土木工程专业英语翻译.doc

精品文档Ch 2 Overview of Engineering MechanicsAs we look around us we see a world full of things: machines, devices, tools; things that we have designed, 当我们环顾四周，我们可以看到充满物质的世界：机器，仪器，工具：这些被我设计、建造和使用过 built and used; things made of wood, metals, ceramics, and plastics. We know from experience that some 的东西： 这些东西是由木头，金属，陶瓷和塑料做成。我们从经验可以知道一些东西比别的东things are better than others; they last longer, cost less, are quieter, look better, or are easier to use.比别的东西好： 他们比较耐用，低成本，安静，看起来好点，或者使用比较简单。Ideally, however, every such item has been designed according to some set of functional requirements; as 不管怎么样，最理想的是这样一个东西都是被设计者所认为的那样根据某些“使用要求”设计出来的。perceived by the designersthat is, it has been designed so as to answer the question, Exactly what function 也就是说他的设计是为了回答这些问题，确切的说它应该执行怎么样的功should it perform? In the world of engineering, the major function frequently is to support some type of能？ 在工程的领域里，最主要的功能是经常支持一些由于重力，惯性，压力等作用产 loading due to weight, inertia, pressure etc. From the beams in our homes to the wings of an airplane, there 生的荷载。 从我们家里的梁柱要飞机的双翼，这些都是由材料尺寸和must be an appropriate melding of materials, dimensions, and fastenings to produce structures that will 紧固件适当的组合，从而生产的结构在合理成本和使用周期的基础上可靠的履行它的职责。perform their functions reliably for a reasonably cost over a reasonable lifetime.In practice, engineering mechanics methods are used in two quite different ways:在实践中，工程力学方法用于两种完全不同的方式。1. The development of any new device requires an interactive, iterative consideration of form, size, materials, 任何新设计的发展要求都在尺寸，材料，荷载，耐久度，安全性和成本等方面进行交互、反复的考虑。loads, durability, safety, and cost.。2. When a device fails (unexpectedly) it is often necessary to carry out a study to pinpoint the cause of failure 当一个设计以外的失败的时候，必须经常的展开研究去查明失败的原因和确定可能的校正措施。and to identify potential corrective measures. Our best designs often evolve through a successive elimination of 我们最好的设计是经常通过逐渐的消除缺点来实现的。weak points.To many engineers, both of the above processes can prove to be absolutely fascinating and enjoyable, not to 对于许多工程师，上述的过程被证明它是极具吸引力和令人愉悦的，更不用说（有时）是有利可图的。mention (at times) lucrative.In any real problem there is never sufficient good, useful information; we seldom know the actual loads and 在任何真正的问题当中从未有足够好的，有用的信息，我们很少知道实际的荷载和任何精确的工作条operating conditions with any precision, and the analyses are seldom exact. While our mathematics may 件。 并且分析的结构很少是精确的。虽然我们的数学可以很精确，precise, the overall analysis is generally only approximate, and different skilled people can obtain different 所有的分析结果一般仅仅是近似的，和不同掌握技术的人可以获得不同的解决方案。solutions. In the study of engineering mechanics most of the problems will be sufficiently idealized to 在工程力学的研究当中，大多数的问题都将被足够的理想化，以便允许得到唯一的答案。permit unique solutions, but it should be clear that the real world is far less idealized, and that you usually 但是我们应该清楚意识到“真实的世界”远不是理想化的，你通常不得不执行will have to perform some idealization in order to obtain a solution.一些理想化以便获得答案。The technical areas we will consider are frequently called statics and strength of materials, statics 我们将考虑的技术领域通常叫做“静力学”和“材料力学”。静力学是指力作用于静止物体上的一种referring to the study of forces acting on stationary devices, and strength of materials referring to the effects 研究， “材料力学”是指那些力作用在结构上的of those forces on the structure (deformation, loading limits, etc.).影响（变形，荷载极限等）。While a great many devices are not, in fact, static, the methods developed here are perfectly applicable to 然而在实际上许多的设备并不是静力学的问题，如果额外的荷载被考虑，这里的研究方法完全适用于dynamic situations if the extra loadings associated with the dynamics are taken into account (we shall briefly 动力学情形，以至于在动力的情况下也被考虑在内（我们应该简单的提一下是怎么样被做到的）mention how this is done). Whenever the dynamic forces are small relative to the static loadings, the system 只要动力学的力相对于静力荷载来说很小，这个系统通常可以考虑为静力学is usually considered to be static.的问题。In engineering mechanics, we will begin to appreciate the various types of approximations that are inherent 在工程力学里，我们将开始正确评价各种类型在实际问题中本身就存在的近似方法。in any real problem:Primarily, we will be discussing things which are in equilibrium, i.e., not accelerating. However, if we look 首先，我们将会讨论处于平衡及不产生加速度的物体。然而如果我们看的够仔细，所有东西是运动的。closely enough, everything is accelerating.We will consider many structural members to weightless but they never are.我们会把一些结构构件考虑成失重，但他们从来都不是。We will deal with forces that act at a pointbut all forces act over an area.我们要处理的力作用在一个点上但是所有的力作用在一个区域上。We will consider some parts to be rigidbut all bodies will deform under load.我们会认为一些结构是刚性的但是所有的构件都在何在下变形。We will make many assumptions that clearly are false. But these assumptions should always render the 我们将做很多显然错误的假设。 但是这些假设应该总是使得问题更加容易处理。problem easier, more tractable. You will discover that the goal is to made as many simplifying assumptions 你将发觉目标是尽可能的做简单的假设，而没有严重降低结果。as possible without seriously degrading the result.Generally there is no clear method to determine how completely, or how precisely, to treat a problem. If our 通常没有明确的方法去可以完美的确定或者精确的处理这个问题。 如果我analysis is too simple, we may not get a pertinent answer; if our analysis is too detailed, we may not be able们的分析结构太过于简单，我们可能得不到正确的答案，如果我们的分析太过于详细，我们可能不能 to obtain any answer. It is usually preferable to start with a relatively simple analysis and then add more 或者任何的答案。 通常我们更喜欢的是从相对简单的分析开始，然后增加更多的细节以便于得到detail as required to obtain a practical solution.必须的实际结果。During the past two decades, there has been a tremendous growth in the availability of computerized 在过去二十年中，在计算机解决问题方法的实用性有了相当大的发展，methods for solving problems that previously were beyond solution because the tie required to solve them 这些问题以前是不能解决的，因为需要解决他们时间不允许。would have been prohibitive. At the same time the cost of computer capability and use has decreased by 同时计算机的内存能力和使用成本已经降下了许多个数量级。orders of magnitude. We are experiencing an influx of personal computers; on campus, in the home, and in 我们正在经历个人计算机进入校园，家庭和商场的时代。business.Ch 4 Stress Limits in DesignHow large can we permit the stresses to be? Or conversely: How large must a part be to withstand a given set 我们能够允许的最大应力是多少？反过来，构件必须要多少才能够承受一组给定的荷载呢？ of loads？what are the overall conditions or limits that will determine the size and material for a part? 将决定构件的尺寸和材料的整体状况或限制条件是什么？Design limits are based on avoiding failure of the part to perform its desired function. Because different parts 设计极限是基于构件执行设定功能避免遭受失败。 因为不同的构件must satisfy different functional requirements, the conditions which limit load-carrying ability may be quite 满足不同的功能要求， 极限承载能力的条件在不同的原理可能完全的不同。different for different elements. As an example, compare the design limits for the floor of a house with those 例如，比较房屋楼板的设计极限和那些飞机的双翼。for the wing of an airplane.If we were to determine the size of the wooden beams in a home such that they simply did not break, we 如果我们确定了房屋木梁的尺寸，以致他们仅仅不会断掉，我们不会因为他们这样而非常开心；would not be very happy with them; they would be too springy. Walking across the room would be like 他们太过于有弹性，穿过房间就行走在潜艇夹板上。walking out on a diving board.Obviously, we should be concerned with the maximum deflection that we, as individuals, find acceptable. 显然我们应该关心我们每个人所能接受的最大挠度。This level will be rather subjective, and different people will give different answers. In fact, the same people 这个标准是非常主观的，不同的人给出不同的答案。事实上，相同的人给出不同的答案取决于他们may give different answers depending on whether they are paying for the floor or not!是否会为这个楼板付钱。An airplane wing structure is clearly different. If you look out an airplane window and watch the wing during 飞机机翼的结构式显然不同。如果你从飞机窗户往外看，你会看到机翼在强对流天气中，你将看到很turbulent weather, you will see large deflections; in fact you may wish that they were smaller. However, you 的挠度。 事实上，你会希望他们更小一点。然而你知道最重要的know that the important issue is that of structural integrity, not deflection.是结构的整体性而不是挠度。We want to be assured that the wing will remain intact. We want to be assured that no matter what the pilot 我们想要确保机翼保持完好无缺，我们想要确保无论飞行员做了什么和无论天气是怎么样，双翼也将and the weather do, that wing will continue to act like a good and proper wing. In fact, we really want to be 继续表现得良好和合适的双翼 事实上，我们真的想要assured that the wing will never fail under any conditions. Now that is a pretty tall order; who knows what 确保机翼在任何情况下没有失败。 。由于这是非常艰难的任务。谁知道最坏的条the worst conditions might be?件是怎样的呢？Engineers who are responsible for the design of airplane wing structures must know, with some degree of 那些负责飞机机翼结构设计的工程师一定懂得， 一定程度的把握最有certainty, what the worst conditions are likely to be. It takes great patience and dedication for many years to 可能的最坏条件是什么。 他需要花费许多年的极大耐心和贡献去收集足够assemble enough test data and failure analyses to be able to predict the worst case. The general procedure is 的实验数据和失败失败分析，才能够预知“最坏”的情况。 一般的程序是研究to develop statistical data which allow us to say how frequently a given condition is likely to be 统计数据让我们解释在特定情况下可能会遇到的频率每1000小时一次，或者10000小时一次，encounteredonce every 1000 hours, or once every 10000 hours, etc.等等。As we said earlier, our object is to avoid failure. Suppose, however, that a part has failed in service, and we 就像我们早期所说的，我们的目标是避免失败。假设，然而一部分在使用中失败了，我们就会被问到are asked; Why? Error as such can come from three distinctly different sources, any or all of which can “为什么？”“误差”类似的，就会从来自三个截然不同的来源出发，部分或者全部都能导致失败。cause failure:1. Error in design: We the designers or the design analysts may have been a bit too optimistic: Maybe we ignored 设计的误差：我们的设计师或者设计分析者有那么一点过于乐观了：也许我们忽视了一些荷载；some loads; maybe our equations did not apply or were not properly applied; maybe we overestimated the 也许我们的公式不适用或者利用得不当； 也许我们高估了使用者的智慧。intelligence of the user; may we slipped a decimal point. 也许我们忽略了一个小数点。2. Error in manufacture: When a device involves heavily stressed members, the effective strength of the members 制造的误差：当设计涉及到重压力的一部分，这部分的有效应力通过不适当得制造和组装而大大减弱。can be greatly reduced through improper manufacture and assembly: May the wrong material was used; maybe 也许使用了错误的材料；也许the heat treatment was not as specified; maybe the surface finish was not as good as called for; may a part was 热处理不是和指定的一样； 也许表面的完成没有说的那么好； 也许有一部分out of tolerance; may be surface was damaged during machining; maybe the threads were not lubricated at 超出了可承受的范围；也许在制造中损坏了建筑表面； 也许螺纹在组装中不够润滑。assembly; or perhaps the bolts were not properly tightened. 或者螺栓没有适当的拉紧。3. Error in use: As we all know, we can damage almost anything if we try hard enough, and sometimes we do so 使用中的误差：我们都知道，如果我们用力过度的话会损坏所有的东西，和我们有时候是意外的； accidentally: We went too fast; we lost control; we fell asleep; we were not watching the gages; the power went 我们走的太快；我们会失去控制；我们睡着了；我们没有看着计量器；我们精力逐渐减弱，off; the computer crashed; he was taking a coffee break; she forgot to turn the machine off; you failed to lubricate 电脑故障； 他真的在喝咖啡休息； 他忘记了关掉仪器； 你没有给它加润滑it, etc.剂等。Any of the above can happen: Nothing is designed perfectly; nothing is made perfectly; and nothing is used 上面提到的都有可能发生：，没有东西设计得是完美的；没有东西被制造的很完美，和没有东西会被perfectly. When failure does occur, and we try to determine the cause, we can usually examine the design; we 使用得很完美，当失败发生的时候，我们我们尝试去确定原因，我们通常做的是检验设计；我们通常can usually examine the failed parts for manufacturing deficiencies; but we cannot usually determine how 检查失灵的部分，为了弥补制造时的缺失，但是我们通常不能决定这些设备怎么样式正确使用（或the device was used (or misused). In serious cases, this can give rise to considerable differences of opinion, 误用). 。在一些严重的示例中，这会引起相当不同的观点，differences which frequently end in court.这些不同的观点通常只能在法庭上解决。In an effort to account for all the above possibilities, we design every part with a safety factor. Simply put, 在努力解决上述可能性的时候， 我们要用安全系数来设计每一部分。简单的说，the safety factor (SF) is the ratio of the load that we think the part can withstand to the load we expect it to 在荷载中安全系数的比例我们认为这个结构可以承受以我们经验预期的荷载。experience. The safety factor can be applied by increasing the design loads beyond those actually expected, 安全系数应用于超越实际预期而逐渐增加的设计荷载。or by designing to stress levels below those that the material actually can withstand (frequently called design 或者设计的应力水平低于那些材料实际上可以承受的标准（通常称为“设计应力”stresses). Safety factor=SF=failure load/design load 安全系数=SF=破坏荷载/设计荷载 =failure stress/design stress =破坏应力/设计应力It is difficult to determine an appropriate value for the safety factor. In general, we should use larger values 很难确定安全系数的适当值。 一般而言，我们应该用更大的值当：when:1. The possible consequences of failure are high in terms of life or cost.1.失败的可能结果是高周期和成本为条件。2. There are large uncertainties in the design analyses.2.在设计分析里面有很大的不确定性。Values of SF generally range from a low of about 1.5 to 5 or more. When the incentives to reduce structural 安全系数的数值一般在低约1.5到5或更多之间变动，减少结构重量的奖励措施是很重要的（例如飞weight are great (as in aircraft and spacecraft), there is an obvious conflict. Safety dictates a large SF, while 和太空船），有着很冲突。安全条例规定最大的安全系数，当执行要求最小的数值。performance requires a small value. The only resolution involves reduction of uncertainty. Because of 唯一的解决方法是减少不确定性。 由于特别小心，并在extreme care and diligence in design, test, manufacture, and use, the aircraft industry is able to maintain very 设计、 测试、 制造和使用中的特别注意，航空工业能够保持非常令人羡慕的安全纪录，然而使用enviable safety records while using safety factors as low as 1.5.安全因素低至 1.5。We might not that the safety factor is frequently called the ignorance factor. This is not to imply that 我们常常不把安全系数称作未知因素。 但这并不是说工程师无知engineers are ignorant, but to help instill in them humility, caution, and care. An engineer is responsible for 而是帮助他们慢慢灌输谦虚，谨慎和注意。 工程师为他的或她的设计决策his or her design decisions, both ethically and legally. Try to learn from the mistakes of others rather than 负责任， ，在法律和伦理两方面。 尝试从别人的错误中学习而不是你自己本人制造making your own.错误。 Ch 6 Testing of MaterialsThe most common test of building materials is the strength test to destruction. This is partly because strength 大部分建筑材料的测试都是强度破坏的测试。 部分是因为强度是建筑材 is a very important property of a building material, even a material in a non-load-bearing part of the 料很重要的性能， ，甚至是建筑物中非承重部分的材料，building; partly because strength tests are comparatively simple to carry out; and partly because they offer a 部分是因为强度测试比较简单的完成，和部分是因为他们提供了其他性能的指导，guide to other properties, such as durability. 例如耐久性。The strength of a ductile material such as steel, aluminium, or plastics is usually determined by applying a 延展性材料的强度例如钢筋，铝合金，或者塑料通常是通过拉力荷载说决定的。tensile load. A compression test is used for brittle materials such as concrete, stone, and brick because their 压应力的测试用来测试脆性材料例如混凝土，石头，和砖，因为他们的抗拉强度很低tensile strength is low and thus harder to measure accurately. 和因而很难准确测量。The method of testing and the dimensions of the test pieces are laid down in the appropriate standards 测试的方法和试样的尺寸要符合美国材料实验学会、英国标准学会、澳大利亚标准学会等公布的published by the American Society for Testing Materials (ASTM), the British Standards Institution (BSI), the 适当标准。 Standards Association of Australia (SAA), etc.The size and shape of the test specimen are particularly important for brittle materials because they influence 试验的尺寸和形状对于脆性材料尤其重要，因为他们影响了实验可能会发生的裂缝数量。the number of flaws that are likely to occur in the test specimen. For concrete tests, the standard American 对于混凝土测试，美国和澳大利亚的and Australian test specimena cylinder 150mm (6 in.) in diameter and 300 mm (12 in.) longgives a 标准试验是150mm（6in）直径的圆柱和300mm（12in）长给一个比英国标注更低的试验lower result than the standard British test specimena 150-mm cubebecause the former contains more 150mm立方体因为前者可以容纳更多的混凝土。concrete.The speed of testing is also specified. A passage of time is required for both plastic deformation and the 测试的速度也是被指定的。塑性变形和裂缝形成所通过的时间也是被要求的，formation of cracks, and a faster rate of testing thus gives a higher result. 更快的测试速度从而得出更高的结构。For tests on concrete and timber, it is necessary to specify moisture content because this affects the strength.混凝土和木材的测试，指定水的含量是非常有必要的，因为这个影响到他的强度。A test on a single specimen is unreliable because we do not know whether it is an average test specimen or 单一构件的测试是不可靠的，因为我们不知道他是否是一个均匀的式样或者它是否低于或高于细小whether it has fewer or more than the average number of minute flaws. Standard specifications lay down 裂缝的平均数量。 标准规范规定多少构件应该被测how many specimens shall be tested and how they are to be selected.试和他们要怎么样被选择。Tests of factory-made materials carried out by the manufacturer are usually accepted by the user of the 在建造商下完成的由工厂制造的材料测试通常被建筑材料使用者所接受除非他们有理由去怀疑他们building material unless he has reason to doubt their veracity. Since concrete is made on the building site or 的准确性。 自从混凝土在建筑工地生产或者从预拌制brought from a ready-mix concrete plant, its testing becomes the responsibil