高層建筑與鋼結構外文翻譯

1、<p><b>　　畢業(yè)設計（論文）</b></p><p>　　High-rise Building and Steel Construction</p><p>　　HUi Wei-jun1，DONG Han1，WENG Yu-ging2，CHEN Si-lian1，WANG Mao-giu1（1.Central iron & Steel Res

2、earch institute，Beijing 100081，China；</p><p>　　Although there have been many advancements in building construction technology in general. Spectacular archievements have been made in the design and constructi

3、on of ultrahigh-rise buildings. </p><p>　　The early development of high-rise buildings began with structural steel framing. Reinforced concrete and stressed-skin tube systems have since been economically and

4、 competitively used ina number of structures for both residential and commercial purposes. The high-rise buildings ranging from 50 to 110 stories that are being built all over the United States are the result of innovati

5、ons and development of new structual systems. </p><p>　　Greater height entails increased column and beam sizes to make buildings more rigid so that under wind load they will not sway beyond an acceptable lim

6、it. Excessive lateral sway may cause serious recurring damage to partition sceilings. and other architectural details. In addition excessive sway may cause discomfort to the occupants of the building because the irpercep

7、tion of such motion. Structural systems of reinforced concrete as well as steel take full advantage of inherent potential stiffne</p><p>　　In a steel structure for example the economy can be defined in terms

8、 of the total average quantity of steel per square foot of floor area of the building. Curve A in Fig .1 represents the average unit weight of a conventional frame with increasing numbers of stories. Curve B represents t

9、he average steel weight if the frame is protected from all lateral loads. The gap between the upper boundary and the lower boundary represents the premium for height for the traditional column-and-beam frame. Str</p&g

10、t;<p>　　Systems in steel. Tall buildings in steel developed as a result of several types of structural innovations. The innovations have been applied to the construction of both office and apartment buildings. <

11、;/p><p>　　Frame with rigid belt trusses. In order to tie the exterior columns of a frame structure to the interior vertical trusses a system of rigid belt trusses at mid-height and at the top of the building ma

12、y be used. A good example of this system is the First Wisconsin Bank Building1974in Milwaukee.</p><p>　　Framed tube. The maximum efficiency of the total structure of a tall building for both strength and sti

13、ffness to resist wind load can be achieved only if all column element can be connected to each other in such a way that the entire building acts as a hollow tube or rigid box in projecting out of the ground. This particu

14、lar structural system was probably used for the first time in the 43-story reinforced concrete DeWitt Chestnut Apartment Building in Chicago. The most significant use of this sy</p><p>　　Column-diagonal trus

15、s tube. The exterior columns of a building can be spaced reasonably far apart and yet be made to work together as a tube by connecting them with diagonal members interesting at the centre line of the columns and beams. T

16、his simple yet extremely efficient system was used for the first time on the John Hancock Centre in Chicago using as much steel as is normally needed for a traditional 40-story building. </p><p>　　Bundled tu

17、be. With the continuing need for larger and taller buildings the framed tube or the column-diagonal truss tube may be used in a bundled form to create larger tube envelopes while maintaining high efficiency. The 110-stor

18、y Sears Roebuck Headquarters Building in Chicago has nine tube bundled at the base of the building in three rows. Some of these individual tubes terminate at different heights of the building demonstrating the unlimiteda

19、rchitectural possibilities of this latest structur</p><p>　　Stressed-skin tube system. The tube structural system was developed for improving. The resistance to lateral forces wind and earthquake and the co

20、ntrol of drift lateral building movement in high-rise building. The stressed-skin tube takes the tube system a step further. The development of the stressed-skin tube utilizes the faade of the building as a structural el

21、ement which acts with the framed tube thus providing an efficient way of resisting lateral loads in high-rise buildings and resulting</p><p>　　Because of the contribution of the stressed-skin faade the frame

22、d members of the tuberequire less mass and are thus lighter and less expensive. All the typical columns and spandrelbeams are standard rolled shape sminimizing the use and cost of special built-up members. The depth requ

23、irement for the perimeter spandrel beams is also reduced and the need for up setbeams above floors which would encroach on valuable space is minimized. The structural system has been used on the 54-story One Mellon B<

24、/p><p>　　Systems in concrete. While tall buildings constructed of steel had an early start development of tall buildings of reinforced concrete progressed at a fast enough rate to provide a competitive chanllen

25、ge to structural steel systems for both office and apartment buildings. </p><p>　　Framed tube. As discussed above the first framed tube concept for tall buildings was usedfor the 43-story DeWitt Chestnut Apa

26、rtment Building. In this building exterior columns were spaced at 5.5ft 1.68m centers and interior columns were used as needed to support the 8-in .-thick 20-m flat-plate concrete slabs.</p><p>　　Tube in tub

27、e. Another system in reinforced concrete for office buildings combines the traditional shear wall construction with an exterior framed tube. The system consists of an out erframed tube of very closely spaced columns and

28、an interior rigid shear wall tube enclosing the central service area. The system Fig .2 known as the tube-in-tube system made it possible to design the world’s present tallest 714ft or 218mlightweight concrete building t

29、he 52-storyOne Shell Plaza Building in Houston fo</p><p>　　Systems combining both concrete and steel have also been developed an example of which is the composite system developed by skid more Owings ampMerr

30、il in which an exteri.</p><p>　　An optical micrograph and a phase map of the as-received base material are shown in Fig. 4. The base material has atypical microstructure of wrought duplex stainless steels co

31、n-sisting of ferrite matrix with austenite islands. OIM analysis revealed that the austenite islands contained a higher number of grain boundaries (mostly twin type boundaries) than the ferrite.</p><p>　　OIM

32、 analysis also revealed that the ferrite content was about 51%. Average grain sizes of austenite and ferrite phases in the base material were about 4.3 and 5.1 m, respectively. Optical microstructures of regions “A,” “B,

33、” “C” and “D” shown in Fig. 3 are indicated in Fig. 5. Region B lies on the weld centre, and region D is located on the border of the stir zone and TMAZ. Regions A and C are located around 2 mm away from the weld centre

34、at the retreating and advancing sides, respectively. Regi</p><p>　　B, while region C seems to contain finer austenite islands than region B. Distribution of the austenite islands is finest in the stir zone a

35、t the advancing side, as shown in micrograph of region D. In this region, D, the austenite in the stir zone exhibits an average grain size of lying immediately adjacent to elongated austenite islands in the TMAZ. Phase m

36、aps of regions, CEN and in the weld are shown in All regions consist of a ferrite matrix with the austenite islands similar to that of the b</p><p>　　contain more grain boundaries than the base material. The

37、 grain size profile ( Fig. 8) showed that the austenite and ferrite grains in the stir zone were smaller than those in the base material. Additionally, the phase maps showed that both the austenite and ferrite phases in

38、 the stir zone did not exhibit a heavily deformed microstructure, e.g. many low angle grain boundaries. Both the grain size profile and phase maps suggest that dynamic recrystallisation occurred both in the austenite and

39、 fe</p><p>　　In the case of the duplex stainless steels, however, de-formation is localized in the ferrite matrix at high temper-atures, because the ferrite phase is relatively weaker than the austenite. Con

40、sequently, the recrystallised grains are often formed in ferrite phase more easily than in austenite phase. Some research] suggests that the recrystallised grains in the ferrite phase are formed</p><p>　　By

41、continuous dynamic recrystallisation, which is charac-terized by strain-induced progressive rotation of subgrains with little boundary migration. In the present study, the du-plex stainless steel experienced plastic defo

42、rmation by therotating tool at relatively high temperatures during FSW. As such, it is likely that the ferrite matrix in the stir zone under-goes continuous dynamic recrystallisation through the samescenario. </p>

43、<p>　　On the other hand, the morphology of austenite islands in the stir zone was much different from that of the base material, as shown in Figs. 5 and 6. This suggests that the austenite islands also experienced

44、intense plastic strain dur-ing FSW, leading to dynamic recrystallisation in the austenite phase. After dynamic recrystallisation, the recrystallised grains grow during the on-cooling thermal cycle . As men-tioned above,

45、since the ferrite phase is more likely to undergo</p><p>　　dynamic recrystallisation than the austenite phase, as a result of the high temperature deformation of FSW, it is likely that the recrystallised fer

46、rite grains would grow early than those of the austenite phase. This is likely the reason why the ferrite phase exhibits a larger grain size than the austenite phase in the stir zone. Region AS5.5, located just outside t

47、he stir zone, had the similar morphology of austenite islands to the as-received base material. Grain size and texture of the austen</p><p>　　lower flow stress at elevated temperature than the austen-ite pha

48、se in the duplex stainless steel, as mentioned above. It is generally known in Al alloys that dislocations intro-duced into the TMAZ rearranged or migrate at tempera-ture producing a recovered microstructure [42–45].How-

49、ever, the ferrite phase in region AS5.5 did not exhibit a de-Fig. 11. Hardness profile across the stir zone in the weld. formed microstructure. This result suggests that the ferrite phase in this region may undergo </

50、p><p>　　the base material, with the exception of the elongation. To-tal elongation to failure based on the standard 51 mm gauge length was roughly 50% of the base material. However, given the amount of reductio

51、n in area as observed in Fig. 12 (b),the actual percentage of ductility of the FSW specimens is likely much higher than reported. All tensile failures oc-curred roughly 7 mm from the weld centre at the retreat-ing side,

52、i.e. near the border of the stir zone and TMAZ, as shown in Fig. 12 (b). This </p><p>　　TMAZ as a result of the higher hardness, which is propor-tional to strength in the metallic materials [9,46] , of the s

53、tir zone. It should be pointed out that the tensile specimens used in this study did not have uniform thickness across the weld. Typically, the thinnest section of a FSW is located at the centerline of the weld, as a res

54、ult of the tilt angle used during welding. This is a reason why the transverse tensile samples consistently fractured near the border of the stir zone and TMAZ, </p><p>　　The authors are grateful to Mr. J.W.

55、 Pew and Mr. J.N.Ostler for technical assistance and acknowledge Prof. K.Ishida and Dr. I. Ohnuma for the thermochemical calcula-tion. They also wish to thank Prof. H. Kokawa, Dr. S.H.C.Park and Dr. J.-Q. Su for their he

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69、gt;<p>　　HUi Wei-jun1，DONG Han1，WENG Yu-ging2，CHEN Si-lian1，WANG Mao-giu1（1.Central iron & Steel Research institute，Beijing 100081，China；</p><p>　　2.Chinese Society for Metals，Beijing 100711，China

70、） </p><p>　　摘要 耐火鋼顧名思義就是對火災有一定抵抗能力的鋼材，日本把耐火鋼歸結于焊接結構用軋制鋼材一類，在我國它屬于建筑用低合金鋼的范疇。耐火鋼不同于普通的建筑用鋼，它要求具有良好的耐高溫性能，作為常溫下的承載材料，只要求在遇到火災的較短時間內（通常為1至3 h）高溫條件下能夠保持較高的屈服強度，常溫下鋼材強度的2/3相當于該材料的長期允許應力值，當發(fā)生火災時，如果耐火鋼的屈服點仍然能保持在此值

71、以上，建筑物就不會倒塌，因此，要求耐火鋼在一定高溫下的屈服強度不低于室溫下屈服強度的2/3。本文研究的目的在于研究提高耐火鋼的強韌性、抗震性及耐火性能。</p><p>　　關鍵字 高層建筑；鋼結構；發(fā)展應用</p><p><b>　　1.導言</b></p><p>　　近年來，盡管一般的建筑結構設計取得了很大的進步，但是取得顯著成績的還

72、要屬超高層建筑結構設計。</p><p>　　最初的高層建筑設計是從鋼結構的設計開始的。鋼筋混凝土和受力外包鋼筒系統(tǒng)運用起來是比較經濟的系統(tǒng)，被有效地運用于大批的民用建筑和商業(yè)建筑中。50 層到 100 層的建筑被定義為超高層建筑。而這種建筑在美國得廣泛的應用是由于新的結構系統(tǒng)的發(fā)展和創(chuàng)新。</p><p>　　這樣的高度需要增大柱和梁的尺寸，這樣以來可以使建筑物更加堅固以至于在允許的限度

73、范圍內承受風荷載而不產生彎曲和傾斜。過分的傾斜會導致建筑的隔離構件、頂棚以及其他建筑細部產生循環(huán)破壞。除此之外，過大的搖動也會使建筑的使用者們因感覺到這樣的的晃動而產生不舒服的感覺。無論是鋼筋混凝土結構系統(tǒng)還是鋼結構系統(tǒng)都充分利用了整個建筑的剛度潛力，因此不能指望利用多余的剛度來限制側向位移。</p><p><b>　　2.典型鋼結構</b></p><p>　　在

74、鋼結構系統(tǒng)設計中，經濟預算是根據每平方英寸地板面積上的鋼材的數量確定的。圖示 1 中的曲線 A 顯示了常規(guī)框架的平均單位的重量隨著樓層數的增加而增加的情況。而曲線 B 顯示則顯示的是在框架被保護而不受任何側向荷載的情況下的鋼材的平均重量。上界和下界之間的區(qū)域顯示的是傳統(tǒng)梁柱框架的造價隨高度而變化的情況。而結構工程師改進結構系統(tǒng)的目的就是減少這部分造價。</p><p>　　鋼結構中的體系：鋼結構的高層建筑的發(fā)展是

75、幾種結構體系共同創(chuàng)新的結果。這些創(chuàng)新的結構已經被廣泛地應用于辦公大樓和公寓建筑中。</p><p>　　鋼性帶式桁架的框架結構：為了聯系框架結構的外柱和內部帶式桁架，可以在建筑物的中間和頂部設置剛性帶式桁架。1974 年在米望基建造的威斯康森銀行大樓就是一個很好的例子。</p><p>　　框架筒結構： 如果所有的構件都用某種方式互相聯系在一起，整個建筑就像是從地面發(fā)射出的一個空心筒體或是

76、一個剛性盒子一樣。這個時候此高層建筑的整個結構抵抗風荷載的所有強度和剛度將達到最大的效率。這種特殊的結構體系首次被芝加哥的 43 層鋼筋混凝土的德威特紅棕色的公寓大樓所采用。但是這種結構體系的的所有應用中最引人注目的還要屬在紐約建造的 100 層的雙筒結構的世界貿易中心大廈。</p><p>　　斜撐桁架筒體： 建筑物的外柱可以彼此獨立的間隔布置，也可以借助于通過梁柱中心線的交叉的斜撐構件聯系在一起，形成了一個共

77、同工作的筒體結構。這種高度的結構體系首次被芝加哥的 John Hancock 中心大廈采用。這項工程所耗用的剛才量與傳統(tǒng)的四十層高樓的用鋼量相當。</p><p>　　紐約世界貿易中心大廈</p><p>　　筒體： 隨著對更高層建筑的要求不斷地增大。筒體結構和斜撐桁架筒體被設計成捆束狀以形成更大的筒體來保持建筑物的高效能。芝加哥的 110 層的 Sears Roebuck 總部大樓有 9

78、 個筒體，從基礎開始分成三個部分。這些獨立筒體中的終端處在不同高度的建筑體中，這充分體現出了這種新式結構觀念的建筑風格自由化的潛能。這座建筑物 1450 英尺（442 米）高，是世界上最高的大廈。</p><p>　　薄殼筒體系統(tǒng)：這種筒體結構系統(tǒng)的設計是為了增強超高層建筑抵抗側力的能力（風荷載和地震荷載）以及建筑的抗側移能力。</p><p>　　薄殼筒體是筒體系統(tǒng)的又一大飛躍。薄殼筒體

79、的進步是利用高層建筑的正面（墻體和板）作為與筒體共同作用的結構構件，為高層建筑抵抗側向荷載提供了一個有效的途徑，而且可獲得不用設柱，成本較低，使用面積與建筑面積之比又大的室內空間。</p><p>　　由于薄殼立面的貢獻，整個框架筒的構件無需過大的質量。這樣以來使得結構既輕巧又經濟。所有的典型柱和窗下墻托梁都是軋制型材，最大程度上減小了組合構件的使用和耗費。托梁周圍的厚度也可適當的減小。而可能占據寶貴空間的墻上鐓

80、梁的尺寸也可以最大程度地得到控制。這種結構體系已被建造在匹茲堡洲的 One Mellon 銀行中心所運用。</p><p>　　鋼筋混凝土中的各體系：雖然鋼結構的高層建筑起步比較早，但是鋼筋混凝土的高層建筑的發(fā)展非?？?，無論在辦公大樓還是公寓住宅方面都成為剛結構體系的有力競爭對手。</p><p>　　框架筒：像上面所提到的，框架筒構思首次被 43 層的迪威斯公寓大樓所采用。在這座大樓中，

81、外柱的柱距為5.5英尺（1.68米）。而內柱則需要支撐 8 英寸厚的無梁板。</p><p>　　筒中筒結構：另一種針對于辦公大樓的鋼筋混凝土體系把傳統(tǒng)的剪力墻結構與外框架筒相結合。該體系由柱距很小的外框架與圍繞中心設備區(qū)的剛性剪力墻筒組成。這種筒中筒結構（如插圖 2）使得當前世界上最高的輕質混凝土大樓（在休斯頓建造的獨殼購物中心大廈）的整體造價只與 35 層的傳統(tǒng)剪力墻結構相當。</p><

82、p>　　鋼結構與混凝土結構的聯合體系也有所發(fā)展。Skidmore Owings 和 Merrill 共同設計的混合體系就是一個好例子。在此體系中，外部的混凝土框架筒包圍著內部的鋼框架，從而結合了鋼筋混凝土體系與鋼結構體系各自的優(yōu)點。在新奧爾良建造的 52 層的獨殼廣場大廈就是運用了這種體系。</p><p>　　鋼結構是指在建筑物結構中鋼材起著主導作用的結構，是一個很寬泛的概念。大部分的鋼結構都包括建筑設計

83、，工程技術、工藝。通常還包括以 主梁、次梁、桿件，板等形式存在的鋼的熱軋加工工藝。上個世紀七十年代，除了對其他材料的需求在增長，鋼結構仍然保持著對于來自美國、英國、日本、西德、法國等國家的鋼材廠鋼材的大量需求。</p><p>　　發(fā)展歷史：早在 Bessemer 和 Siemens-Marton開放式爐工藝出現以前，鋼結構就已經有幾十年的歷史了。而直到此工藝問世之后才使得鋼材可以大批生產出來供結構所用。對鋼結構

84、諸多問題的研究開始于鐵結構的使用，當時很著名的研究對象是 1977 年在英國建造的橫跨斯沃河的 Coalbrook dale 大橋</p><p>　　橫跨斯沃河的 Coalbrook dale 大橋</p><p>　　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了建筑安裝設計以及連接工藝的發(fā)展。鐵結構對材料的需求量較小是優(yōu)勝于磚石結構的主要方面。長久以來一直用木材制作的

85、三角桁架也換成鐵制的了。承受由直接荷載產生的重力作用的受壓構件常用鑄鐵制造，而承受由懸掛荷載產生的推力作用的受拉構件常用熟鐵制造。</p><p>　　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。隨后，1819 年角鋼問世，1894 年第一個工字鋼被建造出來作為 （5.4 米）巴黎火車站的頂梁。此工字鋼長 17.7 英尺） 。</p><

86、;p>　　1851 年英國的 Joseph Paxtond 為倫敦博覽會建造了水晶宮。據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。此建筑的風荷載抵抗力是由對角拉桿所提供的。在金屬結構的發(fā)展歷史中，有兩個標志性事件：首先是從木橋發(fā)展而來的格構梁由木制轉化為鐵制；其次是鍛鐵制的受拉構件與鑄鐵制的受壓構件受熱后通過鉚釘連接工藝的發(fā)展。</p><p>　　十九世紀五六十年代，Besseme

87、r 與 Siemens-Martin 工藝的發(fā)展使鋼材的生產能滿足結構的需求。鋼的受拉強度與受壓強度都好于鐵。這種新型的金屬常被有想象力的工程師所利用，尤其倍受那些參與過英國、歐洲以及美國的道橋建設的工程師的喜愛。</p><p>　　其中一個很好的例子就是 Eads 大橋（1867-1874）（也被稱為路易斯洲大橋）。在這座大橋中，每隔 500 英尺（152.5 米）設有由鋼管加強肋形成的拱橋英國的 Firth

88、 of Forth ，長度為 350 英尺（107）米。這些懸索橋設有管件支撐直徑大約為 12 英尺（3.66 米）大橋以及其他結構在引導鋼結構的發(fā)展，規(guī)范的實施，許用應力的設計方面起到了很重要的作用。1907 年 Quebec 懸索大橋的偶然破壞揭露了二十世紀初期由于缺乏足夠的理論知識，甚至是缺乏足夠的理論研究的基礎知識，而導致在應力分析方面出現了很多的不足。但是，這樣的損壞卻很少出現在金屬骨架的辦公大樓中。因為盡管在缺乏縝密的分析的

89、情況下這些建筑也表現出了很高的實用性。在上個世紀中葉，沒有經過任何特殊合金強化、硬化過的普通碳素鋼已經被廣泛地使用了。</p><p>　　在 1889 年巴黎召開的世界博覽會上，金屬結構表現出了在超高層建筑運用上的內在潛力。在這次會上，法國著名的橋梁設計師埃非爾展示了他的杰作-300 米高的露天開挖的鐵塔。無論是它的高度（比著名的金字塔的兩倍還高），架設的速度-人數不多的工作人員僅用幾個月的時間就完成了整個工程

90、任務，還是很低的工程造價都使它脫穎而出。</p><p>　　首批摩天大廈：在剛結構發(fā)展的同時，美國的另一個是也蓬勃的發(fā)展起來了。1884-1885 年，芝加哥的工程師 Maj.William Le Baron Jennny 設計了家庭保險公司大廈。這座大廈也是金屬結構的，有十層高。大廈的梁是鋼制的，而柱是鑄鐵所制。鑄鐵制的過梁支撐著窗洞口上方的砌體，同時也需要鑄鐵制的柱支撐著實心砌體的天井與界墻提供抵抗風載的側

91、向支撐。用不到十年的功夫，芝加哥和紐約已經有超過 30 座辦公大樓是利用這種結構。鋼材在這些結構中起了非常大的作用。這種結構利用鉚釘把梁與柱連接在一起。有時為了抵抗風荷載還是在豎向構件和橫向構件的連接點出貼覆上節(jié)點板來加固結構。此外，輕型的玻璃幕墻結構代替了老式的重質砌體結構。</p><p><b>　　3.發(fā)展歷程</b></p><p>　　盡管幾十年來之中建筑

92、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。十九世紀的最后幾年，基本結構形狀工字型鋼的厚度已經達到 20 英寸 ， （0.508 米）非對稱的 Z 字型鋼和 T 型鋼可以與有一定寬度和厚度的板相聯結，使得構件具體符合要求的尺寸和強度。1885 年最重的型鋼通過熱軋生產出來，每英寸不到 100 磅（45 千克）。到二十世紀六十年代這個數字已經達到每英寸 700 磅（320 千克）。</p><p>

93、　　緊隨著鋼結構的發(fā)展，1988 年第一部電梯問世了。安全載客電梯誕生，以及安全經濟的鋼結構設計方法的發(fā)展促使建筑高度迅猛增加。1902 年在紐約建造的高 286 英寸（87.2米）的 Flatiron 大廈不斷地被后來的建筑所超越。這些建筑分別是高 375 英尺（115 米） ，的時代大廈（1904）（后來改名為聯合化工制品大廈）。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

94、）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。</p><p>　　房屋高度與高寬比的不斷增加也帶來了許多的問題。為了控制道路的阻塞要對建筑的縮進設計進行限定。側向的支撐的設置也是其中一項技術問題，例如埃非爾鐵塔所采用的對角支撐的體系對于要靠太陽光來照明的辦公大廈就不用了。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

95、才是可靠的。隨著現代內部采光體系的不斷發(fā)展，抵抗風荷載的對角支撐又重新的被利用起來了。芝加哥的 John Hancock中心就是一個很顯著的例子。外部的對角支撐成為此結構立面的一個很顯眼的部分。</p><p>　　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</p><p><b>　　帝國大廈</b></p><p>　

96、　勃發(fā)展，但是二十世紀二十年代又恢復了這一趨勢。1931 年建造的帝國大廈把詞潮流推向了頂峰。102 層高 1250 英尺（381 米）的帝國大廈在后來的 40 年一直保持著世界最高的地位。它的建造速度充分證明了這種新的結構形式已經被當時的技術所掌握。</p><p>　　此次項工程所需要的梁 是由用精密儀器控制的駁船和卡車負責運輸的。是由 Bayonne 海灣對岸的軍械庫所提供的。共由九架起重機將這些梁提升到指

97、定的位置。由工業(yè)軌道裝置把鋼材和其他材料移到每一層上去。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。</p><p>　　二十世紀三十年代席卷全世界的大蕭條以及第而次世界大戰(zhàn)使鋼結構的發(fā)展又一次受到了阻礙。但是與此同時，焊接代替了鉚釘連接則是一個很重要的發(fā)展。</p><p>　　十九世紀末，利用焊接把各個鋼零件相連接已取得了很好的成績，并在第一次世界大

98、戰(zhàn)中被運用于救生船的修理。但直到第二次世界大戰(zhàn)后才用于建筑結構中。同時在連接領域中又一進步就是高強螺栓代替了鉚釘。</p><p>　　二戰(zhàn)結束后，歐洲，美國，日本等國都擴大了對在不定應力（包括超過屈服點的情況）作用下各種結構鋼的性質的研究，并進行了更為精確、系統(tǒng)的分析。此后，許多國家采用了一些更為自由靈活的設計規(guī)范和更為理想化的彈性設計規(guī)范。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，