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Lesson 1Compression MembersNew Words1. achieve achievement 2. eccentricity center, 中心; eccentric 偏心的；eccentricity 偏心，偏心距3. inevitable evitable 可避免的 avoidable; inevitable 不可避免的 unavoidable 4. truss 桁架 triangular truss, roof truss, truss bridge5. bracingbrace 支柱，支撑；bracing, 支撑，撑杆6. slender 细长，苗条；stout; slenderness7. buckle压曲，屈曲；buckling load8. stocky stout9. convincingly convince, convincing, convincingly10. stub树桩， 短而粗的东西；stub column 短柱11. curvature曲率；curve, curvature12. detractordetract draw or take away; divert; belittle， 贬低，诽谤；13. convince14. argumentdispute, debate, quarrel, reason, 论据（理由）15. crookedness crook 钩状物，v弯曲，crooked 弯曲的16. provision规定，条款Phrases and Expressions1. compression member2. bending moment shear force, axial force3. call upon (on) 要求，请求，需要4. critical buckling load临界屈曲荷载 critical 关键的，临界的5. cross-sectional area6. radius of gyration回转半径 gyration 7. slenderness ratio长细比8. tangent modulus切线模量9. stub column短柱10. trial-and-error approach试算法11. empirical formula经验公式 empirical 经验的12. residual stress残余应力residual13. hot-rolled shape热轧型钢 hot-rolled bar 14. lower bound 下限upper bound 上限16. effective length 计算长度Definition （定义）Compression members are those structural elements that are subjected only to axial compressive forces: that is, the loads are applied along a longitudinal axis through the centroid of the member cross section, and the stress can be taken as fa=P/A, where fa is considered to be uniform over the entire cross section. 受压构件是仅受轴向压力作用的构件，即：荷载是沿纵轴加在其截面形心上的，其应力可表示为，式中，假定fa在整个截面上均匀分布。 This ideal state is never achieved in reality, however, and some eccentricity of the load is inevitable. 然而，现实中从来都不可能达到这种理想状态，因为荷载的一些偏心是不可避免的。This will result in bending, but it can usually be regarded as secondary and can be neglected if the theoretical loading condition is closely approximated. 这将导致弯曲，但通常认为它是次要的，如果理论工况是足够近似的，就可将其忽略。This cannot always be done if there is a computed bending moment, and situation of this type will be considered in Beam-Columns. 但这并非总是可行的，如有计算出的弯矩存在时，这种情形将在梁柱理论中加以考虑。The most common type of compression member occurring in buildings and bridges is the column, a vertical member whose primary function is to support vertical loads. 在建筑物和桥梁中最常见的受压构件就是柱，其主要功能就是支承竖向荷载。In many instances these members are also called upon to resist bending, and in these cases the member is a beam-column. Compression members can also be found in trusses and as components of bracing systems. 在许多情况下，它们也需要抵抗弯曲，在此情况下，将它们称为梁柱。受压构件也存在于桁架和支撑系统中。Column Theory （柱理论）Consider the long, slender compression member shown in Fig.1.1a. 考虑如图1.1.a所示的长柱If the axial load P is slowly applied, it will ultimately reach a value large enough to cause the member to become unstable and assume the shape indicated by the dashed line. 如果慢慢增加轴向荷载P，它最终将达到一个足够大的值使该柱变得不稳定(失稳)，如图中虚线所示。 The member is said to have buckled, and the corresponding load is called the critical buckling load. 这时认为构件已经屈曲，相应的荷载称为临界屈曲荷载。If the member is more stocky, as the one in Fig.1.1b, a larger load will be required to bring the member to the point of instability. 如果该构件更粗短些，如图1.1b所示，则需要更大的荷载才能使其屈曲。For extremely stocky members, failure may be by compressive yielding rather than buckling. 对特别粗短的构件，破坏可能是由受压屈服引起而非由屈曲引起。For these stocky members and for more slender columns before they buckle, the compressive stress P/A is uniform over the cross section at any point along the length. 对这些短柱以及更细长的柱，在其屈曲前，在其长度方向上任意点处横截面上的压应力P/A都是均匀的。As we shall see, the load at which buckling occurs is a function of slenderness, and for very slender members this load could be quite small. 我们将会看到，屈曲发生时的荷载是长细程度的函数，非常细长的构件的屈曲荷载将会很低。If the member is so slender (a precise definition of slenderness will be given shortly) that the stress just before buckling is below the proportional limitthat is, the member is still elasticthe critical buckling load is given by 如果构件如此细长（随后将会给出细长程度的精确定义）以致即将屈曲时的应力低于比例极限即，构件仍是弹性的，临界屈曲荷载如下式给出： (1.1)where E is the modulus of elasticity of the material, I is the moment of inertia of the cross-sectional area with respect to the minor principal axis, and L is the length of the member between points of support. 式中E为材料弹性模量，I为关于截面副主轴的惯性矩，L 为支座间的距离。For Eq1.1 to be valid, the member must be elastic, and its ends must be free to rotate but not translate laterally. This end condition is satisfied by hinges or pins. 要使方程1.1成立，构件必须是弹性的，且其两端必须能自由转动，但不能侧向移动。This remarkable relationship was first formulated by Swiss mathematician Leonhard Euler and published in 1975. 此著名公式是瑞士数学家欧拉于1975年提出的。The critical load is sometimes referred to as the Euler load or the Euler buckling load. The validity of Eq.1.1 has been demonstrated convincingly by numerous tests. 因此有时将临界荷载称为欧拉荷载或欧拉临界荷载。欧拉公式的有效性（正确性）已由许多试验充分证实。It will be convenient to rewrite Eq.1.1 as follows: 方程1.1可方便地写为 (1.1a)where A is the cross-sectional area and r is the radius of gyration with respect to the axis of buckling. The ratio L/r is the slenderness ratio and is the measure of a compression members slenderness, with large values corresponding to slender members. 式中A 为截面面积，r为关于屈曲轴的回转半径，L/r为长细比，它是对受压构件细长程度的一种度量，该值越大，构件越细长。If the critical load is divided by the cross-sectional area, the critical buckling stress is obtained: 如果将屈曲荷载除以截面面积，便可得到以下屈曲应力：(1.2)This is the compressive stress at which buckling occur about the axis corresponding to r. 这便是绕相应于r的轴发生屈曲时的压应力。Since buckling will take place as soon as the load reaches the value by Eq.1.1, the column will become unstable about the principle axis corresponding to the largest slenderness ratio. This usually means the axis with the smaller moment of inertia. 由于一旦荷载达到式1.1之值，柱将在与最大长细比对应的主轴方向变得不稳定（失稳），通常该轴是惯性矩较小的轴。Thus, the minimum moment of inertia and radius of gyration of the cross section should be used in Eq.1.1 and 1.2. 因此，应在方程1.1和1.2中采用截面的最小惯性矩和最小回转半径。Early researchers soon found that Eulers equation did not give reliable results for stocky, or less slender, compression members. 早期的研究者很快发现对短柱或不太细长的受压构件，欧拉公式并不能给出可靠的结果，This is because of the small slenderness ratio for members of this type, which results in a large buckling stress (from Eq.1.2). 这是因为这种构件的长细比较小，从而产生较高的屈曲应力。If the stress at which buckling occurs is greater than the proportional limit of the material, the relation between stress and strain is not linear, and the modulus of elasticity E can no longer be used. 如果屈曲发生时的应力大于材料的比例极限，应力应变关系就不再是线性的，也不能再用弹性模量E。This difficulty was initially resolved by Friedrich Engesser, who proposed in 1889 the use of a variable tangent modulus Et in Eq.1.1. 这一困难最初由Friedrich Engesser 所克服，他在1889年将可变的切线模量用于方程1.1. For a material with a stress-strain curve like the one in Fig.1.2, E is not a constant for stress greater than the proportional limit Fpl. The tangent modulus Et is defined as the slope of the tangent to the stress-strain curve for values of f between Fpl and Fy. 对于如图1.2所示的应力应变曲线(的材料)，当应力超过比例极限时，E并非常数，当应力处于Fpl和Fy之间时，将切线模量定义为应力应变曲线的切线的斜率，If the compressive stress at buckling, Pcr/A, is in this region, it can be shown that 如果屈曲时的压应力在此范围时，可以证明(1.3)This is identical to the Euler equation, except that Et is substituted for E. 除公式中将E代之以Et外，上式与欧拉公式完全相同。Effective Length（计算长度）Both the Euler and tangent modulus equations are based on the following assumptions: 欧拉和切线模量方程都是基于如下假定：1. The column is perfectly straight, with no initial crookedness. 柱完全竖直，无初始弯曲。2. The load is axial, with no eccentricity. 荷载是轴向加载，无偏心。3. The column is pinned at both ends. 柱在两端铰结。The first two conditions mean that there is no bending moment in the member before buckling. 前两(假定)条件意味着在屈曲前无弯矩存在。As mentioned previously, some accidental moment will be present, but in most cases it can be neglected. 如前所述，可能偶然会存在一些弯矩，但在大多数情况下都可被忽略。The requirement for pinned ends, however, is a serious limitation, and provisions must be made for other support conditions. 然而，铰结要求是一个严重的局限，必须对其它支撑条件作出规定。The pinned-end condition is one that requires that the member be restrained from lateral translation, but not rotation, at the ends. 铰结条件要求约束构件两端不发生侧移，但并不约束转动。Since it is virtually impossible to construct a frictionless pin connection, even this support condition can only be closely approximated at best. 由于实际上不可能构造无摩擦铰连接，即使这种支撑条件最多也只能是非常近似。Obviously, all columns must be free to deform axially. 显然，所有柱必须在轴向自由变形。 In order to account for other end conditions, the equations for critical buckling load will be written as 为了考虑其它边界条件，将临界荷载写为如下形式 or (1.4)where KL is the effective length, and K is called the effective length factor. Values of K for different cases can be determined with the aid of the Commentary to the AISC Specification. 式中KL为计算长度，K称为计算长度系数，各种情况下的K值可借助于AISC（美国钢结构学会American Institute of Steel Construction）规范的条文说明加以确定。Lesson 2 Introduction to structural designNew words1. framework frame+work=frame 构架，框架; frame structure, 框架结构2. constraintvt. constrain 约束，强迫；n. constraint 约束 3. collaborate vt. 合作，通敌；collaboration, collaborative 4. evaluation vt. evaluate, value; assess, assessment5. fixturevt. fix, fixture 固定设备，固定物，夹具6. partition vt. n 分割，划分， make apart; partition wall7. overlook8. cranen. 超重机，鹤9. fatigue vt.vi.n 疲劳 fatigue strength, fatigue failure10. driftv.n 漂流，漂移，雪堆11. enumerate v. list 列举12. plumbingn. (卫生，自来水)管道，plumber 管道工13. ventilation n. 通风， ventilate, ventilate a room, a well-ventilated room, vent 通风口14. accessibility n. 可达性， access, n. vt. 通道，接近；accessible 易接近的，可达到的 15. coden. vt 代码，编码，规范16. administer v. 管理，执行；administrate, 管理 17. metropolitan a. 大城市，of metropolis 18. consolidatev. 巩固，strengthen，reinforce; consolidation19. prescriptionn. 规定，命令，药方；prescribe 20. municipalityn. 市政当局，直辖市， municipal government21. specification n. 详述，规格, 规范；specify 22. mandaten. 书面命令，委托，Phrases and expressions 1. functional design功能设计2. bending moment弯矩3. dead load4. live load5. nonstructural components非结构构件6. force due to gravity7. gravity load8. building code9. design specifications 设计规程10. nonprofit organization非赢利组织，弄non-government organization 11. the National Building Code12. the Uniform Building Code13. the Standard Building Code14. Building Officials and Code Administrators International (BOCA) 国际建筑公务员与法规管理人员联合会15. AISC美国钢结构学会 American Institute of Steel Construction 16. AASHTO 美国公路和运输工作者协会American Association of State Highway and Transportation Officials17. AREA美国铁道工程协会the American Railway Engineering Association 18. AISI美国钢铁学会American Iron and Steel InstituteIntroduction to Structural DesignStructural design The structural design of building, whether of structural steel or reinforced concrete, requires the determination of the overall proportions and dimensions of the supporting framework and the selection of the cross sections of individual members. 建筑结构设计，不论是钢结构还是钢筋混凝土结构，都需要确定其支承结构的整体比例和尺寸以及各构件的截面尺寸。In most cases the functional design, including the establishment of the number of stories and the floor plan, will have been done by an architect, and the structural engineer must work within the constraints imposed by this design. 在大多数情况下，功能设计，包括楼层层数和楼层平面的确定，将要由建筑师来完成，因而结构工程师必须在此约束条件下工作。Ideally, the engineer and architect will collaborate throughout the design process so that the project is completed in an efficient manner. 在理想状态下，工程师和建筑师将在整个设计过程中协同工作从而高效地完成设计工作。In effect, however, the design can be summed up as follows: 然而，事实上，设计过程可概括如下：The architect decides how the building should look; the engineer must make sure that it doesnt fall down. 建筑师确定建筑物的外观，工程师必须确保其不会倒塌。Although this is an oversimplification, it affirms the first priority of the structural engineer: safety. Other important considerations include serviceability (how well the structure performs in terms of appearance and deflection) and economy. 尽管这样说过分简单，但它明确了工程师的第一个主要任务，即，确保安全。其它要考虑的因素包括适用性（就外观和挠曲而言其工作性能如何）。An economical structure requires an efficient use of materials and construction labor. Although this can usually be accomplished by a design that requires a minimum amount of material, savings can often be realized by using slightly more material if it results in a simpler, more easily constructed projects. 经济的结构要求对材料和人工的有效使用，尽管这通常都能通过要求最少材料来取得，但通过采用稍多的材料，但能使建筑物更简单和更容易建造常常会实现节约的目的。LoadsThe forces the act on a structure are called loads. They belong to one of two broad categories, dead load and live load. 作用在结构物上的各种力称为荷载，它们属于一两种广义类型，恒载和活载。Dead loads are those that are permanent, including the weight of the structure itself, which is sometimes called the self-weight. 恒载是那些永久荷载，包括结构自身的重量，有时也称为自重。Other dead loads in a building include the weight of nonstructural components such as floor coverings, suspended ceilings with light fixtures, and partitions. 其它建筑物恒载包括非结构构件的重量，如楼面面层、带有灯具的吊顶以及隔墙。All of the loads mentioned thus far are forces due to gravity and are referred to as gravity loads. 至此所提的各种荷载都是由重力所引起，因而称为重力荷载。Live loads, which can also be gravity loads, are those that are not as permanent as dead loads. 活载也可以是重力荷载，它们是那些不如恒载那样永久的荷载。This type may or may not be acting on the structure as any given time, and the location may not be fixed. 这类荷载可能也可能不总是作用在结构物上，且作用位置也可能不是固定的。Examples of live load include furniture, equipment, and occupants of buildings. 活荷载包括家具、设置和建筑物的居住者。In general, the magnitude of a live load is not as well defined as that of a dead load, and it usually must be estimated. In many cases, a given structural member must be investigated for various positions of the live load so that a potential failure situation is not overlooked. 通常，活荷载的大小不如恒载那样确定，常常必须估计。在许多情况下，必须研究活荷载作用在一给定的结构构件的各个位置以便不会漏掉每个可能的破坏情形。Building codesBuilding must be designed and constructed according to the provisions of a building codes, which is a legal document containing requirements related to such things as structural safety, fire safety, plumbing, ventilation, and accessibility to the physically disabled. 建筑物必须根据各种建筑规范的条款设计和建造，规范是一种法律文件，包含各种要求，如建筑安全、防火安全、上下水、通风和体残人的可达性等。A building code has the force of law and is administered by a governmental entity such as a city, a county, or, for some large metropolitan areas, a consolidated government. 建筑规范具有法律效力，由政府部位发布，如城市、县、对于大的城区，如联合政府。Building codes do not give design provisions, but they do specify the design requirements and constraints that must be satisfied. 建筑规范并不给出设计规定，但却规定设计必须满足的各种要求和约束条款。Of particular importance to the structural engineer is the prescription of minimum live loads for buildings. 对结构工程师特别重要的是建筑物的最小活荷载规定。Although the engineer is encouraged to investigate the actual loading conditions and attempt to determine realistic values, the structure must be able to support these specified minimum loads. 尽管鼓励工程师研究实际荷载工况以确定真实的荷载值，结构必须能支承这些规定的最小荷载。Design specificationsIn contrast to building codes, design specifications give more specific guidance for the design of structural members and their connections. 与建筑规范不同，设计规程给出结构构件及其连接的更具体的指南。They present the guidelines and criteria that enable a structural engineer to achieve the objectives mandated by a building code. 它们给出各种方针和标准，使结构工程师能建筑规范所规定的目标。Design specifications represent what is considered to be good engineering practice based on their latest research. 根据其最新研究，设计规程结出认为是好的工程作法。They are periodically revised and updated by supplements or by completely new editions. 它们通过补充或通过发布新版本得到定期修订和更新。As with model building codes, design specifications are written in a legal format by nonprofit organizations. 如同一般建筑规范，设计规程由非赢利组织编写。They have no legal standing on their own, but by presenting design criteria and limits in the form of legal mandates and prohibitions, they can easily be adopted, by reference, as part of a building code. 尽管它们本身并无法律地位，但却以法令和禁令的形式给出设计准则和限制，以参考文献的形式，它们可容易地被录入，并作为建筑规范的一部分。Lesson 3New words1. colloidal胶状的，胶体的，colloid 胶体2. sieven,v. 筛，过筛，过滤3. samplen.vt. 样品，取样 specimen4. meshn.v 网孔，网格，分网格5. cumulative a. 积累的；cumulate, cumulation 6. gradingn. 级配，等级；grade7. sedimentationn. 沉淀; sediment 8. suspensionn. 悬浮；suspend bridge cable-stayed bridge 9. agitatev. 搅动，混合；disturb10. hydrometern. （液体）比重计11. viscosityn. 黏性；viscoidal 12. flakyn. 薄片状的，of flake 13. pipetten. 吸液管14. irrecoverablea. 不可恢复的 irretrievable 15. concave a. 凹的；convex 凸的16. permeabilityn. 渗透性; permeate, permeable seep seepage Phrases and expressions1. frost susceptibility霜冻敏感性2. sieving method筛分法3. semi-logarithmic curve半对数曲线4. grading curve级配曲线 5. wet sieving湿法筛分6. dispersing agent分散剂7. Stokes law斯托克定律8. unit weight重度 9. coefficient of grading级配系数10. sedimentation method沉降法11. particle-size distribution粒径分布Text Particle Size Analysis 粒径分析The range of particle sizes encountered in soils is very wide: from around 200mm down to the colloidal size of some clays of less than 0.001mm. 在各种土中所遇到的粒径范围很大，大到200mm小到小于0.001mm的一些粘土胶粒。Although natural soils are mixtures of various-sized particles, it is common to find a predominance occurring within a relatively narrow band of sizes. 尽管天然土都是由各种粒径的颗粒组成，但通常可发现其主要组成颗粒出现在一个比较小的粒径范围内。When the width of this size band is very narrow the soil will be termed poorly-graded, if it is wide the soil is said to be well-graded. 当这一粒径范围非常小时，称这种土级配较差，而当其较大时，称这种土级配良好。A number of engineering properties, e.g. permeability, frost susceptibility, compressibility, are related directly or indirectly to particle-size characteristics. 土的许多工程特性，如渗透性、霜冻敏感性、可压缩性等都直接或间接的与土的级配特性有关。Fig.3.1 shows the British Standard range of percentage of particle sizes. 图3.1为粒径百分数的英国标准范围。The particle-size analysis of a soil is carried out by determining the weight percentage falling within bands of size represented by these divisions and sub-divisions. 通过确定落入由这些粒径分组和子组所代表的粒径范围的重量百分比，对土进行粒径分析。In the case of a coarse soil, from which fine-grained particles have been removed or were absent, the usual process is a sieve analysis. 对于粗粒土，它里面的细粒土被除去或本身就无细颗粒，常用的方法就是筛分法。A representative sample of the soil is split systematically down to a convenient sub-sample size and then oven-dried. 此法是将要分析土的一代表样本系统地分为方便的子样本，然后烘干。This sample is then passed through a nest of standard test sieves arranged in descending order of mesh size. 再使烘干的土样通过一组筛孔尺寸由大至小放置的标准试验筛。The weight of soil retained on each sieve is determined and the cumulative percentage of the sub-sample weight passing each sieve calculated. 称量每个筛中剩下的土样的重量，并计算出通过每个筛的累计百分数。From these figures the particle-size distribution for the soil is plotted as a semi-logarithmic curve (Fig.3.2) known as grading curve. 根据这些数据，以半对数曲线的形式描出该土的粒径分布图，即所谓的级配曲线。细粒粗粒非常粗大颗粒粘土胶粒粉土砂砾石石块细中粗细中粗细中粗卵石块石Where the soil sample contains fine-grained particles, a wet sieving procedure is first carried out to remove these and to determine the combined clay/silt fraction percentage. 在土样中含有细土粒的场合，首先用湿筛分法将其除去，并确定粘粒/粉粒总共所占的分数。A suitable-sized sub-sample is first oven-dried and then sieved to separate the coarsest particles (20mm). 将一适量的分土样烘干，并过筛分开最粗的颗粒（20mm的颗粒）The sub-sample is then immersed in water containing a dispersing agent and allowed to stand before being washed through a 63mm(micron) mesh sieve. 然后将土样浸入含有分散剂的水中，并在将其用63微米筛过筛前搁置起来（并将其搁置一会，再用63micron的筛子过筛）。The retained fraction is again oven-dried and passed through a nest of sieves. 将筛中保留的部分烘干，并用一组筛子过筛。After weighing the fractions retained on each sieve and calculating the cumulative percentage passing each sieve, the grading curve is drawn. 称量落在每个筛中土重，并计算出通过每个的累计百分数后，就可描出级配曲线。The combined clay/silt fraction is determined from the weight difference and expressed as a percentage of the total sub-sample weight. The coarsest fraction (20mm) can also be sieved and the results used to complete the grading curve. 由重量差确定粘粒/粉粒的总重，并将其表示为子土样总重的百分数。最粗的部分（即粒
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