土建专业毕业设计外文翻译--建筑中的结构设计及建筑材料-建筑结构(编辑修改稿)

土建专业毕业设计外文翻译--建筑中的结构设计及建筑材料-建筑结构(编辑修改稿)内容摘要：

were bound together with mortar or bitumen, a tar like substance, or some other binding agent. The Greeks and Romans sometimes used iron rods or claps to strengthen their building. The columns of the Parthenon in Athens, for example, have holes drilled in them for iron bars that have now rusted away. The Romans also used a natural cement called puzzling, made from volcanic ash, that became as hard as stone under water. Both steel and cement, the two most important construction materials of modern times, were introduced in the nieenth century. Steel, basically an alloy of iron and a small amount of carbon had been made up to that time by a laborious process that restricted it to such special uses as sword blades. After the invention of the Bessemer process in 1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile force which, as we have seen, tends to pull apart many materials. New alloys have further, which is a tendency for it to weaken as a result of continual changes in stress. 3 Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone and clay, which is heated and then ground into a power. It is mixed at or near the construction site with sand, aggregate small stones, crushed rock, or gravel, and water to make concrete. Different proportions of the ingredients produce concrete with different strength and weight. Concrete is very versatile。 it can be poured, pumped, or even sprayed into all kinds of shapes. And whereas steel has great tensile strength, concrete has great strength under pression. Thus, the two substances plement each other. They also plement each other in another way: they have almost the same rate of contraction and expansion. They therefore can work together in situations where both pression and tension are factors. Steel rods are embedded in concrete to make reinforced concrete in concrete beams or structures where tensions will develop. Concrete and steel also form such a strong bond─ the force that unites them─ that the steel cannot slip within the concrete. Still another advantage is that steel does not rust in concrete. Acid corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid. The adoption of structural steel and reinforced concrete caused major changes in traditional construction practices. It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fireresistant floors. Both these changes served to reduce the cost of c。