【正文】 1250 英尺（ 381 米）的帝國(guó)大廈在后來(lái)的 40 年一直保持著世界最高的地位。由九架起重機(jī)將這些梁提升到指定的位置。但是與此同時(shí)，焊接代替了鉚釘連接則是一個(gè)很重要的發(fā)展。 二戰(zhàn)結(jié)束后，歐洲，美國(guó)，日本等國(guó)都擴(kuò)大了對(duì)在不定應(yīng)力（包括超過(guò)屈服點(diǎn)的情況）作用下各種結(jié)構(gòu)鋼的性質(zhì)的研究，并進(jìn)行了更為精確、系統(tǒng)的分析。ade of the building as a structural element which acts with the framed tube, thus providing an efficient way of resisting lateral loads in highrise buildings, and resulting in costeffective columnfree interior space with a high ratio of to gross floor area. Because of the contribution of the stressedskin fa231。 and in 1849 the first I beams, feet () long , were fabricated as roof girders for a Paris railroad station. Two years later Joseph Paxton of England built the Crystal Palace for the London Exposition of 1851. He is said to have conceived the idea of cage constructionusing relatively slender iron beams as a skeleton for the glass walls of a large, open structure. Resistance to wind forces in the Crystal palace was provided by diagonal iron rods. Two feature are particularly important in the history of metal construction。 decade by decade this figure rose until in the 1960s it exceeded 700 pounds (320 kilograms) per foot. Coincident with the introduction of structural steel came the introduction of the Otis electric elevator in 1889. The demonstration of a safe passenger elevator, together with that of a safe and economical steel construction method, sent building heights soaring. In New York the 286ft () Flatiron Building of 1902 was surpassed in 1904 by the 375ft (115m) Times Building ( renamed the Allied Chemical Building) , the 468ft (143m) City Investing Company Building in Wall Street, the 612ft (187m) Singer Building (1908), the 700ft (214m) Metropolitan Tower (1909) and, in 1913, the 780ft (232m) Woolworth Building. The rapid increase in height and the heighttowidth ratio brought problems. To limit street congestion, building setback design was prescribed. On the technical side, the problem of lateral support was studied. A diagonal bracing system, such as that used in the Eiffel Tower, was not architecturally desirable in offices relying on sunlight for illumination. The answer was found in greater reliance on the bending resistance of certain individual beams and columns strategically designed into the skeleton frame, together with a high degree of rigidity sought at the junction of the beams and columns. With today’s modern interior lighting systems, however, diagonal bracing against wind loads has returned。 an industrialrailway setup moved steel and other material on each floor. Initial connections were made by bolting , closely followed by riveting, followed by masonry and finishing. The entire job was pleted in one year and 45 days. The worldwide depression of the 1930s and World War II provided another interruption to steel construction development, but at the same time the introduction of welding to replace riveting provided an important advance. Joining of steel parts by metal are welding had been successfully achieved by the end of the 19th century and was used in emergency ship repairs during World War I, but its application to construction was limited until after World War II. Another advance in the same area had been the introduction of highstrength bolts to replace rivets in field connections. Since the close of World War II, research in Europe, the ., and Japan has greatly extended knowledge of the behavior of different types of structural steel under varying stresses, including those exceeding the yield point, making possible more refined and systematic analysis. This in turn has led to the adoption of more liberal design codes in most countries, more imaginative design made possible by socalled plastic design ?The introduction of the puter by shortcutting tedious paperwork, made further advances and savings possible. （ TwoDay CANMET/CI International Symposium on Concrete Technology for Sustainable Development, April 1920,2020） 畢業(yè)設(shè)計(jì)實(shí)習(xí)調(diào)研報(bào)告 結(jié)合畢業(yè)設(shè)計(jì)情況，根據(jù)實(shí)習(xí)調(diào)研的情況及所查閱的文獻(xiàn)資料，撰寫 3000 字以上的報(bào)告： （小 4 號(hào)宋體， 倍行距） ????。ade. World War I brought an interruption to the boom in what had e to be called skyscrapers (the origin of the word is uncertain), but in the 1920s New York saw a resumption of the height race, culminating in the Empire State Building in the 1931. The Empire State’s 102 stories (1,250ft. [381m]) were to keep it established as the highest building in the world for the next 40 years. Its speed of the erection demonstrated how thoroughly the ne