【文章內(nèi)容簡介】 job sites more easily than can structural steel. As a result, reinforced concrete is frequently used in remote areas. 5 .材料的供應(yīng) 。砂 、 碎石 、 水泥和混凝土攪拌 設(shè)備 是 被 非常廣泛使用 的 ，以及鋼筋比結(jié)構(gòu)鋼更容易運到 多數(shù)工地 。因此，鋼筋混凝土在偏遠地區(qū)經(jīng)常使用。 On the other hand, there are a number of factors that may cause one to select a material other than reinforced concrete. These include: 另一方面，有一些因素可能會導(dǎo)致選擇鋼筋混凝土以外的 材料 。這些措施包括： 1. Low tensile strength. The tensile strength concrete is much lower than its pressive strength ( about 1/10 ), and hence concrete is subject to cracking. In structural uses this is overe by using reinforcement to carry tensile forces and limit crack widths to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly or may allow peration of water. When this occurs, water or chemicals such as road deicing salts may cause deterioration or staining of the concrete. Special design details are required in such cases. In the case of waterretaining structures, special details and / of prestressing are required to prevent leakage. 1 .低抗拉強度?；炷?的抗拉 強度是遠低于其 抗壓 強度（約 1 / 10 ） ，因此， 混凝土易經(jīng)受裂縫 。在結(jié)構(gòu)用途 時 ，用鋼筋 承受拉力 ，并限制裂縫寬度在允許的范圍內(nèi)來克服 。不過，在設(shè)計和施工中 如果不 采取 措施 ，這些裂縫可能會有礙觀瞻，或可允許水的 浸入 。發(fā)生這種情況時，水或化學(xué) 物質(zhì) 如道路除冰鹽可能會導(dǎo)致混凝土 的 惡化或 污染 。這種情況下 ， 需要特別設(shè)計的 措施 。在水支擋結(jié)構(gòu) 這種情況下 ， 需要 特別的 措施 和 /或 預(yù)應(yīng)力，以 防止泄漏。 2. Forms and shoring. The construction of a castinplace structure involves three steps not encountered in the construction of steel or timber structures. These are ( a ) the construction of the forms, ( b ) the removal of these forms, and (c) propping or shoring the new concrete to support its weight until its strength is adequate. Each of these steps involves labor and / or materials, which are not necessary with other forms of construction. 2 .支摸 。建 造 一個現(xiàn)澆結(jié)構(gòu) 包括 三個步驟 ，在 鋼或木結(jié)構(gòu) 的 施工中 是 遇 不 到的。這些都是（ a） 支摸 （ b） 拆摸 （ c ） 安裝支撐 ，直至其 達到足夠的 強度以支 承 其重量。上述每個步驟，涉及勞動 力 和 /或材料， 在其他結(jié)構(gòu)形式中，這是沒有必要的 。 3. Relatively low strength per unit of weight for volume. The pressive 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 parable steel structure. As a result, longspan structures are often built from steel. 3 . 每單位重量 或 量 的 相對低強度。該混凝土抗壓強度大約是 鋼材抗壓強度 5 至 10 ％ ，而其單位密度大約是 鋼材密度的 30 ％。因此，一個混凝土結(jié)構(gòu)， 與 鋼 結(jié)構(gòu) 相比， 需要較大的體積和較大重量的材料。因此，大跨度結(jié)構(gòu)，往往 建成鋼結(jié)構(gòu) 。 4. Timedependent volume changes. Both concrete and steel undergoapproximately the same amount of thermal expansion and contraction. Because there is less mass of steel to be heated or cooled, and because steel is a better concrete, a steel structure is generally affected by temperature changes to a greater extent than is a concrete structure. On the other hand, concrete undergoes frying shrinkage, which, if restrained, may cause deflections or cracking. Furthermore, deflections will tend to increase with time, possibly doubling, due to creep of the concrete under sustained loads. 4 .時間依賴的量的變化?；炷僚c鋼進行大約同樣數(shù)量的熱膨脹和收縮 時，有 比較少量 的鋼材加熱或冷卻，因為鋼 與混凝土相比 是一個較好的 導(dǎo)體 ，鋼結(jié)構(gòu)比混凝土結(jié)構(gòu)在更大程度上 更易 受溫度變化。另一方面， 混凝土 經(jīng)歷了 干 縮，如果 被抑 制，可能會導(dǎo)致 變形 或開裂。此外， 變形 隨著時間的推移將趨于增加，由于混凝土 在 持續(xù)的負荷 下的徐變 ，可能會增加一倍。 In almost every branch of civil engineering and architecture extensive use is made of reinforced concrete for structures and foundations. Engineers and architects requires basic knowledge of reinforced concrete design throughout their professional careers. Much of this text is directly concerned with the behavior and proportioning of ponents that make up typical reinforced concrete structuresbeams, columns, and slabs. Once the behavior of these individual elements is understood, the designer will have the background to analyze and design a wide range of plex structures, such as foundations, buildings, and bridges, posed of these elements. 幾乎在 土木工程和建筑 的每一個分支中 ，鋼筋混凝土 在 結(jié)構(gòu)和 基礎(chǔ)領(lǐng)域內(nèi)都得到了 廣泛 的 使用。 因此