超大跨径悬索桥的现场振动试验

采用环境脉动法对西堠门大桥进行了现场振动试验,测试了大桥的固有模态.介绍了所采用的测试方法,并通过有限元分析对大桥动力特性进行了试验与理论的相互比较.     

天津柳林大桥全桥有限元动力特性研究

介绍了柳林大桥工程概况和全桥有限元模型建立方法,通过ANSYS程序进行了全桥动力特性分析,得到了大桥前10阶自振模态对应的频率、周期,分析了全桥模态特征,从而为进行大桥抗风、抗震研究提供了依据。     

牛栏江大桥模态测试及数值模拟

模态是结构的固有特性,结构模态参数由结构刚度、质量分布等因素决定,是决定结构动力特性和衡量数值分析结果可靠性的重要参数。本文通过合理选择传感器和数据采集器,克服了信号弱的困难,经现场测试得到牛栏江大桥竖向、顺桥向和横桥向的固有频率,并通过对比分析有限元模拟结果和现场实测结果,证明引桥质量对主跨模态参数影响很小,为实验室中进行主跨刚构部分的地震反应分析和伪动力试验提供了重要基础。     

基于健康监测系统斜拉桥有限元模型修正的实现

目前结构健康监测成为解决工程结构安全性和耐久性的前沿性课题。以深圳湾公路大桥斜拉桥为工程背景,采用健康监测系统提供的数据获得斜拉桥的拉索索力和模态参数。在分析设计变量对模态参数变化的灵敏度特性的基础上对建立的有限元模型进行修正,比较快速有效地得到了能够较好的反映大桥动力特性的基准有限元模型,为大桥的健康监测和损失预警研究提供了基础。     

基于模型分析的健康监测振动测点布置分析

建立了石首长江公路大桥有限元模型,对大桥主梁前10阶振型模态进行分析。利用模态置信准则(MAC)对大桥健康监测系统主梁振动传感器布置进行评价和优化布置,提出3种优化方案,并得出相应结论。结果表明,大桥监测方案中拥有5个测试自由度的振动测点布置并非最优,通过增加测试自由度数量或者在不改变测试自由度数量下进行测点优化,不能同时兼顾经济性和优化效果,而基于模型选择初始测试自由度位置再进行优化的方式可以达到理想效果。     

桥梁水中施工平台钢管桩动力特性分析

介绍了平台钢管桩动力特性的求解方法。由于洪水期水流与钢管桩产生涡激振动,故首先需要分析钢管桩自身的动力特性,也就是确定钢管桩的固有频率。动力特性求解就是模态求解,在详细讨论了模态求解的原理和方法的基础上,对大桥平台钢管桩进行了模态求解分析,并讨论了不同物理参数对结构的固有频率的影响。结果表明,钢管桩的固有频率与其自身长度、桩外径以及管壁厚度成反比。     

基于响应功率谱传递比的应变模态参数识别方法研究

结构工程在建成服役后,其动力灾变和安全服役问题突出。在研究结构动力灾变机理和动力安全性评估时,一个关键问题就是正确地识别结构工作时的动力特性或模态参数。近年来,应变模态参数由于其对结构损伤较位移模态参数具有的更高的灵敏度等优点而受到较为广泛地关注,应变模态参数识别也成为了结构健康监测领域的研究热点。文章对基于功率谱传递比的应变模态参数识别方法进行了研究。论文构建了应变功率谱传递比的概念,证明了应变功率谱传递比函数在系统极点处具有与两测点应变振型之比等价的特性,并将其用于结构应变模态分析。最后,通过数值算例和实验梁振动测试分析验证了方法的准确性和有效性。     

梁桥固有特性测试方法

固有特性（固有频率、阻尼比、振型）是桥梁检测的重要内容。文章对近几年提出的模态测试方法理论进行了阐述,包括模态综合法、复模态法、曲率模态法、应变模态法等。分析了简支梁桥固有特性的解析方法,并应用模态理论,实测了简支梁桥的固有特性。为梁桥固有特性工程实测提供了理论上的准备。     

基于动力性能指标的巴东大桥震后工作状态评估

如今大跨度桥梁的应用越来越广泛,其结构的健康监测和工作状态的评估已成为当今土木工程界研究的热点。近几年来,随着振动测试、模态分析、动力识别等技术的不断发展,为桥梁工作状态评估提供了可靠依据。该文以2013年12月16号发生过地震的巴东长江公路大桥为研究背景,采用环境随机激振法,对桥梁进行基于动力性能指标的振动测试,通过计算机进行模态识别技术得到被测结构的动力特性,进而利用动力性能指标对大桥震后的工作状态进行评估。     

大跨度连续刚构桥模态分析与测试

采用大型有限元软件midas civil 2010对东江南特大桥特征值进行分析,取前3阶竖向振动频率与实际值进行对比,并将桥梁振动模态实验检测方法用于无损检测中,指出采用该方法对桥梁结构进行动力测试,无需封桥,值得推广。     

Environmental effects on the dynamic characteristics of the Gülburnu Highway Bridge

This paper investigates environmental effects on dynamic characteristics of isolated highway bridges constructed with the balanced cantilever method using ambient vibration test. The Gülburnu Highway Bridge located on the Giresun-Espiye state highway is selected as an application. Measurement time, frequency span and effective mode number are selected by considering similar studies found in the literature. The first measurement tests are conducted in June 2009 and traffic over the bridge is used as a source of ambient vibrations to obtain the dynamic characteristics such as natural frequencies, mode shapes and damping ratios. The second measurement tests are conducted in November 2011 using ambient vibrations and the dynamic characteristics are obtained, experimentally. The output-only modal identification of the bridge is effectively carried out using the enhanced frequency domain decomposition method in the frequency domain and stochastic subspace identification method in the time domain. At the end of the study, experimentally identified dynamic characteristics are compared with each other and environmental effects are investigated in detail. The analysis results reveal that the identified natural frequencies provide an effective indication for changes of dynamic characteristics of the bridge due to environmental effects. Significant variability in the identified natural frequencies is changing by up to maximum 14%.     

钢管混凝土拱桥动力特性的有限元分析

桥梁结构的动力特性是结构动力分析、抗震分析的重要参数,采用通用有限元软件ANSYS对朝阳市东大桥钢管混凝土拱桥的动力特性进行了分析,得到了其振型和频率,并对大桥的动力性能做了评价,有助于今后建立大桥的档案和健康诊断评估。     

Investigation on dynamic behaviour of a full-scale reinforced concrete bridge subjected to strong earthquakes using an automated analysis platform

In this paper, the condition of a full-scale concrete bridge subjected to strong earthquakes is evaluated using vibration-based analyses. A new computational toolkit is developed in MATLAB environment for damage identification and long-term monitoring. Two types of parametric and non-parametric analysis methods are carried out on monitoring data. Moreover, a dynamic performance index is proposed based on an AutoRegressive Moving Average with eXogenous excitation (ARMAX) model. This index utilises the response predicted from an ARMAX model to evaluate bridge behaviour during strong earthquakes. Based on the results, a minor but permanent drop of 0.05?Hz in natural frequency of the first transverse and vertical modes is observed after the first strong earthquake. Also, a significant drop in frequency of the first transverse mode is observed during the two strong earthquakes. The results of the index show that the bridge did not follow linear behaviour during the two strong earthquakes as expected from a linear system. A close to flag-shaped force-displacement relationship is also observed during the first strong earthquake that can be an indication of nonlinearity in bridge behaviour. The analysis results illustrate the efficiency of the new monitoring platform for long-term monitoring and management of large datasets.     

Continuous dynamic monitoring of a centenary iron bridge for structural modification assessment

A multi-channel continuous dynamic monitoring system has been installed in a centenary iron arch bridge on late November 2011. The historic infrastructure, completed in 1889 and crossing the Adda river about 50 km far from Milan, is the most important monument of XIX century iron architecture in Italy and is still used as roadway and railway bridge. The monitoring project follows a series of preliminary ambient vibration tests carried out on the bridge since June 2009. The paper describes the bridge structure and its dynamic characteristics identified from the experimental studies developed since 2009, the installed monitoring system and the software developed in LabVIEW for automatically processing the collected data. Subsequently, the tracking of automatically identified natural frequencies over a period of about 18 months is presented and discussed, highlighting the effects of environmental and operational conditions on the bridge dynamic characteristics as well as the detection of structural changes, mainly based on natural frequencies shifts.     

艾溪湖大桥的动力特性分析

以江西南昌艾溪湖大桥为研究对象,采用MIDAS/Civil空间梁格法建立了该桥的空间有限元模型,并对其进行了动力特性分析,得到该桥的自振频率和振型。分析结果显示该桥具有基本周期长、自振频率较低、模态密集、振型相互耦合等特点,为进一步进行地震作用和气动稳定性研究提供了基础,也为艾溪湖大桥动力测试提供理论数据。     

Ambient vibration testing and updating of the finite element model of a simply supported beam bridge

An ambient vibration test on a concrete bridge constructed in 1971 and calibration of its finite element model are presented. The bridge is characterized by a system of post-tensioned and simply supported beams. The dynamic characteristics of the bridge, i.e. natural frequencies, mode shapes and damping ratios were computed from the ambient vibration tests by using the Eigensystem Realization Algorithm (ERA). Then, these characteristics were used to update the finite element model of the bridge by formulating an optimization problem and then using Genetic Algorithms (GA) to solve it. From the results of the ambient vibration test of this type of bridge, it is concluded that two-dimensional mode shapes exist: in the longitudinal and transverse; and these experimentally obtained dynamic characteristics were also achieved in the analytical model through updating. The application of GAs as optimization techniques showed great versatility to optimize any number and type of variables in the model.     

Experimental and analytical system identification of Eynel arch type steel highway bridge

This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the Ayvac?k county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat U?urlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others.     

自锚式悬索桥动力性能研究

结合一座自锚式悬索桥的工程设计实例,建立了该桥的空间力学计算模型,利用子空间迭代法计算该桥梁结构的自振频率和振型,分析了自锚式悬索桥的动力特性,探讨了桩—土相互作用后对结构的影响。     

桥梁防撞系统动力特性分析

研究了桥墩防撞系统的动力特性。首先阐述了空间杆系结构有限元分析的基本原理,然后采用大型商业化软件ANSYS建立了桥墩防撞系统的三维有限元模型。在此基础上,简要阐述了结构动力特性分析的基本原理,研究了桥墩防撞系统的动力特性并分析了结构频率和振型的特点。     

Experimental and analytical system identification of Eynel arch type steel highway bridge

This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the Ayvacık county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat Uğurlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others.