考虑地震非平稳性的隧道纵向抗震可靠度分析

考虑地震运动的非平稳性,将沉埋隧道地震反应分析的数学模型应用于隧道纵向随机地震响应及其抗震动力可靠度分析。从有限元动力分析的基本原理出发,利用脉冲响应函数和傅立叶变换原理,结合随机振动理论,研究了将地震荷载作为非平稳随机过程时隧道纵向随机地震响应及其抗震动力可靠度分析方法,建立了地下结构随机地震响应数字特征及其抗震动力可靠度的计算表达式。以南京长江越江隧道初步设计方案(沉管段)为例,计算了其在非平稳随机过程地震动作用下的动力反应均方根值和纵向抗震动力可靠度,并研究了管段接头的抗震可靠度。     

任意排列双柱体的风致干扰效应

研究了5种不同宽度和5种不同高度比的两个正方形截面柱体间在不同地貌类型下的静力和动力干扰效应。结果显示,不同宽度比的施扰物体的动态干扰效应存在较大的差异,且宽度比受扰物体小的施扰物体在较低折算风速下会诱发涡激共振问题而产生较为严重的动力干扰效应,这个结果也澄清了已有文献的一些错误的结论。回归分析发现不同配置间干扰因子所存在的相关性并得到可以描述不同因素对干扰效应影响的定量关系,这些结果在很大程度上简化了干扰效应研究结果描述的繁杂性,同时使结构在受扰后的风荷载取值更趋于简洁和合理。文中根据对于试验数据的归纳分析结果,提出了一些可供规范修改时参考的建议。     

随机车辆参数行车激励对桥梁实测频率的影响研究

在以桥梁结构振动频率作为损伤识别的参考时,针对现场随机车辆参数行车激励对桥梁实测频率的干扰问题,通过建立实验室缩尺模型桥,并采用模型小车模拟现场随机车辆参数行车激励的方法,对随机车辆参数干扰实测频率的问题进行了研究。研究结果表明,随机车辆参数会干扰桥梁实测频率。通过对实测频率进行概率统计获得桥梁结构振动的统计频率的方法可以有效解决在进行损伤识别时随机车辆参数行车激励对桥梁结构实测频率的干扰问题,为真实车辆行驶条件下的桥梁动力损伤识别提供稳定可用的关键指标。     

随机结构的非线性动力反应分析

提出了随机结构非线性动力反应分析的概率密度演化方法.根据结构动力反应的随机状态方程,引入扩展状态向量,建立了随机结构非线性动力反应的概率密度演化方程.以单自由度保守系统的非线性自由振动为例,分析了反应的概率密度演化.研究表明随机结构非线性动力反应概率密度具有典型的演化特征,通过与精确解答和Monte Carlo分析结果的对比表明本文建议的概率密度演化方法具有良好的计算精度和较小的计算工作量.     

带地下室高层结构在地震作用下的时程分析

建立了带地下室高层结构在多支座干扰条件下的动力计算模型,编制了相应的时程分析程序,对地下室底板和顶板同时输入地震激励,考察了结构的动力反应并与惯常采用的单支座干扰时程分析结果进行了比较。     

地下结构非平稳随机地震响应分析

从有限元动力分析的基本原理出发,利用脉冲响应函数和傅立叶变换原理,研究了将地震荷载作为非平稳随机过程时地下结构随机地震响应分析方法,导出了非平稳随机地震加速度作用下地下结构动力响应的数字特征计算表达式。通过算例分析了某一隧道在7度非平稳随机地震作用下的位移和应力均方根响应。     

超高层建筑间的干扰效应:建筑外形的影响及干扰因子分布的相关特征

采用高频底座力天平方法,研究了不同断面形状的施扰建筑对一正方形断面受扰建筑的静力和动力干扰影响,分析了正方形断面施扰建筑和正方形切角断面施扰建筑的干扰效应的相关性。结果显示:施扰建筑结构断面的特征尺寸对其所产生的干扰响应起着关键性的作用,当施扰建筑的特征尺度相同时,切角和正方形截面施扰建筑的包络干扰因子(EIF)分布存在明显的相关性,并由此得到了一类特征尺寸相同的不同断面施扰建筑对包络干扰因子分布影响的回归关系(相关系数大于0.91,回归余差小于0.08),较大程度地简化了干扰响应研究结果的繁杂程度,简化了受扰建筑的荷载取值过程。     

考虑桨叶旋转效应的海上风力发电高塔系统随机风振响应与动力可靠度分析

研究了考虑桨叶旋转效应的海上风力发电高塔系统随机动力响应与风振可靠度分析.在风场模拟中,桨叶风荷载需要考虑旋转效应的影响.因此,对塔体风荷载,直接采用基于物理机制的随机Fourier谱,而对桨叶风荷载,则采用考虑桨叶旋转机制的随机Fourier谱概念.在此基础上,结合概率密度演化理论,对海上风力发电高塔系统进行了随机动力响应分析以及基于塔顶位移响应的风振动力可靠度分析.结果表明,上述方法能够有效地进行此类结构的随机动力响应及可靠度分析.     

刚性连体位置对非对称双塔连体结构动力可靠度的影响

考虑地震动的非平稳性,变化连体位置,对非对称双塔连体结构运用虚拟激励法进行非平稳随机激励下的动力可靠度研究。采用刚度退化的 Bouc-Wen 模型模拟塔楼各楼层的滞变特性,建立非线性化动力方程。运用混合精细积分法对每一时刻的响应进行求解,得到连体位置变化时非对称连体结构在非平稳随机激励下的时变方差。基于首次超越破坏准则与 Markov 假定,研究非平稳随机地震激励下连体结构的动力可靠度。运用上述理论,在8度罕遇地震作用下对某非对称双塔连体结构进行随机地震响应与动力可靠度分析。研究结果表明,地震作用下结构的层间位移响应呈现强烈的非平稳性,变化连体位置对连体结构的随机地震响应与动力可靠度将产生显著影响。     

基于风洞试验的双塔楼超高层建筑风荷载与风致响应

当超高层建筑的高度和间距都比较接近的时候,相互的干扰效应对结构的表面风荷载与结构的风致响应都会产生较大影响。基于刚性模型表面测压风洞试验,得到了双塔楼超高层建筑表面各测点的风压时程。在此基础上,通过数据处理,得到结构的三维动力风荷载模型,进而分别采用频域法进行结构动力响应分析。最后,通过分析结构表面风荷载与风致响应,研究了塔楼之间的干扰对结构风荷载的影响以及对结构风致响应的影响,结果表明:当双塔连线与来流方向平行时,三维风荷载和风致响应都会明显增大,干扰效应影响十分明显。     

弯矩波形扰动对纯弯梁弯扭屈曲的影响

推导了弯矩波形扰动作用下纯弯梁含转角θ的整体稳定微分方程,用数值方法逼近该方程的解,并取一个实际截面作为算例,得出了弯矩波形扰动对纯弯梁弯扭屈曲的影响,结果表明弯矩波形扰动降低了纯弯梁的弯扭屈曲稳定系数。     

结构试验中一种高保真的数字滤波算法

结构试验中在采集诸如荷载挠度曲线等数据时,由于受到外界环境不可预测的信号的干扰,往往会使采集的数据产生很大的漂移,而且漂移是随机的,不可预测的,这就严重歪曲了试验的真实曲线,给试验的分析处理带来了困难。本文根据随机干扰信号的特点,采用了一种三阶段的数字滤波算法,每个阶段采用不同的滤波思想,逐步地将干扰信号过滤出去,还原结构试验曲线的真实面貌,并通过两个具体不同的实例,验证了算法的可行性。     

Timoshenko versus Euler beam theory: Pitfalls of a deterministic approach

The selection criteria for Euler-Bernoulli or Timoshenko beam theories are generally given by means of some deterministic rule involving beam dimensions. The Euler-Bernoulli beam theory is used to model the behavior of flexure-dominated (or “long”) beams. The Timoshenko theory applies for shear-dominated (or “short”) beams. In the mid-length range, both theories should be equivalent, and some agreement between them would be expected. Indeed, it is shown in the paper that, for some mid-length beams, the deterministic displacement responses for the two theories agrees very well. However, the article points out that the behavior of the two beam models is radically different in terms of uncertainty propagation. In the paper, some beam parameters are modeled as parameterized stochastic processes. The two formulations are implemented and solved via a Monte Carlo-Galerkin scheme. It is shown that, for uncertain elasticity modulus, propagation of uncertainty to the displacement response is much larger for Timoshenko beams than for Euler-Bernoulli beams. On the other hand, propagation of the uncertainty for random beam height is much larger for Euler beam displacements. Hence, any reliability or risk analysis becomes completely dependent on the beam theory employed. The authors believe this is not widely acknowledged by the structural safety or stochastic mechanics communities.     

钢与混凝土结合梁的可靠度分析

本文建立对桥梁中钢与钢筋混凝土结合梁可靠度分析的半随机过程模型,研究了考虑车辆荷载（包括活载和冲击荷载）与恒载组合作用于下结合梁的可靠度评估。ＴＲ荷载组合规则被用来考虑荷载效应之间的关系。运用系统可靠度评估的方法,结合梁被模型化为由混凝土板、剪力传递器和钢梁串联而成的结构系统。工程设计的数值算例表明,本文提出的可靠度分析模型可用于进行结合梁目标可靠度设计。     

连续梁桥模态参数识别的随机子空间方法

简要介绍了协方差随机子空间方法,在此基础上,采用一等截面连续梁桥作为算例,通过ANSYS程序进行建模分析,对该连续梁桥进行识别,讨论了系统阶次的选择对识别结果的影响。     

基于累积损伤的在役钢结构吊车梁的疲劳可靠性评估

从Miner累积损伤的定义出发,视累积损伤为随机过程,临界损伤为随机变量,考虑腐蚀情况下疲劳抗力的衰减,提出了在役钢结构吊车梁疲劳可靠度分析方法。对某在役钢结构吊车梁随时间变化的疲劳可靠性进行了评估,预测该钢结构吊车梁剩余疲劳寿命,为进一步维修决策提供依据。     

Random field stiffness properties and reliability of laminated wood beams

This paper discusses a representation of the within-specimen variability in modulus of elasticity E for wood, utilising stationary random processes. These are used in the reliability study of a laminated wood beam for the serviceability limit state of maximum deflection. The reliability of the beam is also considered with different mechanical models: simple ones using ordinary beam theory and a more elaborate one based on a stochastic finite element formulation. Results compare the different mechanical models and, for the finite element approach, the effect that fluctuations in E within each lamination have on the beam reliability.     

On the behavior of thin walled composite beams with stochastic properties under matrix cracking damage

Thin walled composite beam structures are prone to damage which results in change in the performance of these structures. The change in the performance due to damage may get confused with the variation in the performance due uncertainties in the properties of these structures. Here, the performances of the thin walled composite beam under matrix cracking damage having material uncertainties are studied. The cross-sectional stiffness properties are obtained using thin walled beam formulation, which is based on a mixed force and displacement method. The stochastic behaviors of material properties are obtained from previous experimental and analytical studies. The effects of matrix cracking are introduced through the changes in the extension, extension–bending and bending matrices of composites. The effects of matrix cracking on out-of-plane bending, inplane bending and torsion cross-sectional properties are studied at different crack densities for stochastic material properties. Further, the effects of matrix cracking and uncertainties on measurable properties such as deflections and frequencies are studied. Results show that the beam responses at different crack densities get mixed due to the material uncertainties. The estimates of variance obtained for observable system properties due to uncertainty can be used for developing more robust damage detection algorithms.     

Comparison of methods of including stochastic factors into deterministic models of indoor air quality

The paper discusses problems connected with the inclusion of stochastic factors in deterministic models of indoor air quality (IAQ). Three different methods are shortly presented: quasi-dynamic multizone modelling with generation of input data time series; multizone modelling based on the theory of stochastic differential equations: and Monte Carlo simulation with independent random generation of stochastic parameters. The described methods are compared using a computer simulation of carbon dioxide concentration in a simple two-compartment office. The comparison of simulation results shows that the way in which stochastic disturbances are included in the models does not have an important influence on mean value of predicted carbon dioxide concentration. At the same time, the analysis of standard deviations indicates that the method of disturbance generation and its later incorporation into the IAQ models have a great influence on the probability distribution of estimated concentrations. Finally, there is a discussion on the main advantages and disadvantages of each of the proposed methods.     

大跨度桥梁随机风场的模拟

本文针对用于大跨度桥梁抖振时域分析的随机风场和Davenport相干函数的特点,对模拟多变量平稳随机过程的谐波合成法进行了改进.文中直接导出了互谱密度矩阵S(ω)的Cholesky分解的显式表达式;在不失精度的前提下,适当减少了部分余弦项;同时在模拟中运用了FFT技术,从而简化了计算过程,提高了计算速度.文章最后利用改进后的方法模拟了跨度为1000m的一座悬索桥的主梁随机风场,验证了方法的有效性.