土木工程专业英语带译文课件.ppt

1、土木工程英语土木工程英语1Chapter 6 Reinforced Concrete Chapter 6土木工程英语土木工程英语2Conversation1.Our concrete material is mixed in a rotating-drum batch mixer at the job site. 我们用的混凝土是在现场的间歇式转筒搅拌机中搅拌的。2. Quality of concrete depends on proper placing, finishing, and curing. 混凝土的质量取决于适当的灌注、抹光和养护。3. The workers tend to

2、start the final finishing now. 工人们现在打算开始最后的抹光作业。4. The concrete can be made stronger by pre-stressing in our factory. 在我们厂里可以使混凝土通过预加应力得到增强。Chapter 6土木工程英语土木工程英语5. Most of construction material can be tested in our laboratory. 我们的实验室可以检验大部分建筑材料。6. We shall finish the civil work by the end of the yea

3、r.在年底前我们将完成土建工作。Cement steel and timber are the most important construction materials used in civil engineering.水泥、钢材和木材是土建工程中最重要的建筑材料。7. These are the anchor bolts (rivets, unfinished bolts, high-strength structural bolts) for the structure.这是用于结构的锚定螺栓（铆钉、粗制螺栓、高强度结构用螺栓）。3土木工程英语土木工程英语48. The holes o

4、f anchor bolts will be grouted with normal (Portland, non-shrinkage) cement mortar.这些地脚螺孔将灌入普通（波特兰，无收缩）水泥砂浆。9. We usually measure the strength of concrete at 28 days after which has been cast.我们通常在混凝土灌注后28天测定其强度。10. The average compressive strength of samples is 500kg/cm2.试样的平均抗压强度为500公斤/平方厘米Chapter

5、 6土木工程英语土木工程英语5Text Reinforced concrete is concrete in which reinforcement bars (“rebars”) （钢筋）, reinforcement grids（钢筋网）, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Conc

6、rete refers only to concrete that is reinforced with iron or steel. 钢筋混凝土是由混凝土，钢筋（钢筋），钢筋网（钢筋网），钢板网，钢板或纤维组成，这些被用来加强混凝土的张力。 它由法国园丁约瑟夫莫尼尔于1849年发明，并于1867年获得专利。混凝土仅指用钢或钢加固的混凝土。Chapter 6土木工程英语土木工程英语Other materials used to reinforce concrete can be organic and inorganic fibres as well as composites in diff

7、erent forms. Concrete is strong in compression, but weak in tension, thus adding reinforcement increases the strength in tension. In addition, the failure strain of concrete in tension is so low that the reinforcement has to hold the cracked sections together. For a strong, ductile and durable const

8、ruction the reinforcement shall have the following properties:其他用于加固混凝土的材料可以是有机和无机纤维以及不同形式的复合材料。 混凝土压缩强度大，但抗拉性弱，因此加入钢筋可增加抗拉强度。 另外，混凝土的拉伸破坏应变很小，依靠钢筋拉力来控制裂缝。 对于坚固，延展性和耐用的结构，钢筋应具有以下特性：6土木工程英语土木工程英语7High strength 高强度High tensile strain 高拉伸应变Good bond to the concrete 与混凝土结合良好Thermal compatibility 热兼容性Dur

9、ability in the concrete environment 在具体环境中的耐久性Chapter 6土木工程英语土木工程英语In most cases reinforced concrete uses steel rebars that have been inserted to add strength.在大多数情况下，钢筋混凝土采用钢筋加入以增加强度。Use in constructionConcrete is reinforced to give it extra tensile strength; without reinforcement, many concrete bu

10、ildings would not have been possible.增强混凝土的抗拉强度; 没有钢筋水泥，许多混凝土建筑物将不可能实现。8土木工程英语土木工程英语Reinforced concrete can encompass many types of structures and components, including slabs, walls, beams, columns, foundations, frames and more.钢筋混凝土可以包括许多类型的结构和构件，包括平板，墙，梁，立柱，基础，框架等等。Reinforced concrete can be class

11、ified as precast or cast in-situ concrete.钢筋混凝土可以分为预制或现浇混凝土。9土木工程英语土木工程英语Much of the focus on reinforcing concrete is placed on floor systems. Designing and implementing the most efficient floor system is a key to creating optimal building structures. Small changes in the design of a floor system ca

12、n have significant impact on material costs, construction schedule, ultimate strength, operating costs, occupancy levels and end use of a building.大部分建筑注重加强混凝土的地板系统。 设计和实施最高效的地板系统是创建最佳建筑结构的关键。 地板系统设计的微小变化会对建筑物的材料成本，施工进度，最终强度，运营成本，入住率和最终用途产生重大影响。10土木工程英语土木工程英语11Behavior（性能）（性能）of reinforced concreteM

13、aterialsConcrete is a mixture of of Coarse (stone or brick chips) and Fine (generally sand) aggregates with a binder material (usually Portland cement). When mixed with a small amount of water, the cement hydrates form microscopic opaque crystal lattices encapsulating and locking the aggregate into

14、a rigid structure. 混凝土是粗粒（石块或砖块）和细粒（通常是沙粒）与粘结材料（通常是波特兰水泥）的混合物。 当与少量水混合时，水泥水合物形成微观不透明晶格，将聚集体封装并锁定在刚性结构中。Chapter 6土木工程英语土木工程英语Typical concrete mixes have high resistance to compressive stresses (about 4,000 psi (28 MPa); however, any appreciable tension (e.g., due to bending) will break the microscopi

15、c rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension.典型的混凝土混合料对压缩应力具有很高的抵抗力（约4,000 psi（28 MPa）; 然而，任何可观的张力（例如由于弯曲）都会破坏微观的刚性格子，导致混凝土开裂和分离。 出于这个原因，典型的无筋混凝土必须被很好地支撑以防止张力的发展。12

16、土木工程英语土木工程英语13If a material with high strength in tension, such as steel, is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A reinforced concrete section where the concrete resists the compression

17、and steel resists the tension can be made into almost any shape and size for the construction industry.如果钢筋等高强度的材料置于混凝土中，则复合材料钢筋混凝土不仅能抵抗压缩，还能抵抗弯曲和其他直接拉伸作用。 钢筋混凝土部分的混凝土抗压缩和钢筋抗张力可以制成几乎任何形状和大小的建筑构件。Chapter 6土木工程英语土木工程英语Key characteristics Three physical characteristics give reinforced concrete its spec

18、ial properties.三种物理特性赋予钢筋混凝土其特殊性能。First, the coefficient of thermal expansion of concrete is similar to that of steel, eliminating large internal stresses due to differences in thermal expansion or contraction.首先，混凝土的热膨胀系数与钢相似，消除了由于热膨胀或收缩差异而产生的巨大内部应力。14土木工程英语土木工程英语15Second, when the cement paste wit

19、hin the concrete hardens this conforms to the surface details of the steel, permitting any stress to be transmitted efficiently between the different materials. Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel.其次，当混凝土内的水泥浆硬化时，钢筋表面的

20、构造，可以在不同材料之间有效地传递任何应力。 钢筋通常是粗糙的或波纹状的，以进一步改善混凝土和钢之间的粘结或内聚力。Chapter 6土木工程英语土木工程英语16土木工程英语土木工程英语17Third, the alkaline（碱性的）chemical environment provided by the alkali reserve (KOH, NaOH) and the portlandite (calcium hydroxide) contained in the hardened cement paste causes a passivating film to form on t

21、he surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions。第三，硬化水泥浆中含有的碱性物质（KOH，NaOH）和氢氧化钙（氢氧化钙）提供的碱性（碱性的）化学环境会在钢的表面形成钝化膜，比在中性或酸性条件下更耐腐蚀Chapter 6土木工程英语土木工程英语. When the cement paste exposed to the air and meteoric water reacts with the atmosph

22、eric CO2, portlandite and the Calcium Silicate Hydrate (CSH) （水化硅酸钙）of the hardened cement paste become progressively carbonated and the high pH gradually decreases from 13.5 12.5 to 8.5, the pH of water in equilibrium with calcite (calcium carbonate) and the steel is no longer passivated.当暴露于大气中的水泥

23、浆与大气中的二氧化碳发生反应时，硬化水泥浆体的硅酸钙水化硅酸钙（CSH）逐渐碳化，高pH值从13.5 12.5至8.5，与方解石（碳酸钙）的水的pH平衡并且钢也不再钝化。18土木工程英语土木工程英语19As a rule of thumb, only to give an idea on orders of magnitude, steel is protected at pH above 11 but starts to corrode below 10 depending on steel characteristics and local physico-chemical conditi

24、ons when concrete becomes carbonated. Carbonation of concrete along with chloride ingress are among the chief reasons for the failure of reinforcement bars in concrete.作为一个经验法则，只有在数量级上给出一个说法，钢在pH值高于11时受到保护，但在混凝土碳化时取决于钢的特性和局部物理化学条件而开始腐蚀到10以下。 混凝土碳化和氯化物侵入是混凝土中是钢筋破坏的主要原因。Chapter 6土木工程英语土木工程英语The relati

25、ve cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some columns. Reinforcing bars are normally round in cross-section and vary in diameter. Reinforced concrete structures sometimes have provisions suc

26、h as ventilated hollow cores to control their moisture & humidity.典型钢筋混凝土所需钢材的相对横截面积通常很小，大多数钢筋混凝土板的1和某些钢柱的6不等。 钢筋通常横截面为圆形，直径不等。 钢筋混凝土结构有时会提供诸如通风中空芯以控制其湿度和湿度。20土木工程英语土木工程英语21Reinforcement and terminology of Beams梁的加固和术语梁的加固和术语A beam bends under bending moment（弯矩）, resulting in a small curvature. At t

27、he outer face (tensile face) of the curvature the concrete experiences tensile stress, while at the inner face (compressive face) it experiences compressive stress.梁在弯矩（弯矩）下弯曲，导致小曲率。 在曲率的外表面（拉伸面），混凝土经受拉应力，而在内表面（压应面）则经受压应力。A singly-reinforced beam is one in which the concrete element is only reinforc

28、ed near the tensile face and the reinforcement, called tension steel, is designed to resist the tension.单筋梁是其中混凝土构件仅在拉伸面附近被增强的梁，并且被称为拉伸钢的增强件被设计为抵抗张力。Chapter 6土木工程英语土木工程英语A doubly-reinforced beam is one in which besides the tensile reinforcement the concrete element is also reinforced near the compre

29、ssive face to help the concrete resist compression. The latter reinforcement is called compression steel. When the compression zone of a concrete is inadequate to resist the compressive Moment positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the sect

30、ion.双筋梁是除了抗拉钢筋之外还在靠近压缩面处加强混凝土元件以帮助混凝土抵抗压缩的梁。 后一种钢筋称为压缩钢筋。 当混凝土的压缩区域不足以抵抗压缩力矩正向力矩时），如果建筑师限制该部分的尺寸，则必须提供额外的加固。22土木工程英语土木工程英语23An under-reinforced beam is one in which the tension capacity of the tensile reinforcement is smaller than the combined compression capacity of the concrete and the compression

31、 steel (under-reinforced at tensile face). When the reinforced concrete element is subject to increasing bending moment, the tension steel yields，while the concrete does not reach its ultimate failure condition. As the tension steel yields and stretches, an “under-reinforced” concrete also yields in

32、 a ductile manner, exhibiting a large deformation and warning before its ultimate failure. In this case the yield stress of the steel governs the design.少筋梁是其中拉伸钢筋的拉伸能力小于混凝土和压缩钢的组合压缩能力（在拉伸面处欠加固）的梁。 当钢筋混凝土构件受弯矩增加时，钢筋屈服，而混凝土未达到其最终破坏状态。 随着拉伸钢的屈服和拉伸，“欠加固”的混凝土也会以延性方式屈服，在最终失效之前表现出较大的变形。 在这种情况下，钢的屈服应力决定了设计

33、。Chapter 6土木工程英语土木工程英语An over-reinforced beam is one in which the tension capacity of the tension steel is greater than the combined compression capacity of the concrete and the compression steel (over-reinforced at tensile face). So the “over-reinforced concrete” beam fails by crushing of the compr

34、essive-zone concrete and before the tension zone steel yields, which does not provide any warning before failure as the failure is instantaneous.超筋梁是其中拉伸钢的拉伸能力大于混凝土和压缩钢的组合压缩能力（在拉伸面处过度增强）的梁。 因此，“过度加强的混凝土”梁通过压缩区混凝土的破碎而失效，并且在张拉区钢材屈服之前不会发出任何警告，因为失效是瞬时的。24土木工程英语土木工程英语25A balanced-reinforced beam is one i

35、n which both the compressive and tensile zones reach yielding at the same imposed load on the beam, and the concrete will crush and the tensile steel will yield at the same time. This design criterion is however as risky as over-reinforced concrete, because failure is sudden as the concrete crushes

36、at the same time of the tensile steel yields, which gives a very little warning of distress in tension failure.适筋梁是在梁上相同的施加载荷下，压缩区和拉伸区都达到屈服的，并且混凝土将被压扁并且拉伸钢将同时屈服。 然而，这种设计标准与过度加固的混凝土一样危险，因为在拉伸钢筋屈服的同时混凝土破坏会导致破坏突然发生，这在拉伸破坏时几乎没有发生危险的警告。Chapter 6土木工程英语土木工程英语Steel-reinforced concrete moment-carrying(弯矩承载)

37、elements should normally be designed to be under-reinforced so that users of the structure will receive warning of impending collapse. The characteristic strength is the strength of a material where less than 5% of the specimen shows lower strength。钢筋混凝土受弯构件通常应设计为不超筋，以便结构使用者能够收到即将崩塌的警告。 特征强度是一种材料的强度

38、，其中少于5的试样表现出较低的强度。26土木工程英语土木工程英语27The design strength or nominal strength is the strength of a material, including a material-safety factor. The value of the safety factor generally ranges from 0.75 to 0.85 in Allowable Stress Design. 设计强度或名义强度是材料的强度，包括材料安全系数。 允许应力设计中的安全系数值通常在0.75至0.85之间。The ultimat

39、e limit state is the theoretical failure point with a certain probability. It is stated under factored loads and factored resistances.极限状态是具有一定概率的理论失效点。 它是在分解载荷和因素阻力下陈述的。Chapter 6土木工程英语土木工程英语Common failure modes of steel reinforced concrete钢筋混凝土的常见破坏模式Reinforced concrete can fail due to inadequate s

40、trength, leading to mechanical failure, or due to a reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. When rebar corrodes, the oxidation products (rust) expand and tends to flake, cracking the concrete and unbonding the rebar

41、 from the concrete. Typical mechanisms leading to durability problems are discussed below.由于强度不足，钢筋混凝土可能会失效，导致机械故障或耐久性降低。 腐蚀和冻结/解冻循环可能会损坏设计不合理的钢筋混凝土。 当钢筋受到腐蚀时，氧化产物（铁锈）膨胀并趋于剥落，使混凝土开裂并使钢筋与混凝土脱开。 下面讨论导致耐久性问题的典型机制。28土木工程英语土木工程英语29Mechanical failure Cracking of the concrete section can not be prevented;

42、however, the size of and location of the cracks can be limited and controlled by reinforcement, placement of control joints, the curing methodology and the mix design of the concrete. Cracking defects can allow moisture to penetrate and corrode the reinforcement. This is a serviceability failure in

43、limit state design. Cracking is normally the result of an inadequate quantity of rebar, or rebar spaced at too great a distance. The concrete then cracks either under excess loading or due to internal effects such as early thermal shrinkage when it cures.混凝土部分的开裂是无法防止的; 然而，裂缝的大小和位置可以通过加固，控制缝的位置，固化方法

44、和混凝土的混合设计来限制和控制。 开裂缺陷可能使水分渗透并腐蚀钢筋。 这是极限状态设计中的可维护性故障。 裂纹通常是由于螺纹钢数量不足或钢筋间距太大而造成的。 混凝土随后会在过载或由于内部影响（如固化时的早期热收缩）而破裂。Chapter 6土木工程英语土木工程英语Ultimate failure leading to collapse can be caused by crushing of the concrete, when compressive stresses exceed its strength; by yielding or failure of the rebar, whe

45、n bending or shear stresses exceed the strength of the reinforcement; or by bond failure between the concrete and the rebar.当压缩应力超过其强度时，导致混凝土破碎的最终失效可能是由混凝土的破碎引起的; 通过屈服或失败的钢筋，当弯曲或剪切应力超过钢筋的强度时; 或混凝土和钢筋之间的粘结失败。30土木工程英语土木工程英语31Carbonation Carbonation, or neutralisation, is a chemical reaction between ca

46、rbon dioxide in the air with calcium hydroxide and hydrated calcium silicate in the concrete. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5. This highly alkaline environment is one in which the embedded steel is passivated and is prote

47、cted from corrosion. According to the Pourbaix diagram for iron, the metal is passive when the pH is above 9.5. 碳化或中和是空气中的二氧化碳与混凝土中的氢氧化钙和水合硅酸钙之间的化学反应。 波特兰水泥混凝土孔隙中的水通常是碱性的，其pH值范围为12.5至13.5。 这种高度碱性的环境是嵌入钢钝化并防腐蚀的环境。 根据铁的普贝图，当pH高于9.5时，金属是不会被腐蚀的Chapter 6土木工程英语土木工程英语The carbon dioxide in the air reacts wi

48、th the alkali in the cement and makes the pore water more acidic, thus lowering the pH. Carbon dioxide will start to carbonate the cement in the concrete from the moment the object is made. This carbonation process will start at the surface, then slowly move deeper and deeper into the concrete. The

49、rate of carbonation is dependent on the relative humidity of the concrete - a 50% relative humidity being optimal. If the object is cracked, the carbon dioxide in the air will be better able to penetrate into the concrete. 空气中的二氧化碳与水泥中的碱反应，使孔隙水变酸，从而降低pH值。 二氧化碳将开始使混凝土中的水泥发生碳酸盐化。 这种碳酸化过程将从表面开始，然后慢慢地向混

50、凝土深入。 碳化速度取决于混凝土的相对湿度 - 50的相对湿度是最佳的。 如果物体破裂，空气中的二氧化碳会更好地渗透到混凝土中。32土木工程英语土木工程英语When designing a concrete structure, it is normal to state the concrete cover for the rebar (the depth within the object that the rebar will be). The minimum concrete cover is normally regulated by design or building codes