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《应用力学学报》2016,(5)
针对有限元建模中由于各种误差(如建模误差等)会给计算结果精度带来影响的问题,提出了一种利用模型修正来提高有限元计算结果精度的方法。首次使用了一阶优化方法,以所测试的模态频率和振型为参考,对有限元模型进行修正。首先,以某航空发动机模拟机匣为研究对象,对其进行模态测试,得到其模态频率和振型。然后,以机匣的前10阶计算模态频率与测试模态频率之间误差最小为优化目标,使用Nastran软件对各部件有限元模型中单元的弹性模量进行了修正,并计算了模型修正前后的机匣模态频率和振型,同时与测试模态频率和振型进行对比。结果表明,修正后的有限元模型计算结果与测试结果吻合良好,二者模态振型一致,模态频率的最大误差不超过1%。由此说明修正弹性模量的模型修正方法合理、可行,适用于工程上大型复杂结构的有限元准确建模。 相似文献
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利用振动模态测量值和神经网络方法的结构损伤识别研究 总被引:7,自引:1,他引:7
提出了一种基于模态测量参数和神经网络的结构损伤检测方法,建造了两种输入方式的BP神经网络,即自振频率以及结合自振频率与振型,并讨论了不同数量的输入信息对结构损伤检测精度和计算效率的影响。证明了输入的参数越多,神经网络就越聪明,训练的收敛速度越快;以及在保证一定的测量精度的情况下,基于频率与振型的损伤识别结果要好于基于频率的检测结果。最后,通过对3层框架模型的4种损伤工况下的结构损伤检测结果的分析,认为利用模态测量参数和神经网络方法能够准确地识别结构损伤的位置,而且能较精确地识别结构损伤的大小。 相似文献
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针对大型可展开环形桁架天线结构开展了模态实验和有限元仿真分析。首先设计加工了环形桁架实验模型,采用锤击法对自由边界条件下环形桁架结构进行了实验模态分析,得到环形桁架结构的前六阶固有频率及其对应模态振型,并通过模态置信准则对实验结果进行了可靠性分析。其次,建立了环形桁架实验模型的有限元模型并进行模态分析,仿真得到其前六阶固有频率和模态振型。最后详细对比分析了实验结果与有限元仿真结果。结果表明:二者固有频率误差小于5%,且实验模态振型与有限元仿真模态振型一致,证明了本文分析结果真实可靠;同时,分析得到了环形桁架结构第一、二阶振型为椭圆形,第三、四阶振型为三角形,第五、六阶振型为四边形。 相似文献
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近海风电支撑结构的自振特性是此类结构抗震设计的基础.以某海上风电场1.5MW风电基础支撑体系为背景,考虑流固耦合效应,采用有限元方法对近海风电支撑体系的自振频率和振型进行了计算分析.文中首先将单桩无水工况的数值结果与解析结果做了比较,验证了本文有限元模型的准确性.在此基础上,分单桩有水、单桩无水、四桩有水和四桩无水四种工况进行了支撑体系的自振特性分析,给出了前十阶自振频率和振型,探讨了势流体水层对近海风电支撑体系自振特性的影响.结果表明:水层的存在对单桩体系的前两阶自振频率以及四桩体系的前四阶自振频率影响甚小;总体而言,水层对单桩体系三阶以后的自振频率的影响要明显大于对四桩体系五阶以后的自振频率的影响;本文选取的近海风电支撑体系的各阶频率均能有效避开马达转动频率和叶轮扫略频率. 相似文献
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大范围运动细长柔性空间结构动力学特性分析 总被引:2,自引:2,他引:0
自由-自由边界无约束状态的细长柔性空间结构大范围运动时的动力学特性对整体结构运动分析和运动控制系统设计具有极其重要的作用。通过浮动坐标系建立结构的运动学关系;借助假设模态法对结构变形进行变量分离;利用Lagrange’s方程建立了结构的刚柔耦合振动方程;再通过Rayleigh-Ritz法,以无大范围运动时的振型函数作为基本解组,得到了大范围运动影响下的结构振动特征方程,求解该方程得到了结构频率和振型。通过几组数值算例的对比分析,指出了非耦合模型和耦合模型下结构频率及振型之间的差异。 相似文献
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粘滞阻尼器减震结构非线性随机振动的时域显式降维迭代随机模拟法 总被引:1,自引:0,他引:1
粘滞阻尼器在大型复杂结构减震设计中应用广泛。由于粘滞阻尼器的非线性阻尼力特性,粘滞阻尼器减震结构非平稳随机地震反应分析是一个典型的局部非线性随机振动问题。利用减震结构动力响应时域显式表达式的降维列式优势,仅针对与粘滞阻尼器相关的局部自由度进行非线性迭代计算,提出了局部非线性随机振动问题的时域显式降维迭代随机模拟法,为设置粘滞阻尼器的大型复杂减震结构非线性地震反应分析提供一种高效的随机振动方法。以安装了四个纵桥向粘滞阻尼器的某主跨1200m悬索桥为工程实例,开展E2水准地震激励下的非线性随机振动分析。计算结果显示,设置阻尼器后,主梁的纵桥向位移得到明显控制,降幅达到80%,大桥的关键截面内力也有5%左右的降幅。 相似文献
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《International Journal of Solids and Structures》2002,39(9):2401-2417
This paper presents a unified approach on determination of the effective stress range based on equivalent law of strain energy and fatigue damage model, so as to provide an efficient approach for accurately assessing effective fatigue stress of existing bridge under traffic loading. A new theoretical framework to relate variable- and constant-amplitude fatigue is proposed in this paper. Different formulation for calculating effective stress range can be derived by the proposed theory, which include the effective stress range by the root mean square, by Miner's law and a new effective stress range based on the nonlinear fatigue damage model. Comparison of the theoretical results of fatigue damage under the effective stress range of the variable-amplitude stress spectrum and experimental data of fatigue damage under realistic traffic loading has confirmed the validity of the proposed theory. As a way to relate variable-amplitude fatigue data with constant-amplitude data, the effective stress range provides the most convenient way for evaluating fatigue damage under variable-amplitude loading. The proposed theory is then applied to provide an efficient approach for accurately assessing fatigue damage of existing bridges under traffic loading, in which online strain history data measured from bridge structural health monitoring system is available. The proposed approach is applied to evaluate the effective stress range for the purpose of the fatigue analysis of a deck section of a long-span steel bridge––the Tsing Ma Bridge in Hong Kong. 相似文献
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F. J. Carrión-Viramontes J. A. López-López J. A. Quintana-Rodríguez A. Lozano-Guzmán 《Experimental Mechanics》2008,48(2):153-161
An experimental study for cables in a stayed bridge is presented. In this analysis, the tensions on the cables were calculated
considering linear and nonlinear approaches; for the nonlinear analysis a 2D model was used to evaluate vibration modes and
responses under wind and traffic loads. The 8 semi-harp cable stayed bridge used for this study has 112 cables and vibration
measurements were done under normal operational conditions. Tensions computed from the nonlinear model were compared with
those from the traditional linear model, where average differences were within 3.3%. The estimated tensions from vibration
tests have good correlation with the experimental values measured from load tests, while the vibration procedure was carried
out in less than 2 days without limiting the bridge operation; converse to the load tests where approximately 30 days are
necessary and the bridge traffic has to be closed for short periods during measurements. 相似文献
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柔性桥台合理加筋间距的力学模型试验 总被引:1,自引:0,他引:1
桥头跳车是公路工程中普遍且复杂的问题,加筋土结构的柔性桥台的应用,可能在根本上避免错台的出现和桥头跳车的产生。然而,其加筋间距的确定具有较大的盲目性。对土工织物加筋柔性桥台进行了4组大模型结构力学试验,对不同加筋间距下柔性桥台的工程特性进行了详尽的对比分析。试验结果表明,土工织物加筋柔性桥台的合理间距为30—50cm。 相似文献
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Barış Sevim Alemdar Bayraktar Ahmet Can Altunişik Sezer Atamtürktür Fatma Birinci 《Nonlinear dynamics》2011,63(4):755-770
Historic masonry arch bridges are vital components of transportation systems in many countries worldwide, ensuring the ready
access of goods and services to millions of people. The structural failure of these historic structures would severely and
adversely impact the economies of these nations due to the massive disruptions of transportation systems accompanying such
failures. To successfully maintain these aging masonry structures, performance assessment must incorporate the unique mechanical
characteristics of masonry. Therefore, the preferred analysis technique must go beyond a linear approach. This study assesses
the earthquake performance of a restored historical masonry arch bridge through nonlinear finite element analysis incorporating
the Drucker–Prager damage criterion. The case study structure is the Mikron Arch Bridge, a nineteenth century Ottoman Era
structure built over the Firtina River near Rize, Turkey, and restored in 1998. The Mikron Arch Bridge was first subjected
to ambient vibration testing, during which accelerometers were placed at several points on the bridge span to record the bridge
vibratory response. The investigators then used Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification
techniques to extract the experimental natural frequencies, mode shapes, and damping ratios from these measurements. Experimental
results were compared with those obtained by the linear finite element analysis of the bridge. Good agreement between mode
shapes was observed during this comparison, though natural frequencies disagree by 8–10%. The boundary conditions of the linear
finite element model of Mikron Arch Bridge are adjusted such that the analytical predictions agree with the ambient vibration
test results. By introducing the Drucker–Prager damage criterion, the calibrated linear FE model was next extended into a
nonlinear model. Nonlinear analysis of seismic behavior of Mikron arch bridge was performed considering the acceleration record
of Erzincan earthquake in 1992 that occurred near the Mikron Bridge region. The displacement and stress results were observed
to be allowable level of the stone material. Moreover, linear FE model calibrations elicited a significant influence on the
nonlinear FE model simulations. 相似文献
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在瑞利法和Southwell频率合成法的基础上导出了桥墩复合振动基频的计算公式,将基频表示成各惯性元和复原元所组成子系统的频率合成。然后用有限元建模来验证该方法,并分析了不同基础约束刚度和墩顶附加质量对桥墩基频的影响。计算结果表明本文导出的公式与有限元计算结果很接近。该方法适用于各种基础类型的桥墩和高耸结构基频的估算。 相似文献
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预应力混凝土箱梁横向框架效应有限元分析 总被引:2,自引:1,他引:1
以预应力混凝土箱梁桥顶板纵向开裂为工程背景,以箱梁顶板与腹板交接处两个角点的转角为基本未知量,基于箱梁纵向一维单元,利用最小势能原理推导出箱梁横向框架效应有限单元法的单元刚度矩阵,及相应的单元等效节点力,对比计算表明,该有限单元法计算精度与理论分析基本一致。实桥分析表明:现行规范计算箱梁角点弯矩相对安全,对于中点弯矩相对偏于不安全,设计过程不充分考虑混凝土箱梁横向框架效应可能导致顶板的纵向开裂。本文提出的有限单元法具有概念简单、运算速度快等优点,弥补了目前商业程序的不足,对工程设计具有一定的参考意义和推广价值。 相似文献
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A local adjoint technique is developed in order to determine the most sensitive location to perturbations of steady states near bifurcation points in the case of confined flows with free‐surface boundary. Transitions to stationary or periodic flows are studied. The method is validated by comparison of its results with those given by a time approach. It is then applied to the stability study and the feedback control of thermocapillary flows in liquid bridge. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献