土木工程专业英语(苏小卒)课文翻译3~5单元.doc

Unit 3 (从第三段开始)现代水泥发明于1824年，称为波特兰水泥。它是石灰石和粘土的混合物，加热后磨成粉末。在或靠近施工现场，将水泥与砂、骨料（小石头、压碎的岩石或砾石）、水混合而制成混凝土。不同比例的配料会制造出不同强度和重量的混凝土。混凝土的用途很多，可以浇筑、泵送甚至喷射成各种形状。混凝土具有很大的抗压强度，而钢材具有很大的抗拉强度。这样，两种材料可以互补。They also complement each other in another way: they have almost the same rate of contraction and expansion. They therefore can work together in situations where（在情况下） both compression and tension are factors（主要因素）. Steel rods（钢筋） are embedded in（埋入）concrete to make reinforced concrete in concrete beams or structures where tension will develop（出现）. Concrete and steel also form such a strong bond - the force that unites（粘合） them - that the steel cannot slip（滑移） with the concrete. Still（还有） another advantage is that steel does not rust in concrete. Acid（酸） corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid. 它们也以另外一种方式互补：它们几乎有相同的收缩率和膨胀率。因此，它们在拉、压为主要因素时能共同工作。在出现拉力的混凝土梁或结构中，将钢筋埋入混凝土而成钢筋混凝土。混凝土与钢筋形成如此强大的结合力这个力将它们粘合在一起以致于钢筋在混凝土中不会滑移。还有另一个优势是钢筋在混凝土中不会锈蚀。酸能腐蚀钢筋，而混凝土会发生碱性的化学反应，与酸相反。The adoption of structural steel and reinforced concrete caused major changes in traditional construction practices（施工作业）. It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fire-resistant floors（防火地面）. Both these changes served to（有利于） reduce the cost of construction. It also became possible to erect（建造）buildings with greater heights and longer spans. 结构钢与钢筋混凝土的采用使传统的施工作业发生了明显的变化。对多层建筑，再也没必要采用厚的石墙或砖墙，且施工防火地面变为容易得多。这些变化有利于降低建筑的成本。它也使建造高度更高和跨度更大的建筑物成为可能。Since the weight of modern structures is carried（承受） by the steel or concrete frame, the walls do not support the building. They have become curtain walls, which keep out the weather and let in light. In the earlier steel or concrete frame building, the curtain walls were generally made of masonry; they had the solid look of bearing walls（承重墙）. Today, however, curtain walls are often made of lightweight materials such as glass, aluminum, or plastic, in various combinations. 由于现代结构的重量由钢或混凝土框架承受，墙体不再支承建筑物。它们成为幕墙，将日晒风吹雨打阻挡在外，而让光线进入。在较早的钢或混凝土框架建筑中，幕墙一般由砌体构成；它们具有承重墙的结实外观。但是今天，幕墙通常由轻质材料组成，如玻璃、铝或塑料，并形成不同的组合。Another advance in steel construction（结构） is the method of fastening together（连在一起） the beams. For many years the standard method was riveting. A rivet is a bolt with a head that looks like a blunt screw（圆头螺丝钉） without threads（螺纹）. It is heated, placed in holes through the pieces of steel（钢构件）, and a second head is formed at the other end by hammering（锤击）it to hold it in place（固定就位）. Riveting has now largely been replaced by welding, the joining together of pieces of steel by melting（熔化） a steel material between them under high heat. 钢结构中的另一个进步是梁的连接方式。在很多年里，连接的标准方式是铆接。铆钉是个有头的螺栓，看上去象个没有螺纹的圆头螺丝钉。铆钉加热后穿过钢构件之间的孔洞，并通过锤击另一端而形成第二个铆钉头，从而将其固定就位。如今铆接已大量地被焊接所替代，钢构件间的连接通过在高热下熔化它们之间的钢材料（即焊条）进行。Prestressed concrete is an improved form of reinforcement（加强方法）. Steel rods are bent into the shapes to give them the necessary degree of tensile strength. They are then used to prestress （对.预加应力）concrete, usually by one of two different methods. The first is to leave channels in a concrete beam that correspond to（相应于） the shapes of the steel rods. When the rods are run through the channels, they are then bonded to the concrete by filling the channels with grout, a thin mortar or binding agent. In the other (and more common) method, the prestressed steel rods are placed in the lower part of a form（模板） that corresponds to the shape of the finished structure（成品结构）, and the concrete is poured around them. Prestressed concrete uses less steel and less concrete. Because it is so economical, it is a highly desirable（非常理想） material.预应力混凝土是加强法的改进形式。将钢筋弯成一定的形状以使它们具有必要的抗拉强度，然后用该钢筋对混凝土施加预应力，通常可采用两种不同方法中的任何一种。第一种方法是在混凝土梁中按钢筋的形状留下孔道，当钢筋穿过孔道后，通过在孔道内灌注薄砂浆（一种稀薄的砂浆或粘合剂）将钢筋与混凝土粘结在一起。另一种（更常用的）方法是将预应力钢筋置于按成品结构的形状设置的模板的较低部位，然后将混凝土倒入（模板）而包围着钢筋。预应力混凝土使用了较少的钢筋和混凝土，由于它是如此的经济，因此是一种非常理想的材料。Prestressed concrete has made it possible to develop（建造） buildings with unusual shapes, like some of the modern sports arenas, with large space unbroken by any obstructing supports（阻碍的支撑物）. The uses for this relatively new structural method are constantly being developed（不断地扩大）. 预应力混凝土使建造独特形状的建筑物成为可能，象一些现代的运动场，它具有不受任何支撑物阻挡视线的大空间。这种较新的结构方法的使用正在不断地被扩大。The current tendency is to develop（采用） lighter materials, aluminum, for example, weighs much less than steel but has many of the same properties. Aluminum beams have already been used for bridge construction and for the framework of a few buildings. 目前的趋势是采用较轻的材料。例如，铝的重量比钢轻得多，但具有很多相同的性能。铝材梁已经用于桥梁建筑和一些建筑的框架。Lightweight concretes, another example, are now rapidly developing（发展） throughout the world. They are used for their thermal insulation(绝热性). The three types are illustrated below（举例说明如下）: (a) Concretes made with lightweight aggregates; (b) Aerated concretes (US gas concretes) foamed（起泡） by whisking（搅拌）or by some chemical process during casting; (c) No-fines concretes. 另一个例子是轻质混凝土，如今已在全世界快速地发展，因它们的绝热性而被采用，其三种类型举例说明如下：(a)轻质骨料制成的混凝土；(b)通过浇筑时搅拌或一些化学方法起泡而成的加气混凝土（US加气混凝土）；(c)无细骨料混凝土。All three types are used for their insulating properties（绝热性）, mainly in housing, where they give high（非常） comfort in cold climates and a low cost of cooling（降温成本）in hot climates. In housing, the relative weakness of lightweight concrete walls is unimportant, but it matters（有重大关系） in roof slabs, floor slabs and beams. 这三种类型的混凝土都是由于它们的绝热性而被使用，主要用于房屋，使其在寒冷的气候中非常舒服，在炎热的气候中降温的成本不高。在房屋中，墙采用较薄弱的轻质混凝土不重要，但是屋面板、楼面板和梁（采用轻质混凝土）则有重大关系。In some locations, some lightweight aggregates cost little more than（几乎等于） the best dense（致密） aggregates and a large number of （大量） floor slabs have therefore been built of lightweight aggregate concrete purely for its weight saving, with no thought of（没考虑） its insulation value. 在某些地区，一些轻质骨料的费用几乎等于最致密的骨料，因此大量的楼面板采用轻骨料混凝土制作纯粹是节约重量，而没考虑它的绝热价值。The lightweight aggregate reduces the floor dead load（恒载） by about 20 per cent resulting in（导致）considerable savings in the floor（楼盖结构） steel in every floor and the roof, as well as in the column steel and (less) in the foundations. One London contractor（承包商）prefers to use lightweight aggregate because it gives him the same weight reduction in the floor slab as the use of hollow tiles, with simpler organization and therefore higher speed and profit. The insulation value of the lightweight aggregate is only important in the roof insulation, which is greatly improved（改进）. 轻质骨料使楼面的恒载减少了约20%，因而大量的节约了每层楼面以及屋面的楼盖结构中的钢材和柱子与基础中（较少）的钢材使用量。一位伦敦的承包商宁愿使用轻质骨料，因为这使楼面板上减少的重量与用空心砖相同，且组织更简单，因而速度和利润更高。轻质骨料的绝热价值只在屋面绝热时显得重要，它已被大大地改进了。作业练习通过两篇 Reading Materials 的学习，进一步了解建筑材料中最常用的混凝土材料的一些特点、种类和性能等，从而更多地掌握一些专业词汇和句法。Unit 4 材料力学教学目标了解构件（主要为梁）的设计过程了解单轴应力与多轴应力对失效理论的影响熟悉材料力学中涉及的专业词汇熟悉科技类文献常用句型熟悉in general、usually、frequently的不同含义与 be referred to as、be known as、that is、be defined as、in other words 等的用法Introduction 介绍Mechanics of Materials deals with（研究）the response of various bodies, usually called members（构件）, to applied forces（施加力）. In Mechanics of Engineering Materials the members have shapes that either exist in actual structures or are being considered for their suitability（根据其需要）as parts of proposed（拟建的）engineering structures. The materials in the members have properties that are characteristic of commonly used（常用的）engineering materials such as steel, aluminum, concrete, and wood. 材料力学用以研究不同物体（通常称为构件）对施加力的响应。在工程材料力学中，构件的形状可以是实际结构中存在的，也可以根据其需要而进行考虑（设计），作为拟建工程结构的部件。构件中材料的性能即是常用的工程材料如钢材、铝材、混凝土和木材的特性。As you can see already from the variety of materials, forces, and shapes mentioned, Mechanics of Engineering Materials is of interest to（对.有价值）all fields of engineering. The engineer uses the principles of Mechanics of Materials to determine if the material properties and the dimensions of a member are adequate to（足以）ensure that it can carry its loads safely and without excessive distortion. In general（通常）, then, we are interested in both the safe load that a member can carry and the associated（相关的）deformation. Engineering design would be a simple process if the designer could take into consideration（考虑）the loads and the mechanical properties of the materials, manipulate（利用）an equation, and arrive at（得到）suitable dimensions. Design is seldom that simple. Usually（通常）, on the basis of（根据）experience, the designer selects a trial（试算） member and then does an analysis to see if that member meets the specified requirements. Frequently（常常）, it does not and then a new trial member is selected and the analysis repeated. This design cycle（设计周期） continues until a satisfactory solution is obtained. The number of cycles（循环次数） required to find an acceptable design diminishes as the designer gains experience.正如你已经从提到的各种各样的材料、力和形状所看到的，工程材料力学对所有的工程领域都有价值。工程师利用材料力学的原理来确定是否该材料的性能和构件尺寸足以保证它能安全地承受荷载且没有过多的变形。通常，我们关心的是构件能承受的安全荷载及其相应的变形。如果设计者能通过考虑荷载和材料的力学性能，并利用公式得到合适的构件尺寸，那么工程设计将是一个简单的过程。然而设计很少那么简单。通常，根据经验，设计者选择一个试算构件，然后进行分析，看它是否满足规定的要求。它常常不会满足要求，则再选择一个新的试算构件，再进行分析。这样的设计不断重复，直至得到一个满意的结果。当设计师拥有一定的经验后，为得到一个可接受的设计所需要的循环次数会减少。Design of Axially Loaded Members 轴向力构件的设计 To give you some insight into （使.有一些了解）the design cycle, an extremely simple member will be dealt with first. That member is a prismatic bar with a force, P, acting along its longitudinal axis in the direction（纵轴向）such that it tends to elongate the bar. Such a force is referred to as（称为）an axial tensile load（轴向拉力）, and we can readily imagine it trying to（努力.）pull the fibers apart and to cause failure on a transverse plane（横向平面）. It is safe to assume that all fibers of the bar, in regions remote from（远离）the point of application of the load, are being pulled apart with the same load intensity（荷载强度）. With this assumption, the load intensity or stress is uniform on a transverse plane and is given by when P is in（以.为单位）Newtons and A is in square metres, stress,? ,is in Newtons per square metre (N/m2), which is by definition（根据定义）Pascals (Pa).为了使你对设计周期有一些了解，首先研究一个非常简单的构件。构件是个棱形的杆件，其上沿着它的纵轴向作用一个力P，这样往往使杆件在该方向上伸长。这样的力称为轴向拉力，我们能容易地想象它在努力地将纤维拉开，导致横向平面的破坏。安全地假定杆件的所有纤维在远离荷载施加点的区域以相同的荷载强度被拉开。在此假定下，荷载强度或应力在横向平面上是均匀的，为 当P的单位为牛顿、A的单位为平方米时，应力的单位为牛顿每平方米（N/m2），根据定义为帕斯卡（Pa）。For a given axial load and given dimensions, the stress can be calculated from (4-1) and compared with（与.相比）the stress that can be safely carried by the material. The safe stress, known as（称为）the design stress or allowable stress（许用应力）, is determined by tests performed on material made to（按照） the same specifications as the part being considered. A safety factor（安全系数）, frequently imposed by a legally established code（法规）, is applied to the strength, as determined by tests, to give the allowable stress. The allowable stress, ?a , is given bywhere ?f is the stress at which the material fails (failure to be defined later) and n is the safety factor.对已知的轴向力和（构件）尺寸，可根据公式（4-1）计算出应力，并与材料能安全承受的应力作比较。安全应力，称为设计应力或许用应力，它是通过对材料的试验来确定的，该（试验）材料按照与所考虑（验算）的杆件相同的规范制作。根据法规规定，通常对试验所确定的强度考虑安全系数后得到许用应力。许用应力 ?a 为这里，?f 为材料失效（失效在下文有定义）时的应力，而n为安全系数。Before approving（核准）trial dimensions, the designer makes certain（确信）that the design is safe by determining that the inequality（不等式）is satisfied. The inequality is usually more convenient in the form不等式常常以更合适的形式出现，即在核准试算的尺寸之前，设计者通过确定不等式成立而确信设计的安全，即It might at first（起先）seem that the designer would always dimension（选定.的尺寸）the cross section（横截面） so that the stress would exactly equal the allowable stress. However, it may be very costly to produce parts that have nonstandard sizes, so it is usually more economical to waste some material by selecting the next（接近的）larger standard size above that required by the allowable stress. Departure from（背离）standard sizes is justified（合理的） in cases where the penalty（不利后果）for excess weight is very severe, as in aircraft（航天器）or space-ship（宇宙飞船）design. 起先似乎设计者总是在选定横截面的尺寸，以使应力恰好等于许用应力。但是，生产非标准尺寸部件的成本可能很高，因此，通常人们会选择比按许用应力要求的尺寸大一些的标准尺寸部件，这样尽管浪费了一些材料，但总体上更经济。但不选择标准尺寸的做法在诸如航天器和宇宙飞船的设计中证明是合理的，因为多余重量产生的不利后果是很严重的。Design of Beams 梁的设计Up to this point（至此）we have looked at（考虑）the beam problem as a problem in analysis; that is（即）, for a given set of loads, span, and cross section we have been calculating the stress. The more commonly encountered problem is to select a standard section, or design a member, for a given span and loads without exceeding a certain allowable stress. Under some conditions the allowable stress may be dependent upon the dimensions and shape of the cross section, in which case the selection of the member becomes more difficult. For the present（暂时）we will take the allowable stress as though（似乎）it depends only on the strength of the material and the safety factor.至此，我们已经考虑了梁的问题而进行了（问题）分析，即对给定的一组荷载、跨度和横截面，我们已经计算了应力。更常遇到的问题是在不超过某个许用应力下对一个给定的跨度和荷载选择一个（构件的）标准截面，或设计一个构件。在某些条件下，许用应力可能依赖于横截面的尺寸和形状，这种情况下的构件选择会变得比较困难。暂时我们将采用许用应力法，似乎它只取决于材料的强度和安全系数。A trial member will be acceptable（合格）when the stress is equal to, or less than, the allowable stress, that is, ifFor design purposes this inequality is more useful in the formIn the usual design process the maximum bending moment is taken from（取自于）the bending moment diagram（弯矩图） and the allowable stress is determined (quite frequently in accordance with（根据）the rules of some legally constituted code) from standard strength tests in combination with（与.结合）a safety factor. The right-hand side of (4-6) is then known, and it remains（仍然是） to select or design a member that will satisfy the inequality. When a standard section is to be used, the tables（表格）could be searched until a member is found such that the combination of I and c satisfies (4-6). This takes more time than is really necessary, since the tables also provide the value of I/c for each member under the heading（标题）S, the section modulus（截面模量）. 当试算构件的应力等于或小于许用应力时，也就是说，如果在通常的设计过程中，最大的弯距从弯距图上取得，而许用应力通过标准强度试验并考虑安全系数后确定（往往是根据一些法规的规则）。这样，已知式（4-6）右手边的值，则仍然是选择或设计构件以满足该不等式。当使用标准截面时可以查找表格，直至找到的构件其I和c值的组合能满足式（4-6）。这样花费的时间比实际需要的多，因为表格中在截面模量S的标题下也提供了每一个构件的I/c的值。试算构件即为合格。根据设计的需要，（上述）不等式以下列形式出现更有用，即That is, the section modulus is defined as（定义为）To select a member, the S column（列） is consulted（查阅） and any member that satisfies (4-8) could be used. The members with very high values of S will obviously be understressed（应力不足的）and wasteful of material. The best design, if there are no other constraints, will be that which satisfies (4-8) with the minimum amount of material. With tabulated values of S available it is much more convenient to use (4-6) in the formThe smallest acceptable S does not necessarily coincide with（符合）the most economical member. To select the lightest and most economical standard section, the listed values of mass should be examined to find the lightest member with an acceptable S. The problem becomes much more complex if built-up（组合）member is being designed because its cost will depend upon the combined costs of web plate, angles and cover plates as well as fabrication（装配）costs so that the lightest member is not necessarily the most economical.截面模量定义为为选择构件而查阅S这一列，则任何满足式（4-8）的构件都可采用。显而易见，对S值很高的构件，其应力是不足的，并浪费了材料。如果没有其他的限制，最好的设计将是以最少的材料满足式（4-8）。能接受的最小的S值不必是最经济的构件。为了选择最轻和最经济的标准截面，应检查列出的质量值，以找到能接受的S值下的最轻构件。如果在设计一个组合构件时，则问题变得复杂得多，因为它的费用将依赖于腹板、角钢和盖板的费用以及装配的费用，因此，最轻的构件未必是最经济的构件。根据表格中得到的值S，将式（4-6）以下列形式使用要方便得多，即Deflections Due to Bending 弯曲挠度The main purpose of this chapter（本节） was to develop（提出）the flexure（屈曲）formulas, and to provide some experience in applying them. Statically indeterminate（超静定）cases were encountered and some insight（认识） gained as to（就.）the difficulty and importance of this category of problem. 本节的主要目的是提出屈曲公式，并在运用公式时提供一些经验。当遇到超静定的情况时，就此类问题的难点和重点获得一些认识。Superposition（叠加法）was presented（提出） as the preferred（优先的）method for solving certain problems. However, becoming familiar with（熟悉）superposition was more important than finding solutions to the problems（问题的答案） because superposition has application in many areas of stress analysis and will be used frequently in our future studies. 为解决某些问题，叠加法作为优先的方法被提出。但是，熟悉叠加法远比找到问题的答案重要，因为叠加法已经用于应力分析的很多领域，而且，在我们今后的研究中还会经常使用。Moment-area（弯距图面积法）was found to be a convenient method for solving various problems. It is a method that becomes quite complicated and requires further development（展开） when more advanced structures are encountered. At the present stage it is sufficient for you to be acquainted with（了解）the fundamentals（基本原理）of the method. Deflection of long-radius（长半径） curved beams was introduced（引入）to illustrate the power of the principles underlying（构成.的基础）the moment-area method and so that you would appreciate（知道）the differences between straight and curved beams. 为解决不同的问题，发现弯距图面积法是一种很便利的方法。但当遇到更先进的结构时，此法会变得非常复杂，需要进一步地展开。对你来说在目前阶段了解此法的基本原理已经足够了。引入长半径曲梁的挠度来举例说明构成弯距图面积法基础的原理的功效，使你能知道直梁与曲梁之间的区别。This chapter afforded an opportunity to become familiar with singularity functions （奇异函数）, and you have seen that certain problems can be greatly simplified by their use. It must be appreciated（意识到）that merely an introduction to the topic has been given; there is much more to learned by those who have a special interest. To illustrate a serious limitation（缺陷） at our present stage, we can express distributed loads （分布荷载） that are variable and are intermittent, but we cannot write a load function for concentrated loads. If we had taken the next step and dealt with the concentrated load, we would have encountered the source of the expression（表达式）“singularity function”, but having regard for（考虑）the scope of this book we have stopped short of（达不到）that step.本节使你熟悉了奇异函数，并发现通过利用它们能大大地简化某些问题。但必须意识到仅仅是介绍了题目，对那些有特殊兴趣的人还有很多要学。我们可以表示变化的、间断的分布荷载，但不能写出集中荷载的荷载函数，说明了在我们目前阶段（该函数）还存在着严重的缺陷。如果我们进入下一步去研究集中荷载，便会遇到奇异函数表达式的来源，但是考虑到本书的范围，我们不再进入那一步。Failure Theories 失效理论In the design of a member subjected to a uniaxial（单轴的） load, the stress was compared with the stress to cause failure in test specimens（试件）that had also been subjected t