributions of the structural parameters are consistent through each updated FE models, and the characteristic features of the target structure such as non-symmetric mode shapes are relatively well captured.     

Estimation of gross weight,suspension stiffness and damping of a loaded truck from bridge measurements

Particle filter method (PFM) based on Bayesian inference gives a reliable estimate of hidden parameters from the noisy measured signal. A new method of vehicle parameter identification based on measured bridge response has been proposed using PFM. An uncoupled iterative technique is utilised for solving bridge vehicle interaction problem which has been used as a forward solution of the PFM. A field test under moving truck has been conducted on an existing pre-stressed concrete bridge to collect response data at different locations. Based on the extracted bridge natural frequencies and measured peak acceleration responses at five sensor locations, finite element model of the tested bridge has been updated using response surface-based model updating technique. In addition to estimation of test truck parameters using measured bridge response, dynamic wheel load induced in the bridge has been determined. Excellent agreement has been found between the measured and reconstructed bridge response using estimated parameters.     

Response surface‐based finite‐element model updating of a historic masonry minaret for operational modal analysis

This study aimed to use the response surface (RS) method for finite element (FE) model updating, using operational modal analysis (OMA). The RS method was utilized to achieve better agreement between the numerical and field‐measured structure response. The OMA technique for the field study was utilized to obtain modal parameters of the selected historic masonry minaret. The natural frequencies and mode shapes were experimentally determined by the enhanced frequency domain decomposition (EFDD) method. The optimum results between the experimental and numerical analyses were found by using the optimization method. The central composite design was used to construct the design of experiments, and the genetic aggregation approach was performed to generate the RS models. After obtaining the RS models, an attempt was made to converge the natural frequency values corresponding to the five‐mode shapes with the frequency values identified by the experimental analysis. ANSYS software was used to perform 3D finite element (FE) modeling of the historic masonry minaret and to numerically identify the natural frequencies and mode shapes of the minaret. The results of the experimental, initial, and updated FE model were compared with each other. Significant differences can be seen when comparing the experimental and analytical results with the initial conditions.     

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.     

Probabilistic Baseline of Finite Element Model of Bridges under Environmental Temperature Changes

The material properties and structural stiffness of actual bridges fluctuate with variations in environmental temperature; therefore, it is not appropriate to use a determined finite element model (FEM) as the baseline model for localizing the structural damage of bridges. To address this issue, we proposed the concept of the probabilistic baseline of FEM of bridges under variable environmental temperature, that is, we established reasonable probability distributions of the physical parameters of bridges that are suitable for damage localization with varying environmental temperature. First, a method is presented to obtain the probabilistic baseline of FEM of bridges, which imports cluster analysis into stochastic FEM updating. Unlike the conventional methods, the measured natural frequencies first are classified into different clusters using the Gaussian mixture method (GMM), with each cluster consisting of measured data that satisfy the same Gaussian distribution. Then, the conventional methods of stochastic FEM updating can be conveniently implemented to obtain the probabilistic baseline of FEM for each cluster. Second, for each cluster, the mean values and covariance of the updating parameters are updated in two sequential steps, and a new approach is proposed for determining the initial covariance of the updating parameters. The results of an actual example show that predetermining a reasonable initial covariance for the updating parameters can accurately and efficiently obtain the updated results. Finally, the effectiveness of the presented method is verified through the monitoring data of an actual bridge.     

Model Updating Technique Based on Modal Participation Factors for Beam Structures

This article proposes a model updating technique based on modal participation factors for a beam structure. In this model updating technique, the error functions of the dynamic characteristic differences between measurement and model are generated as the number of modes under consideration and minimized using the multiobjective optimization techniques. A modal influence factor defined by modal participation factors for each mode is presented for the selection of the best solution from among Pareto solutions. The selection rule represented in this article makes it possible to reflect the contributions of each mode on the behavior of a structure. The model is updated using natural frequencies measured in an impact hammer test of a beam structure and the validity of the updated model is confirmed by the strain responses measured from the test. It is found that the bending stiffness of the beam structure as the parameter for model updating can be identified by the proposed techniques. Furthermore, through comparing the models updated by the simple sum model updating and the technique in this research, it is verified that the proposed technique is more appropriate for the model updating.     

Three-dimensional finite element modelling of long-span cable-stayed bridges

Finite element (FE) modelling is a prominent way to simulate both static and dynamic characteristics of cable-stayed bridges to understand their structural complexities. Many initial FE models have not been successful in the analysis of the structural behaviour of cable-stayed bridges. This paper presents the details of an updated FE modelling procedure for long-span cable-stayed bridges. The design information of Tatara Bridge with an 850-m main span is considered for numerical studies. The dynamic properties of the FE model, including mode shapes and natural frequencies, are compared with field vibration test results to validate the presented modelling process. Sensitivity analysis of structural parameters is also applied to update effective parameters and understand the structural behaviour of the bridge. The new and beneficial aspects presented in this paper regarding FE modelling procedure and finding effective material and structural parameters will be useful for future design and analysis of cable-stayed bridges.     

消能减震建筑结构的附加有效阻尼比估计

为估计一栋实际消能减震建筑结构在地震作用下的附加有效阻尼比,提出了一种基于有限元模型修正技术的阻尼比估计和验证方法。考虑到结构初始有限元模型存在较大模型误差,采用基于结构振动模态参数的直接模型更新方法修正初始有限元模型,其中,对于实测振型不完整问题,利用振型扩阶方法补充完整振型。基于模态应变能概念,利用整体结构模态参数识别值,推导了油阻尼器支撑系统附加给结构的有效阻尼比和有效频率的计算公式,并估计了主体结构的频率和阻尼比。以一组实际地震动监测数据为例,采用建议方法估计有效阻尼比和有效频率,通过对比修正模型的预测响应与实际监测数据,验证了建议方法的有效性。     

Effect of the model updating on the earthquake behavior of steel storage tanks

In this paper, effect of the finite element model updating on the earthquake behavior of steel storage tanks considering fluid-structure interaction is investigated. For this purpose, a cylindrical steel storage tank filled some liquid fuel oil located in Trabzon, Turkey is selected as an example. Initial finite element model of the storage tank is developed by ANSYS software and dynamic characteristics (natural frequencies, and mode shapes) are determined analytically. Ambient vibration tests are conducted on the storage tank under natural excitations to obtain dynamic characteristics (natural frequencies, mode shapes and damping ratios), experimentally. Peak Picking technique in the frequency domain is used to extract experimental dynamic characteristics. When the analytically and experimentally identified dynamic characteristics are compared to each other, some differences are found between both results. To minimize these differences, initial finite element model of the storage tank is updated according to experimental results using some uncertainties modeling parameters such as elasticity modulus. To investigate the effect of finite element model updating on the earthquake behavior of the storage tank, earthquake analyses are performed before and after model updating. In the earthquake analyses, YPT330 component of 1999 Kocaeli earthquake is selected and applied to the models in the horizontal directions. It is seen from the analyses that the displacements and the stresses after model updating are more effective than the displacements and the stresses before model updating.