Plastic Axisymmetric Collapse of Thin-Walled Circular Cylinders and Cones Under Uniform External Pressure

This paper reports on two theoretical investigations and an experimental investigation into the plastic axisymmetric buckling of two thin-walled conical shells and several thin-walled circular cylindrical shells, under uniform external pressure.

One of the theoretical investigations was a non-linear finite element solution for plastic axisymmetric buckling, which gave good results.

The other theoretical solution was for the plastic non-symmetric bifurcation buckling of thin-walled circular cylinders. This second solution was a very simple one and, although it was based on plastic lobar buckling, it gave very good predictions for plastic axisymmetric collapse. This latter observation prompted the conclusion that there may be a link between plastic lobar buckling and plastic axisymmetric buckling.     

Vibration analysis of cylindrical shells in contact with an annular fluid region

An experimental and numerical investigation of the vibratory modal characteristics of a vertical thin-walled cylindrical shell containing water, or oil, in an adjacent coaxial region is presented. A system of two fluid-coupled cylindrical shells is studied. In addition to the effect of increasing liquid level in the shell, the effects of the thickness of the liquid layer in the annular region between the vibrating outer shell and another coaxial rigid cylinder, or between two thin coaxial cylindrical shells, are studied. Experimental results were obtained using the standard modal analysis technique and the time average holographic method. In parallel, computation of natural frequencies and mode shapes of the coupled fluid-structural vibrations were carried out by means of the finite element method operated within the framework of the ANSYS program package. The comparison between experimental results and finite element results was found to be reasonable in most of the cases studied. The fundamental influence of the viscosity of the fluid in the narrow annulus upon the dynamic behaviour of the shell is discussed.     

金属波纹拱壳屋顶有限元模型的自动生成

用细化有限元模型网格的方法来模拟金属波纹拱壳屋顶结构实际的波纹形状是一种有效的分析方法 ,但却使得网格非常密集 ,有限元模型比较复杂。应用有限元网格自动剖分理论 ,采用平面超单元变换剖分法 ,编写程序实现了金属波纹拱壳结构有限元模型网格的自动剖分 ,大大节省了计算机建模时间 ,并避免了在手动建模及划分有限元网格时所出现的误操作     

A nonlinear finite element computer program for thin-walled members

A nonlinear finite element computer program has been developed to analyse thin-walled metal structural members. The program has the ability to handle both geometrical and material nonlinearities so that the post-buckling behaviour and ultimate strength of members can be predicted. A bending-membrane rectangular element with six degrees of freedom at each node forms the basic type of element used in the program. Marguerre's shallow shell theory is adopted for the strain-displacement relationships and hence the bifurcation point at buckling can be bypassed by providing an initial inperfection. The finite element formulation is based on the total Lagrange coordinate system and the flow theory of plasticity. Explicitly shown in the paper is the formation of the tangent stiffness matrix and the tridiagonal block form of solution procedure. Two problems of a square tube and a channel section beam subjected to pure bending were tested and found to be in close agreement with previous theoretical work.     

Deformation and buckling of axially compressed cylindrical shells with local loads in numerical simulation and experiments

By means of geometrically non-linear modeling of the test process for high-quality specimens of thin-walled cylinders using a shell finite element implemented in ANSYS, it has been proved that this numerical approach is applicable for design of real axially compressed circular cylindrical shells under external local quasi-static loads.     

Vibration of thin-walled ring-stiffened circular cylinders and cones

This paper presents a theoretical and an experimental investigation into the free vibration characteristics of thin-walled ring-stiffened circular cylinders and cones. Three ring-stiffened circular cylinders and three ring-stiffened circular cones were machined from a solid mild steel shaft. For each family of vessels, the only variable was the depth of the ring stiffeners. The theoretical investigation was based on the finite element method, and comparison between theory and experiment was found to be good.     

Analysis of hyperbolic cooling towers with local imperfections

Two methods to analyse hyperbolic cooling towers with local imperfections are presented. One method relies on the finite element technique. For this a specialized finite-element program, which can model any arbitrary imperfections while retaining the advantage offered by the basically axisymmetric nature of the shell, was developed. The other method is an approximate procedure, which may be implemented with a purely axisymmetric analysis capability. The two methods are compared through numerical studies. A cooling tower shell with a bulge-type imperfection is examined under dead load and wind load conditions. It is concluded that the finite-element model presented is effective for the analysis of such shells, while the equivalent-load method may be adequate for some cases. Also, it is shown that both meridional and circumferential stress resultants may be radically influenced by a small bulge imperfection.     

砌体墙—钢筋混凝土筒体组合结构静力分析

在理论分析基础上,利用ANSYS软件建立有限元模型,分别对普通砌体结构、筒体在中部和筒体在两边的组合结构进行了静力分析,对比说明设有筒体的组合结构能提高整体抗震性能。     

后张拉整体成型局部双层柱面网壳成型过程的研究

局部双层柱面网壳可以通过后张拉闭合平板网架中预留缝隙的方法张拉而成。提出一种可用于张拉成型局部双层柱面网壳的平板理论模型,给出预测成型形状的理论公式。利用ANSYS 10.0有限元计算程序,通过不同节点连接方式模型的对比分析给出最适合张拉的理想模型。     

单层椭球形网壳考虑下部结构减震性能分析

通过大型有限元分析软件ANSYS对40m跨单层椭球形网壳结构进行研究和参数分析.模型中的下部结构采用钢筋混凝土柱,以考虑对网壳的影响,并对单层椭球形网壳是否考虑下部结构的两种计算模型进行了自振振型下的模态比较.文中提出此类网壳屈曲约束支撑的布置方式,等截面替换了网壳内的部分杆件,并对有屈曲约束支撑单层椭球形网壳的减震性能进行分析.结果表明,下部结构对结构整体的影响不可忽略,合理布置约束屈曲支撑的网壳结构减震效果较好.     

结合实例研究大直径塔筒局部稳定问题

因建筑造型的需要,大直径塔筒在工程设计中的应用日益广泛。由于塔筒的稳定性与塔筒的几何尺寸、初始缺陷以及加载和约束方式等诸多因素有着密切的关系,如何确保大直径塔筒的局部稳定成为设计中的重点。本文采用数值分析方法系统研究了不开洞和开洞塔筒在一定的轴力与弯矩范围内,内部加劲形式变化对于极限承载能力的影响,明确了不同加劲形式的加劲效率。另外,对影响不开洞和开洞塔筒局部稳定的各几何参数进行了深入的参数化分析,并提出了改善屈曲强度的有效方法。     

工字型钢梁双重非线性分析

利用通用分析软件ANSYS分别建立＂工＂字型梁的梁单元和壳单元模型,对比分析了静力作用下,两种模型的应力和位移,发现采用壳单元模型的计算结果低于梁单元模型的分析结果,壳单元模型能更好地模拟结构的失稳破坏。     

圆筒壁内的温度分布计算及分析

选用第一类边界条件下柱坐标形式的导热微分方程计算其筒壁内的温度分布,然后用ANSYS（空间有限元法）分析并与导热微分方程进行了比较,指出用ANSYS分析软件计算较省时,且分析结果较准确。     

On the modelling of different types of imperfections in silo shells

The assessment of imperfections is most important for determining the load-bearing capacity of a thin-walled shell structure. Different ways of modelling imperfections are discussed in this paper and steel silo shells are used as an application. Buckling tests were performed on different types of model shell - standard quality and high quality with reduced heat input during welding. For the numerical studies two different approaches were used as well: an axisymmetric approach with substitute geometric imperfections and an FEM approach, where the nodal coordinates were derived from surveying the specimen. It was found that there is considerable gain in the buckling strength due to the presence of the granular solid. The larger the initial imperfections in the shell the greater the gain in strength compared to the empty cylinder. The modelling of the uneveness of the edges with uneven dead loading is also discussed.     

有限元在计算简支梁屈曲荷载中的应用

介绍了有限元ANSYS中壳元模型的建立步骤,并利用有限元ANSYS程序对简支梁屈曲荷载进行了求解,通过理论分析与有限元结果的比较,验证了有限元ANSYS程序计算结果的正确性,并为外形和受力复杂的简支杆件的稳定承载能力的计算提供了参考依据。     

Vibration and elastic instability of thin-walled domes under uniform external pressure

Two thin-walled varying meridional curvature axisymmetric shell elements are presented for the vibration and elastic instability of thin-walled hemi-ellipsoidal domes under uniform external pressure. The theoretical analysis is an extension of previous work carried out by the author, where for the two elements presented in the present report, a cubic and a quadratic variation was assumed for the meridional and the circumferential displacements along the meridian of these elements. In the previous study, only linear variations were assumed for the meridional and circumferential displacements along the meridian of these elements. Comparisons were made between experiment and theory for both buckling and vibration of hemi-ellipsoidal shell domes, which varied from very flat oblate vessels to very long prolate vessels. In general, agreement between experiment and theory was good for the hemi-spherical dome and the prolate vessels, but not very good for the fat oblate vessels. Additionally, the two new elements gave poorer results than the original simpler element for the cantilever mode of vibration, but better results for the lobar modes of vibration.     

某电除尘器侧墙板合理形式研究

运用有限元软件ANSYS与Midas,对某大型电厂300MW机组电除尘器壳体部分侧墙板建立有限元模型,分析荷载作用下几种壳体形式的受力性能,在不影响使用情况下为减少除尘器壳体的用钢量和受力性能提出建议。     

ANSYS与AutoCAD的模型转换技术及其工程应用

针对ANSYS建模较为困难的弱点,建议利用通用绘图软件AutoCAD作为前处理软件建模,再将其通过接口程序转换为ANSYS的有限单元模型。通过探讨AutoCAD的几何模型与ANSYS有限单元模型之间的互相转换技术,将CAD的二次开发程序与ANSYS的命令流文件有机结合,构建简便的数据接口。探讨了转换过程中存在的问题,并利用人工智能语言Visual Lisp编制转换程序。通过两个工程实例的应用,证明了程序的可行性,也表明了此种转换技术对于有限元软件的工程应用有较好的实用价值。     

Deflection of castellated beams subjected to uniformly distributed transverse loading

This paper presents an analytical solution for determining the deflection of castellated/cellular beams with hexagonal/circular web openings, subjected to a uniformly distributed transverse load. The solution is derived using the principle of minimum potential energy. To validate the derived analytical solution, three-dimensional linear finite element analysis is performed using four-node shell elements built-in ANSYS software. Good agreement between the finite element result and the present analytical solution is demonstrated.     

冷弯薄壁型钢开口三肢拼合立柱轴压性能有限元分析

建立了考虑材料、几何和接触非线性的有限元模型,利用ANSYS有限元程序分析了长细比、螺钉连接间距、截面板件最大宽厚比对冷弯薄壁型钢开口三肢拼合立柱轴压性能的影响。结果表明:立柱长细比对A、B两类截面拼合立柱轴压承载力和轴压性能有很大影响,随着立柱长细比的增大,立柱轴压极限承载力逐渐降低;当螺钉连接间距为450、300、150mm时,A、B两类截面拼合立柱轴压极限承载力和刚度变化均不大;由于基本构件板材厚度不同引起截面板件最大宽厚比的不同,对A、B两类截面3种长度的拼合立柱的承载力和刚度影响很大;对于A、B两类截面立柱,当立柱长度和截面厚度相同时,基本构件腹板高度由89mm增加到140mm,拼合截面轴压立柱轴压极限承载力变化不大。