框支剪力墙的“3-M”柔度矩阵法

本文基于空间协同平面分析,应用柔度法原理,将总剪力墙每层处的弯矩作为未知量,推导出框支剪力墙的“3-M”柔度方程组。方程组的求解可以用追赶法在SHA-RP PC-1500 袖珍机上实现。文中举一实例加以说明。     

基于框-剪结构协同工作的抗振墙数量优化研究

针对当前抗震墙数量优化中多是定性分析的现状,根据框架-剪力墙结构整体受力特点,采用横向分类方法,将空间框-剪结构分解量化为榀结构形式。基于有限元思想及框剪结构空间协同分析的离散化原理建立了其力学分析模型及剪力墙优化模型,该力学分析模型能较好地反映结构整体工作性能的主要特征及考虑剪力墙剪切变形的影响,动力分析采用振型分解法计算地震作用,以遗传算法作为优化方法确定出了剪力墙的最优数量。计算结果表明该方法具有较高的精度,可为结构的设计提供参考。     

修正的RC剪力墙构件Park-Ang损伤模型

基于Park-Ang 损伤模型，提出了用于钢筋混凝土剪力墙构件的修正损伤模型．通过对已有钢筋混凝土剪力墙试验结果的统计分析，总结了其累积耗能组合系数的影响因素，并拟合出该系数与试件参数：剪跨比、轴压比、配筋率的关系式．修正的损伤模型需满足加载至破坏时损伤指标为1.0 的上界条件，结果表明，根据本文修正的损伤模型计算的钢筋混凝土剪力墙试件损伤指标在统计意义上满足该条件．最后，根据构件性能水准的相关研究，本文将钢筋混凝土剪力墙构件的性能水准划分为：基本运行，生命安全和接近倒塌，分别对应了构件骨架曲线相应关键点：屈服点、峰值点和极限破坏点，根据本文修正损伤模型计算的各水准损伤指标临界值分别为：0.02、0.45 和1.00．     

钢筋混凝土轴对称球扁壳基于双剪屈服准则的极限分析

导出了基于双剪屈服准则的钢筋混凝土球扁壳的屈服条件，并利用此屈服条件求解出其极限荷载。     

用双剪屈服准则对钢筋混凝土板进行塑性铰线的极限分析

利用双剪屈服准则建立了用机动法计算钢筋混凝土薄板极限载荷的新的塑性铰线理论，并导出了双向布置钢筋的钢筋混凝土板的屈服条件，实例计算表明其更符合实验结果。     

钢筋混凝土联肢剪力墙的非线性有限元分析

本文推导了一种带转动自由度的四节点狭长矩形墙板单元与一种分层高精度二节点厚梁单元,二者的组合既合理地描述了联肢剪力墙墙体与连梁的连续性,又具有计算精度高,计算量少的特点。为分析钢筋混凝土的非线性,本文采用应变硬化的弹塑性应力应变关系描述受压混凝土及钢筋,用线弹性应力应变关系描述受拉混凝土,混凝土开裂后的非线性现象则以一些经验公式给予反映。算例表明,本文建立的有限元计算模型用于钢筋混凝土联肢剪力墙的加载全过程分析是合理的,并且计算效率高。     

钢筋混凝土框架—剪力墙结构非线性抗震分析的一种空间力学模型

将钢筋混凝土框架－剪力墙结构离散为能模拟梁、柱、墙抗震性能的单元，采用杆系－层间模型进行结构的非线性抗震分析。本文的空间力学模型可考虑局部楼板变形对结构地震反应的影响，并可沿任意角度输入相互垂直的两个地震动水平分量，适用于框架一剪力墙复杂结构的非线性抗震分析。     

剪力墙的面外刚度对建筑结构计算结果的影响

剪力在钢筋混凝土建筑结构中有着广泛的应用,在计算时一般都忽略剪力面外刚度的贡献。本文利用一种同时具有面内刚度和面外刚度的剪力墙模型,研究了剪力墙的面外刚度对整体结构的控制位移和固有频率的影响。结果表明,剪力面外刚度的贡献与剪力墙之间的耦合程度以及是要用刚性楼板假定有关,在大型复杂的纵横剪力墙结构中,剪力墙面外刚度的贡献不可忽略。     

钢筋混凝土圆球壳基于双剪屈服准则无矩理论的极限分析

利用已建立的基于双剪屈服准则的钢筋混凝土壳体的屈服条件,研究了圆球壳屈服时无矩理论下内力状态,导出了壳体各区域的本构关系和塑性屈服条件,并用机动法和静力平衡法计算了圆球壳在竖向均布载下的极限载荷.计算结果与用已有的塑性屈服线理论计算结果相符.     

基于可靠度和功能的框架—剪力墙结构抗震优化设计

作为结构抗震设计的发展方向,近年来基于功能的结构抗震设计思想引起了地震工程界的广泛重视,并取得了迅速发展,其基本思想就是在充分考虑结构抗震设计中的不确定性的情况下,采用基于“投资－效益”准则和强调结构“个性”的设计,本文讨论了基于可靠度和功能的结构抗震优化设计思想,建立了钢筋混凝土呆－剪力墙结构 抗震优化设计模型,给出了结构可靠度的近似计算方法,最后计算了钢筋混凝土框架－剪力墙的算例。     

有限元—传递矩阵法求解链式结构非线性系统的动力响应

本文提出一分析多自由度非线性振动系统时域响应的数值计算法,并就一三自由度非线性系统,分别计算了此系统具有一个非线性弹簧、两个非线性弹簧和三个非线性弹簧三种情况下的动态响应;通过与对应的线性系统响应结果的比较,验证了此法的有效性、可靠性和多种优点.     

聚能射流侵彻的一种耦合算法

介绍了一种能有效模拟聚能射流侵彻过程的计算方法，即二维数值解和解析解相耦合的方法。实际应用表明，此方法计算结果准确可靠，经济省时，其软件是聚能装药优化设计的实用工具。     

Diffusion velocity for a three-dimensional vorticity field

A discussion is presented on the existence of a diffusion velocity for the vorticity vector that satisfies extensions of the Helmholtz vortex laws in a three-dimensional, incompressible, viscous fluid flow. A general form for the diffusion velocity is derived for a complex-lamellar vorticity field that satisfies the property that circulation is invariant about a region that is advected with the sum of the fluid velocity and the diffusion velocity. A consequence of this property is that vortex lines will be material lines with respect to this combined velocity field. The question of existence of diffusion velocity for a general three-dimensional vorticity field is shown to be equivalent to the question of existence of solutions of a certain Fredholm equation of the first kind. An example is given for which it is shown that a diffusion velocity satisfying this property does not, in general, exist. Properties of the simple expression for diffusion velocity for a complex-lamellar vorticity field are examined when applied to the more general case of an arbitrary three-dimensional flow. It is found that this form of diffusion velocity, while not satisfying the condition of circulation invariance, nevertheless has certain desirable properties for computation of viscous flows using Lagrangian vortex methods. The significance and structure of the noncomplex-lamellar part of the viscous diffusion term is examined for the special case of decaying homogeneous turbulence.     

非线性振动系统周期运动及其稳定性的数值研究

§1引言确定型非线性振动系统的运动可分类如下: 1.非定常运动;2.定常运动:(1)周期运动,(2)各态历经运动,(3)浑沌运动。其中非定常运动是一暂态过程,会随着时间的增长逐步衰减乃至实际上消失。定常运动中的各态历经运动,指系统至少有两个互不通约(即其比值为无理数)的振动频率,因此运动虽然局      

Online terrain estimation for autonomous vehicles on deformable terrains

In this work, a terrain estimation framework is developed for autonomous vehicles operating on deformable terrains. Previous work in this area usually relies on steady state tire operation, linearized classical terramechanics models, or on computationally expensive algorithms that are not suitable for real-time estimation. To address these shortcomings, this work develops a reduced-order nonlinear terramechanics model as a surrogate of the Soil Contact Model (SCM) through extending a state-of-the-art Bekker model to account for additional dynamic effects. It is shown that this reduced-order surrogate model is able to accurately replicate the forces predicted by the SCM while reducing the computation cost by an order of magnitude. This surrogate model is then utilized in an unscented Kalman filter to estimate the sinkage exponent. Simulations suggest this parameter can be estimated within 4% of its true value for clay and sandy loam terrains. It is also shown in simulation and experiment that utilizing this estimated parameter can reduce the prediction errors of the future vehicle states by orders of magnitude, which could assist with achieving more robust model-predictive autonomous navigation strategies.     

Backlund变换理论发展简述及其新方法

本文首先简要介绍Bcklund变换理论的发展过程,然后介绍一种寻找微分方程Bcklund变换的新方法——wahlquist-Estabrook过程。该方法是目前处理微分方程Bcklund问题的最有效方法.尽管该方法在理论上可应用于任意维数的偏微分方程组,但是实际上它所能处理的主要是二维问题。例如,在应用该方法处理完整Navicr-Stokcs方程(四维问题)时,所得到的是无意义结果.但是,在应用该方法处理定常二维Navicr-Stokcs方程时,确实可以得到正常的Bcklund映射,以及Bcklund变换.     

Hausdorff dimensnon of set generated by exceptional oscillations of a class of N-parameter Gaussian processes

A class of N-parameter Gaussian processes are introduced, which are more general than the N-parameter Wiener process. The definition of the set generated by exceptional oscillations of a class of these processes is given, and then the Hausdorff dimension of this set is defined. The Hausdorff dimensions of these processes are studied and an exact representative for them is given, which is similar to that for the two-parameter Wiener process by Zacharie (2001). Moreover, the time set considered is a hyperrectangle which is more general than a hyper-square used by Zacharie (2001). For this more general case, a Fernique-type inequality is established and then using this inequality and the ments is required for showing the representative of the Hausdorff dimension by Zacharie (2001). This property is absent for the processes introduced here, so we have to find a different way.     

A Uniform Exponential Spectrum for Linear Flows on Vector Bundles

For linear flows on vector bundles we define a uniform exponential spectrum. For a compact invariant set for the projected flow we obtain this spectrum by taking all accumulation points for the time tending to infinity of the union over the finite time exponential growth rates for all initial values in this set. Using direct arguments we show that for a connected compact invariant set this spectrum is a closed interval whose boundary points are Lyapunov exponents. For a compact invariant set on which the flow is chain transitive we show that this spectrum coincides with the Morse spectrum. In particular, this approach admits a straightforward analytic proof for the regularity and continuity properties of the Morse spectrum without using cohomology or ergodicity results.     

Spatial properties of Wohlhart symmetric mechanism

The aim of this paper is to present a new analytical resolution to find closure equations of Wohlhart symmetric mechanism and to give some interesting spatial properties of this mechanism. These properties are used to put in evidence possible industrial applications for this type of mechanism. First, it concerns the analytic resolution of the twelve equations system obtained from the closure equation, system particularized for the case of Wohlhart symmetric mechanism. The matrix form of closure equations is written for a single loop overconstrained mechanism composed by six revolute joints, mechanisms called 6R. A kinematical analysis is made, putting in evidence some interesting kinematical and geometrical properties. These properties allow us to consider a new spatial disposition for this mechanism, by imposing three non-successive joints to remain in a determined plan. Thus, we obtain a translator, a possible future industrial application for this type of overconstrained mechanism.     

Qualitative behaviors of the continuous-time chaotic dynamical systems describing the interaction of waves in plasma

In this paper, a new Lorenz-like chaotic system describing the interaction of three resonantly coupled waves in plasma is studied. Explicit ultimate boundedness and global attraction domain are derived according to stability theory of dynamical systems. The innovation of the paper is that this paper not only proves this chaotic system is globally bounded for the parameters of this system but also gives a family of mathematical expressions of global exponential attractive sets for this system with respect to the parameters of this system. Furthermore, the exponential rate of the trajectories is also obtained. Finally, numerical localization of attractor is presented.