09 Chapter 9 Structure Analysis and Computer Application.pptx

第1页：结构的组成与节点

Chapter 9 Structure Analysis and Computer ApplicationSection A Structures（结构分析与计算机应用）（结构）To construct is to put together structural elements to createa structure, a cohesive whole that meets previously-determined demands.The structural elements are linked toone another by means ofjoints([dʒɔint]n.接头，接缝，接合点；vt.连接，接合；adj.连接的，联合的，共有的).The structure is linked toits normally fixed environment throughsupports([sə'pɔ:t]vt.支撑，扶持，支持；n.

支撑，支承，支撑物，支柱).建造就是把结构单元拼装到一起形成，从而形成满足预定要求的具有连贯整体的一个结构。

结构单元相互之间是通过节点来联系的。结构通过支撑与外界环境相联系。

第2页：结构单元的分类

Structural elementsAs far as structural mechanics is concerned (strength andstiffness), one always tries to make the most efficient use ofthe specific properties of a limited number ofbuildingblocks(构件，结构单元), or structural elements.The way ofmodelling in structural mechanics allows one to distinguishthe following four types of structural elements

结构单元就结构力学而言，我们常常要有效利用有限数量的结构构件或结构单元。结构力学正确建模方法是要求我们区分以下四种结构单元：

第3页：点单元

Particle elementA particle element is a zero-dimensional structural element:all dimensions of the element are negligibly small withrespect to those of other elements. The dimensions of theelement play a subordinate role.

◆点单元点单元是一个零维结构单元，单元所有方向的尺寸相对于其它单元尺寸来讲，小得可以忽略不计。

单元尺寸在结构分析中不是主要考虑因素。

第4页：面单元

Surface elementA surface element is a two-dimensional structural element：one dimension of the element (the thickness) is considerablysmaller than the other two dimensions (the length and width).In the two-dimensional model, all the properties of theelement are assigned to a plane.With plates, the referenceplane is a flat plane. With shells, the reference plane is curved.Plates are also given other names, such asslab（[slæb]n.板，平板）, floor, wall anddisc（[dict]n.

(圆,轮,研磨)盘,圆片[板,面,盘刀],圆[甩油]环, (钢丝绳机的)轮圈）.◆面单元面单元是二维结构单元，单元一个方向（厚度方向）的尺寸与另两个方向（长度方向和宽度方向）相比小得多。

在二维模型中，单元所有的性质都可以放在一个假定的参考面中来考虑。例如，平板的参考面是一平面，壳的参考面是一曲面。平板也有其他名称，如楼板、地板、墙和圆形板等。

第5页：空间单元

Spatial elementA spatial element is a three-dimensional structural element:all the dimensions of the element are of the same order ofmagnitude（[‘mægnitju:d]n.大小，值，量值，量级）as those ofother elements and are therefore not negligible.

空间单元空间单元是三维结构单元，单元所有方向的尺寸同其它单元尺寸是同数量级的，因此单元各方向尺寸不可忽略。

第6页：结构单元间的节点

Joints between structural elementsTwo bodies can be joined together in a wide variety ofways. For joints between structural elements, in the sameplane, there are two kinds

结构单元间节点两个物体能够通过多种方式相连，同一平面内结构单元间的节点有两种：铰节点（铰）和刚性节点（完全刚性或刚性较大的节点）。

第7页：铰节点与刚性节点的区别

Hinged joints（铰节点）(hinges);*Fixed joints（刚性节点）(entirely rigid or infinitely rigid joints).In a hinged joint, or hinge, the joined parts can not translatewith respect to one another, but can rotate freely with respect toone another.In a rigid joint, the joined parts cannot translatewith respect to one another, nor can they rotate with respect toone another.The forces that the structural elements exert onone another in a joint are referred to as interaction forces or jointforces.

铰节点（或铰）中，被铰接的部分之间不能相对移动，但是可以自由地相对转动。

刚性节点中，被连接部分相互间既不能相对移动，也不能相对转动。结构单元在节点上相互作用力称为内力或节点力。

第8页：实际铰接点的理想化

Hinges will always have a certain amount of resistance torotation,even if only due to the occurrence of friction. If thisresistance is limited, the joint can be idealised as a frictionlesshinge. When the resistance to rotation in a jointis very large,the joint tends to be represented as infinitely stiff.The realitywill always lie between these two extremes.Spring joints(弹性节点)are joints in which the magnitude of the acting interactionforces is related to the deformation in the joint.

由于摩擦力等因素的存在，铰在转动过程中将或多或少受到阻力的影响。

若这种阻力较小，则可以把其理想化为无摩擦力的情况；若这种阻力较大，则可以把其视为无穷刚度实际结构中使用的铰接点通常介于上述两种极端情况构件。之间。弹性铰接点是指那些作用力与其变形相关的铰构件。

第9页：结构的支承

SupportsMost structures are not free-floating, but are joined to afixed environment. The joints between the structure and itsfixed environment are called supports.

支承大部分结构不是自由悬浮的，而是与固定的外部物体相连，连接结构与固定体的节点称为支承。

第10页：支承反力

The interaction forces that act in the supports on thestructure are known as support reactions. They act in thedirection in which displacement of the structure is prevented.The forces that the structure exerts on the supports (forexample on the foundation) are called support forces orsupport actions.The support forces are equal and opposite tothe support reactions.

作用在结构上支撑中相互作用力称为支承反力，沿着阻碍结构位移的方向作用。

结构作用在支承支承上的力（如作用在基础上）称为支承力或支承反力。方向相反。支承力与支承反力大小相等

第11页：四种支承类型

There are four types of supports:* bar supports;* roller supports;* hinged supports;* (fully)fixed supports.

有四种支承类型：杆支撑、滚动支承、铰链支承和固定支承。

第12页：平面结构体系

Planar structures(面状结构，平面结构)A spatial structure can often be viewed as a system ofplanar structures composed of line elements. It is thereforecertainly worth investigating the properties of such planarstructures in more detail.Based amongst other things on thenature of the joints and the external appearance, varioustypes of plana rstructures can be distinguished.

平面结构空间结构常被视为由线单元构成的平面结构体系。

因此，应该对这种平面结构的特性有更加细致地了解。根据铰节点的性质以及结构外部表现形式的不同，我们可以划分出许多类型的平面结构。

第13页：格栅梁

Beam grillages.Beam grillages are planar structures that areloaded normal to their plane, see Figure 9.4.A beam grillageconsists of two cooperative beam layers: beams andgirders.The beams and girdersare generally placed in two mutuallyperpendicular directions.

格栅梁格栅梁荷载作用在其平面上的平面结构，见图9.4。

Fig. 9.4A beam grillage格栅梁由两组相互作用的梁组成的，即主次梁。主次梁位置相互垂直。

第14页：格栅梁的应用

Beams grillagesare often used as floor structures inbridges and buildings. Lock doors are also sometimes builtas a system of beams and girders.Afaçade(立面）made ofposts and girders(columns and beams), withperpendicular（正面的）wind loading, can sometimes also be seen as abeam grillage.Calculating the forces and deformations in a beamgrillage is in fact a three-dimensional problem.

格栅梁常用于桥梁和建筑物中的楼面结构。

水闸门也通常是格栅梁结构体系。由柱和梁组成的立面，受到正面风载荷作用时，有时也被视为格栅梁。实际上，计算格栅梁的受力和变形是三维问题。

第15页：框架结构

Frames.Frames are planar, bent beams structures thatare loaded in the plane of the structure. Such structures areoften used to cover a space (warehouse(仓库）, sports arena,and so forth).

框架平面的、弯曲梁结构，荷载作用在结构平面内。

Figure 9.5 shows a number of simple examples of frames.InFigure 9.6, both fixed supports have been replaced by hingedsupports, so that the structure is now referred to as a two-hinged frame.

图9.5显示了一组框架结构的简单例子。

Fig. 9.5 Examples of fixed framesFig.9.6 Examples of two-hinged frames图9.

6中，多有的固定支承均被替代成铰支承，这时结构成为两铰框架。

第16页：三铰框架与两铰拱

If the structure with hinged supports itself consists of twoparts joined by a hinge, this is referred to as a three-hingedframe (see Figure 9.7).If the beam structure is not bent butarched, then the structure in Figure 9.8a is called a two-hingedarch, and the structure in Figure 9.8b a three-hinged arch.

如果有铰支承的结构本身由铰连接的两部分组成，这种结构成为三铰框架（见图9.7）。

Fig.9.8(a) Atwo-hinged arch and (b)a three-hinged arch如果非弯曲梁结构呈拱形，则图9.8a中的结构为两铰拱，9.8b中的结构为三铰拱。

第17页：Section B 计算机辅助设计

Section B Computer-aided Design（

计算机辅助设计）OverviewComputer-aided design (CAD) is the use of computertechnology for the design of objects, real or virtual.Thedesign of geometric models for object shapes, in particular,is often called computer-aided geometric design (CAGD).概述计算机辅助设计（CAD）是使用计算机技术进行实体设计、仿真或模拟。通常把用于物体形状的几何模型的设计称为计算机辅助几何设计（CAGD）。

第18页：CAD的符号信息表达

HoweverCADofteninvolvesmorethanjustshapes.Asinthemanualdraftingoftechnicalandengineeringdrawings,theoutputofCADoftenmustconveyalsosymbolic([sim'bɔlik]n.代号；adj.象征的，符号的)informationsuchasmaterials,processes,dimensions,andtolerances,accordingtoapplication-specificconventions.然而CAD不止仅限于形状的设计。因为在手册中规定，技术工程图的绘制、CAD

的输出必须也要按照特定应用的约定来传达物体的符号信息，如材料、工艺、大小和允许误差。

第19页：CAD软件的建模功能

Current Computer-Aided Design software packagesrange from 2Dvector(['vektə]n.向量，矢量)-based draftingsystems to 3D solid and surface modellers.Modern CADpackages can also frequently allow rotations in threedimensions, allowing viewing of a designed object from anydesired angle, even from the inside looking out.Some CADsoftware is capable of dynamic mathematic modeling, inwhich case it may be marketed as CADD—computer-aideddesign and drafting.

目前计算机辅助设计软件程序包内容涵盖了基于二维矢量的绘图系统到三维实体和曲面的建模。

当前的CAD软件也能使所建模型沿三个方向任意旋转，可以从不同的角度观察物体，甚至能够由内向外看。一些CAD软件能够进行动态数学建模，在这种情况下CAD可以被当作CADD（计算机辅助设计及绘图）使用。

第20页：CAD的技术优势

CAD has become an especially important technology withinthe scope of computer-aided technologies, with benefits such aslower product development costs and a greatly shorteneddesign cycle.CAD enables designers to lay out and developwork on screen, print it out and save it for future editing, savingtime on their drawings.CAD在计算机辅助技术方面已经成为一种特别重要的技术，它的应用有利于降低产品的开发成本和显著缩短设计周期。CAD

能够使设计者在电脑屏幕上进行设计和开发，为了以后编辑方便，可将其打印和存储起来，节省了设计师绘图的时间。

第21页：CAD的应用领域

CAD is an important industrial art extensively used inmany applications, including automotive, shipbuilding, andaerospace industries, industrial and architectural design,prosthetics([prɔs'θetiks]n.修复学,装补学(假肢,假眼,假牙), andmany more.CAD is also widely used to produce computeranimation([.æni'meiʃən]n.活泼,生气;卡通制作,动画)for specialeffects in movies, advertising, technical manuals.CAD是一项重要的工业艺术，在许多应用中被广泛使用，包括汽车、造船、航空航天工业、工业与建筑设计、修复学等等。CAD

也广泛应用在电影中特殊效果的电脑动画制作上，同时也可用于制作广告和技术指导手册。

第22页：CAD的经济意义

The modernubiquity([ju:‘bikwəti]n.到处存在,普遍存在)andpower of computers means that even perfume bottles andshampoo([ʃæm’pu:]n.洗头(洗发剂)；vt.洗发)dispensers([dis‘pensə]n.药剂师,配药员;分配器，分装机)are designed using techniquesunheard of by shipbuilders of 1960s.Because of its enormouseconomic importance, CAD has been a major driving force forresearch in computational geometry, computer graphics (bothhardware and software), anddiscrete differential geometry(离散微分几何).

当今计算机的普及和强大的功能，意味着即使香水瓶、洗发水分配器这样的产品的设计，采用的是二十世纪60年代造船专家从未听说过的技术。

由于其巨大的经济重要性，计算机辅助设计已成为研究计算几何、计算机图形学（硬件和软件）以及离散微分几何的主要驱动力。

第23页：CAD软件技术的发展

Software technologiesOriginally software for Computer-Aided Design systems wasdeveloped with computer languages such as Fortran, but withthe advancement of object-oriented programming methods thishas radically changed.Typical modern parametric feature basedmodeler and freeform surface systems are built around anumber of key C (programming language) modules with theirown APIs.软件技术起初的计算机辅助设计系统软件是随着计算机语言发展起来的，例如Fortran语言。但是随着面向对象程序设计方法的进步，计算机辅助设计系统已经发生了根本性的改变。在一些关键的附有API的C

语言模块的基础上，建立了基于建模软件和自由曲面系统的典型的现代参数特征。

第24页：CAD系统的构成

ACADsystemcanbeseenasbuiltupfromtheinteractionofagraphicaluserinterface（[‘intə(:).feis]n.界面,接触面）(GUI)withNURBSgeometryand/orboundaryrepresentation(B-rep)dataviaageometricmodelingkernel（[’kə:nl]n.核心，中心，精髓[计算机]核心）.Ageometryconstraintenginemayalsobeemployedtomanagetheassociativerelationshipsbetweengeometry,suchaswireframegeometryinasketchorcomponentsinanassembly.通过一种带有NURBS几何图形的用户界面（FUI）和/或通过几何建模核心的边界代表（B-rep）值的交互，建立了CAD

系统。也可以用几何约束求解引擎处理几何图形之间的关联关系，如线框几何图形的绘制或部件的装配。

第25页：CAD硬件与操作系统

Hardware and OS technologiesToday most Computer-Aided Design computers areWindows based PCs.Some CAD systems also run on one ofthe Unix operating systems and with Linux.Some CADsystems such as QCad, NX or CATIA V5 provide multiplatformsupport including Windows, Linux, UNIX and Mac OS X.硬件和操作系统技术目前大多数用于计算机辅助设计的计算机是基于PCs的Windows操作系统。一些CAD系统在某种Unix操作系统和Linux系统中也一些CAD系统例如QCad, NX或CATIA V5提供了包括可运行。Windows, Linux, UNIX和Mac OS X

多个支持平台。

第26页：CAD的硬件配置要求

Generally no special hardware is required with the possibleexception of a good graphics card, depending on the CADsoftware used.However for complex product design, machineswith high speed (and possibly multiple) CPUs and largeamounts of RAM are recommended.CAD was an applicationthat benefited from the installation of a numericcoprocessor（[cəu'prəucesə]n.

协处理器)especially in early personalcomputers.在使用CAD软件时，除了要求高质量的显卡，一般来说不需要专门的硬件。不过在设计复杂产品时，推荐使用配有高速运转的CPU和大容量随机存取存储器的计算机。用软件，受益于数字协处理器的安装，尤其是在早期的个人电脑中。CAD是一种应

第27页：CAD的人机界面

The human-machine interface is generally via a computermouse but can also be via a pen and digitizing graphics tablet.Manipulation of the view of the model on the screen is alsosometimes done with the use of a spacemouse/SpaceBall.Some systems also support stereoscopic glasses for viewingthe 3D model.

人机界面一般是通过计算机鼠标但是也能够通过笔和数字绘图板。

屏幕上观察到的模型的操作有时也可用spacemouse/SpaceBall处理。有些系统也支持立体眼镜观看三维模型。

第28页：CAD的发展历史

HistoryThe beginnings of CAD can be traced to year 1957, when Dr.Patrick J. Hanratty developed PRONTO, the first commercialnumerical-control programming system.In 1960, IvanSutherland MIT's Lincoln Laboratory created SKETCHPAD,which demonstrated the basic principles and feasibility ofcomputer technical drawing..历史CAD的出现可以追溯到1957年，Patrick J. Hanratty博士开发出了最早的商业数控程序系统——PRONTO。1960年，Ivan Sutherland麻省理工学院林肯实验室开发出SKETCHPAD，

证实了计算机技术制图的基本原理及可行性。

第29页：二维时代

2D Time.The first CAD systems served as mere replacements ofdrawing boards. The design engineer still worked in 2D to create technicaldrawing consisting from 2D wireframeprimitives(['primitiv]n.图元，基元)(line, arc, B spline ...).Productivity of design increased, but many argue thatonlymarginally(['mɑ:dʒinəli]adj.有限的；adv.在边上,边际地)due tooverhead–design engineers had to learn how to use computers and CAD.Nevertheless modifications and revisions were easier, and over time CADsoftware and hardware became cheaper and affordable for mid sizecompanies. CAD programs grew in functionality and user friendliness.二维时代第一代CAD系统仅仅取代了绘图板。设计工程师仍然以二维方式创建由二维线框单元（直线、弧线、曲线等等）构成的技术图形。设计效率提高了，但设计师必须学习如何使用计算机和CAD的费用是非常有限的，所以引起了较多争议。设计师不得不学习如何使用计算机和CAD。然而，由于修改变得越来越容易，而且CAD软硬件越来越便宜，对于中等规模的公司也可以买得起。CAD

程序的多功能性和用户友好性越来越强。

第30页：三维时代

3D Time.3D wireframe features were developed in thebeginning of the sixties, and in 1969 MAGI released SynthaVision, first commercially available solid modeler program. Solidmodeling further enhanced the 3D capabilities of CAD systems.NURBS, mathematical representation of freeform surfaces,appeared in 1989--first on Silicon Graphics workstations.In1993 CAS Berlin developed an interactive NURBS modeler forPCs, called NöRBS.

三维时代三维线框特征出现于二十世纪六十年代，1969年MAGI推出了首款商用实体模型程序Syntha Vision，实体建模进一步增强了CAD系统的三维功能。硅谷图形工作站首先于1989年制作出表示数学自由曲面的NURBS（非均匀样条曲面）。1993年CAS Berlin开发出一款计算机互动曲面建模程序，称为NöRBS。

第31页：约束与自下而上装配

MCAD systems introduced the concept of constraintsthat enable you to define relations between parts inassembly.Designers started to use abottom-up(从下到上)approach when parts are created first and then assembledtogether.Modeling is more intuitive, precise and lateranalysis, especiallykinematics([.kaini'mætiks]n.运动学)easier.MCAD

系统引入了使你能够定义组装部分之间相互关系的约束思想。当部件形成然后组装在一起时，设计师开始使用自建模更加直观和准确，而且以后的运动分下而上的组装方法。析也更加容易。

第32页：CAD的应用现状

Present.CAD / CAE / CAM systems are now widelyaccepted and used throughout the industry. These systemsmoved from costly workstations based mainly on UNIX tooff-the-shelf(非专业化设计的；现成产品；位务变数)PCs.3D modelinghas become anorm([nɔ:m]n.标准，规范), and it can be foundeven in applications for the wider public, like 3D buildingsmodeling in Google Maps, house furnishing (IMSI Floorplan),or garden planning. Advanced analysis methods like FEM,flow simulations are anubiquitous([ju:'bikwitəs]adj.到处存在的,普遍存在的)part of the design process.现状目前CAD/CAE/CAM系统在全行业内被广泛接受和使用。这些系统由主要基于UNIX的费用较高的工作站转移到现成的个人电脑平台中。三维建模已经成为标准，甚至为广大公众所使用，像谷歌地图、房屋装修或园林规划中三维建筑的建模。FEM、

流体仿真等高级分析方法普遍存在于设计过程中。

第33页：CAD的未来发展

FutureThe past of CAD has been full of unmet expectations. Thiscontinues. Some anticipate 3D modelling without flat screensor mouse pointers--a fully immersive 3D environment wheremodelling tools include special gloves and goggles. In thefuture, designing will be closer to sculpting than painting.未来发展CAD

过去始终没有达到令人满足的期望值，还将继续。一些人期待着不通过平板显示器和鼠标指针实现三维模型的建模——一个完全身临其境的三维环境，建模工具包括特殊的手套和护目镜。将来，设计将更接近于雕塑，而非绘画。

第34页：沉浸式技术的现实局限

Up to now, 3D goggles causenausea, immersivetechnologies are expensive and complex, and mostdesigners prefer using a keyboard, stylus, and mouse.While some of these optimistic predictions may cometrue, the more likely course is that the future changes willevolve in ways we do not see now.Still, some trends seemmore likely to succeed and be widely adopted than others.

到目前，三维立体眼镜引起眩晕，身临其境的技术比较复杂且成本较高，大多数设计师仍偏好于使用键盘、触针和鼠标。

而其中一些乐观的预言可能成为现实，更可能的进程是未来的变化将会以我们目前看不到的方式发展。然而，某些趋势比其它的更有可能成功并且被广泛接受。