土木工程专业英语-Reinforced Concrete Structures.ppt

Click to edit Master text styles,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,土木工程专业英语,Reinforced Concrete Structures,钢筋混凝土结构,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 of reinforced concrete construction,stems from,（归因于）,the wide availability of,reinforcing bars,（钢筋）,and the,constituents,（组成部分）,of concrete,gravel,sand,and cement,the relatively simple skills required in concrete,construction,（施工）,and the,economy,（经济性）,of reinforced concrete compared to other form of construction.,Concrete and reinforced concrete are used in bridges,buildings of,all sorts,（各种各样）,underground structures,water tanks,television towers,offshore oil exploration and production structures,（近海石油开采和生产结构）,dams,and even in ships.,混凝土与钢筋混凝土作为建筑材料在每个国家被使用着。,在很多国家，包括美国和加拿大，钢筋混凝土是建造的建筑物中主要的结构材料。,钢筋混凝土建筑物通用的特性归因于能大量得到钢筋和混凝土的组分（即碎石、砂和水泥），混凝土施工需要相对简单的技术，以及与其他形式的建筑相比钢筋混凝土的经济性。,混凝土与钢筋混凝土用于桥梁、各种房屋、地下结构、水箱、电视塔、近海石油开采和生产结构、大坝甚至船舶。,Mechanics of Reinforced Concrete,Concrete is strong in compression but weak in tension.,As a result,cracks,develop,（形成）,whenever,（每当）,loads,or,restrained shrinkage,（收缩限制）,or temperature changes,give rise to,（导致）,tensile stresses,in excess of,（超过）,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,（拉压力偶）,involving tension in the concrete.,Such a beam fails very suddenly and completely when the first crack forms.,In a reinforced concrete beam,steel bars,（钢筋）,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.,钢筋混凝土的力学,混凝土受压强、受拉弱。,因此，每当受荷、收缩受阻或温度变化引起的拉应力超过混凝土的抗拉强度时，便会发生开裂。,在素混凝土梁中，因外力引起的力矩由内部的拉-压形成的力偶来抵抗，此力偶中包含了混凝土的拉力。,当第一条裂缝形成时，此梁会突然、完全地失效。,在钢筋混凝土梁中，钢筋埋置在混凝土内的方式应能使混凝土开裂后在钢筋中产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 weight and,hydrostatic pressure,（静水压力）,of the wet concrete,and any forces applied to it by workers,concrete,buggies,（料车）,wind,and so on.,The,reinforcement,（钢筋）,is placed in this form and,held in place,固定就位）,during the,concreting,（用混凝土浇筑）,operation.,After the concrete has hardened,the forms are,removed,（拆除）,.,钢筋混凝土构件的施工包括以在建构件的形状搭建模板或模具。,模板必须足够强劲以支承湿混凝土的重量和静水压力，以及任何由工人、混凝土料车、风等施加给它的力。,钢筋置于模板中，并在混凝土浇筑过程中固定就位。当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 materials and on,a number of,（许多）,value decisions,（价值判断）,.,Economy,Frequently,the,foremost,（最重要的）,consideration is the,overall cost,（总费用）,of the structure.,This is,of course,a,function of the costs,（费用函数）,of the materials and the labor necessary to erect them.,Frequently,however,the overall cost is affected as much or more by the,overall construction time,（总的建造时间）,since the contractor and owner must,allocate,（分配）,money,（资金）,to carry out the construction and will not,receive a return on this investment,（收回投资）,until the building is ready for,occupancy,（居住）,.,影响一个结构选择混凝土的因素,一个结构选择由混凝土、钢材、砌体还是木材建造取决于材料的可得性和许多价值判断。,经济性,最重要的考虑常常是该结构的总费用。,当然，这是一个建造结构而必需的材料和劳动力费用的函数。,但是，总费用经常同样地或更多地受总的建造时间的影响，因为承包商和业主必须分配资金来进行建造，并直到建筑物可以使用才能收回投资。,As a result,financial savings,（财务的节约）,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,forming,（加工）,will generally,pay off,（使人得益）,in reduced overall costs.,In many cases the,long-term economy,（长期的经济性）,of the structure may be more important than the first cost.,As a result,maintenance,（维护）,and,durability,（耐久性）,are important considerations.,因快速施工而使财务的节约可足以抵消增加的材料费用。,设计者为使设计和加工标准化所采取的任何措施通常都将在降低的总费用中得益。,在很多情况下，结构长期的经济性可能比初始费用更重要。,因此，维护和耐久性是重要的考虑因素。,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,（塑性状态）,and is given the desired shape and,texture,（密度）,by means of the,forms and the,finishing techniques,（加工技术）,.,This allows such,elements,（构件）,as flat plates or other types of slabs to serve as load-bearing elements while providing the finished floor and,ceiling surface,（楼面和顶棚面）,.,Similarly,reinforced concrete 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,（决定）,by the designer and not by the availability of standard manufactured members.,材料对建筑和结构功能的适应性,钢筋混凝土系统常常允许设计者将建筑和结构的功能结合起来。,混凝土的优势是能以塑性的状态放置，并通过模板和加工技术给出需要的形状和密度。,当楼面和顶棚面完成时，允许这些构件诸如平面板或其他类型的板充当受力构件。,类似地，钢筋混凝土墙除了能抵抗重力、风或地震荷载外，还能提供建筑上吸引人的外观。,最后，尺寸和形状的选择由设计者来决定，而不是由标准制造构件的可得性来决定。,Fire Resistance,The structure in a building must withstand the effects of a fire and remain,standing,（直立）,while the building is,evacuated,（撤空）,and the fire is,extinguished,（熄灭）,.,A concrete building,inherently,（固有地）,has a 1-to 3-hour,fire rating,（耐火等级）,without special,fireproofing,（防火）,or other,details,（说明）,.,Structural,steel or timber,（钢结构或木结构）,buildings must be fireproofed to attain similar fire ratings.,抗火性,当房屋被撤空、火被熄灭时，建筑中的结构必须经得起火的影响，并仍能保持直立。,混凝土房屋在没有采取特殊的防火措施或其他说明的情况下本来就有,1-3,小时的耐火等级。,钢结构或木结构的房屋必须采取防火措施，以得到相似的耐火等级。,Rigidity,The occupants of a building may be,disturbed,（干扰）,if their building,oscillates,（摇动）,in the wind or the floors vibrate as people,walk by,（走过）,.,Due to the greater,stiffness and mass,（刚度和质量）,of a concrete structure,vibrations are seldom a problem.,Low Maintenance,Concrete members inherently require less maintenance than do structural,steel or timber members,（结构钢构件或结构木构件）,.,This is,particularly true,（尤其正确）,if dense,air-entrained concrete has been used for surfaces exposed to the atmosphere,and if care has been taken in the design to provide adequate,drainage off and away,（使水排出）,from the structure.,刚性,如果房屋在风中摇动，或者人们走过时底板振动，则房屋的居住者可能会被干扰。,由于混凝土结构具有较大的刚度和质量，振动很少成为问题。,低维护性,混凝土构件比结构钢构件或结构木构件需要的维护本来就少。,特别是当暴露在空气中的表面混凝土采用密实的加气混凝土，并在设计中小心地让水分充分地排出结构时更是如此。,Availability of Materials,Sand,gravel,cement,and concrete,mixing facilities,（搅拌设施）,are very widely available,and,reinforcing steel,（钢筋）,can be transported to most,job sites,（施工现场）,more easily than can,structural steel,（结构钢）,.,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 select a material,other than,（,.,除外，不是,.,）,reinforced concrete.These include,：,材料的可得性,砂、碎石（砾石）、水泥以及混凝土的搅拌设施可以非常广泛的得到，且钢筋比结构钢更容易地运至多数施工现场。因此，钢筋混凝土经常用在偏远的区域。,另一方面，有许多因素可能导致一个人选择的材料不是钢筋混凝土。这包括：,Low Tensile Strength,As stated,（叙述）,earlier,the tensile strength of concrete is much lower than its compressive strength(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,（宽度）,to within acceptable values.,Unless care is taken in design and construction,however,these cracks may be,unsightly,（难看）,or may,allow,（使,.,能）,penetration,（渗透）,of water.,低的抗拉强度,正如前面所述的，混凝土的抗拉强度比它的抗压强度要低得多（约,1/10,），因而混凝土易遭受开裂。,在结构使用中，通过采用钢筋承受拉力，并限制裂缝宽度在可接受的数值内来克服这一点。,但是，除非在设计与施工中小心谨慎，否则这些裂缝可能会难看或使水渗透。,Forms and Shoring,The construction of a,cast-in-place structure,（现浇结构）,involves,（涉及）,three,steps,（步骤）,not encountered in the construction 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,（支撑）,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 other,forms of construction,（建筑形式）,.,模板和支撑,现浇结构的施工涉及到三个步骤在钢结构或木结构的施工中不会遇到。,它们是,(a),模板的施工；,(b),模板的拆除；,(c),支撑新浇混凝土支撑其重量直至混凝土达到足够的强度。,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,（类似的）,steel structure.,As a result,long-span structures,（大跨结构）,are often built from steel.,相对低的单位重量或单位体积的强度,混凝土的抗压强度大约是钢材的,5%-10%,，而它的单位密度约是钢材的,30%,。,因此，混凝土结构与类似的钢结构相比需要较大的材料体积和较重的材料重量。,因此，大跨结构常常由钢材制造。,Time-dependent volume changes,Both concrete and steel undergo approximately the same amount of thermal expansion and contraction.,Because there is less mass of steel to be,heated or cooled,（变热或变冷）,and because steel is a better,conductor,（导体）,than concrete,a steel structure is generally affected by temperature changes to a greater,extent,（程度）,than is a concrete structure.,On the other hand,concrete undergoes drying,shrinkage,（干缩）,which,if restrained,may cause deflections or cracking.,Furthermore,deflections will tend to increase,with time,（随时间）,possibly,doubling,（双倍）,due to,creep,（徐变）,of the concrete under,sustained loads,（持续荷载）,.,体积随时间变化,混凝土与钢筋都经过了大约相同量的热膨胀和收缩。,因为变热或变冷的钢材质量较少，且钢材与混凝土相比是一种较好的导体，因此，钢结构通常受温度变化的影响程度比混凝土结构要大。,另一方面，混凝土经历了干缩，如果受到约束，干缩可能会引起挠度或开裂。,而且，挠度往往会随着时间增加，其值由于混凝土在持续荷载作用下的徐变而可能会是两倍。,本 讲,结束,