土木工程专业英语 中英文对照 unit5（基础教育）

1、Unit 5 第五单元Structural Analysis 结构分析1智囊经验教学目标了解结构分析的假定和几种方法了解结构分析中运用的几个定理熟悉结构力学中的专业词汇熟悉科技类文献中的常用句型熟悉as a consequence、 as a result、for these reasons、therefore 以及as a consequence of、as a result of 的含义；state 的不同用法；relate to、relate.to、be related to 的区别；be equal to、be equated to、equal 的用法； with respect to

2、、regarding、considering、as to 的用法2智囊经验 A structure consists of（由.组成）a series of connected parts used to support loads. Notable（显著的） examples include buildings, bridges, towers, tanks, and dams. The process（过程）of creating any of these structures requires planning（规划）, analysis, design, and constructio

3、n（施工）. Structural analysis consists of （包括）a variety of mathematical procedures（数学程序）for determining such quantities as the member forces and various structural displacements（位移） as a structure responds to its loads. Estimating realistic loads for the structure considering（根据）its use and location is

4、 often a part of structural analysis. 结构由一系列相连的用以支撑荷载的构件组成。显著的例子包括建筑、桥梁、塔、水箱和大坝等。建造这些结构中的任何一个的过程需要规划、分析、设计和建造。结构分析包括各种各样的数学程序以确定诸如当一个结构对荷载有响应时构件的力和不同结构位移的大小。根据结构的使用和位置来估计它的实际荷载经常是结构分析的一部分。3智囊经验 Only two assumptions are made regarding（关于）the materials used in the structures of this chapter. First, th

5、e material has a linear stress-strain relationship（线性的应力-应变关系）. Second, there is no difference in the material behavior when stressed in tension vis-a-vis（与.相比）compression. The frames and trusses studied are plane structural systems（平面结构体系）. It will be assumed that there is adequate bracing perpendi

6、cular to（垂直于）the plane so that no member will fail due to an elastic instability（弹性失稳）. The very important consideration regarding such instability will be left for the specific（具体的）design course. 4智囊经验All structures are assumed to undergo only small deformations as they are loaded. As a consequence

7、（因此）we assume no change in the position or direction of a force as a result of （由于）structural deflections（变位）. Finally, since linear elastic materials and small displacement are assumed, the principle of superposition will apply in all cases. Thus the displacements or internal forces that arise from

8、 two different forces systems applied one at a time（一次一个）may be added algebraically（几何相加）to determine the structures response when both system(s) are applied simultaneously.5智囊经验 关于本章结构中所用的材料只作了两点假设。首先，材料具有线性的应力应变关系。其次，材料的性能在受拉和受压时没有区别。研究的框架和桁架是平面结构体系。假定垂直于平面的方向有足够的支撑，因而构件不会因为弹性失稳而失效。一个非常重要的关于这种失稳的考

9、虑留待具体的设计过程。假定所有的结构在它们加荷时只经历小的变形。因此，我们假定当结构变位时荷载的位置与方向不变。最后，因为假定了线弹性材料和小位移，叠加原理将适用于所有的情况。这样当两种不同的力系同时施加时，可以由不同的力系一次施加一个引起的位移或内力几何相加来确定结构的响应。6智囊经验 In the real sense（真正意义上）an exact analysis of a structure can never be carried out since estimates always have to be made of the loadings and the strength o

10、f the materials composing（构成）the structure. Furthermore, points of application（作用点）for the loadings must also be estimated. It is important, therefore, that the structural engineers develop（形成）the ability to model（模拟）or idealize（使.理想化）a structure so that he or she can perform a practical force analy

11、sis of the members. 真正意义上对一个结构准确的分析是永远也不可能进行的，因为总是不得不估计荷载和构成结构的材料的强度。而且，必须估计荷载的作用点。因此，结构工程师有能力模拟一个结构或使其理想化很重要，这样，他或她能对构件进行实际的力的分析。7智囊经验 Structural members are joined together in various ways depending on the intent（意图）of the designer. The two types of joints most often specified（规定的）are the pin conn

12、ection and the fixed joint（节点）. A pin-connected joint allows some freedom for slight（轻微）rotation, whereas the fixed joint allows no relative rotation between the connected members. In reality, however, all connections exhibit（显现）some stiffness toward joint rotations, owing to friction（摩擦）and materia

13、l behavior. When selecting a particular model for each support（支座）or joint, the engineer must be aware of how the assumptions will affect the actual performance（运行）of the member and whether the assumptions are reasonable for the structural design. In reality, all structural supports actually exert（产

14、生）distributed surface loads（面荷载）on their contacting members. 8智囊经验 The resultants（合力） of these load distributions are often idealized as the concentrated forces（集中力）and moments, since the surface area （表面积）over which the distributed load acts is considerably smaller than the total surface area of th

15、e connecting members. The ability to reduce an actual structure to（将.简化为）an idealized form can only be gained by experience. In engineering practice, if it becomes doubtful（不明确）as to how to model a structure or transfer the loads to the members, it is best to consider several idealized structures an

16、d loadings and then design the actual structure so that it can resist（抵抗）the loadings in all the idealized models.9智囊经验 结构构件根据设计者的意图采用不同的方式连在一起。最常规定的两种节点是铰接节点和固定节点。铰接节点允许有一些轻微的转动自由，而固定节点不允许相连的构件有相对的转动。但是，事实上由于摩擦和材料的特性使所有的连接对节点的转动显现出一些刚度。当为每一个支座或节点选择一个特定的模型时，工程师必须知道该假设将如何影响构件的实际运行，以及该假设是否对结构的设计是合理的。实

17、际上，所有的结构支座在它们接触的构件上产生分布的面荷载。这些荷载分布的合力常常理想化为集中力和弯矩，因为分布荷载作用的表面面积比相连的构件的总的表面面积小很多。将一个实际的结构简化成一种理想的形式的能力只有通过经验才能获得。在工程实践中，如果就怎样模拟一个结构或将荷载传递给构件变得难以确定时，最好考虑几个理想的结构和荷载，然后设计实际的结构，使它在所有理想的模型中都能抵抗荷载。10智囊经验 It may be recalled（回想）from statics that a structure or one of its members is in equilibrium（处于平衡） when

18、it maintains a balance of force and moment. When all the forces in a structure can be determined strictly from these equations, the structure is referred to as statically determinate（静定的）. Structures having more unknown forces than available equilibrium equations（平衡方程）are called statically indetermi

19、nate. As a general rule, a structure can be identified as（确定）being either statically determinate or statically indeterminate by drawing free-body diagrams（隔离体图）of all its members, or selective parts of its members, and then comparing the total number of unknown reactive force and moment components（分

20、量）with the total number of available equilibrium equations. 11智囊经验 从静力学可以回想起当一个结构或它的一个构件维持力和弯矩的平衡时即处于平衡状态。当一个结构中所有的力能严格地根据这些方程式来确定，该结构称为静定的。如果结构上未知的力比能得到的平衡方程多时称为超静定结构。作为一般的规律，一个结构可以通过画出所有构件或经选择的部分构件的隔离体图，然后比较未知的反力和弯矩的分量总数目与可用的平衡方程总数目是否相等来确定其是静定结构还是超静定结构。12智囊经验 In particular, if a structure is stati

21、cally indeterminate, the additional equations（附加方程）needed to solve for（求解）the unknown reactions（反力）are obtained by relating the applied loads and reactions to the displacement or slope（转角）at different points on the structure. These equations, which are referred to as compatibility equations（相容性方程或协调

22、方程）, must be equal in number to the degree of indeterminacy（不确定次数）of the structure. Compatibility equations involve（涉及）the geometric and physical properties of the structure. 特别地，如果一个结构是超静定的，可以通过建立作用力和反力与结构不同点上的位移或转角的关系来得到用以求解未知反力所需的附加方程。这些称为相容性方程的方程式在数量上必须等于结构的不确定次数。相容性方程涉及结构的几何和物理性能。13智囊经验 There a

23、re two fundamental methods of analysis for trusses: the method of joints and the method of sections. Both start with（从.着手）a free-body diagram of the truss as a whole（基本上）, from which the equilibrium equations are written and solved for the support reactions（支座反力）. 有两种分析桁架的基本方法：节点法和截面法。两种方法基本上都从桁架的隔离

24、体图着手，根据它可以写出平衡方程并求解支座反力。14智囊经验 The method of joints: After the support reactions have been found, a joint is selected that has no more than（不超过）two members connecting for which the axial forces are unknown. The free-body diagram of that joint is drawn, the forces are summed（合计）in two directions, and

25、 each sum is equated to（等于）zero. When drawing the free-body diagram, it is a good idea to assume that the unknown forces are tensions and to show（表示）them so on the free-body diagram by their exerting a pull on（对.施加拉力）the joint. When this is assumed, the resulting sign（符号）of the unknowns when evaluat

26、ed（计算）will match（符合）the conventional（习惯的）+ for tension and for compression. Once a joint has been analyzed, its members become knowns, and adjacent joints（相邻节点）, which might have had three or more unknowns, can then be solved since some of these unknowns have become knowns. This process（过程）continues

27、 from joint to joint, each time selecting a joint whose number of unknown members does not exceed 2.15智囊经验节点法：求出支座反力后，选择一个节点其上连接着轴向力未知的构件不超过两根。画出节点的隔离体图，将力在两个方向上进行合计，每个方向（力）的合计等于零。当画出隔离体图时，有个好主意是假定未知力是拉力，并在隔离体图上通过对该节点施加一个拉力来表示。这样假定后，未知力计算结果的符号将与习惯的正为拉力负为压力相符。一旦一个节点已经被分析，其上的构件成为已知构件，相邻的节点可能曾经有三个或更多的未

28、知力，但因为其中的一些已经成为已知，因此也能求出。这个过程从一个节点到另一个节点连续进行，每次选择的节点其上未知构件（力）的数量不超过两根。16智囊经验 Almost all truss systems are configured（装配）so that analysis using the method of joints must begin at one end and proceed（继续）joint by joint toward the other end. If it is necessary to evaluate the forces carried by a member

29、located（位于）some distance from the ends, the method of joints requires the calculation of the forces in many members before the desired one is reached. The method of sections provides a means（方法）for a direct calculation in these cases. After the support reactions have been calculated the truss is cut

30、 through（切开）(analytically分析上) so that one part of the truss is completely severed from the rest. When this is done, no more than three unknown members should be cut. If possible（如果可能）the cut（切口）should pass through the member or members whose internal forces are to be found. A free-body diagram of th

31、e part of the truss on one side of（在.一边）this section is drawn, and the internal forces are found through the equilibrium equations. Since the system of forces（力系）on the free-body diagram is a plane non-concurrent（非共点）force system, three equilibrium equations may be written and solved for the three u

32、nknowns.17智囊经验 几乎所有的桁架体系是装配的，因此采用节点法进行的分析必须从一个端点开始，并一个节点连着一个节点地朝另一个端点继续进行。如果有必要计算位于端部一定距离的构件上的力，节点法需要在到达这根要求（计算）的构件之前计算很多构件中的力。在这些情况下截面法提供了一个直接计算的方法。当求出支座反力后，桁架（在分析上）被切开，从而一部分桁架同其余部分完全分离。当这样切开时，应该切出不超过三个构件的力是未知的。如果可能，切口应穿过将要求解内力的构件。画出在截面一边的桁架部分的隔离体图，并通过平衡方程式求解内力。由于隔离体图上的力系是平面非共点的，因而可以写出三个平衡方程式并求出三个未

33、知力。18智囊经验 Influence lines（影响线）have important application for（应用）the design of structures that resist large live loads（活荷载）. An influence line represents（代表）the variation of either the reaction, shear, moment, or deflection at a specific （特定的）point in a member as concentrated force moves over the mem

34、ber. Once this line is constructed（作图）, one can tell at a glance（一眼便知）where a live load should be placed on the structure so that it creates（引起）the greatest influence at the specified point. Furthermore, the magnitude（大小）of the associated （相关的）reaction, shear, moment, or deflection at the point can

35、then be calculated from the ordinates（纵坐标）of the influence-line diagram. 19智囊经验For these reasons（因此）, influence lines play an important part in the design of bridges, industrial crane rails（吊车轨道）, conveyors, and other structures where loads move across their span（全长）. Although the procedure（步骤）for c

36、onstructing an influence line is rather basic（基本的）, one should clearly be aware of the difference between constructing an influence line and constructing a shear or moment diagram. Influence lines represent the effect of a moving load only at a specified point on a member, whereas shear and moment d

37、iagrams represent the effect of fixed loads at all points along the axis of the member.20智囊经验 影响线在设计抵抗大量活荷载的结构时有着重要的应用。一根影响线代表着当集中力在构件上移动时构件上一个特定点的反力、剪力、弯矩或挠度的变化。一旦画出这根线，任何人一眼便知活荷载应该置于结构的哪个位置才能对这个特定的点引起最大的影响。而且，这点上相关的反力、剪力、弯矩或挠度可从影响线图的纵坐标上计算出来。因此，影响线在桥梁、工业吊车轨道、输送机和其它有荷载在整个结构长度上移动的结构设计中扮演着重要的角色。虽然画出一

38、条影响线的步骤是相当基本的，但任何人应该清楚地意识到画一条影响线与画一条剪力或弯矩图的区别。影响线只代表着移动荷载对构件上特定点的影响，而剪力和弯矩图代表固定荷载对沿着构件轴线的所有点的影响。21智囊经验 Deflections of structures can occur from various sources（原因）, such as loads, temperature, fabrication errors, or settlement. In design, deflections must be limited in order to prevent cracking of a

39、ttached（附属的） brittle materials such as concrete or plaster (石膏) . Furthermore, a structure must not vibrate or deflect（变位）severely in order to “appear” safe for its occupants（居住者）. More important, though（然而）, deflections at specified points in a structure must be computed if one is to analyze static

40、ally indeterminate structures. We often determine the elastic deflections of a structure using both geometrical and energy methods. Also, the methods of double integration（双重积分）are used. The geometrical methods include the moment-area theorems（弯矩图面积定理）and the conjugate-beam method（共轭梁法）, and the ene

41、rgy methods to be considered are based on virtual work（虚功）and Castiglianos theorem（卡氏最小功定理）. Each of these methods has particular advantages or disadvantages.22智囊经验 结构的挠度可以因不同的原因而发生，如荷载、温度、制造错误或沉降。设计中，挠度必须加以限制以阻止附属的脆性材料如混凝土或石膏的开裂。而且，为了向居住者显示安全性，结构不能严重地振动或变位。而更重要的是如果有人要分析超静定结构，必须计算出结构中规定点的挠度。我们通常采用几何

42、法和能量法来确定结构的弹性挠度。也采用双重积分法。几何法包括弯矩图面积定理和共轭梁法，而考虑的能量法是基于虚功定理和卡式最小功定理。每一种方法都有其特别的优缺点。23智囊经验 We can determine the equation of the elastic curve by integration of equation d2v / dx2 = M / EI. Solution of this equation requires two successive（连续的）integrations to obtain the deflection v of the elastic curve

43、. For each integration, it is necessary to introduce（引入）a “constant of integration”（积分常数）, and then solve for the constants to obtain a unique solution（唯一解）for a particular（特定的）problem. It should be realized that the method of double integration is suitable only for elastic deflections（变位）such that

44、the beams slope is very small. Furthermore, the method considers only deflections due to bending. 我们可以通过对方程d2v / dx2 = M / EI的积分来确定弹性曲线的方程。该方程的求解需要两个连续的积分，以获得弹性曲线的挠度v。对每次积分，有必要引入积分常数，求出该常数以获得一个特定问题的唯一解。应该了解到双重积分法只适合于弹性变位，因而梁的转角是非常小的。而且，该法只考虑了由于弯曲引起的挠度。24智囊经验 The initial ideas（最初的概念）for the two momen

45、t-area theorems were developed（提出）by Otto Mohr and later stated formally（正式确定）by Charles E. Greene in 1872. These theorems provide a semi-graphical （半图解）technique for determining the slope of the elastic curve and its deflection due to bending. They are particularly advantageous（有利）when used to solv

46、e problems involving beams especially those subjected to a series of concentrated loadings or having segments（段）with different moment of inertia（惯性矩）. Theorem 1: The change in slope（转角变化）between any two points on the elastic curve equals the area of the M / EI diagram between these two points. Theor

47、em 2: The deviation（偏差）of the tangent（正切）at point B on the elastic curve with respect to（相对于）the tangent at point A equals the “moment” of the M / EI diagram between the two points A and B computed about point A (the point on the elastic curve), where（这里）the deviation tA/B is to be determined.25智囊经验

48、 最初的关于两个弯矩图面积定理的概念是由Otto Mohr提出，后来由Charles E. Greene在1872年正式加以确定。这些定理为确定弹性曲线由于弯曲引起的转角和挠度提供了半图解的方法。当用以解决包括梁在内的问题，特别是那些承受一组集中加载的梁或有着不同惯性矩的梁段时，它们（指弯矩图面积定理）是特别得有利。定理1：弹性曲线上任何两点之间转角的变化等于这两点之间的M / EI图的面积。定理2：弹性曲线上B点的正切相对于A点的正切的偏差等于点A与点B之间的M / EI图对A点（该点在弹性曲线上）的矩，这里偏差tA/B将被确定。26智囊经验 The conjugate-beam metho

49、d was first presented（提出）by Otto Mohr in 1860. Essentially（本质上）, it requires the same amount of computation（计算量）as the moment-area theorems to determine a beams slope or deflection; however, this method relies only on the principles of statics and hence its application will be more familiar（常见）. The

50、 basis for the method comes from（来自于）the similarity（相似性）between both dV/dx = - and d2M/dx2 = - , which relate a beams internal shear and moment to its applied loading, and d/dx = M/EI and d2y/dx2 = M/EI, which relate the slope and deflection of its elastic curve to the internal moment. 共轭梁法首先在1860年由

51、Otto Mohr提出。本质上说，它与弯矩图面积定理一样在确定梁的转角或挠度上需要相同的计算量；但是这种方法只依赖于静力学的原理，因此，它的应用更常见。该法的基础来自于dV/dx=-和d2M/dx2=-之间的相似性，它将梁的内部剪力和弯矩与它施加的荷载联系起来，而d/dx = M/EI和d2y/dx2 = M/EI将弹性曲线的转角和挠度与内部弯矩联系起来。27智囊经验 Note that the shear V compares with（与.对应）the slope , the moment M compares with the displacement y and the intensi

52、ty of the external load compares with the area under the M/EI diagram. To make use of this comparison we will consider a beam having the same length as the real beam, but referred to here as the “conjugate beam”. 注意剪力V与转角相对应，弯矩M与位移y相对应，而外力的强度与M/EI图下的面积相对应。为了利用这些对应，我们将考虑一根与实际梁一样长的梁。但是这里称为共轭梁。28智囊经验In

53、 general, though（然而）, remember that if the real support allows a slope, the conjugate support must develop（产生）a shear; and if the real support allows a displacement, the conjugate support must develop a moment, note that the conjugate beam is “loaded” with the M/EI diagram, in order to conform to（与.

54、一致）the load on the real beam. We can therefore state（陈述）two theorems related to the conjugate beam, namely（即）, Theorem 1: The slope at a point in the real beam is equal to the shear at the corresponding point（相应点）in conjugate beam. Theorem 2: The displacement of a point in the real beam is equal to

55、the moment at the corresponding point in the conjugate beam.29智囊经验 然而通常要记住如果实际的支座允许一个转角，共轭的支座必须产生一个剪力；如果实际的支座允许一个位移，共轭的支座必须产生一个弯矩，注意共轭梁用M/EI图来加荷，以便与实际梁上的荷载一致。因此，我们可以陈述与共轭梁相关的两种定理，即，定理1：实际梁上某一点的转角等于共轭梁上相应点的剪力。定理2：实际梁上某一点的位移等于共轭梁上相应点的弯矩。30智囊经验 For more complicated loadings or for structures such as tr

56、usses and frame, it is suggested（建议）that energy methods be used for the computation. All energy methods are based on the conservation of energy principle（能量守恒原则）, which states（规定）that the work（功）done by all the external forces acting on a structure, Ue, is transformed into（转化为）internal work or strai

57、n energy（应变能）UI, which is developed（形成）when the structure deforms（变形）. 对于较复杂的荷载或结构如桁架和框架，建议应该采用能量法来计算。所有的能量法是基于能量守恒原则，它规定了作用在结构上的所有外力作的功Ue转化成内部功或结构变形时形成的应变能UI 。31智囊经验 The principle of virtual work was developed by John Bernoulli in 1717 and is sometimes referred to as the unit-load method（单位荷载法）. It

58、 provides a general means（一般方法）of obtaining the displacement and slope at a point on a structure, be it（无论是）a beam, frame, or truss. Before developing the principle of virtual work, it is necessary to make some general statements（一般规定）regarding the principle of work and energy. 虚功原理在1717年由John Berno

59、ulli提出，有时称为单位荷载法。它提供了获得结构上某一点的位移和转角的一般的方法，不管该结构是梁、框架还是桁架。在提出虚功原理之前，关于功和能量的原理有必要作些一般规定。32智囊经验If we take（取）a deformable（可变形）structure of any shape or size and apply a series of external loads P to it, it will cause internal loads u at points throughout the structure. It is necessary that the external

60、and internal loads be related by the equation of equilibrium. As a consequence of（通过）these loadings, external displacement will occur at the P loads and internal displacement will occur at each point of internal load u. 如果我们取一个任何形状或尺寸的可变形结构，并对它施加一组外力P，它将导致整个结构上的点产生内力u。有必要通过平衡方程将内外力联系起来。通过这些荷载，外部的位移发