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,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,Lesson 6,Concepts of Structural Analysis,Concepts of Structural Analysis,Structures can be classified in a variety of ways.The casual observer might first consider classifying structures according to their respective functions:bridges,ships,aircraft,towers,and so on.This basis for structural classification is in fact fundamental;all structures have some functional reasons for existence.It is the need to fulfill some function that prompts the designer to give life to a structure.,参考译文,结构可以以不同的方式进行分类。不经意的观察者可能首先考虑根据各自的功能分类结构：桥梁、船舶、飞机、塔，等等。这一结构分类建立于根本领实:所有结构由于一些功能原因而存在。它需要实现某些提示结构设计者赋予一个结构以生命的功能。,casual kjul adj.随便的；非正式的；临时的；偶然的,n.便装；临时工人；待命士兵,fulfill fulfil vt.履行；实现；满足；使结束等于fulfil,Concepts of Structural Analysis,feasible fi:zbl adj.,可行的；可能的；可实行的,aesthetically i:s,etikli adv.,审美地；美学观点上地,manner mn n.,方式；习惯；种类；规矩；风俗,serviceable s:visbl adj.,有用的，可供使用的；耐用的,Furthermore,it is the need for a safe serviceable,feasible,and aesthetically pleasing fulfillment of a function that dictates the form,material,and manner of loading of a structure,参考译文,此外，分类也是对决定了结构形式、材料和荷载种类的功能的结构平安、维修、可行、美观圆满实现的需要。,可意译为：,此外，某种功能需要决定了结构形式、材料和荷载种类，分类也是对这种结构的平安、维修、可行、美观等圆满实现的需要。,Concepts of Structural Analysis,Once the form and material have been determined,a structure may be further classified according to either its form(e.g.,an arch,truss,or suspension structure)or the material out of which it is constructed (e.g.,steel,concrete,or timber).The form and material of a structure in turn dictate its behavior.which in turn dictates the character of the analytical model.Fig.6.1 illustrates schematically the relationships among the function a structure is to fulfill,the form and material and loading on the structure,the behavior of the structure,and the analytical model of the structure,参考译文,一旦确定了形式和材料，结构既可以根据其形式 例如，拱、桁架或悬吊结构或根据其构造材料(如钢、混凝土或木材来进一步分类。结构的形式和材料反过来决定其特性，也就是反过来要求解析模型的特征。Fig.6.1 图示说明结构要满足的功能、结构的形式、材料和荷载、结构性能和结构解析模型之间的关系。,Concepts of Structural Analysis,Fig.6.1 Relationship between the function of a structure and its analytical model,Concepts of Structural Analysis,At this point we need to discuss some of the aspects of structural behavior indicated in Fig61 and to explain their respective relationships to the form and material of the structure.A structure is linear if its response to loading,say displacement at a point,is directly proportional to the magnitude of the applied load.If this proportionality does not exist,the structure is said to be nonlinear.Structural nonlinearities are of two types：(1)material nonlinearities that arise when stress is not proportional to strain，,参考译文,此时，我们需要讨论图6.1 所述结构某些方面的特性，并解释它们与结构的形式和材料的各自之间的关系。如果结构对荷载的响应，指某点的位移，与施加的负载大小成正比，结构是线性的。如果不存在此比例，结构是非线性的。结构的非线性效应有两种类型：1 当应力与应变不成比例时出现的材料的非线性，,Concepts of Structural Analysis,and(2)geometric nonlinearities that arise when the configuration of the structure under load is markedly changed from the unloaded configuration(The presence of cables in a structure often leads to geometric nonlinearity because displacements can occur owing to a change in cable sag,which can be shown to be nonlinearly related to the force in the cable.)Materials,and therefore structures built from them,may be classified as elastic,plastic,or viscoelastic.Elastic materials rebound to their initial configuration when the load is removed,whereas plastic materials retain a permanent set,参考译文,和(2)当荷载作用下结构形态明显有别于卸载结构形态时出现的几何非线性。结构中缆绳的形态往往导致几何非线性，因为由于绳擞度的改变位移可能发生，这可以看成是与缆绳中的力非线性相关。材料，及由其建造的结构，可划分为弹性、塑性或粘弹性。弹性材料在负载移除时反弹到其初始状态，而塑性材料保持永久变化。,cable sag,绳擞度,viscoelastic,viskuilstik adj.,力,粘弹性的,Concepts of Structural Analysis,The deformations of viscoelastic materials depend on time and therefore load history,whereas the deformations of elastic and plastic materials do not.A structural system is unconservative or conservative depending on whether or not energy is lost from the system during a cycle of loading and unloading.Energy is generally lost if a system does not recover its initial shape after unloading owing either to plastic behavior of the material or to friction forces within or between parts of the structure,参考译文,弹性材料在负载移除时反弹到其初始状态，而塑性材料保存永久变化。粘弹性材料的变形取决于时间也就是其加载史，而弹性和塑性材料的变形与其无关。一个结构体系守恒或非守恒取决于能量是否在加载和卸载周期中从系统丧失。如果卸载后系统不能恢复其初始形状能量一般会丧失，这可归因于材料的塑性性质或结构内部或结构部件之间的摩擦力。,conservative kns:vtiv adj.1.,守旧的，保守的,2.,稳健的；谨慎的,3.,不时新的，传统标准的,Concepts of Structural Analysis,All these behavioral aspects of the structure will have a significant influence on the nature of the analysis used in studying the structure.In addition,in developing the analytical model it will be necessary to consider whether the structural material is homogeneous or nonhomogeneous and whether it is isotropic,orthotropic,or anisotropic.,参考译文,homogeneous,hmdi:nis;,hu-adj.,1.同种类的，同性质的；相同特征的,2.由类似成分(或局部)组成的,3.均匀的，均质的，均一的,isotropic,aisutrpik adj.,1.【物理学、生物学】各向同性的,2.【动物学】等轴性的亦作 isotropous,orthotropic,:trpik adj.植 直生的，正交的；,正交各向异性的,anisotropic n,aisutrpik adj.物 各向异性的；物 非均质的,参考译文,所有这些
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