大型橋梁及施工外文翻譯--大跨度橋梁

1、<p>　　Large Span Bridge</p><p>　　Suspension Bridge</p><p>　　The suspension bridge is currently the only solution in excess of 600 m, and is regarded as competitive for down to 300. The worl

2、d’s longest bridge at present is the Verrazano Narrows bridge in New York. Another modern example is the Severn Bridge in England. </p><p>　　The components of a suspension bridge are: (a) flexible cables, (b

3、) towers, (c) anchorages, (d) suspenders, (e) deck and ，(f) stiffening trusses. The cable normally consists of parallel wires of high tensile steel individually spun at site and bound into one unit .Each wire is galvaniz

4、ed and the cable is cover with a protective coating. The wire for the cable should be cold-drawn and not of the heat-treated variety. Special attention should be paid to aesthetics in the design of the rowers. The </p

5、><p>　　The side span to main span ratio varies from 0.17 to 0.50 .The span to depth ratio for the stiffening truss in existing bridge lies between 85 and 100 for spans up to 1,000m and rises rather steeply to 1

6、77. The ratio of span to width of deck for existing bridges ranges from 20 to 56. The aerodynamic stability will have be to be investigated thoroughly by detailed analysis as well as wind tunnel tests on models.</p>

7、;<p>　　The cable-stayed bridge</p><p>　　During the past decade cable-stayed bridges have found wide application, s\especially in Western Europe, and to a lesser extent in other parts of the world.<

8、/p><p>　　The renewal of the cable-stayed system in modern bridge engineering was due to the tendency of bridge engineering in Europe, primarily Germany, to obtain optimum structural performance from material wh

9、ich was in short supply-during the post-war years.</p><p>　　Cable-stayed bridges are constructed along a structural system which comprises an orthotropic deck and continuous girders which are supported by st

10、ays, i.e. inclined cables passing over or attached to towers located at the main piers. </p><p>　　The idea of using cables to support bridge span bridge span is by no means new, and a number of examples of t

11、his type of construction were recorded a long time ago. Unfortunately the system in general met with little success, due to the fact that the statics were not fully understood and that unsuitable materials such as bars a

12、nd chains were used to form the inclined supports or stays. Stays made in this manner could not be fully tensioned and in a slack condition allowed large deformations of t</p><p>　　Wide and successful applic

13、ation of cable-stayed systems was realized only recently, with the introduction of high-strength steels, orthotropic decks, development of welding techniques and progress in structural analysis. The development and appli

14、cation of electronic computers opened up new and practically unlimited possibilities for exact solution of these highly statically indeterminate systems and for precise stoical analysis of their three-dimensional perform

15、ance.</p><p>　　Existing cable-stayed bridges provide useful data regarding design, fabrication, erection and maintenance of the mew system. With the construction of these bridges many basic problems encounte

16、red in their engineering are shown to have been successfully solved. However, these important data have apparently never before been systematically presented.</p><p>　　The application of inclined cable gave

17、a new stimulus to construction of large bridges. The importance of cable-stayed bridges increased rapidly and within only one decade they have become so successful that they have taken their rightful place among classica

18、l bridge system. It is interesting to note now how this development which has so revolutionized bridge construction, but which in fact is no new discovery, came about.</p><p>　　The beginning of this system,

19、probably, may be traced back to the time when it was realized that rigid structures could be formed by joining triangles together. Although most of these earlier designs were based on sound principles and assumptions, th

20、e girder stiffened by inclined cables suffered various misfortunes which regrettably resulted in abandonment of the system. Nevertheless, the system in itself was not at all unsuitable. The solution of the problem had un

21、fortunately been attempted in </p><p>　　The renaissance of the cable-stayed, however, was finally successfully achieved only during the last decade. </p><p>　　Modern cable-stayed present a three

22、-dimensional system consisting of stiffening girders, transverse and longitudinal bracings, orthotropic-type deck and supporting parts such as towers in compression and inclined cables in tension. The important character

23、istics of such a three-dimensional structure is the full participation of the transverse construction in the work of the main longitudinal structure. This means a considerable increase in the moment of inertia of the con

24、struction which permits a</p><p>　　Long span concrete bridges are usually of post-tensioned concrete and constructed either as conditions beams types or as free versatile structures. Many methods have been d

25、eveloped for continuous deck construction. If the clearance between the ground and bottom of the deck is small and the soil is firm, the superstructure can be built on staging. This method is becoming obsolete. Currently

26、, free-cantilever and movable scaffold systems are increasingly used to save time and improve safety.</p><p>　　The movable scaffold system employs movable forms stiffened by steel frames. These forms extend

27、one span length and are supported by steel girders which rest on a pier at one end and can be moved from span to span on a second set of auxiliary steel girders.</p><p>　　An economical construction technique

28、 known as incremental push-launching method is developed by Baur-Leonhard team. The total continuous deck is subdivided longitudinally into segments of 10 to 30 m length depending on the length of spans and the time avai

29、lable for construction. Each of these segments is constructed immediately behind the abutment of the bridge in steel framed forms, which remain in the same place for concreting all segments .The forms are so designed as

30、to be capable of being m</p><p>　　The free-cantilever system was pioneered by Dyckerhoff and Willmann in Germany .In this system , the superstructure is erected by means of cantilever truck in sections gener

31、ally of 3.5 m .The cantilever truck ,whose cost is relatively small and which is attached firmly to permanent construction , emits by repeated use the construction of large bridges . The avoidance of scaffold from below,

32、 the speed of work and the saving in labor cost result in the construction being very economical. The free-</p><p>　　Another technique is the use of the pneumatic caisson .The caisson is a huge cylinder with

33、 a bottom edge that can cut into the water bed. When compressed is pumped into it ,the water is forced out .Caissons must be used with extreme care .for one thing, workers can only stay in the compression chamber for sho

34、rt periods of time .For another , if they come up to normal atmospheric pressure too rapidly ,they are subject to the bends ,or caisson disease as it is also called , which is a crippling or</p><p>　　When ex

35、tra strength is necessary in the piers, they sometimes keyed into the bedrock-that is ,they are extended down into the bedrock .This method was used to build the piers for the Golden Gate Bridge in San Francisco ,which i

36、s subject to strong tidies and high winds ,and is located in an earthquake zone .The drilling was carried out under water by deep-sea divers .</p><p>　　Where bedrock cannot be reached ,piles are driven into

37、the water bed .Today ,the piles in construction are usually made of prestressed concrete beams .One ingenious technique ,used for the Tappan Zee Bridge across the Hudson River in New York ,is to rest a hollow concrete bo

38、x on top of a layer of piles .When the box is pumped dry ,it becomes buoyant enough to support a large proportion of the weight of the bridge .</p><p>　　Each type of bridge indeed each individual bridge pres

39、ents special construction problems. With some truss bridges , the span is floated into position after the piers have been erected and then raised into place by means of jacks or cranes .Arch bridges can be constructed ov

40、er a false work ,or temporary scaffolding. This method is usually employed with reinforced concrete arch bridges .With steel arches ,however ,a technique has been developed whereby the finished sections are held in place

41、 by wi</p><p>　　With suspension bridges ,the foundations and the towers are built first .Then a cable is run from the anchorage-concrete block in which the cable is fastened-up to the tower and across to the

42、 opposite tower and anchorage .A wheel that unwinds wire from a reel puns along this cable .When the reel reaches the other side ,another wire is placed on it ,and the wheel returns to its original position .When all the

43、 wires have been put in place ,another machine moves along the cable to compact and to bi</p><p>　　The loads to be considered in the design of substructures and bridge foundations include loads and forces tr

44、ansmitted from the superstructure, and those acting directly on the substructure and foundation.</p><p>　　AASHTO loads .Section 3 of AASHTO specifications summarizes the loads and forces to be considered in

45、the design of bridges (superstructure and substructure). Briefly , these are dead load ,live load , impact or dynamic effect of live load , wind load , and other forces such as longitudinal forces , centrifugal force ,th

46、ermal forces , earth pressure , buoyancy , shrinkage and long term creep , rib shortening , erection stresses , ice and current pressure , collision force , and earthquake stresse</p><p><b>　　大跨度橋梁<

47、/b></p><p><b>　　懸索橋</b></p><p>　　懸索橋是現行的跨徑超過600m大橋的唯一解決方案，而且對跨徑在300m以上的橋梁它也是被認為是一種很有競爭力的方案。現在世界上最大跨徑的橋梁是紐約的威拉查諾（Verrazano）海峽大橋，另一個是英國的塞溫（Savern）大橋。</p><p>　　懸索橋的組成部分有

48、：柔性，主塔，錨碇，吊索（掛索），橋面板和加勁桁架。主纜是有一組平行的單根高強鋼絲在現場扭在一起并綁扎成型的鋼絲束組成的。每根鋼絲都是 經過渡鋅處理的，并且整個用保護層覆蓋著。所用的鋼絲應該是冷拔鋼絲而不是經過熱處理的各種鋼絲。在進行主塔設計時應該特別注意其在美學上的要求。主塔很高而且具有足夠的柔性，使其每一座塔頂都可認為是與主纜鉸接。主纜的兩端很安全的錨固在非常堅實的錨碇上。吊索把橋面板上的荷載傳遞到主主纜上。吊索也是有高強鋼絲制成的

49、而且通常是豎直的。橋面板通常是有加勁鋼板，肋或槽型板，橫梁制成的異性結構。提供一些加勁梁連接在其主塔之間，能夠起到控制空氣動力運動并限制橋面板局部傾角變化。如果加勁系統(tǒng)不適當，由于風引起的豎向振動也許會導致結構傾斜，就像塔科瑪（Tacoma）海峽大橋的悲劇性的破壞所表明的那樣。</p><p>　　邊跨與主跨的跨徑比的變化范圍是0.17~0.50。 在現有的采用加勁梁的橋梁上， 當跨徑高大 1000米時跨徑與橋梁

50、的建筑高度之比為85與100之間?，F有的橋梁的跨徑與橋面板寬度之比約為20~56。橋梁結構的空氣動力穩(wěn)定性必須得通過對其模型的風洞試驗及細部分析進行全面的研究。</p><p><b>　　斜拉橋體系 </b></p><p>　　在過去的十年間，斜拉橋得以廣泛的應用，尤其實在歐洲，而在世界其它地區(qū)，應用相對少一些。</p><p>　　在現代

51、橋梁工程中，斜拉橋體系的重新興旺起來是由于歐洲（主要是德國）的橋梁工程師有一種趨勢，即從因為戰(zhàn)爭而短缺的材料上獲得最佳的結構性能。斜拉橋是有按各向異性橋面板和由吊索支撐的連續(xù)梁構成的體系建造起來的，這些吊索是一些穿過或固定的位于主橋墩的索塔頂上的傾斜主纜。</p><p>　　用主纜來支撐橋跨并不是一種新思想，在很早以前就有大量此類結構的的記載。不幸的是這一體系只有很少成功的例子，這是由于人們對靜力學的原理沒有完

52、全弄明白，并且還沒有構成傾斜支撐或吊索的適當的材料，例如主纜和鋼鏈等。這種吊索在它們能夠按計劃承擔拉力之前不能完全被拉緊，而應處于允許橋面板產生較大變形的松弛狀態(tài)。</p><p>　　斜拉體系的廣泛的成功的應用只在近年來，隨著高強鋼，各種異性橋面板的引入、焊接技術的發(fā)展和結構分析方法的進步才得以實現。電子計算機的發(fā)展和應用，導致了解決高次超靜定體系的精確值及它們的三維空間性能的精確靜力分析的新的無實際限制的可能

53、性。</p><p>　　現有的斜拉橋提供了許多關于設計、制造、安裝和維修的有用的數據。隨著這些橋梁的建造，許多工程中遇到的基本問題已表明的到了成功的解決。然而這些重要的數據很顯然在這以前決沒有被系統(tǒng)的揭示出來。</p><p>　　斜吊索的應用對大型橋梁建造帶來了一個新刺激。斜拉橋的重要性迅速增加起來，并且在僅三十年間這種橋梁類型就變的這樣成功，已使其在古典橋梁體系中取得了它應有的地位。

54、如果我們注意到這種橋梁建造帶來如此徹底的變革的發(fā)展是怎樣發(fā)生的話，我們都會感興趣的，因為這一發(fā)展事實上并沒有什么任何新發(fā)現。</p><p>　　這一體系的開始也許可以追溯到人們開始認識到通過三角形連接在一起能夠構成剛性結構的時代。</p><p>　　盡管大多數這種設計是基于結構堅固的原理和假定的，但斜拉加勁梁還是遭受各種各樣的不幸事故，而最終令人遺憾的導致了這一體系被放棄。盡管這樣，這

55、一體系并不是完全不適應，只是問題的解決被不幸的應用錯誤的方式去嘗試。</p><p>　　然而，斜拉體系的復興只是在近十年來才最終獲得成功。</p><p>　　現代的斜拉橋提出了加勁梁、橫向及縱向聯系梁、各項異性橋面板和支撐部分（例如處于受壓狀態(tài)的索塔及受拉狀態(tài)的斜吊索）組成的三維空間體系。象這種空間三維結構的重要特征是橫向結構全部參與主要縱向結構的工作狀態(tài)。這就意味著結構的慣性矩大大增

56、加，這使的橋的建筑高度可以減少，并且使用鋼材是最經濟的。</p><p>　　大跨度橋梁經常是連續(xù)梁形式或懸臂梁形式的預應力混凝土橋梁。以前許多的施工方法已發(fā)展為連續(xù)梁橋的施工方法。如果模板和地面之間的距離較小并且土質堅硬，橋梁的上部結構可以使用支架施工方法。不過這種施工方法已經越來越過時了。目前，自由懸臂法和移動模架法的應用漸廣并能節(jié)省時間和提高安全性。</p><p>　　移動模架法是

57、利用固定在鋼制臺架上的移動系統(tǒng)而形成，這種系統(tǒng)能夠達到一跨長并支承在一端支承在橋墩上并借助于第二根鋼導梁逐跨移動的鋼梁上。</p><p>　　一種經濟的施工方法是被廣泛知曉的由Baur-leonhard團隊所發(fā)展的使用廣泛的頂推法。整個的連續(xù)梁被劃分成10-30米長度的節(jié)段，這種劃分主要依據跨徑和能夠利用的施工時間。每個節(jié)段在橋臺后面的鋼模上能夠快速澆注，鋼模可以周轉使用而澆注所有的節(jié)段。這樣設計模板是為了能夠

58、橫向移動或在鉸上轉動，以便在混凝土充分硬化后脫模。在第一節(jié)段的頂端安裝上一個由輕型桁架組成的鋼導梁，以實現第一節(jié)段以后的節(jié)段順利架設而防止在施工出現過大的懸臂部分。第二節(jié)段及以后的節(jié)段可以直接在第一節(jié)段的硬化面上澆注并在施工過程中將節(jié)段連接起來。頂推是通過支承在橋臺上的液壓千斤頂實現的，由于聚四氟乙烯的滑塊的摩擦系數只有0.02，低效能的千斤頂就足夠完成長度甚至達數百米的橋梁的頂推。這種方法可以應用在長度在120米左右的直線橋梁或曲線橋

59、梁上。</p><p>　　自由懸臂法是由法國的Dyckerhoff和Willmann所創(chuàng)始。這種施工方法中，橋梁的上部結構是通過節(jié)段長度基本在3.5米的懸臂機上施工，懸臂機的費用相對比較低并且固定在橋梁承重結構上，由于它的重復利用性使它能在長橋上使用。由于施工速度的加快和時間的節(jié)省使得這種施工方法的費用比較低從而避免了使用臺架施工，自由懸臂法比較適用于橋墩較高并且懸臂能伸到跨徑中部的橋梁上。</p>

60、<p>　　另一種施工方法是整體沉箱法。沉箱是一種底邊有刃腳的大型圓筒，其刃腳可以切入水底。當壓縮空氣進入沉箱內部時水就會被排出。沉箱的利用必須嚴加注意。首先，工人們只能在這種壓縮空氣的空間里呆很短的時間；另一方面，如果工人們從沉箱進入正常的大氣壓條件下過于迅速，他們將比較容易患上潛水?。ㄒ脖环Q作沉箱病），這在能使人致殘的甚至致命的環(huán)境中由于血液中氧氣過多所引起的一種病。當St.louis市的密西西比河Eads上的橋在18

61、67-1874年施工時，由于人們對在壓縮空氣中工作的危險性認識不足，最后由于患潛水病而導致14人死亡。</p><p>　　當在橋墩上有外力作用時，基樁經常需要嵌入基巖，也就是說它們的下部一直延伸到基巖。這種方法曾經用來建造位于強風和地震區(qū)域的舊金山金門大橋的橋墩。鉆孔是在水下由深水潛水員進行的。在不能到達基巖的地方，樁通常被打進河床。今天，在施工的基樁基本上是預應力混凝土結構。在建造紐約哈德遜河上的泰平.吉橋時

62、所采用的一種巧妙技術是將一個空心混凝土箱置于橋樁層上，當它里面的水被抽干時，它的浮力足夠支承橋梁重力的一大部分。</p><p>　　每一種類型的橋梁實際上代表了特殊的問題。許多桁架橋的施工是先將橋上桁架運到已施工完畢的基樁位置，然后在利用千斤頂或起重機架設到適當位置。拱橋是在腳手架或臨時腳手架上施工的，這種方法通常用于預應力混凝土拱橋。然而對鋼拱橋來說已發(fā)展了一種技術，用這種技術將已裝好的部分借助起支承作用的主

63、纜控制就位（鋼拱在安裝過程中還沒有合攏前，是兩個懸臂，需要用主纜拉住兩個懸臂以免傾倒）。當主纜中的拉力增加時，起重機就沿著拱橋的頂部移動以架設新的鋼拱。</p><p>　　對懸索橋來說，需要首先施工基礎和索塔。這時主纜從錨碇（一個固定主纜的大混凝土塊）穿過直至索塔并且通過另一索塔而錨固在錨碇上，然后從卷線盤上放松主纜的輪子沿著主纜運動，當卷線盤到達另一面時，另一根鋼絲又裝進卷線盤并最終到達它的原位置。當所有的主

64、纜被放在固定的位置后，另一臺機器沿著主纜移動并對其進行張拉錨固。當主纜施工完畢時，逐漸開始在支架上從兩端向中間施工。</p><p>　　在橋梁下部結構和基礎設計中要考慮的荷載包括：從上部結構傳下來的荷載和直接作用于下部結構的基礎的荷載。</p><p>　　AASHTO荷載。 AASHTO規(guī)范第三部分總結了橋梁設計（上、下部結構）要考慮的荷載和作用力。主要有：恒載、活載、活載沖擊力或動力