外文翻譯---混凝土，鋼筋混凝土和預(yù)應(yīng)力混凝土

1、<p>　　Concrete, Reinforced Concrete, and Prestressed Concrete</p><p>　　Concrete is a stone like material obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggre

2、gate, and water to harden in forms of the shape and dimensions of the desired structure. The bulk of the material consists of fine and coarse aggregate. Cement and water interact chemically to bind the aggregate particle

3、s into a solid mass. Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture workability that enabl</p><p>　　These properties depend to a very substantial de

4、gree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in

5、 the forms of humidity and hardened. The process of controlling conditions after placement is known as curing. To protect against the unintentional production of substandard concrete, a high degree of skillful control an

6、d supervisio</p><p>　　The factors that make concrete a universal building material are so pronounced that it has been used, in more primitive kinds and ways than at present, for thousands of years, starting

7、with lime mortars from 12,000 to 600 B.C. in Crete, Cyprus, Greece, and the Middle East. The facility with which , while plastic, it can be deposited and made to fill forms or molds of almost any practical shape is one o

8、f these factors. Its high fire and weather resistance are evident advantages. Most of the const</p><p>　　To offset this limitation, it was found possible, in the second half of the nineteenth century, to use

9、 steel with its high tensile strength to reinforce concrete, chiefly in those places where its low tensile strength would limit the carrying capacity of the member. The reinforcement, usually round steel rods with approp

10、riate surface deformations to provide interlocking, is places in the forms in advance of the concrete. When completely surrounded by the hardened concrete mass, it forms an integ</p><p>　　In more recent time

11、s, it has been found possible to produce steels, at relatively low cost, whose yield strength is 3 to 4 times and more that of ordinary reinforcing steels. Likewise, it is possible to produce concrete 4 to 5 times as str

12、ong in compression as the more ordinary concrete. These high-strength materials offer many advantages, including smaller member cross sections, reduced dead load, and longer spans. However, there are limits to the streng

13、ths of the constituent materials beyond w</p><p>　　A special way has been found, however, to use steels and concrete of very high strength in combination. This type of construction is known as prestressed co

14、ncrete. The steel, in the form of wires, strands, or bars, is embedded in the concrete under high tension that is held in equilibrium by compressive stresses in the concrete after hardening, Because of this precompressio

15、n, the concrete in a flexural member will crack on the tension side at a much larger load than when not so precompressed. Pr</p><p>　　混凝土，鋼筋混凝土和預(yù)應(yīng)力混凝土</p><p>　　混凝土是一種經(jīng)過(guò)水泥，沙子和砂礫或其他材料聚合得到經(jīng)過(guò)細(xì)致配比的混合

16、物，在液體變硬使材料石化后可以得到理想的形狀和結(jié)構(gòu)尺寸。材料的大部分由粗骨料及小顆粒組成。水泥和水的相互作用化學(xué)反應(yīng)后生成一個(gè)堅(jiān)實(shí)的總粒子。要廣泛的更好的使用混凝土的性能可通過(guò)調(diào)整組成材料的比例。特殊的水泥，特殊的骨料和外加劑，用特殊的方法混合可以是混凝土更廣泛的被應(yīng)用。</p><p>　　這些特性取決于一對(duì)組合的比例相當(dāng)大的程度上徹底將各種成分混合，以及對(duì)濕度和溫度的調(diào)整，將它放在時(shí)刻保持的條件濕度中使其硬化

17、?？刂坪蟮陌仓靡阎獥l件的固化過(guò)程。為了防止出現(xiàn)不合標(biāo)準(zhǔn)的水泥，對(duì)于從整個(gè)過(guò)程由個(gè)體組成部分，重量配比，混合程度，放置位置，直到完成固化的這個(gè)過(guò)程，一個(gè)嚴(yán)格的管理和監(jiān)督無(wú)疑在生產(chǎn)過(guò)程中是必要的。</p><p>　　有很多原因使混凝土成為如此普遍的建筑材料，相比現(xiàn)代，它已被用于更原始的方式，千百年來(lái)開始于公元前12,000年到6000年例如克里特島，塞浦路斯，希臘，和中東。實(shí)際上該材料可以被放入任何形狀的模具就是其

18、中的因素之一。它的高耐火性的優(yōu)勢(shì)是顯而易見的。大部分組成材料除水泥和添加劑外，通常可以以較低的成本從本地或在距離工地近的地方獲得。它的抗壓強(qiáng)度，像天然石頭，是很高的，這使得它在結(jié)構(gòu)中主要受壓縮作用，如列和拱。另一方面，相比于天然寶石它是一個(gè)比較脆性材料，相較它的抗壓強(qiáng)度它的抗拉強(qiáng)度很小。它在結(jié)構(gòu)構(gòu)件中承受拉力時(shí)容易完全被拉斷，這就阻止了混凝土結(jié)構(gòu)達(dá)到最經(jīng)濟(jì)的效益。</p><p>　　為了彌補(bǔ)這種局限性，在19世

19、紀(jì)后半期發(fā)現(xiàn)，利用其抗拉強(qiáng)度高的鋼材，形成鋼筋混凝土，主要是在那些抗拉強(qiáng)度低將限制該構(gòu)件的承載能力的地方。鋼筋完全被硬化混凝土包裹住，形成結(jié)構(gòu)一個(gè)的組成部分。已知的兩種材料，形成鋼筋混凝土?xí)r結(jié)合各自的許多優(yōu)點(diǎn)：在相對(duì)較低的成本，良好的耐火性能，混凝土良好的抗壓強(qiáng)度和鋼筋良好的抗拉強(qiáng)度高，有了更大的延展性和韌性。正是這種結(jié)合，增加了幾乎無(wú)限的可能性，加強(qiáng)了一系列的建筑結(jié)構(gòu)，例如混凝土橋梁，水壩，坦克，水庫(kù)，以及其他結(jié)構(gòu)的穩(wěn)定性。</

20、p><p>　　使用鋼材可以降低自重，可以增加更長(zhǎng)的壽命。然而，對(duì)組成材料的優(yōu)點(diǎn)界限的某些問(wèn)題的出現(xiàn)是不可避免的?？梢钥隙ǖ氖牵呀?jīng)被發(fā)現(xiàn)可能消耗的成本相對(duì)較低，其屈服強(qiáng)度是普通鋼筋的3至4倍。同樣，它的抗壓縮強(qiáng)度是普通混凝土的4至5倍。這些高強(qiáng)度材料對(duì)截面較小的構(gòu)件也會(huì)產(chǎn)生很多缺點(diǎn)，這樣高強(qiáng)度鋼筋，更會(huì)導(dǎo)致周圍低強(qiáng)度混凝土開裂，會(huì)出現(xiàn)很難看的并且明顯降低了結(jié)構(gòu)的耐久性的大裂痕。這限制了高強(qiáng)度鋼筋不得高于80

21、ksi，跟據(jù)許多的準(zhǔn)則和規(guī)范，屈服強(qiáng)度達(dá)到 60 ksi鋼鐵是最常用的。</p><p>　　一種特殊的方式被發(fā)現(xiàn)，使用鋼材的組合非常高強(qiáng)度混凝土。這種建筑類型被稱為預(yù)應(yīng)力混凝土。鋼鐵，以一根根鋼筋的形式，嵌入在通過(guò)高技術(shù)產(chǎn)生的預(yù)壓混凝土中。由于這一預(yù)壓的混凝土，在一個(gè)彎構(gòu)件混凝土受到張力側(cè)在比預(yù)壓時(shí)，不會(huì)受到更大的負(fù)荷。預(yù)應(yīng)力大大減少在這種結(jié)構(gòu)一般在加載時(shí)產(chǎn)生的拉伸變形和裂縫，從而使這些高強(qiáng)度材料，更加效地加以