【正文】 a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. The choice of structural system is made by the architect of engineer early in the design, based on the following considerations: 被建成的結構材料的 選擇 是 混凝土， 還是 鋼材 、砌體 ， 或 木材 ， 取決于是否有材料和一些價值 決策 。結構體系 的選擇 是由建筑師 或 工程師早在設計的基礎上 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. 。 常常 首要考慮的是結構 的總造價 。當然，這是 隨著材 料 的成本 和安裝構件的必需 勞動力 改變的 。 然而，總投資常常更受總工期的影響，因為承包商和業(yè)主必須借款或貸款以便完成建設，在建筑物竣工前他們從此項投資中將得不到任何回報 。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。因此，金融儲蓄，由于快速施工可能多于抵消增加材料成本?；谶@個原因，設計師可以采取任何措施規(guī)范設計 來減輕削減的成本 。 In many cases the longterm economy of the structure may be more important than the first cost. As a result, maintenance and durability are important consideration. 在許多情況下，長期的經(jīng)濟結構可能比第一成本更重要。因此，維修和耐久性是重要的考慮因素。 2. Suitability of material for architectural and structural function. A reinforced concrete system frequently allows the designer to bine the architectural and structural functions. Concrete has the advantage that it is placed in a plastic condition and is given the desired shape and texture by means of the forms and the finishing techniques. This allows such elements ad flat plates or other types of slabs to serve as loadbearing elements while providing the finished floor and / or ceiling surfaces. 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 of shape is governed by the designer and not by the availability of standard manufactured members. 2 .用于建筑與結構功能適宜的材料。鋼筋混凝土 體系 經(jīng)常讓設計師 將 建筑與結構的 功 能 相結合 。 混凝土被放置在塑性條件下借助于模板和表面加工來造出想要的形狀和結構，這是它 具有的優(yōu)勢。 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件 。同樣，鋼筋混凝土墻壁能提供有吸引力的建筑表面 ，還有 能力抵御重力 、 風力，或地震荷載。最后，大小 和 形狀 的選擇是由設計師而不是由 提供構件 的標準 決定的 。 3. Fire resistance. The structure in a building must withstand the effects of a fire and remain standing while the building is evacuated and the fire is extinguished. A concrete building inherently has a 1 to 3hour fire rating without special fireproofing or other details. Structural steel or timber buildings must be fireproofed to attain similar fire ratings. 3 .耐火 性 。 建筑結構必須經(jīng)受得住火災的襲擊 ，并且當人員疏散及大火撲滅之時建筑物仍然保持不倒 。 鋼筋混凝土建筑特殊的防火材料及其他構造措施情況下，自身具有 13 個小時的耐火極限。鋼結構或木結構必須采取防火措施才能達到類似的耐火極限。 4. Low maintenance. Concrete members inherently require less maintenance than do structural steel or timber members. This is particularly true 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 from the structure. Special precautions must be taken for concrete exposed to salts such as deicing chemicals. 4 .低維護。混凝土構件 本身 比結構鋼或木材 構件 需要更少的維修。如果致密 ， 尤其如此，加氣混凝土已經(jīng)被用于暴露于大氣中 的 表面，如果在設計 中 已經(jīng)采取謹慎措施，以提供足夠的排水和遠離的結構。必須采取 的 特別預防措施 是讓混凝土 接觸到鹽，如除冰化學品。 5. Availability of materials. Sand, gravel, cement, and concrete mixing facilities are very widely available, and reinforcing steel can be transported to most