薄壁曲箱梁考虑剪力滞效应的一维离散有限元法

本文以薄壁曲梁理论、乌曼斯基第二理论为基础,推导了薄壁曲箱梁一维离散有限元方程,建立了相应的结构分析模型.算例不仅说明本文方法和计算模型简便易用,同时与三维有限元法相比可以缩减离散自由度,且保持了较高的计算精度.     

压型板的有限元分析及数值计算

采用有限元法对压型板进行了详细的分析并建立了相应的有限元计算公式。在三维分析中,提出一个等效正交各向异性模型（包括拉伸和弯曲刚度）。并对压型板的非线性和自由振动特性进行分析及数值计算。算例与有限元软件包ANSYS的计算进行比较,结果表明,本文方法具有很好的适用性。     

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.     

薄壁梁在剪切变形下的扭转分析

第一部分针对剪切变形下的薄壁梁提出扭转分析理论。采用Vlasov薄壁梁理论假定梁截面的静许用应力区,采用能量补充原则表达假定应力场下的控制区相容条件。依靠自然边界条件将扭曲变形与内力联系起来。文中采用新理论分析了一个扭转梁的例子,旨在阐明其对实际问题的应用性。第二部分采用基于力的有限元方法分析该解决方案,假设两个分别具有线性和双曲线复合力矩的有限元模型。相比基于动力学假定的传统梁理论计算结果,有限元分析结果提供的刚度更低。     

合肥新桥国际机场航站楼箱形曲梁承载性能分析北大核心CSCD

为得到合肥新桥国际机场航站楼钢结构屋盖中箱形曲梁构件的承载性能,以箱形曲梁部分为重点研究对象,采用千斤顶单拉加载的方式,进行了3个箱形曲梁模型的试验研究。建立了试验构件的有限元模型,将试验结果与有限元计算结果进行了对比和分析,有限元计算有效地模拟了试验构件的承载性能,试验结果和有限元结果吻合较好,证明了设计的合理性和安全性。试验得到了不同面外支撑对构件承载性能的影响。通过施加大小不同的初始缺陷,分析了初始缺陷对于转换节点构件承载性能的影响。试验模型的有限元分析与试验数据相互验证,为设计提供了理论依据。     

薄壁杆系结构自由振动精确求解的动力刚度法

将动力刚度法应用于薄壁杆系结构自由振动的分析.采用常微分方程求解器COLSYS求解薄壁杆件单元动力刚度所满足的常微分方程边值问题获得单元动力刚度的数值精确解,基于COLSYS求解单元动力刚度的网格采用Wittrick-Williams算法获得单元固端频率的计数,调用COLSYS求解单元动力刚度对频率的导数所满足的常微分方程边值问题获得其数值精确解.由此建立起薄壁杆系结构自由振动精确求解的导护型牛顿法,求得精确的频率和振型.本文数值算法的计算结果与文献以及ANSYS软件的计算结果吻合很好,表明本文方法准确、可靠、有效,可进一步推广应用于其他复杂结构自由振动的分析.     

薄壁组合箱梁的自由振动

研究薄壁叠加组合梁的自由振动。建立了适用于薄壁组合箱梁截面动力性能的一般分析模型。该模型基于古典叠加理论，考虑任意层压板叠合次序情况下弯曲和扭转的耦合，也就是非对称和对称以及各种边界条件。对薄壁组合梁，建立基于位移的一维有限元模型以预测自振频率和相应的振型，并由Hamilton原理派生出运动方程；考虑薄壁组合梁纤维角度、模数比、振动频率的边界条件以及组合形式的影响，得出计算结果。     

非线性油气悬架振动系统研究

分析了半桥油气悬架系统的非线性刚度特性和非线性阻尼特性,建立了半桥油气悬架系统的二自由度非线性振动数学模型。通过MATLAB对二自由度非线性振动数学模型进行了仿真计算,结果显示了油气悬架良好的刚度和阻尼特性。分析了油气悬架系统设计中的关键因素及其对系统动态特性的影响因子大小,对油气悬架的参数优化设计及工程实际产品设计具有参考价值。     

非线性油气悬架振动系统研究

分析了半桥油气悬架系统的非线性刚度特性和非线性阻尼特性,建立了半桥油气悬架系统的二自由度非线性振动数学模型.通过MATLAB对二自由度非线性振动数学模型进行了仿真计算,结果显示了油气悬架良好的刚度和阻尼特性.分析了油气悬架系统设计中的关键因素及其对系统动态特性的影响因子大小,对油气悬架的参数优化设计及工程实际产品设计具有参考价值.     

工字形截面圆弧曲梁的非线性理论

从任意开口薄壁截面圆弧曲梁精确的翘曲位移出发 ,针对常见的单轴对称工字形、槽形和无对称轴的H形截面曲梁 ,通过参数分析找到一个统一的数学表达式 ,给出相应的应力、应变计算式。在这个基础上 ,依据大变形理论 ,建立了工字形截面圆弧曲梁非线性分析的基本理论 ,并考虑了横向正应力的影响。推导过程中未就材料性质做任何假定 ,所以该理论同样可以应用于曲梁弹塑性阶段的分析。最后给出单轴对称工字形截面两种常见放置条件下曲梁的总势能表达式。     

薄壁曲线箱梁考虑翘曲、畸变和剪滞效应的空间分析

提出一种能同时考虑拉压、弯曲、扭转、扭转翘曲、畸变、剪滞效应及它们之间交互作用的每节点有14个自由度的薄壁曲线箱梁空间分析单元,并直接从流动的圆柱极坐标系下一点处的位移-应变-应力关系出发,结合薄壁曲线箱梁理论和有限元技术,推导出该单元的刚度矩阵.通过模型试验[15][4]验证了本文方法的正确性.     

Nonlinear free vibration analysis of asymmetric thin-walled circularly curved beams with open cross section

A finite element formulation is present for the nonlinear free vibration of thin-walled curved beams with non-symmetric open across section. The kinetic and potential energies are derived by the virtual principle. The energy functional includes the effect of flexural–torsional coupling, the torsion warping and the shear center location. For finite element analysis, cubic polynomials are utilized as the shape functions of the two nodal thin-walled curved elements. Each node possesses seven degrees freedom including the warping degree of freedom. The nonlinear eigenvalue problem has been solved by the direct iteration technique. The results are compared with those for straight beams as available in the literature. The results for nonlinear free vibration analysis of curved beams for various radii and subtended angle are presented.     

An efficient formulation for thin-walled beams curved in plan

An efficient formulation is developed for the elastic analysis of thin-walled beams curved in plan. Using a second-order rotation tensor, the strain values of the deformed configuration are calculated in terms of the displacement values and the initial curvature by adopting the right extensional strain measure. The principle of virtual work is then used to obtain the nonlinear equilibrium equations, based on which a finite element beam formulation is developed. The accuracy of the method is confirmed through comparison with test results, shell finite element formulations and other curved beam formulations from the literature. It is also shown that the results of the developed formulation are very accurate for the cases where initial curvature is large.     

曲线箱梁桥的地震反应分析

根据薄壁箱梁的翘曲扭转理论,建立了可以考虑截面翘曲和偏心影响的3维空间曲线箱梁桥的位移模式和能量泛函,利用有限元列式建立了动力方程。并编制了相应的程序。最后通过算例说明了翘曲扭转对曲线箱梁桥影响较大,不可忽略。     

Mechanics of thin-walled curved beams made of composite materials, allowing for shear deformability

In this paper, a new theoretical model is developed for the generalized linear analysis of composite thin-walled curved beams with open and closed cross-sections. In the present model two important concepts concerning to composite thin-walled curved beams are addressed. The first one is the incorporation in the model of what is called full shear deformability, i.e. shear flexibility due to both bending and non-uniform warping is considered. The second feature is connected with the constitutive aspects, and it contemplates the use of different hypotheses that can be adopted in the formulation. These topics are treated in a straightforward way by means of the Linearized Principle of Virtual Work. In order to obtain the motion equations of the model a non-linear displacement field, whose rotations are formulated by means of the rule of semitangential transformation, is employed. This model allows the study of many problems of statics, free and forced vibrations with arbitrary initial stresses and linear stability of composite thin-walled curved beams with general cross-sections. A discussion about the constitutive equations is performed in order to explain characteristic features of the effects included in the theory. This paper presents the theoretical formulation together with finite element procedures that are developed to obtain the numerical approximations to the general equations of thin-walled shear-deformable composite curved beams. For this kind of structural member, iso-parametric finite elements are introduced. Numerical examples are carried out in several topics of statics, dynamics and buckling problems, focusing attention in the validation of the theory with respect to experimental data and with 2D and 3D computational approaches. Also, new parametric studies are performed in order to show the influence of shear deformability on the mechanics of the thin-walled composite curved-beams with open and closed cross-sections as well as to illustrate the utility of the model.     

Numerical analysis of elastic-plastic bending of curved beams with thin-walled cross-section

It is well known that, when a curved beam is subject to bending, the shape of its cross-section is flattened and collapse occurs as the rigidity is reduced. It is important for design to determine the nonlinear behavior of such beams. This paper describes the elastic-plastic large deformation analysis of a curved beam with a thin-walled cross-section by the finite element method. The analytical formulation is developed by extending the kinematic work hardening model proposed by Ziegler. Several representative cases are computed.     

Static analysis of thin-walled structures using polynomial and exact solutions. Application to thin-walled pipes

A new finite element procedure for the static analysis of beam thin-walled structures of open or closed cross-section is presented. The method is a combined or mixed one, based on the superposition of beam and shell strains and displacements. An essential part of this work is the development of new shape functions (which are either ‘exact’, or polynomial) for the interpolation of the shell displacements.The above method is applied to the thin-walled curved pipe problem and compared to the von Karman approach. Excellent results are obtained, as well as a drastic reduction of the total number of nodal variables.     

薄壁轴压焊接方管柱整体稳定-局部稳定相互作用问题的研究

本文采用曲壳有限单元法计算了具有各种宽厚比的薄壁轴压焊接方管截面的极限承载力,以及相应的长柱构件的柱子曲线。计算时计入了各种初始缺陷。通过将本文计算结果与各规范设计方法计算结果的比较,分析了规范方法的误差原因,提出了改进的薄壁方管截画有效面积的计算公式和轴压焊接薄壁方管柱的设计方法。经与本文理论计算结果相比,证明本文建议的设计方法精度较好。     

Free vibration analysis of horizontally curved steel I-girder bridges

Presented herein is a finite element formulation for free vibration analysis of horizontally curved steel I-girder bridges. Stiffness as well as mass matrices of the curved and the straight beam elements is formulated. Each node of both of them possesses seven degrees of freedom including the warping degree of freedom. The curved beam element is derived based on the Kang and Yoo's thin-walled curved beam theory in 1994. A computer program is developed to carry out free vibration analyses of the various bridges. Comparing with the frequencies using the general purpose program ABAQUS, the validity of the presented numerical formulation is shown. The numerical formulation is extensively applied to investigate free vibration characteristics of the bridges considering effects of the initial curvature, boundary condition, modeling method, and degrees of freedom of cross frame. Invaluable information which help practicing engineers better understand the vibration characteristics is provided.