土木工程外文资料翻译---混凝土与钢筋混凝土的特性.doc

理工学院毕业设计(论文)外文资料翻译专 业： 土 木 工 程 姓 名： 韦 伟 学 号： 09L1401122 外文出处：English in Architecture and Construction 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 签名： 年 月 日附件1：外文资料翻译译文混凝土与钢筋混凝土的特性混凝土是一种人造组合石材，主要由四种成分组成；珀特兰水泥，水，沙子和粗骨料。水泥和水混合成水泥浆，将沙子和石子粘合在一起。理想的骨料级配应使泥浆的体积最小，仅将每块骨料包上薄薄的一层即可。大多数结构混凝土是碎石混凝土，但是轻质的结构混凝土（大约是碎石混凝土密度的2/3）正日益得到普及。混凝土基本上是一种几乎没有抗拉强度的抗压缩材料。所以，混凝土抗拉强的低也导致混凝土抗剪强度低。在产生拉伸应力和剪应力的部位加入钢筋克服这些缺陷。在荷载作用下，钢筋混凝土梁实际上会有许多沿垂直于主拉应力方向的微裂缝。这些部位的拉应力完全被钢筋所承担。给定混凝土的钢牙强度是其组成成分的质量和比例以及新浇混凝土的养护方法的函数，（养护是硬化过程，在此期间，必须防止混凝土过干，因为水分的存在是进行化学反应所必需的。）坚硬并具有良好的级配粗骨料对于优质混凝土是至关重要的。然而，决定其强度的最重要因素是其配料中的含水率。水泥适当水化需要最小量的水分。为了操作和浇筑混凝土需要多加一些水，但是过量的水分是、会导致强度明显降低。由珀特兰水泥协会出版的“混凝土混合物的设计与控制”一书中全部包含了这类以及其他一些论题。这是一本优秀的参考书，它涉及混凝土配料设计以及适合的施工实践。美国混凝土协会出版了广泛采用的专用于钢筋混凝土结构要求的规范。混凝土被认为是作“可成型的”或“可模性的”结构材料。与其他材料相比，混凝土易制成曲线型构件和各种曲面。混凝土没有固定的纹理，但它呈现其成模材料的纹理，因此混凝土可呈现各种各样的外观。制造混凝土无论原材料还是人工费都相当便宜，普通水泥的基本材料在世界各地都可得到。（然而，应注意的是混凝土所必需的钢筋在不发达国家可能不容易得到。）就这种材料的特性而言，钢筋混凝土最佳的 结构用途实在那些要求连贯性的和刚性的建筑结构中。钢筋混凝土具有整体性，可自动实现固定连接或连续连接。这些抗弯节点使得许多低层混凝土建筑物在横向荷载作用下不需要辅助斜支撑系统。实质上混凝土梁与混凝土柱的连接与钢和木结构的连接大不一样，聪明的设计人员是不会护士这些差异的。（这些药店不适合于预制结构件，这些预制结构件通常不以连续方式连接。）混凝土本身是耐火的，不需要单独的保护系统。由于它的质量，混凝土也可以用作为有效的隔声材料。从缺点方面考虑，遗憾的是混凝土相当重，经常可见有混凝土结构仅支撑它本身重量就消耗了它大部分的承载能力。制造低密度而保持其高性能水准的混凝土通常会导致成本提高。不过使用轻质混凝土有时能产生综合经济效益。混凝土比大多数其他建筑材料需要更多的质量监督。现代化的输送搅拌混凝土的供应厂商遍布美国各城市，其混合物通常具有均匀的高质量。然而，现场或临时搅拌的混凝土需要技术性监督。无论在何种混凝土的施工中漏加钢筋或错放钢筋位置都会导致构件的承载能力降低。无论是操作或养护条件不好或二者兼而有之都能严重削弱混凝土的强度。由于种种原因，大多数建筑规范都要求在施工的各个阶段进行独立的现场检查。适当的混凝土浇筑也多少取决于周围气候条件。更重要的是，过高的温度以及低于（或接近于）冰点的温度都能使混凝土施工非常困难。附件2：外文原文（复印件）Properties of Concrete and Reinforced ConcreteConcrete is a man-made conglomerate stone composed of essentially four ingredients: portland cement, water, sand, and coarse aggregate. The cement and water combine to make a paste that binds the sand stones together .Ideally, the aggregates are graded so that the volume of paste is at a minimum , merely surrounding every piece with a thin layer. Most structural concrete is stone concrete ,but structural lightweight concrete (roughly two-thirds the density of stone concrete)is becoming increasingly popular.Concrete is essentially a compressive material having almost no tensile strength ,so concretes weakness in tension also causes it to be weak in shear. These deficiencies are overcome by using steel bars for reinforcement at the places where tensile and shearing stresses are generated. Under load , reinforced concrete beams actually have numerous minute cracks which run at right angles to the direction of major tensile stresses. The tensile forces at such locations are being taken completely by the steel “re-bars.”The compressive strength of a given concrete is a function of the quality and proportions of its constituents and the manner in which the fresh concrete is cured. (Curing is the process of hardening during which time the concrete must be prevented form “drying out” ,as the presence of water is necessary for the chemical action to progress.) Coarse aggregate that is hard and well graded is particularly essential for quality concrete .The most important factor governing the strength , however ,is the percentage of water used in the mix .A minimum amount of water is needed for proper hydration of water used in the mix .A minimum amount of water is needed for proper hydration of the cement .Additional water is needed for handling and placing the concrete ,but excess amounts cause the strength to drop markedly .These and other topics are fully covered in the booklet, “Design and Control of Concrete Mixtures, ” published by the Portland Cement Association. This is an excellent reference ,treating both concrete mix design and proper construction practices. The American Concrete Institute publishes a widely adopted code specifying the structural requirements for reinforced concrete.Concrete is known as the “formable” or “moldable” structural material. Compared to other materials ,it is easy to make curvilinear members and surfaces with concrete. It has no inherent texture but adopts the texture of the forming material, so it can range widely in surface appearance. It is relatively inexpensive to make, both in terms of raw materials and labor ,and the basic ingredients of Portland cement are available the world over. (It should be noted, however, that the necessary reinforcing bars for concrete may not be readily available in less-developed countries.)The best structural use of reinforced concrete ,in terms of the characteristics of the material, is in those structures requiring continuity and or rigidity. It has a monolithic quality which automatically makes fixed or continuous connections. These moment-resistant joints are such that many low-rise concrete buildings do not require a secondary bracing system for lateral loads. In essence, a concrete beam joins a concrete column very differently from the way steel and wood pieces join, and the sensitive designer will not ignore this difference. (These remarks do not apply to precast structural elements, which are usually not joined in a continuous manner.)Concrete is naturally fireproof and needs no separate protection system. Because of its mass, it can also serve as an effective barrier to sound transmission.In viewing the negative aspects, concrete is unfortunately quite heavy and it is often noted that a concrete structure expends a large portion of its capacity merely carrying itself. Attempts to make concrete less dense, while maintaining high quality levels, have generally resulted in increased costs. Nevertheless, use of lightweight concrete can sometimes result in overall economies.Concrete requires more quality control than most other building materials. Modern transit-mixed concrete suppliers are available to all U.S. urban areas and the mix is us