土木专业英语教案(黎永建上传)1.22012.ppt

The principal（主要的） construction materials of earlier times were wood and masonry（圬工） brick（砖）, stone, or tile（瓦）, and similar materials. The courses or layers were bound together with mortar（砂浆） or bitumen（沥青）, a tarlike（焦油般的） substance, or some other binding agent（粘结料）. The Greeks and Romans sometimes used iron(铁) rods（杆、棒） or clamps（夹子、夹板） to strengthen their buildings.早期主要的建筑材料是木材和砌体，如砖、石、瓦以及类似的材料。砖层之间通过砂浆、沥青（一种焦油状的物质）或其他一些粘合剂粘合在一起。希腊人和罗马人有时用铁条或夹子来加固他们的房屋。 The columns of the Parthenon（帕提翁神庙） in Athens（雅典）, for example, have holes drilled in them for iron bars(棒、条) that have now rusted （锈蚀） away. 例如，帕提侬神庙的柱子上就又原来安装铁棍的钻孔，现在铁棍已经锈蚀殆尽。 The Romans also used a natural cement（水泥） called pozzolana（火山灰）, made from volcanic ash（火山灰）, that became as hard as stone under water.罗马人也用称作白榴火山灰的天然水泥，它用火山灰制作，在水中会变得与石头一样坚硬。 Both steel （钢材）and cement, the two most important construction materials of modern time, were introduced in the nineteenth century.作为现代两种最重要的建筑材料，钢材与水泥在十九世纪得到了推广。 Steel, basically an alloy(合金) of iron and a small amount of carbon（碳）, been made up to that time by a laborious（艰难的、辛苦的） process that restricted it to such special used as sword(剑) blades（叶片、刃）. After the invention of the Bessemer process in 1856, steel was available in large quantities at low prices. 钢是铁和少量碳的合金，在那时炼制过程艰难，这限制它只能在一些特殊的地方使用，比如剑刃。在1856年发明了贝塞麦炼钢法后，钢材才得以大量低价获得。 The enormous advantage of steel is its tensile strength（抗拉强度）; that is, it does not lose its strength when it is under a calculated degree of tension, a force which, as we have seen, tends to pull apart（拉断） many materials. New alloys have further increased the strength of steel and eliminated some of its problems, such as fatigue（疲劳）, which is a tendency for it to weaken as a result of continual changes in stress. 钢材最大的优势是抗拉强度，当它承受很高的拉力时，也不会破坏，而这么大的拉力足可以把很多材料拉断。新的合金进一步提高了钢材的强度，并消除了一些缺点，如疲劳，即在连续的应力变化下导致强度减弱的趋势。 Modern cement, called Portland cement（波特兰水泥）, was invented in 1824. It is a mixture of lime