外文翻譯--斜拉橋的未來

1、<p><b>　　中文1590字</b></p><p>　　between towers increase if the number of cables </p><p>　　increase and the angle of inclination of the cables</p><p>　　remains the sam

2、e.</p><p>　　B.READING MATERIAL</p><p>　　FUTURE OF CABLE-STAYED BRIDGES</p><p>　　I would like to begin with a view back on the development of cable-stayed bridges during the last 25

3、years.It started with Dischinger's publication shortly after the end of Word War II. He pointed mainly to the necessity of gonging to high steel stresses in the stays to produce stiffness in the system.The first brid

4、ge following Dischinger's recommendations,was built in Sweden,designed by Demag,a German steel construction firm,consulted by Dischinger.</p><p>　　Then in 1953-54 the three Duesseldorf bridges were desig

5、ned,all of them,with parallel stay cables but different tower arrangements,in order to have a family of similarly appearing bridges.</p><p>　　The fundamental concept of these early designs was retained for o

6、ver almost 20 years,which it took to built them. We learned by detailing and erecting these bridges.</p><p>　　In these bridges,only a few stay cables were chosen;some engineers designed their bridges with ev

7、en only one stay cable.</p><p>　　This resulted in large cable forces causing difficulties to anchor the cables in the beam structure. Heavy cross beams were necessary, the ropes had to be formed.</p>

8、<p>　　To gain sufficient space for the anchors, adjustment of cable lengths becomes difficult. In addition, the large distance between the stay cables complicate the erection requiring heavy equipment, auxiliary tru

9、sses,even auxiliary piers were necessary to build the Maracaibo bridge and the Kniebridge.</p><p>　　Auxiliary stayes were needed for cantilevering the beam plate girder to the next stay cable. In addition, l

10、ong spans between supports provided by stay cables,cause large bending moments in the continuous beam and hereby a considerable depth of the girders is needed.</p><p>　　Form all of this experience, we conclu

11、ded for our later and future designs ,that</p><p>　　a) a large number of stay cables should be chosen in a way b) that one anchorage socket can be used to simplify the placing of the cable, c) by short spaci

12、ng of the cables, bridge girder bending moments are low so that a depth of 1 to 2 m is sufficient, just providing a deflection line curvature satisfying traffic requirements and providing safety against buckling in the d

13、eflected stage. d) The spacing of the cables should be such, that no heavy erection equipment is needed to cantilever out for</p><p>　　In order to satisfy these rules, my office developed a new type of cable

14、 anchorage in cooperation with BBR Switzerland, which allows ultimate cable forces up to almost 2,000 tons, using parallel wires or strands of very high strength, inside a polyethylene tube for perfect corrosion protecti

15、on. The anchorage was developed to get high fatique strength, therefore called High Amplitude(HiAm) cable. These cables can be prefabricated and shipped on reels and allow a simple and inexpensive erection.</p>&l

16、t;p>　　Several bridges have been designed lately using these principles:The Pasco bridge, bridges in Parana, Argentina, and others.</p><p>　　As we designed these bridges, I knew already the favorable effec

17、t of system damping in multi-stay cable bridges by experience which I had gained from the behavior of a pedestrian stay cable bridge in Stuttgart, but we had to prove the dynamic safety for these larges. A dynamic model

18、test was made at the Ismes Institute of Profssor Oberti in Italy, 18 m long designed for full dynamic similitude. Short and long trains or just locomotives could run on the rails with different speeds-no adverse osci<

19、/p><p>　　Then the test engineers excited artificially oscillations going through all possible modes and frequencies and at many points of the bridge. Whenever they succeed in building up a small amplitude, it b

20、roke quickly again down to small amplitudes. It was impossible to find a mode of oscillation which would build up large amplitudes by resonance.</p><p>　　Any mode of oscillation broke down as soon as the amp

21、litudes starts to grow, because each of the cables has a different natural frequency and disturbs the oscillation of deck structure by interference so strongly, that large amplitudes cannot develop. We get a very effecti

22、ve system damping which does not allow resonance oscillation with dangerous amplitudes.</p><p>　　Of course, this effect is only obtained with stiff and highly stressed cables and with a sufficient number of

23、cables in close spacing. We must recognize that the dynamic behavior of the suspension bridge is perfectly different from that of a multi stay cabled bridge. In s suspension bridge without stiffening girder, there is ful

24、l freedom for the dangerous first antimetric mode of oscillation, combining torsional and bending movement. Small force can excite this mode of oscillation and build up l</p><p>　　The multi stay cable bridge

25、-on the other side-cannot oscillate in low order modes, it especially cannot move into combined torsional and flexural oscillations. With stays along the edges of the bridge, torsional oscillations are almost impossible

26、and flexural oscillations assume quickly high order modes with only small amplitudes. The important fact is,that resonance is impossible for the reasons described.</p><p>　　As a consequence, we must learn th

27、at the theories which were developed to check aerodynamic safety of suspension bridges are not valid for multi stay cabled bridges. Wind tunnel tests with sectional models must be made with realistic restraint by system

28、damping which, however, is difficult to imitate for a sectional model.</p><p>　　* * *</p><p>　　Fritz Leonhardt, Dr. Ing. Stuttgart, Germany </p><p>

29、<b>　　斜拉橋的未來</b></p><p>　　我想先簡單回顧一下在過去25年間斜拉橋發(fā)展歷史，二戰(zhàn)結(jié)束后不久，迪斯欽格便在其著作中提出了斜拉橋這一概念。在著作中，迪斯欽格主要指出，在斜拉橋這個系統(tǒng)中，支索上所承受的巨大鋼筋壓力對維持橋的穩(wěn)定性有重要作用。第一座依據(jù)迪斯欽格的建議建立的斜拉橋位于瑞典。這座橋是由德國一家名為德馬格的鋼鐵建筑公司設(shè)計(jì)的，而這家公司正是由迪斯欽格擔(dān)任指導(dǎo)。&

30、lt;/p><p>　　然后在1953-1954年間，共有3座杜塞爾多夫橋相繼建成。這3座橋全部都是平行的鋼筋支索。但支柱的設(shè)計(jì)卻各不相同。這樣做的目的是為了建造一個擁有相似造型的橋梁群。</p><p>　　在將近20年的時間里，橋梁建設(shè)一直都是在應(yīng)用這些早期的基本設(shè)計(jì)理念。我們通過研究這些橋梁的細(xì)節(jié)部位和建造橋梁模型來學(xué)習(xí)這些理念。</p><p>　　這些橋只選擇

31、了幾根鋼纜，一些工程師設(shè)計(jì)的橋甚至只有一根鋼纜。這跟鋼纜在橫梁結(jié)構(gòu)的橋上的固定造成巨大纜繩壓力。沉重的交叉橫梁是必要的，繩子也是必要的。為了給支柱營造足夠的空間，纜繩長度的調(diào)整變得困難起來。此外，鋼纜之間的巨大空間使得需要沉重設(shè)備的建設(shè)變得復(fù)雜，輔助構(gòu)架，甚至輔助墩對馬拉開波橋和尼克橋的建造都是必要的。將支柱大梁連接到下一個鋼纜需要用到輔助支索。此外，鋼纜提供的支撐之間的長墩距造成連續(xù)支柱的巨大彎曲，因此，大梁需要有足夠的深度。<

32、/p><p>　　從所有這些經(jīng)驗(yàn)我們得出這樣的結(jié)論，我們今后或未來的設(shè)計(jì)</p><p>　　A）多數(shù)鋼纜應(yīng)該選擇這種形式；B）固定處的凹口可簡化鋼索的排列方法；C)通過縮短鋼索的間距，橋梁彎曲幾率降低，因此1到2米的深度已足夠提供一條偏斜直線曲度，并在偏斜階段保證交通安全；D）排列鋼索應(yīng)切記，橋梁懸臂上不能累加重物以影響接下來鋼索的排列；E)可行的混凝土大梁的排列方法是6米到12米，而鐵梁則

33、需8米到16米。</p><p>　　為滿足以上要求，我方與瑞士BBR公司合作研發(fā)出了一種新型斜拉橋，鋼索可承重高達(dá)兩千噸，在聚乙烯鋼管中，采用了高強(qiáng)度平行結(jié)構(gòu)金屬線以防止腐蝕，新型斜拉橋可承受高壓，因此被稱為高振幅鋼索。這些鋼索可提前制造且造法簡單，成本低。近期所造的一些大橋均采用了這些準(zhǔn)則：畢加索大橋，巴西，阿根廷境內(nèi)以及其他的一些大橋。由于我參與設(shè)計(jì)了這些橋梁，又加上在斯圖加特市步行斜拉橋的經(jīng)歷，我已了解斜

34、拉橋減震系統(tǒng)的優(yōu)勢。然而我們?nèi)孕枳C明這些大振幅的動力安全性。意大利Ismes研究所的Oberti教授進(jìn)行了一項(xiàng)動力模型測試，為證明完全動力相似性設(shè)計(jì)了一個18米長的鋼管。只有長短途火車和當(dāng)?shù)氐哪ν熊嚹芤圆煌囁僭跇蛏闲旭?，至今未發(fā)現(xiàn)反振幅。</p><p>　　然后，在橋的許多地方進(jìn)行各種形式和頻率的人為晃動后，測試工程師們很興奮。每次當(dāng)他們想要成功建成一個大振幅時，它就會很快垮掉變成一個小振幅，不可能找到一個震

35、動模型可通過共振來加大振幅。</p><p>　　任何震動模型在振幅開始增強(qiáng)時垮掉，因?yàn)槊織l纜索有不同的自然頻率，木制結(jié)構(gòu)受到的擺動力太強(qiáng)而不能成為大的振幅，我們發(fā)現(xiàn)一個很有效的系統(tǒng)，可抑制危險振幅共振的發(fā)生。當(dāng)然，用堅(jiān)實(shí)并可承受重壓的纜索，在緊湊的間隔內(nèi)安置足夠數(shù)量的纜索可出現(xiàn)這種效果。我們必須認(rèn)識到，吊橋的動態(tài)活動和斜拉橋的動態(tài)活動完全不同。沒有堅(jiān)固大梁的大橋，第一個非公制危險的震動模型很容易和扭轉(zhuǎn)彎曲活動有

36、關(guān)。很小的外力既可引起模型的晃動并通過共振增強(qiáng)大的振幅，加大幅度的彎曲，加大扭曲的堅(jiān)固性可加固構(gòu)架來減輕擺動浮動。用彎曲的自然頻率和扭轉(zhuǎn)擺動之間的不同，主要用來避免共振。裝配模型測驗(yàn)和有關(guān)吊橋問題的理論，得到很好的發(fā)展。另一方面，吊橋在低層次的模型中不會擺動，尤其不會彎曲。因?yàn)樵跇虻倪吘売袪克鳎沟眯崩瓨驇缀醪粫l(fā)生扭曲性的搖擺，且會出現(xiàn)一些很小幅度的彎曲性的擺動。重要的一點(diǎn)是，綜上所述，吊橋不可能發(fā)生共振。因此，我們必須認(rèn)識到，那些用