【正文】 w construction technique had been mastered. A depot across the bay at Bayonne, ., supplied the girders by lighter and truck on a schedule operated with military precision。 and second, the joining of wroughtiron tension members and castiron pression members by means of rivets inserted while hot. In 1853 the first metal floor beams were rolled for the Cooper Union Building in New York. In the light of the principal market demand for iron beams at the time, it is not surprising that the Cooper Union beams closely resembled railroad rails. The development of the Bessemer and SiemensMartin processes in the 1850s and 1860s suddenly open the way to the use of steel for structural purpose. Stronger than iron in both tension and pression ,the newly available metal was seized on by imaginative engineers, notably by those involved in building the great number of heavy railroad bridges then in demand in Britain, Europe, and the . A notable example was the Eads Bridge, also known as the St. Louis Bridge, in St. Louis (18671874), in which tubular steel ribs were used to form arches with a span of more than 500ft (). In Britain, the Firth of Forth cantilever bridge (188390) employed tubular struts, some 12 ft () in diameter and 350 ft (107m) long. Such bridges and other structures were important in leading to the development and enforcement of standards and codification of permissible design stresses. The lack of adequate theoretical knowledge, and even of an adequate basis for theoretical studies, limited the value of stress analysis during the early years of the 20th century, as occasionally failures, such as that of a cantilever bridge in Quebec in 1907, failures were rare in the metalskeleton office buildings。Merril in which an exterior closely spaced framed tube in concrete envelops an interior steel framing, thereby bining the advantages of both reinforced concrete and structural steel systems. The 52story One Shell Square Building in New Orleans is based on this system. Steel construction refers to a broad range of building construction in which steel plays the leading role. Most steel construction consists of largescale buildings or engineering works, with the steel generally in the form of beams, girders, bars, plates, and other members shaped through the hotrolled process. Despite the increased use of other materials, steel construction remained a major outlet for the steel industries of the , , , Japan, West German, France, and other steel producers in the 1970s. Early history. The history of steel construction begins paradoxically several decades before the introduction of the Bessemer and the SiemensMartin (openhearth) processes made it possible to produce steel in quantities sufficient for structure use. Many of problems of steel construction were studied earlier in connection with iron construction, which began with the Coalbrookdale Bridge, built in cast iron over the Severn River in England in 1777. This and subsequent iron bridge work, in addition to the construction of steam boilers and iron ship hulls , spurred the development of techniques for fabricating, designing, and joining. The advantages of iron over masonry lay in the much smaller amounts of material required. The truss form, based on the resistance of the triangle to deformation, long used in timber, was translated effectively into iron, with cast iron being used for pression ., those bearing the weight of direct loadingand wrought iron being used for tension ., those bearing the pull of suspended loading. The technique for passing iron, heated to the plastic state, between rolls to form flat and rounded bars, was developed as early as 1800。計算機在工程上的運用代替了冗長的手工計算，從而更加促進 了鋼結構的發(fā)展，并大大的減低了造價。但直到第二次世界大戰(zhàn)后才用于建筑結構中。先是螺栓連接緊接著鉚釘連接，最后是裝修，整個工程的最終完成只用了一年零 45 天。 次項工程所需要的梁是由 Bayonne 海灣對岸的軍械庫所提供的。 第一次世界大戰(zhàn)暫時中斷了所謂摩天大廈（當時這個詞并沒有確定）的蓬勃發(fā)展，但是二十世紀二十年代又恢復了這一趨勢。而只有考慮到具體的單獨梁與單獨柱的抗彎能力以及梁柱相交處的剛度的框架設計才是可靠的。 1908年在華爾街建造的高 468 英尺（ 143 米）的城市投資公司大廈，高 612 英尺（ 187 米）的星爾大廈，以及 700 英尺（ 214 米）的都市塔和 780 英尺高（ 232 米）的 Woll worth大廈。 緊隨著鋼結構的發(fā)展， 1988 年第一部電梯問世了。 盡管幾十年來之中建筑形式主要是在美國發(fā)展的，但是它卻影響著全世界鋼材工業(yè)的發(fā)展。鋼材在這些結構中起了非常大的作用。大廈的梁是鋼制的，而柱是鑄鐵所制。無論是它的高度（比著名的金字塔的兩倍還高），架設的速度 人數(shù)不多的工作人員僅用幾個月的時間就完成了整個工程任務，還是很低的工程造價都使它脫穎而出。因為盡管在缺乏縝密的分析的情況下 ，這些建筑也表現(xiàn)出了很高的實用性。英國的 Firth of Forth 懸索橋設有管件支撐，直徑大約為 12 英尺（ 米），長度為 350 英尺（ 107）米。鋼的受拉強度與受壓強度都好于鐵。據(jù)說當時他已有這樣的骨架結構構思：用比較細的鐵梁作為玻璃幕墻的骨架。 把鐵加熱到塑性狀態(tài)，使之從卷狀轉化為扁平狀與圓狀之間的某一狀態(tài)的工藝，早在 1800 年就得以發(fā)展了。這座大橋以及后來的鐵橋設計再加上蒸汽鍋爐、鐵船身的設計都刺激