1、8 Bridge Design and Construction橋的設計與建造橋的設計與建造1. New words analysisaccessory= access(increased)oryDerrick=from Derrick, the surname of a London hangmanDebris=orign early 18th cent.: from French dbris, from obsolete dbriser break down Planning. The first step leading to the construction of a modern m

2、ajor bridge is a comprehensive study to determine whether a bridge is needed. 規(guī)劃設計 現(xiàn)代重要的橋梁建造的第一步是廣泛地研究以確定橋梁的必要性。 If it is to be a highway bridge, in the United States for example，a planning study is initiated by a state bridge authority，possibly in cooperation with local government or the federal go

3、vernment . 比如：如果是美國的高速公路橋，是由州橋管理局研究規(guī)劃并確定，同時當?shù)氐恼蚵?lián)邦政府一起參與。 Studies are made to estimate the amount of bridge traffic, the relief of jammed traffic in nearby highway network, the effects on the regional economy, and the cost of the bridge. 橋梁的交通流量、對附近高速公路網(wǎng)交通堵塞的調劑，對當?shù)亟?jīng)濟的影響和橋的造價等因素進行評估研究。 The means for

4、 financing the project, such as public taxes or sale of revenue bonds repaid by toll charges, are considered.Bond n.結合(物), 粘結(劑), 聯(lián)結, 公債, 債券, 合同revenue bond收益?zhèn)?這就決定了工程的投資方式，如公眾收費，依靠過通行費來支付的發(fā)行債券的規(guī)模都要被考慮進來。 If the studies lead to a decision to go ahead with the project, the land needed for the bridge

5、 and its approaches is acquired at the selected site. 如果研究認為其可行信，那么橋選址和占地問題將著手處理。 At this point, field engineering work is started. Accurate land surveys are made. land survey 土地測量 在確定場地時，現(xiàn)場測繪工作開始進行，做好精確的實地測量。 Tides, flood conditions，currents, and other characteristics of the waterway are carefully

6、studied. 潮汐，洪水因素，水流和排水的其它的特征都要仔細研究， Boring samples of soil and rock are taken at possible foundation locations, both on land and under the water. 在陸地和水下的泥土和巖石的鉆孔取樣在基礎可能的位置都要盡可能地進行。 Selection of bridge design.橋梁設計類型的選擇橋梁設計類型的選擇 The chief factors in deciding whether a bridge will be built as a girder

7、, cantilever , truss , arch , suspension , or some other type are： (1) location；for example, cross a river ;(2)purposes ; for example , a bridge for carrying motor vehicles ; ( 3 ) span length ; ( 4 ) strength of available materials ; ( 5 ) cost ; ( 6 ) beauty and harmony with the location . 決定把橋建成梁

8、、懸臂、桁架、拱、懸索或其他類決定把橋建成梁、懸臂、桁架、拱、懸索或其他類型結構的主要因素是：（型結構的主要因素是：（1）地點，如跨越河流；（）地點，如跨越河流；（2）目的，如建橋為了方便交通；（目的，如建橋為了方便交通；（3）跨度；（）跨度；（4）可用）可用材料強度；（材料強度；（5）花費；（）花費；（6）美觀和和諧性。）美觀和和諧性。 Each type of bridge is most effective and economical only within a certain range of span lengths, as shown in the following table

9、: . 每種結構類型的橋，只有在一定跨度范圍內(nèi)，才每種結構類型的橋，只有在一定跨度范圍內(nèi)，才能是最經(jīng)濟和最有效。如下表所示：能是最經(jīng)濟和最有效。如下表所示： 橋的類橋的類型型最佳跨度最佳跨度英尺英尺米米梁橋梁橋2020到到100010006.16.1到到304.8304.8剛架橋剛架橋8080到到30030024.424.4到到91.491.4拱橋拱橋200200到到1000100061.061.0到到304.8304.8桁架橋桁架橋200200到到1400140061.061.0到到426.7426.7 As indicated in the table , there is a consi

10、derable overlap in the range of applicability of the various typesIn some cases，alternative preliminary designs are prepared for several types of bridge in order to have a better basis for making the final 上表表明了不同結構類型的適用性有很多交叉的地方。在一些實例中，在不同的初步設計中，用來比較不同類型的橋是為了在最后有最好的選擇。Selection of materials材料的選擇材料的

11、選擇 The bridge designer can select from a number of modern high-strength materials，including concrete，steel，and a wide variety of corrosion-resistant alloy steels橋梁設計者能選用大量的現(xiàn)代高強材料，包括混泥土、橋梁設計者能選用大量的現(xiàn)代高強材料，包括混泥土、鋼筋和多種耐腐蝕的合金鋼。鋼筋和多種耐腐蝕的合金鋼。 For the Verrazano-Narrows Bridge，for example，the designer used a

12、t least seven different kinds of alloy steel，one of which has a yield strength of 5000 pounds per square inch(psi)(3，515 kgsq cm) and does not need to be painted because an oxide coating forms on its surface and inhibits corrosioninhibit 抑制抑制, 約束約束, 化化醫(yī)醫(yī)抑制抑制 拿拿Varian-Narrows大橋來說，設計者使用了七種不同大橋來說，設計者使用

13、了七種不同的合金鋼，其中之一的合金的屈服強度為的合金鋼，其中之一的合金的屈服強度為50000英鎊英鎊每平方英寸（每平方英寸（3115kg/c）,而且不需要油漆保護，因而且不需要油漆保護，因為有一種氧化膜覆蓋在它的表面而防止腐蝕。為有一種氧化膜覆蓋在它的表面而防止腐蝕。 The designer also can select steel wires for suspension cables that have tensile strengths up to 250，000 psi(17，577 kgsq cm)設計者還選用鋼絲繩作為懸索，它的抗拉強度超過設計者還選用鋼絲繩作為懸索，它的抗拉強

14、度超過250000英鎊每平方英寸（英鎊每平方英寸（17577 kg/c） Concrete with compressive strengths as high as 8,000 psi (5625 kgsq Cm) can now be produced for use in bridges , and it can be given high durability against chipping and weathering by the addition of special chemical agents and control of the hardening process .c

15、hipping 碎屑；小碎片碎屑；小碎片 weathering侵蝕侵蝕,風化風化 現(xiàn) 在 ， 抗 壓 強 度 高 達現(xiàn) 在 ， 抗 壓 強 度 高 達 8 0 0 0 英 鎊 每 平 方 英 尺英 鎊 每 平 方 英 尺（562.5kg/c）的混泥土被生產(chǎn)用于橋梁工程，）的混泥土被生產(chǎn)用于橋梁工程，而且它在增加特殊化學物質后具有很高的抗脆裂而且它在增加特殊化學物質后具有很高的抗脆裂性能和抗風化性能，性能和抗風化性能，Concrete that has been presressed and reinforced with steel wires has a tensile strength o

16、f 250,000psi ( 17,577 kg / sq cm). 用鋼絞線加強的預應力混凝土，其強度達到用鋼絞線加強的預應力混凝土，其強度達到250000英鎊每平方英寸（英鎊每平方英寸（17577 kg/c） Other useful materials for bridges include aluminum alloys and wood. 橋梁使用的其它材料還有鋁合金和木材。橋梁使用的其它材料還有鋁合金和木材。 Modern structural aluminum alloy have yield strengths exceeding 40,000 psi(2,812 kg/sq

17、cm). 現(xiàn)在的鋁合金的屈服強度超過了現(xiàn)在的鋁合金的屈服強度超過了40000每平方英寸每平方英寸（2818 kg/c）。）。 Laminated strips of wood glued together can be made into beams with strengths twice that of natural timber; glue-laminated southern pine, for example, can bear working stresses approaching 30, 000 psi(210.9 kg/sq cm).laminated由薄片疊成的由薄片疊成

18、的 把片狀的木條粘在一起做成的梁是自然木材強度的二把片狀的木條粘在一起做成的梁是自然木材強度的二倍。例如用南部松樹而膠結的梁能承受的工作應力達到倍。例如用南部松樹而膠結的梁能承受的工作應力達到了了3000英鎊每英寸（英鎊每英寸（210.9 kg/c）。）。 Analysis of forces力的分析 A bridge must resist a complex combination of tension, compression, bending, shear, and torsion forces. 一座橋要抵抗一系列的合力，如拉力，壓力，剪力和扭力。 In addition, the

19、structure must provide a safety factor as insurance against failure. 另外，結構還需要一定的安全系數(shù)作為防止破壞的安全儲備。 The calculation of the precise nature of the individual stresses and strains in the structure, called analysis, is perhaps the most technically complex aspect of bridge building. 對結構的各種應力和應變的準確特性進行計算，這就叫

20、應力分析，這或許是橋梁結構中最復雜的技術。 The goal of analysis is to determine all of the forces that may act on each structural member.應力分析的目的是為了確定作用在結構上的各種力。 The forces that act on bridge structural members are produced by two kinds of loads-static and dynamic. 作用在橋梁結構的力都可以分為二類荷載：動荷載和靜荷載。 The static load - the dead w

21、eight of the bridge structure itself -is usually the greatest load. The dynamic, or live, load has components, including vehicles carried by the bridge, wind forces, and accumulations of ice and snow. 靜荷載即橋的自重它往往也是最大的荷載。動荷載或靜荷載有很多，包括橋面上的機動車，風荷載，和積冰積雪荷載。 Although of the total weight of the vehicles m

22、oving over a bridge at any time is generally a small fraction of the static and dynamic load, it presents special problems to the bridge designer because of the vibration and impact stresses created by moving vehicles. 雖然隨時在橋面上移動的車輛的總重量相對于靜荷雖然隨時在橋面上移動的車輛的總重量相對于靜荷載和動荷載來說是一個很少的部分，而對設計者來說，載和動荷載來說是一個很少的

23、部分，而對設計者來說，因為機動車輛產(chǎn)生的振動和沖擊壓力而會出現(xiàn)特殊問因為機動車輛產(chǎn)生的振動和沖擊壓力而會出現(xiàn)特殊問題。題。 For example, the severe impacts caused by irregularities of vehicle motion or bumps in the roadway may momentarily double the effect of the live load on the bridge. 例如：在路面上機動車的不規(guī)則的運動或碰撞對橋例如：在路面上機動車的不規(guī)則的運動或碰撞對橋面產(chǎn)生瞬時雙倍活荷載的作用力。面產(chǎn)生瞬時雙倍活荷載的作用力

24、。 Wind exerts force on a bridge both directly by striking the bridge structure and indirectly by striking vehicles that are crossing the bridge. 風在橋上的作用的力包括：風在橋上的作用的力包括： 直接作用橋結構的力和間接的直接作用橋結構的力和間接的通過作用在通行車輛的力。通過作用在通行車輛的力。 If the wind induces aero elastic vibration, as in the case of the Tacoma Narrow

25、s Bridge, its effect may be greatly amplified. 如果出現(xiàn)空氣彈性振動，在這種情況下的如果出現(xiàn)空氣彈性振動，在這種情況下的Tacoma Narrows大橋的風作用被大大地增大，大橋的風作用被大大地增大， Because of this danger, the bridge designer makes provisions for the strongest winds that may occur at the bridge location. provision n. 供應供應, 提供提供, 供給，準備供給，準備, 防備；食物和飲料規(guī)定防備；食物

26、和飲料規(guī)定, 條款條款, 條件條件 由于這種危險的存在，橋的設計者必須知道橋址處可能發(fā)由于這種危險的存在，橋的設計者必須知道橋址處可能發(fā)生的最大的風。生的最大的風。 Other forces that may act on the bridge, such as stresses created by earthquake tremors, must also be provided for. 還有其它的力作用在橋上，如：地震產(chǎn)生的壓力也必須注意。還有其它的力作用在橋上，如：地震產(chǎn)生的壓力也必須注意。 Special attention must often be given to the d

27、esign of the bridge piers, since heavy loads may be imposed on them by currents, waves, and floating ice and debris. Occasionally a pier may even be hit by a passing hip. 對橋墩的設計要給予特殊的關注，因為橋墩承擔對橋墩的設計要給予特殊的關注，因為橋墩承擔水流，浮冰和漂浮物而產(chǎn)生的重荷載，橋墩通常還有水流，浮冰和漂浮物而產(chǎn)生的重荷載，橋墩通常還有被船撞擊的可能。被船撞擊的可能。 Electronic computers are

28、 playing an ever increasing role in assisting bridge designers in the analysis of forces. 電腦在力分析上協(xié)助橋梁設計者，起著很重要的作用。 The use of precise model testing, particularly for studying the dynamic behavior of bridges, also helps designers. 用一個精確的模型試驗，尤其對橋的動力的活動狀態(tài)的研究也可以幫助設計者。 A scaled-down model of the bridge

29、is constructed, and various gauges to measure strains, accelerations, and deformations are placed on the model. 一個縮尺比例的橋模結構中，布置很多位移計對橋模各處的應力，加速度和變形進行測量。 The model bridge is then subjected to various scaled-down load or dynamic condition to find out what will happen. 橋模在同樣比例的荷載和動力條件作用下，來分析橋的受力行為。 Win

30、d tunnel tests may also be made to ensure that nothing like the Tacoma Narrows Bridge failure can occur. With modern technological aids, there is much less chance of bridge failure than in the past. 風洞試驗也可以確保不再發(fā)生Tacoma Narrows大橋的失敗。在現(xiàn)代技術的幫助下，橋梁事故出現(xiàn)的機會將大大少于以前。 Construction the foundations. 基礎 施工 Cons

31、truction starts with the foundation， which may cost almost as much as the superstructure . 施工都是從基礎開始的，基礎的花費幾乎大大超過上層建筑。 Foundations built in water usually present the greatest difficulties. One of the older methods, which is still used in shadow waters, is to erect cofferdams similar to the ring of c

32、losely spaced piles that the Romans used. 水下基礎通常會遇到很大的困難，有個古老的方法常被用于淺水中，即在小范圍內(nèi)布置垂直圍堰而建橋墩。羅馬人常用這種方法。For constructing foundations in deep water, caissons have long been used .在深水中建基礎一般用沉箱法。the caisson, which is a huge box closed on all sides except the bottom, is lowered onto the river bed.沉箱是一個底部開口其余

33、封閉的大盒子而沉入河床上，Workers inside the caisson, , which is filled with compressed air to keep out the water, dig deeper and deeper, and the caisson sinks as the digging proceeds , When a suitable depth is reached，the caisson is filled with concrete and becomes part of the foundation itself .工人們在為擋水而充滿壓縮空氣的

34、沉箱里，越挖越深，沉箱也跟著下沉。當達到合適的深度后在箱內(nèi)填入混泥土而成為基礎的一部分。 Another deep-water method, less hazardous and less costly than the caisson method, uses steel or concrete piles. 在深水中建基礎的另一種方法比沉箱法更安全和更低的成在深水中建基礎的另一種方法比沉箱法更安全和更低的成本，用于鋼或混泥土橋墩。本，用于鋼或混泥土橋墩。 With modern pile drivers, long heavy piles can be driven even In de

35、ep water. 用現(xiàn)代的打樁機，長重樁可以打入深水中。用現(xiàn)代的打樁機，長重樁可以打入深水中。 The piles can be cut off and capped either above the water level or below it. 樁可以在水面或水下截斷或做成樁帽。樁可以在水面或水下截斷或做成樁帽。 If they are capped below the water level, a prefabricated hollow pier case is floated out to the site, sunk on the piles, and then filled

36、with concrete to form the pier. 如在水下把它們做成樁帽，可把一個預制空心橋墩浮運到場如在水下把它們做成樁帽，可把一個預制空心橋墩浮運到場地內(nèi)并沉入到樁上，然后灌入混泥土形成橋墩。地內(nèi)并沉入到樁上，然后灌入混泥土形成橋墩。 Erecting the superstructure.建造上部結構建造上部結構 After all piers and abutments are in place, the erection of the superstructure begins 當所有的樁和支柱建好后，則上部結構開始建造。當所有的樁和支柱建好后，則上部結構開始建造。 T

37、he method of construction used depends largely on the type of bridge being built. There are six construction methods: falsework , flotation , cantilevering，sliding ,direct lifting, and Suspension. 結構的施工方法有很多種類，共有六類施工方法：結構的施工方法有很多種類，共有六類施工方法：腳手架、浮運、懸臂、滑移、直升和懸掛法。腳手架、浮運、懸臂、滑移、直升和懸掛法。 In falswork constr

38、uction, mainly used in building concrete arch bridges, metal or wood supports are built temporarily to support the erection. 在用腳手架施工時，主要用來建混泥土拱橋，金屬在用腳手架施工時，主要用來建混泥土拱橋，金屬或木支撐都是臨時搭設為支撐上部結構。或木支撐都是臨時搭設為支撐上部結構。 A great deal of ingenuity is often required just to erect the falsework, especially for struct

39、ures over swift rivers or deep canyons. Temporary piles and trestles are commonly used in wide shallow rivers.Trestle 腳手架腳手架, 高架橋高架橋, 三角凳三角凳 腳手架都是根據(jù)需要而靈活搭建的，尤其結構在腳手架都是根據(jù)需要而靈活搭建的，尤其結構在激流河流或深谷上時，臨時橋墩和架子一般在寬而淺激流河流或深谷上時，臨時橋墩和架子一般在寬而淺的河上使用。的河上使用。 In the floatation method, mainly used in building long bri

40、dges , large bridge section are prefabricated on shore and floated out on barges to the bridge site . 浮運法主要用來施工很長的橋梁，主橋部分是在河岸預制的，浮運法主要用來施工很長的橋梁，主橋部分是在河岸預制的，然后用駁船浮移到橋梁位置。然后用駁船浮移到橋梁位置。 The sections are then hoisted into place, either by floating derricks or by winches placed on previously constructed

41、sections of the bridge. 浮吊起重機或卷揚機安裝在已建成橋的部位，然后把預知的主浮吊起重機或卷揚機安裝在已建成橋的部位，然后把預知的主橋部分精確吊到大橋的施工部位。橋部分精確吊到大橋的施工部位。 The cantilevering technique is used not only for cantilever bridges but also for steel arch bridges. 懸臂技術不僅用于懸臂橋中，也用于剛拱橋上，懸臂技術不僅用于懸臂橋中，也用于剛拱橋上， Construction starts at an abutment and extends

42、toward the center piece by piece. Moving derricks and cranes on the completed portion of the structure handle the heavy material. 施工時先建成一個橋臺，然后一步步延伸到中央，施工時先建成一個橋臺，然后一步步延伸到中央，在已建好的結構部分的起重機和吊車，來回移動完成在已建好的結構部分的起重機和吊車，來回移動完成施工材料的運輸。施工材料的運輸。 Sliding construction is used only rarely. In this method, a prefabricated unit, such as a truss, is erected on shore and slid out over a temporary or permanent support until it comes to rest on another Support. 滑移法在施工中很少用到。這種方法，如一個預制滑移法在施工中很少用到。這種方法，如一個預制構件，如桁架結構，豎立在河岸上，然后在臨時或永構件，如