【正文】 se 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。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。 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。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。 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 。這種情況下 ， 需要特別設(shè)計的 措施 。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 。混凝土 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 。 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 。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 。必須采取 的 特別預(yù)防措施 是讓混凝土 接觸到鹽，如除冰化學品。混凝土構(gòu)件 本身 比結(jié)構(gòu)鋼或木材 構(gòu)件 需要更少的維修。鋼結(jié)構(gòu)或木結(jié)構(gòu)必須采取防火措施才能達到類似的耐火極限。 建筑結(jié)構(gòu)必須經(jīng)受得住火災(zāi)的襲擊 ，并且當人員疏散及大火撲滅之時建筑物仍然保持不倒 。最后，大小 和 形狀 的選擇是由設(shè)計師而不是由 提供構(gòu)件 的標準 決定的 。 在 提供成品樓或天花板表面 時，這使得平板或其他形式的板作為受力構(gòu)件 。鋼筋混凝土 體系 經(jīng)常讓設(shè)計師 將 建筑與結(jié)構(gòu)的 功 能 相結(jié)合 。因此，維修和耐久性是重要的考慮因素?；谶@個原因，設(shè)計師可以采取任何措施規(guī)范設(shè)計 來減輕削減的成本 。在一個典型的大型公寓 或 商業(yè)項目 中 ，建筑成本的融資將是總費用 的 一個重要部分。當然，這是 隨著材 料 的成本 和安裝構(gòu)件的必需 勞動力 改變的 。結(jié)構(gòu)體系 的選擇 是由建筑師 或 工程師早在設(shè)計的基礎(chǔ)上 決定的 ，考慮到下列因素： 1. Economy. Frequently, the foremost consideration is the overall const of the structure. This is, of course, a function of the costs 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 since the contractor and owner must borrow or otherwise allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. In a typical large apartment of mercial project, the cost of construction financing will be a significant fraction of the total cost. As a result, financial savings due to rapid construction may more than offset increased material costs. For this reason, any measures the designer can take to standardize the design and forming will generally pay off in reduced overall costs. 。由于當鋼筋放入摸板后才澆筑混凝土，因此混凝土必須能夠流過鋼筋及摸板并完全充滿摸板的每個角落 。 除此之外 ， 梁必須設(shè)計合理 以便它能夠 被 建造。 當模板被移走時 ， 支撐將被安裝來承受混凝土的重量 直到它達到足夠的 強度 來 承受自重 。在混凝土的運作 過程中，鋼筋將被放置在摸板中 。 The construction of a reinforced concrete member involves building a from of mold in the shape of the member being built. The form must be strong enough to support both the weight and hydrostatic pressure of the wet concrete, and any forces applied to it by workers, concrete buggies, wind, and so on. The reinforcement is placed in this form and held in place during the concreting operation. After the concrete has hardened, the forms are removed. As the forms are removed, props of shores are installed to support the weight of the concrete until it has reached sufficient strength to support the loads by itself. 鋼筋混凝土構(gòu)件 的 建造 包括以被建構(gòu)件的形狀支摸板 。這種 梁當出現(xiàn)第一道裂縫時就突然完全地斷裂了 。因此 ， 混凝土 ， 每當 承受荷載時 ，或約束收縮 或 溫度變化，引起拉應(yīng)力，在超過 抗拉 強度 時， 裂縫 開始 發(fā)展。其他 很少