土木工程專業(yè)英語-Reinforced_Concrete_Structures.ppt

1、,土木工程專業(yè)英語,Reinforced Concrete Structures 鋼筋混凝土結(jié)構(gòu),Concrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant（主要的）structural material in engineered construction（建造的建筑物）. The universal（通用的）nature o

2、f reinforced concrete construction stems from（歸因于）the wide availability of reinforcing bars（鋼筋）and the constituents（組成部分）of concrete, gravel, sand, and cement, the relatively simple skills required in concrete construction（施工）, and the economy（經(jīng)濟性）of reinforced concrete compared to other form of con

3、struction. Concrete and reinforced concrete are used in bridges, buildings of all sorts（各種各樣）, underground structures, water tanks, television towers, offshore oil exploration and production structures（近海石油開采和生產(chǎn)結(jié)構(gòu)）, dams, and even in ships.,混凝土與鋼筋混凝土作為建筑材料在每個國家被使用著。 在很多國家，包括美國和加拿大，鋼筋混凝土是建造的建筑物中主要的結(jié)構(gòu)

4、材料。 鋼筋混凝土建筑物通用的特性歸因于能大量得到鋼筋和混凝土的組分（即碎石、砂和水泥），混凝土施工需要相對簡單的技術(shù)，以及與其他形式的建筑相比鋼筋混凝土的經(jīng)濟性。 混凝土與鋼筋混凝土用于橋梁、各種房屋、地下結(jié)構(gòu)、水箱、電視塔、近海石油開采和生產(chǎn)結(jié)構(gòu)、大壩甚至船舶。,Mechanics of Reinforced Concrete Concrete is strong in compression but weak in tension. As a result, cracks develop（形成）whenever（每當(dāng)）loads, or restrained shrinkage（收縮限制

5、）or temperature changes, give rise to（導(dǎo)致）tensile stresses in excess of（超過）the tensile strength of the concrete. In the plain concrete（素混凝土）beam, the moments due to applied loads are resisted by an internal tension-compression couple（拉壓力偶）involving tension in the concrete. Such a beam fails very sudd

6、enly and completely when the first crack forms. In a reinforced concrete beam, steel bars（鋼筋）are embedded in the concrete in such a way that the tension forces needed for moment equilibrium after the concrete cracks can be developed in the bars.,鋼筋混凝土的力學(xué) 混凝土受壓強、受拉弱。 因此，每當(dāng)受荷、收縮受阻或溫度變化引起的拉應(yīng)力超過混凝土的抗拉強度

7、時，便會發(fā)生開裂。 在素混凝土梁中，因外力引起的力矩由內(nèi)部的拉-壓形成的力偶來抵抗，此力偶中包含了混凝土的拉力。 當(dāng)?shù)谝粭l裂縫形成時，此梁會突然、完全地失效。 在鋼筋混凝土梁中，鋼筋埋置在混凝土內(nèi)的方式應(yīng)能使混凝土開裂后在鋼筋中產(chǎn)生平衡力矩所需的拉力。,The construction（施工）of a reinforced concrete member involves building a form or mold（模具）in the shape of the member being built. The form must be strong enough to support the

8、 weight and hydrostatic pressure（靜水壓力）of the wet concrete, and any forces applied to it by workers, concrete buggies（料車）, wind, and so on. The reinforcement（鋼筋）is placed in this form and held in place（固定就位）during the concreting（用混凝土澆筑）operation. After the concrete has hardened, the forms are removed

9、（拆除）.,鋼筋混凝土構(gòu)件的施工包括以在建構(gòu)件的形狀搭建模板或模具。 模板必須足夠強勁以支承濕混凝土的重量和靜水壓力，以及任何由工人、混凝土料車、風(fēng)等施加給它的力。 鋼筋置于模板中，并在混凝土澆筑過程中固定就位。當(dāng)混凝土硬化后便拆除模板。,Factors Affecting Choice of Concrete For a Structure The choice of whether a structure should be built of concrete, steel, masonry, or timber（木材）depends on the availability（可得性）of

10、materials and on a number of（許多）value decisions（價值判斷）. Economy Frequently, the foremost（最重要的）consideration is the overall cost（總費用）of the structure. This is, of course, a function of the costs（費用函數(shù)）of the materials and the labor necessary to erect them. Frequently, however, the overall cost is affec

11、ted as much or more by the overall construction time（總的建造時間）since the contractor and owner must allocate（分配）money（資金）to carry out the construction and will not receive a return on this investment （收回投資）until the building is ready for occupancy（居?。?,影響一個結(jié)構(gòu)選擇混凝土的因素 一個結(jié)構(gòu)選擇由混凝土、鋼材、砌體還是木材建造取決于材料的可得性和許多價值

12、判斷。 經(jīng)濟性 最重要的考慮常常是該結(jié)構(gòu)的總費用。 當(dāng)然，這是一個建造結(jié)構(gòu)而必需的材料和勞動力費用的函數(shù)。 但是，總費用經(jīng)常同樣地或更多地受總的建造時間的影響，因為承包商和業(yè)主必須分配資金來進行建造，并直到建筑物可以使用才能收回投資。,As a result, financial savings（財務(wù)的節(jié)約）due to rapid construction may more than offset（足以抵消）increased material costs. Any measures designer can take to standardize the design and formin

13、g（加工）will generally pay off（使人得益）in reduced overall costs. In many cases the long-term economy（長期的經(jīng)濟性）of the structure may be more important than the first cost. As a result, maintenance（維護）and durability（耐久性）are important considerations.,因快速施工而使財務(wù)的節(jié)約可足以抵消增加的材料費用。 設(shè)計者為使設(shè)計和加工標準化所采取的任何措施通常都將在降低的總費用中得益

14、。 在很多情況下，結(jié)構(gòu)長期的經(jīng)濟性可能比初始費用更重要。 因此，維護和耐久性是重要的考慮因素。,Suitability of Material for Architectural and Structural Function A reinforced concrete system frequently allows the designer to combine the architectural and structural functions（功能）. Concrete has the advantage that it is placed in a plastic condition

15、（塑性狀態(tài)）and is given the desired shape and texture（密度）by means of the forms and the finishing techniques（加工技術(shù)）. This allows such elements（構(gòu)件）as flat plates or other types of slabs to serve as load-bearing elements while providing the finished floor and ceiling surface（樓面和頂棚面）. Similarly, reinforced co

16、ncrete walls can provide architecturally attractive surfaces in addition to having the ability to resist gravity, wind, or seismic loads. Finally, the choice of size or shape is governed（決定）by the designer and not by the availability of standard manufactured members.,材料對建筑和結(jié)構(gòu)功能的適應(yīng)性 鋼筋混凝土系統(tǒng)常常允許設(shè)計者將建筑

17、和結(jié)構(gòu)的功能結(jié)合起來。 混凝土的優(yōu)勢是能以塑性的狀態(tài)放置，并通過模板和加工技術(shù)給出需要的形狀和密度。 當(dāng)樓面和頂棚面完成時，允許這些構(gòu)件諸如平面板或其他類型的板充當(dāng)受力構(gòu)件。 類似地，鋼筋混凝土墻除了能抵抗重力、風(fēng)或地震荷載外，還能提供建筑上吸引人的外觀。 最后，尺寸和形狀的選擇由設(shè)計者來決定，而不是由標準制造構(gòu)件的可得性來決定。,Fire Resistance The structure in a building must withstand the effects of a fire and remain standing（直立）while the building is evacuat

18、ed（撤空）and the fire is extinguished（熄滅）. A concrete building inherently（固有地）has a 1- to 3-hour fire rating（耐火等級）without special fireproofing （防火）or other details（說明）. Structural steel or timber（鋼結(jié)構(gòu)或木結(jié)構(gòu)） buildings must be fireproofed to attain similar fire ratings.,抗火性 當(dāng)房屋被撤空、火被熄滅時，建筑中的結(jié)構(gòu)必須經(jīng)得起火的影響，并仍能

19、保持直立。 混凝土房屋在沒有采取特殊的防火措施或其他說明的情況下本來就有1-3小時的耐火等級。 鋼結(jié)構(gòu)或木結(jié)構(gòu)的房屋必須采取防火措施，以得到相似的耐火等級。,Rigidity The occupants of a building may be disturbed （干擾）if their building oscillates（搖動）in the wind or the floors vibrate as people walk by（走過）. Due to the greater stiffness and mass（剛度和質(zhì)量）of a concrete structure, vibra

20、tions are seldom a problem. Low Maintenance Concrete members inherently require less maintenance than do structural steel or timber members （結(jié)構(gòu)鋼構(gòu)件或結(jié)構(gòu)木構(gòu)件）. This is particularly true（尤其正確）if dense, air-entrained concrete has been used for surfaces exposed to the atmosphere, and if care has been taken

21、in the design to provide adequate drainage off and away （使水排出） from the structure.,剛性 如果房屋在風(fēng)中搖動，或者人們走過時底板振動，則房屋的居住者可能會被干擾。 由于混凝土結(jié)構(gòu)具有較大的剛度和質(zhì)量，振動很少成為問題。 低維護性 混凝土構(gòu)件比結(jié)構(gòu)鋼構(gòu)件或結(jié)構(gòu)木構(gòu)件需要的維護本來就少。 特別是當(dāng)暴露在空氣中的表面混凝土采用密實的加氣混凝土，并在設(shè)計中小心地讓水分充分地排出結(jié)構(gòu)時更是如此。,Availability of Materials Sand, gravel, cement, and concrete mix

22、ing facilities（攪拌設(shè)施） are very widely available, and reinforcing steel（鋼筋）can be transported to most job sites（施工現(xiàn)場）more easily than can structural steel（結(jié)構(gòu)鋼）. As a result, reinforced concrete is frequently used in remote areas. On the other hand, there are a number of factors that may cause one to s

23、elect a material other than （.除外，不是.）reinforced concrete. These include：,材料的可得性 砂、碎石（礫石）、水泥以及混凝土的攪拌設(shè)施可以非常廣泛的得到，且鋼筋比結(jié)構(gòu)鋼更容易地運至多數(shù)施工現(xiàn)場。 因此，鋼筋混凝土經(jīng)常用在偏遠的區(qū)域。 另一方面，有許多因素可能導(dǎo)致一個人選擇的材料不是鋼筋混凝土。這包括：,Low Tensile Strength As stated（敘述）earlier, the tensile strength of concrete is much lower than its compressive str

24、ength (about 1/10), and hence concrete is subject to（易遭受）cracking. In structural uses this is overcome by using reinforcement to carry tensile forces and limit crack widths（寬度）to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly（難看）or m

25、ay allow（使.能）penetration（滲透）of water.,低的抗拉強度 正如前面所述的，混凝土的抗拉強度比它的抗壓強度要低得多（約1/10），因而混凝土易遭受開裂。 在結(jié)構(gòu)使用中，通過采用鋼筋承受拉力，并限制裂縫寬度在可接受的數(shù)值內(nèi)來克服這一點。 但是，除非在設(shè)計與施工中小心謹慎，否則這些裂縫可能會難看或使水滲透。,Forms and Shoring The construction of a cast-in-place structure（現(xiàn)澆結(jié)構(gòu)）involves（涉及）three steps（步驟）not encountered in the construction

26、of steel or timber structures. These are (a) the construction of the forms, (b) the removal（拆除）of these forms, and (c) propping or shoring（支撐）the new concrete to support its weight until its strength is adequate. Each of these steps involves（包含）labor（人工）and/or materials which are not necessary with

27、other forms of construction（建筑形式）.,模板和支撐 現(xiàn)澆結(jié)構(gòu)的施工涉及到三個步驟在鋼結(jié)構(gòu)或木結(jié)構(gòu)的施工中不會遇到。 它們是(a)模板的施工；(b)模板的拆除；(c)支撐新澆混凝土，支撐其重量直至混凝土達到足夠的強度。 每一步都包括其他建筑形式中不必要的人工和/或材料。,Relatively Low Strength Per Unit of Weight or Volume The compressive strength of concrete is roughly 5% to 10% that of steel, while its unit density is roughly 30% that of steel. As a result, a concrete structure requires a larger volume and a greater weight of material than does a comparable（類似的） steel structure. As a result, long-span structures（大跨結(jié)構(gòu)）are often built from st