土木工程专业英语第9次课讲义.doc

土木工程专业英语第9次课讲义
Chapter 7 土木工程专业文献选读
Contents
Lesson 4 Philosophy of Structure Design
结构设计原理
Objectives（教学目标）：本课主要介绍结构设计的基本方法，了解容许应力法和极限状态设计的原则和特点；掌握相关的专业词汇；注意长句的译法。
Key Issues（教学重点）：掌握结构设计的几种方法和适用性。掌握专业词汇；掌握句子表达方式。
I．Translation：
Lesson 4 Philosophy of Structure Design
结构设计原理
Paragraph 1
A structural engineering project can be divided into three phases: planning, design, and construction.
¡ structural engineering 结构工程, 结构工程学
¡ planning 计划编制，规划
¡ 一个结构工程项目可分为三个阶段:规划、设计、施工。
Paragraph2
1.Structural design involves determining the most suitable proportions of a structure and dimensioning the structural elements and details of which it is composed.
¡ Proportion 比, 比率,均衡, 相称,份, 部份,大小; 面积; 容积,比例
¡ Dimensioning 定尺寸，计算
¡ 结构设计包括确定结构最适宜的比例，并确定其组成构件和细部尺寸。
2.This is the most highly technical and mathematical phase of a structural engineering project, but it cannot and certainly should not-be conducted without being fully coordinated with the planning and construction phases of the project.
¡ technical adj.技术的, 技术上的, 技巧方面的
¡ mathematical adj.数学的, 精确的
¡ conduct 进行，实施,引导，指导
¡ coordinate（使）互相配合,（使）协调， 调整
这是结构工程项目中技术性最高、数学严谨性最强的阶段，但若不能同规划和施工阶段充分协调，就不能也不应该付诸实施。
3.The successful designer is at all times fully conscious of the various considerations that were involved in the preliminary planning for the structure and, likewise, of the various problems that may later be encountered in its construction.
¡ conscious adj.有意识的, 有知觉的
¡ consideration n.考虑, 需要考虑的事项, 体谅
¡ be involved in 涉及,有关
¡ preliminary plan初步设计,初步计划
¡ likewise adv.同样地, 照样地, 又, 也
一个成功的设计者总是会全面考虑结构在初步规划中涉及到的各种因素，以及今后施工中可能遇到的各种问题。
Paragraph3
1.Specially, the structural design of any structure first involves the establishment of the loading, and other design conditions that must be resisted by the structure and therefore must be considered in its design.
¡ establishment n.确立, 制定
¡ resist vt.抵抗, 反抗, 抗
特别地，在任何结构的设计中，首先涉及到确定结构所必须承受的因而设计中必须考虑的荷载和其它设计条件。
2.Then comes the analysis (or computation) of the internal gross forces (thrust, shears, bending moments, and twisting moments), stress intensities, strains, deflections, and reactions produced by the loads, temperature, shrinkage, creep, or other design conditions.
¡ internal gross forces 总内力
¡ bending moment 弯矩
¡ twisting moment 扭矩
¡ stress intensity 应力强度
¡ reaction n.反力, 反作用
接下来是分析在荷载、温度、收缩、徐变及其它设计条件下结构所产生的总内力（轴力、剪力、弯矩、扭矩）、应力强度、应变、变形和反力。
3.Finally comes proportioning and selection of materials of the members and connections so as to resist adequately the effects produced by the design conditions。
¡ proportioning 确定(几何)尺寸, 选择参数
¡ connection 连接,接头
最后对各构件及连接进行尺寸设计及材料选择，使之足以抵抗设计条件所产生的作用效应。
4.The criteria used to judge whether particular proportions will result in the desired behavior reflect accumulated knowledge (theory, field and model test, and practical experience), intuition, and judgment.
¡ criteria n.标准
¡ proportion比例,面积, 部分
¡ model test 模型试验
¡ intuition n.直觉, 直觉的知识
¡ judgement n.判断力, 意见, 看法
某设计尺寸是否会达到预期的结构性能，所使用的判断准则反映了知识积累（理论，现场试验及模型试验和实践经验），直觉知识和判断力。
5.For most common civil engineering structures such as bridges and buildings, the usual practice in the past has been to design on the basis of a comparison of allowable stress intensities with those produced by the service loadings and other design conditions.
¡ comparison….with 与…相比较
¡ allowable stress 容许应力
对于象桥梁和房屋这些最常见的土木工程结构来说，过去通常的做法是将使用荷载和其它设计条件下产生的应力与容许应力强度进行比较，然后据此进行设计。
6.This traditional basis for design is called elastic design because the allowable stress intensities are chosen in accordance with the concept that the stress or strain corresponding to the yield point of the material should not be exceeded at the most highly stressed points of the structure.
¡ basis n.基础, 基本, 根据,基本原则或原理
¡ elastic design 弹性设计
¡ in accordance with adv.与...一致, 依照
¡ concept n.观念, 概念
¡ correspond to 相应, 符合,相当于
¡ yield point 屈服点
由于选择容许应力强度的前提概念是：在结构的最大受力点处（的应力或应变）不得超过材料屈服点处的应力或应变，因此这种传统的设计方法称为弹性设计。
7.Of course, the selection of the allowable stresses may also be modified by a consideration of the possibility of failure due to fatigue, buckling, or brittle fracture or by consideration of the permissible deflections of the structure.
¡ modify 修正,更改，修改
¡ buckling 屈曲,纵向弯曲
¡ brittle fracture 脆性断裂,脆性破坏
¡ permissible deflection 允许挠度
当然，考虑到结构也可能会发生疲劳、压曲、脆断破坏或考虑到结构的容许变形量，选择容许应力时也可能会作一些调整。
Paragraph4
1.Depending on the type of structure and the conditions involved, the stress intensities computed in the analytical model of the actual structure for the assumed design conditions may or may not be in close agreement with the stress intensities produced in actual structure by the actual conditions to which it is exposed.
¡ depend on 取决于，依赖
¡ stress intensity 应力强度
¡ analytical adj.分析的, 解析的
¡ assumed condition 假设条件
¡ agreement with 与…一致
根据结构类型和有关条件，在假定设计条件下按选用的结构分析模型 所计算出的应力强度，和实际条件在实际结构中引起的应力强度，可能也可能不十分吻合。
2.The degree of correspondence is not important, provided that the computed stress intensities can be interpreted in terms of previous experience.
¡ correspondence 符合，一致，相当
¡ provided that 假如, 设若，只要….
¡ Interpret v.解释, 说明
¡ in terms of adv.根据, 按照, 用...的话
只要计算出的应力强度能根据以往的经验解释，吻合程度就不重要。
3.The selection of the service conditions and the allowable stress intensities provides a margin of safety against failure.
¡ margin of safety 安全系数
为防止结构失效，在选择使用条件和容许应力强度时提供了安全储备。
4.The selection of the magnitude of this margin depends on the degree of uncertainty regarding loading, analysis, design, materials, and construction and on the consequences of failure.
¡ margin富余
¡ uncertainty n.不确定, 不可靠
¡ regarding prep.关于
储备量值的选择取决于荷载、分析、设计、施工的不确定性程度和失效后果。
5.For example, if an allowable tensile stress of 20000 psi is selected for structural steel with a yield stress of 33000 psi, the margin of safety (or factor of safety) provided against tensile yielding is 33000/20000. or 1.65.
¡ structural steel 结构钢材
(比如，对于屈服应力为33000 psi的结构钢，其容许应力选择为20000psi，那么针对受拉屈服的安全储备（或安全系数）为33000/20000，或1.65。)
Paragraph5
1.The allowable-stress approach has an important disadvantage in that it does not provide a uniform overload capacity for all parts and all types of structures.
¡ allowable-stress approach 容许应力法
¡ uniform adj.统一的, 相同的, 一致的, 始终如一的
¡ overload vt.使超载, 超过负荷 n.超载, 负荷过多，过载
容许应力法的一个很大的缺点，就在于它不能对各种结构类型以及结构各部分，提供统一的超载能力。
2.As a result, there is today a rapidly growing tendency to base the design on the ultimate strength and serviceability of the structure, with the older allowable-stress approach serving as an alternative basis for design.
¡ as a result adv.结果
¡ ultimate strength 极限强度
¡ serviceability适用性
¡ alternative n.二中择一, 可供选择的办法adj.选择性的, 二中择一的
因此，目前日益趋向于基于结构的极限强度和适用性进行设计，以往的容许应力法只作为一种备选设计方法。
3.The newer approach currently goes under the name of strength design in reinforced-concrete design literature and plastic design in steel-design literature.
¡ literature 著作, 文献
目前这种新方法在钢筋混凝土设计文献中统称强度设计，在钢结构设计文献中统称塑性设计。
4. When proportioning is done on the strength basis, the anticipated service loading is first multiplied by a suitable load factor (greater than 1), the magnitude of which depends upon the uncertainty of the loading, the possibility of its changing during the life of structure, and, for a combination of loadings，the likelihood, frequency, and duration of the particular combination.
¡ proportioning 确定(几何)尺寸, 选择参数
¡ anticipated load 预期载荷
¡ multiply 乘, 增加 multiply 8 by 4 以4乘8
¡ load factor 荷载系数, 载荷因子,负载系数
¡ likelihood n.可能, 可能性
¡ frequency 频率
¡ duration n.持续时间
按照强度方法设计构件尺寸时，首先将预期使用荷载乘以适当的大于1的荷载系数，该系数值的大小取决于荷载的不确定性以及结构使用期间内发生变化的可能性，对于荷载组合，还取决于某荷载组合的可能性、出现频率和持续时间。
5.In this approach for reinforced-concrete design, the theoretical capacity of a structural element is reduced by a capacity-reduction factor to provide for small adverse variations in material strengths, workmanship, and dimensions.
¡ theoretical 理论的
¡ adverse adj.不利的,相反的
¡ variation 变化
¡ workmanship技艺,工艺
¡ capacity-reduction factor 承载能力折剪系数
在这种钢筋混凝土设计方法中，考虑到材料强度、施工工艺和结构尺寸的变异性的不利情况，通过承载能力折减系数将结构构件的理论承载能力进行折减。
6.The structure is then proportioned so that, depending on the governing conditions, the increased load would (1) cause a fatigue or a buckling or a brittle fracture failure or (2) just produce yielding at one internal section (or simultaneous yielding at several section) or (3) cause elastic-plastic displacement of the structure or (4) cause the entire structure to be on the point of collapse.
¡ yielding 屈服
¡ elastic-plastic displacement 弹塑性位移
随后设计结构尺寸，根据控制条件的不同，使之满足：荷载增大将会：①引起疲劳、压曲或脆断破坏；或②仅在一处内部截面发生屈服（或在几个截面处同时屈服）；或③结构发生弹塑性位移；或④使整个结构即将坍塌。
Paragraph6
1.Proponents of this latter approach argue that it result in a more realistic design with a more accurately provided margin of strength over the anticipated service conditions.
¡ proponent n. 支持者，拥护者
后一种方法的倡导者认为这种方法更符合实际，它针对预期的使用条件提供更准确的安全储备。
2.These improvements result from the fact that non-elastic and nonlinear effects (that become significant in the vicinity of ultimate behavior of the structure )can be accounted for.
¡ improvement n.改进, 进步
¡ nonlinear effects 非线性效应
¡ vicinity n.邻近, 附近, 接近
¡ ultimate adj.最后的, 最终的, 根本的
¡ behavior of structure 结构工作状况
这些进步是由于它能够考虑结构临近极限状态时重要的非弹性和非线性效应。
Paragraph7
1.In recent decades, there has been a growing concern among many prominent engineers that not only is the term “factor of safety” improper and unrealistic, but worse still a structural design philosophy based on this concept leads in most cases to an unduly conservative and therefore uneconomical design, and in some cases to an unconservative design with too high a probability of failure.
¡ Prominent adj.卓越的, 显著的, 突出的
¡ factor of safety安全系数
¡ unrealistic 不切实际的, 不实在的
¡ unduly adv.不适当地, 过度地, 不正当地
¡ conservative adj.保守的, 守旧的
¡ argue 辩论, 争论 说服, 劝说 主张, 认为, 论证 证明, 表明
¡ probability n.可能性, 或然性, 概率
近几十年，许多杰出的工程师日益关注的是：不但“安全系数”这个术语已不恰当，也不符合实际，而且更糟糕的是，基于此概念的结构设计原理，许多情况下使设计过于保守，因而不经济，而在一些情况下又不稳妥，失效概率很高。
2.They argue that there is no such thing as certainty, either of failure or of safety of a structure but only a probability of failure or a probability of safety.
他们认为不存在结构的失效或安全的确定性这类事情，而只存在失效概率和可靠概率。
3. They feel, therefore, that the variations of the load effects and the variations of structural resistance should be studied in a statistical manner and the probability of survival or the probability of serviceability of a structure estimated.
¡ variation 变化
¡ load effect 荷载效应
¡ structural resistance结构阻力，结构抗力
¡ serviceability n.有用性, 适用性
¡ survival n.继续存在,幸存,存在

4. It may not yet be practical to apply this approach to the design of each individual structure. However, it is believed to be practical to do so in framing design rules and regulations.
¡ design rules and regulations设计标准
因此，他们认为，荷载效应的变异性和结构抗力的变异性应以统计方式进行研究，并计算结构的安全概率或适用概率。
5.It is highly desirable that building codes and specifications plainly state the factors and corresponding probabilities that they imply.
¡ building codes 建筑条例
¡ specification 技术规程
¡ plainly 明确的
采用这种方法设计所有结构也许还不现实，但有人认为采用这种方法制定设计标准还是可行的。人们希望建筑规范明确规定各系数及其相应概率。

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