Lesson 1Compression MembersNew Words1. achieve achievement2. eccentricity center, 中心; ec centric 偏心的；ec centricity 偏心,偏心距3. inevitable evitable 可避免的avoidable; in evitable 不可避免的unavoidable4. truss 桁架triangular truss, roof truss, truss bridge5. bracing brace 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. detractor detract draw or take away; divert; belittle, 贬低,诽谤；13. convince14. argument dispute, 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gyration7. 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 bar14. 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, andthe stress can be taken as f a =P/A, where f a 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f a 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 th e 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 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 limit —that is, the member is still elastic —the 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：22L EIP cr π=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 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. 此着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 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 as follows: 方程可方便地写为2222222)/(r L EA L EAr L EIP cr πππ===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 member ’s 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： 22)/(r L E A P F cr cr π==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 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 and . 因此,应在方程和中采用截面的最小惯性矩和最小回转半径;Early researchers soon found that Euler ’s 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 slendernessthe 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 E tpl . The tangent modulus E t is defined as the slope of the tangent to the stress-strain curve for values of f between F pl and F y . 对于如图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F pl 和F y 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, P cr /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22L IE P t cr π=This is identical to the Euler equation, except that E t is substituted for E. 除公式中将E 代之以E t 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 crooked ness. 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22)/(r KL EAP cr π= or 22)/(r KL AE P t cr π=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 2Introduction to structural designNew words1. framework frame+work=frame 构架,框架; frame structure, 框架结构2. constraint vt. constrain 约束,强迫；n. constraint 约束3. collaborate vt. 合作,通敌；collaboration, collaborative4. evaluation vt. evaluate, value; assess, assessment5. fixture vt. fix, fixture 固定设备,固定物,夹具6. partition vt. n 分割,划分, make apart; partition wall7. overlook8. crane n. 超重机,鹤9. fatigue 疲劳fatigue strength, fatigue failure10. drift 漂流,漂移,雪堆11. enumerate v. list 列举12. plumbing n. 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. code n. vt 代码,编码,规范16. administer v. 管理,执行；administrate, 管理17. metropolitan a. 大城市,of metropolis18. consolidate v. 巩固,strengthen,reinforce; consolidation19. prescription n. 规定,命令,药方；prescribe20. municipality n. 市政当局,直辖市, municipal government21. specification n. 详述,规格, 规范；specify22. mandate n. 书面命令,委托,Phrases and expressions1. 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 organization11. 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 Construction16. 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 Association18. AISI 美国钢铁学会American Iron and Steel InstituteIntroduction to Structural DesignStructural designThe 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 doesn’t 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 buildinginclude 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. col`loidal 胶状的,胶体的,`colloid 胶体2. sieve n,v. 筛,过筛,过滤3. sample . 样品,取样specimen4. mesh 网孔,网格,分网格5. `cumulative a. 积累的；cumulate, cumulation6. grading n. 级配,等级；grade7. sedimentation n. 沉淀; sediment8. suspension n. 悬浮；suspend ~bridge cable-stayed bridge9. agitate v. 搅动,混合；disturb10. hydro meter n. 液体比重计11. viscosity n. 黏性；viscoidal12. flaky n. 薄片状的,of flake13. pipette n. 吸液管14. ir recoverable a.不可恢复的ir retrievable15. con cave a. 凹的；con vex凸的16. permeability n. 渗透性; permeate, permeable seep seepagePhrases 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. Stoke’s 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 . 在各种土中所遇到的粒径范围很大,大到200mm小到小于的一些粘土胶粒;Although natural soils are mixtures of various-sized particles, it is common tofind 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, . 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;shows the British Standard range of percentage of particle sizes. 图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 wereabsent, 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;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 coarsestparticles >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 63mmicron 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;最粗的部分即粒径>20mm的部分也可被过筛,并用其结果完成级配曲线的绘制;A further sub-division of particle-size distribution in the fine-grained fraction is not possible by the sieving method. 不能用筛分法对细粒部分的粒径分布作进一步分组;A processof sedimentation is normally carried out for this purpose. 通常必须用沉降法实现此目的; A small sub-sample of soil is first treated with a dispersing agent and then washed through a63m sieve. 首先将一小子土样用分散剂进行处理,然后洗过63的筛子;The soil/water suspension is then made up to 500 ml,agitated vigorously for a short while and then allowed to settle.再从中取出500ml的土/水悬浮液,充分搅拌一会后让其沉降;The procedure is based on Stoke’s law, which states that the velocity at which a spherical particle will sink due to gravity ina suspension is given by: 此方法是基于斯托克思定律,即在重力作用下球形颗粒在某一悬浮液中下降的速度为Where d=diameter of particle 颗粒直径=unit weight of the grain of particle 颗粒重度s=unit weight of the suspension fluid usually water 悬浮液w的重度通过为水的重度=vescosity of the suspension fluid 悬浮液的黏度Usually h=100mm, 通常h=100mm, giving 由此给出Samples taken at a depth of 100mm, at an elapsed time of t,will not, therefore, include particles of greater size than thediameter d given by 因此在,在深度100mm处,t 时间后所取的悬浮液中将不会有粒径大于式所给出的土粒; but the proportions of particles smaller than d in the suspension willremain unchanged. 但悬浮液中小于d的颗粒所占的比例仍保持不变;The procedure using a hydrometer consists of measuring the suspension density at a depth of 100mm at a series of elapsed-time intervals. 用液体比重计的方法包括以一系列时间间隔在深度100mm处测定悬浮液的比重;The percentage-finer values corresponding to particular diameter . particle sizes are obtained from the density readings, and thus a grading curve for the fine-grained fraction may be drawn. 通过比重读数得到小于某一特定粒径的颗粒的百分数,从而可画出细粒部分的级配曲线;Grading CharacteristicsThe grading curve is a graphical representation of the particle-size distribution and is therefore useful in itself as a means of describing the soil. 级配曲线是粒径分布的一种图形表达,因而可用来作为描述土的手段;For this reason it is always a good idea to include copies of grading curves in laboratory and other similar reports. 因此,人们总是认为在实验室报告或其它报告里附上几份级配曲线是一种好做法; It should also be remembered that the primary object is to provide a descriptive term for the type of soil. 还应牢记的是我们的主要目的是提供对土的类型的描述性术语;This iseasily done using the type of chart by estimating the range of sizes included in the most representative fraction of the soil. 这可容易地通过采用这种级配曲线做到,因为用它能估计出土中最有代表性的成分的粒径范围;For example, the steep curve may be taken to represent a poorly-graded medium sand, indicating a narrow range of sizes. 例如,陡峭的曲线可用来表示级配差的中砂,并表示其粒径范围比较小;A further quantitative analysis of grading curves may be carried out using certain geometric values known as grading characteristics. 通过采用某些称为级配特征的几何值,可进一步对级配曲线进行定量的分析;First of all, three points are located on the grading curve to give the following characteristic sizes: 首先,定出级配曲线上的三个点以给出以下特征粒径：D10=maximum size of the smallest 10 percent of the sample; 只有10%土样通过的最大粒径；D30= maximum size of the smallest 30 percent of the sample; 只有30%土样通过的最大粒径；D60= maximum size of the smallest 60 percent of the sample；只有60%土样通过的最大粒径；From these characteristic sizes, the following grading characteristics are defined: 根据这些特征粒径,定义出如下级配特征：Effective size 有效粒径Uniformity coefficient 均匀系数Coefficient of gradation 级配系数Lesson 4New Words1.u ndergo ndu vt. 经历, 遭受, 忍受; experience2.e vaporation ivprein n.蒸发作用evaporate vapor3.a ttribute tribju:t vt.把…归因于, 把…归咎于,加于, 归结于;ascribe, impute, credit, assign, refer4.s hrinkageshrink rinkid n.收10.distribution distribju:nn.分配, 分发distribute distributor11. upwind pwindadj.逆风的adv.逆风地windward; leeward 12.diminish diminiv.使减少, 使变小diminishment; decrease13.creep kri:p n. 徐变;14.slippage slip缩shrink5.c apillary kpilri adj. 毛细作用的tensioncapillarity6.e vaporate ivpreitv.使蒸发, 消失7.p aste peist n.糊, 粘土团cement paste 8.a mbient mbint adj. 周围的,包围着的surrounding ambient air9.s pecimen spesimin n. 标本, 样品, 样本, 待试验物; sampleslipid n.滑动, 滑移, 滑程slip15.humidityhju:miditin.湿气, 潮湿, 湿度; humidrelative humidity 16.aug`ment: ment v.增加, 增大n.增加; increase, enlarge augmentation17.sustained ssteindadj.持续不变的, 相同的; sustainable development18.fatigue fti:n.疲乏, 疲劳, vt.使疲劳, vi.疲劳strengthPhrases and Expressions1.m oisture content 含8.s ustained load 永久水量,含湿度; water content2.c ement paste 水泥浆mortar3.c apillary tension 毛细管张力,微张力4.g radation of aggregate 骨料级配coarse fine crushed stone, gravel5.T he British Code PC100英国混凝土规范PC100; nowaday BS81106.c oefficient of thermal expansion of concrete 混凝土热膨胀系数7. The Code 英国标准规范荷载,长期荷载9.p ermanent plastic strain 永久的塑性应变stress10.crystal lattice晶格, 晶格11.cement gel 水泥凝胶体12.water-cement ratio 水灰比13.expansion joint 伸缩缝14.stability of the structure 结构的稳定性structural stability15. fatigue strength ofconcrete 混凝土的疲劳强度Text Volume Changes of ConcreteConcrete undergoes volume changes during hardening. 混凝土在硬结过程中会经历体积变化;If it loses moisture by evaporation, it shrinks, but if the concrete hardens in water, it expands. 如果蒸发失去水分,混凝土会收缩；但如果在水中硬结,它便膨胀;The causes of the volume changes in concrete can be attributed to changes in moisture content, chemical reaction of the cement with water, variation in temperature, and applied loads. 混凝土体积变化的原因可归结为含水量的变化、水泥与水的水化反应、温度变化和所施加的荷载;ShrinkageThe change in the volume of drying concrete is not equal to the volume of water removed. The evaporation of free water causes little or no shrinkage. 混凝土干燥时的体积变化量不等于它所失去的水的体积;自由水的蒸发基本不产生收缩;As concrete continues to dry, water evaporates and the volume of the restrained cement paste changes, causing concrete to shrink, probably dueto the capillary tension that develops in the water remaining in concrete. 随着混凝土的不断变干,水分蒸发,受约束水泥浆的体积也变化,导致了混凝土的收缩,这多半是由于残留在混凝土中的水的毛细张力所致; Emptying of the capillaries causes a loss of water without shrinkage. But once the absorbed water is removed, shrinkage occurs. 毛细管变空导致无收缩的水分丢失,但一旦失去吸收的水分,收缩便发生;Many factors influence the shrinkage of concrete caused by the variations in moisture conditions. 许多因素都会影响因水分环境发生变化而产生的混凝土收缩;and water content. The more cement or water content in the concrete mix, the greater the shrinkage. 水灰比：水灰比越大,收缩越大；and fineness of cement. High-early-strength and low-heat cements show more shrinkage than normal portland cement. The finer the cement, the greater is the expansion under moist conditions. 水泥的成分和细度：早强和低热水泥的收缩大于普通水泥,水泥越细,其在潮湿环境中的膨胀越大;, amount, and gradation of aggregate. The smaller the size of aggregate particles, the greater is the shrinkage. The greater the aggregate content, the smaller is the shrinkage. 骨料的类型、含量及其级配：骨料的粒径越小,收缩越大；骨料含量越大,收缩则越小;conditions, moisture, and temperature. Concrete specimens subjected to moist conditions undergo an expansion of 200to300×10-6,but if they are left to dry in air, they shrink. High temperature speeds the evaporation of water and, consequently, increases shrinkage. 外部条件,水分与温度：潮湿环境下的混凝土试件的膨胀量为200to300×10-6,但如果让其在空气中干燥,它们将收缩;高温加速了水分的蒸发,因此也加快了收缩;. Admixtures that increase the water requirement of concrete increase the shrinkage value. 添加剂：使用水量增加的外加剂也增加了收缩值;and shape of specimen. As shrinkage takes place in a reinforced concrete member, tension。
