基于MAC准则的模拟退火算法传感器优化布置研究

基于模态置信度MAC准则，通过建立优化约束条件及目标函数，构建完整的优化数学模型，引入模拟退火算法的抽样和退火过程，使系统能量逐渐降低并达到新的平衡点，如此反复获得模型最优解，基此建立传感器优化配置法。通过某拱塔斜拉桥主梁加速度传感器优化布置工程的实例分析，证明基于MAC准则的模拟退火算法在求解传感器优化布置上，具有优良的并行性和搜索全局的功能。     

斜拉桥风振减振基于H_2范数的ATMD和传感器配置优化

斜拉桥在风荷载作用下易出现多模态参与的大幅振动,宜采用主动式ATMD(active tuned mass damper)减振。针对斜拉桥风振减振设计中的ATMD及传感器的位置和数量配置问题,在建立风荷载作用下斜拉桥与ATMD组合系统模型的基础上,用模态坐标表示H2范数,提出包括外激励影响的分别针对作动器和传感器配置优化的H2范数指标,推导ATMD对结构的共振激振模型,考虑ATMD和加速度传感器的动力性能并对配置指标进行修正,建立能够以开环方式有效实现ATMD和加速度传感器配置的优化方法。以南京长江第三大桥的风振减振为例,定量分析ATMD和加速度传感器的优化位置和数量。结果表明,采用考虑外激励权重的H2范数指标,并结合考虑ATMD动力性能,能够有效实现针对结构多模态参与的风振减振的ATMD和加速度传感器的配置优化。     

基于遗传-模拟退火算法的单层球面网壳结构破坏模式优化

将遗传算法和模拟退火算法相结合,以遗传算法作为基础,将模拟退火机制融入其中,提出遗传-模拟退火算法(GASA)。通过三个经典函数最小值求解,表明混合算法在优化行为、优化效率及稳定性方面均具有明显优势。以构件截面为优化变量,应用构形易损性理论,以结构集簇过程中自由簇构形度Q标准差最小为优化目标,建立单层球面网壳结构倒塌破坏模式优化模型。以一个原型跨度75m、相似比1∶10的单层球壳振动台试验模型为例,采用GASA算法对此试验模型进行倒塌模式优化分析,通过优化前后自由簇构形度变化规律和加速度时程分析结果的对比,表明提出的优化方法及优化模型能够实现单层球面网壳在地震作用下的倒塌模式从无征兆的动力失稳破坏转化为承载力强度破坏。     

结构台阵布设方法在某框架结构中的比较研究

对于高层结构观测台阵,传感器优化布设时应建立具体的量化指标以避免盲目性和主观性。介绍了结构地震反应观测台阵的布设要点和两种传感器优化布设方法,提出改进的MAC法。以某高层框架结构为例,根据有限元模型计算得到振型信息,用有效独立法和模态置信度方法对结构进行优化布设分析,综合考虑优化指标和经济性因素,确定布设方案。     

高铁站房健康监测中传感器优化布置研究

高铁站房形式多样,结构复杂,节点众多,其动力及静力特性的获取均有重要意义.本文分别采用基于结构动力性能及静力性能的传感器布置方法,对高铁站房加速度及应变传感器的布置规律进行了研究.针对高铁站房的结构特点,根据杆件位置将其分成主要构件及一般构件,构建位移控制目标函数,采用基于蒙特卡洛法的构件敏感性分析进行应变传感器优化布置,采用有效独立法进行加速度传感器优化布置.结果 表明,对主体结构起到主要支撑作用的竖向构件以及水平构件的根部位置布置应变传感器,结构模态位移较大位置布置加速度传感器,体现了结构的模态特征.研究成果可为高铁站房及其他公共建筑的传感器优化布置提供参考.     

广州黄埔大桥南汊桥健康监测方案

采用有限元通用程序ANSYS对该桥进行静力与动力分析确定传感器的布设位置，并依据计算的前20阶动力特性结果，采用遗传算法（GA）进行传感器的优化布设，选用精度较高的光纤光栅传感器，能够满足对桥梁长期监测的需要。     

基于多目标遗传算法的阻尼器抗震加固方案研究

通过对快速非支配排序遗传算法(NSGA-Ⅱ)的改进,提出了基于阻尼器空间优化布设的抗震加固方法。采用成对单点交叉改进NSGA-Ⅱ算法的交叉算子,利用基因数匹配改进变异算子,使所有个体含某特定基因的个数在进化迭代过程中始终保持不变,以分析阻尼器个数保持不变情况下的最优布设位置。针对多目标优化可能得到多个Pareto最优解以及地震动输入特性不同导致不同优化布设方案的问题,采用重复概率最大化确定最终的抗震加固方案。单跨混凝土框架结构数值算例分析结果表明,改进NSGA-Ⅱ算法布设的阻尼器能有效减小结构的最大层间位移角和加速度响应;从布设跨数来看,阻尼器通常优先布设在边榀框架和中间榀框架中;从布设层数来看,阻尼器优先布设在中间层。     

基于DDMF/ADMF评价振型参与系数对TMD性能的影响

根据振型降阶技术 ,导出了设置调谐质量阻尼器 (TMD)MDOF结构的位移和加速度动力放大系数 (DDMF/ADMF)。于是TMD的最优化准则可定义为最大位移和加速度动力放大系数最小值的最小化。利用定义的优化准则 ,研究不同振型参与系数值对TMD的最优参数与有效性的影响。     

用粒子群算法选择体育馆监测系统中传感器的最优布点

如何合理、有效地确定传感器的位置,是结构健康监测系统正常、高效运行的前提.基于模态能量和粒子群算法进行传感器优化布置研究.首先,讨论了粒子群算法的基本原理和优点;其次,根据结构模态应变能的大小挑选出结构的主要贡献模态,进而确定监测模态阶数;然后,针对不同的传感器类型,基于位移模态定义适用于加速度传感器的适应度函数,基于应变模态定义适用于应变传感器的适应度函数;最后,以西宁市体育馆钢结构为工程背景,采用粒子群算法对其监测系统中加速度传感器和应变传感器分别进行优化布置.结果表明,该方法优化结果稳定可靠且收敛迅速.     

考虑参数随机性的高层建筑风振舒适度的非线性黏滞阻尼器优化布设

以顶层加速度作为概率特征量，建立目标函数，分别采用基于随机等效线性化系统的频域方法和基于概率密度演化理论的非线性系统时域方法，进行了考虑结构参数随机性的高层建筑风振舒适度控制的黏滞阻尼器优化布设研究。结果表明：在总黏滞阻尼器系数相同的条件下，以顶层加速度标准差和失效概率为目标函数的黏滞阻尼器优化布设方案，在确定性激励作用下均能显著降低结构的风振响应，且相对于未优化的阻尼器均匀满布方案更经济、更有效。以加速度标准差为目标函数的传统阻尼器优化布设本质上是确定性分析方法，对结构可靠度的提高作用有限，而以加速度失效概率为目标函数的阻尼器优化布设，以结构响应的概率密度函数为优化对象，能显著地提高结构的可靠度，有利于改善高层建筑结构的风振舒适度性能。     

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.     

Moving train loads identification on a continuous steel truss girder by using dynamic displacement influence line method

This paper presents a dynamic displacement influence line method for moving load identification on bridge. The finite element model of Poyang Lake continuous truss bridge-train systems is established and the dispersed modal shapes are acquired by modal analysis. Multi-axle moving train loads are identified with simulated annealing genetic algorithm by minimizing the errors between the measured displacements and the reconstructed displacements from the identified moving loads. In the identification process, the dynamic displacement influence line technique is used to calculate the time history displacement responses of the bridge to avoid solving equations of motion of the bridge repetitively. Several important parameters of the bridge-train system are discussed to investigate their effects on the proposed method. The results demonstrate that the proposed method is an accurate and efficient method for moving train load identification on complex bridges.     

Modal Identification Study of Vincent Thomas Bridge Using Simulated Wind-Induced Ambient Vibration Data

Abstract:   In this article, wind-induced vibration response of Vincent Thomas Bridge, a suspension bridge located in San Pedro near Los Angeles, California, is simulated using a detailed three-dimensional finite element model of the bridge and a state-of-the-art stochastic wind excitation model. Based on the simulated wind-induced vibration data, the modal parameters (natural frequencies, damping ratios, and mode shapes) of the bridge are identified using the data-driven stochastic subspace identification method. The identified modal parameters are verified by the computed eigenproperties of the bridge model. Finally, effects of measurement noise on the system identification results are studied by adding zero-mean Gaussian white noise processes to the simulated response data. Statistical properties of the identified modal parameters are investigated under an increasing level of measurement noise. The framework presented in this article will allow us to investigate the effects of various realistic damage scenarios in long-span cable-supported (suspension and cable-stayed) bridges on changes in modal identification results. Such studies are required to develop robust and reliable vibration-based structural health monitoring methods for this type of bridge, which is a long-term research objective of the authors.     

Operational modal testing and FE model tuning of a cable-stayed bridge

The paper presents the results obtained from the application of different output-only modal identification techniques to ambient response data collected in two dynamic tests of a cable-stayed bridge and the subsequent finite element model correlation analysis. The first test, performed by using a traditional data acquisition system with servo-accelerometers, was aimed at investigating the vertical dynamic characteristics of the bridge. In the second test, an innovative radar vibrometer was used for non-contact measurement of deflection time series of the forestays and the identification of local natural frequencies of the stay cables.In the theoretical study, vibration modes were determined using a 3D Finite Element model of the bridge and the information obtained from the field tests, combined with a classic system identification technique, provided a linear elastic model, accurately fitting the modal parameters of the bridge in its present condition.     

大跨度混凝土斜拉桥模态试验技术研究

随着大跨度斜拉桥建设的迅速发展,试验模态分析对于验证设计、建立结构动力学模型以及桥梁安全运行的状态评估具有重要意义。斜拉桥是由索、梁和塔三种受力特点完全不同的构件组成的组合体系,尤其是混凝土斜拉桥由于恒载内力较钢斜拉桥大很多,且振动信号衰减更明显,其模态试验比其它桥型更加困难。本文通过研究混凝土斜拉桥的模态参数特点,发展了一种包含两种方式基于环境激励的桥梁模态试验方法(UINO法),提出了利用互功率谱法进行模态参数识别的分析技术,并以此为基础开发了桥梁模态试验专用软件系统QL-SYMT。通过多座大跨度混凝土斜拉桥的模态试验证明,该系统不仅能有效识别出桥梁的模态参数而且方便易行。     

大跨度预应力混凝土斜拉桥的动力特性研究

以一座大跨度预应力混凝土斜拉桥为例,阐述了斜拉桥动力分析中所采用的几种有限元模型,并根据通用程序建立了典型斜拉桥的三维空间有限元模型,详细分析了该典型斜拉桥结构的动力特性。研究表明:典型斜拉桥结构固有频率很低,模态密集,存在很多耦合振动的情况。     

大跨度半漂浮体系斜拉桥动力特性分析

以某大跨度半漂浮体系斜拉桥为例,采用MIDAS/2010建立有限元模型,桥塔、主梁采用6个自由度的梁单元模拟,斜拉索采用3个自由度的桁架单元模拟,采用子空间迭代法对该桥进行了动力特性分析,所得结果可为设计提供有益指导。     

列车荷载作用下铁路斜拉桥索-梁相关振动研究

为了研究大跨度铁路斜拉桥的索-梁相关振动,基于拉索非线性振动理论,开发了有限元索动力单元,该单元在静力计算中为普通直杆单元,动力特性计算中可以计算拉索局部自振频率,动力时程计算中可以计算拉索非线性振动与整体结构振动的相互作用;编制了计算程序,建立了大跨度铁路斜拉桥有限元模型,同时使用索动力单元模拟斜拉索,最后研究了列车通过斜拉桥时梁、塔的带动下拉索发生索-梁相关振动的特性。结果表明:对于大跨度铁路斜拉桥,列车在设计速度范围内通过桥梁时索-梁相关振动不会导致拉索产生大幅振动。     

超大跨径斜拉桥受力特性分析

就1 600 m斜拉桥在方案试设计过程中遇到的问题进行了一些探讨,对斜拉桥跨径增大后在动力特性方面表现出与常规斜拉桥的不同进行了概念分析;此外,从静力和动力的角度分析了1 600 m斜拉桥在施工长悬臂阶段的受力情况,验证了最大单悬臂状态的施工安全性。     

Influence of Stabilizing Cables on Seismic Response of a Multispan Cable-Stayed Bridge

Abstract:   A recent trend in the design of long-span bridges is multispan cable-stayed bridges with three or more towers. A critical problem of multispan cable-stayed bridges is the stabilization of the central tower(s), which has resulted in increasing application of stabilizing cables. The Ting Kau Bridge in Hong Kong is one of a few multispan cable-stayed bridges adopting stabilizing cables ever built. In this article, the dynamic properties of multispan cable-stayed bridges with stabilizing cables and the effect of stabilizing cables on bridge seismic response are studied by referring to the Ting Kau Bridge. Based on a validated 3D finite-element model, modal analysis is conducted which shows that the longitudinal stabilizing cables bring about a number of global modes with strong modal interaction among the deck, towers, and cables. The seismic response and internal force in the central tower are found to be much larger than those in the side towers. The longitudinal stabilizing cables are very effective in reducing the internal force in the central tower generated by longitudinal earthquake excitation, but insignificantly affect the seismic response in the bridge deck and side towers. As a whole, the stabilizing cables act favorably in the reduction of seismic response of the bridge.