土木工程专业英语课件Unit 7

土木工程专业英语课件

Unit 7 第七单元Reinforced Concrete Structures 钢筋混凝土结构

土木工程专业英语课件

教学目标 了解钢筋混凝土的力学性能 了解采用混凝土结构的优缺点 了解国外建筑规范的发展历史 熟悉钢筋混凝土结构中的专业词汇 熟悉科技类文献的常用句型 熟悉institute、association、society的用法； regulation、specification、code的用法；result in、 give rise to、lead to的用法；reinforcing bar、 reinforcing steel、steel bar、reinforcement的含 义；involve、include、cover的用法；due to、 stem from、because of的用法；construction、 function、compressive、allow、form的不同含义。

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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.

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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。

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Mechanics of Reinforced Concrete 钢筋混凝土的力学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.

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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。

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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。

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Factors Affecting Choice of Concrete For a Structure 影响一个结构选择混凝土的因素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). 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。

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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). 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.

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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。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。

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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.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。

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Suitability of Material for Architectural and Structural Function A reinforced concrete systemfrequently 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.

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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。

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Fire Resistance The structure in a building mustwithstand 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。

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Rigidity

The occupants of a building may be disturbed (干扰)if their building oscil

lates(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.

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。

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Low Maintenance Concrete members inherentlyrequire 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, airentrained 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.

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。