Lesson_8-BridgeDesignandConstruction

1、Lesson 8 Bridge Design and Construction橋梁的設(shè)計(jì)與建造橋梁的設(shè)計(jì)與建造New words and phrases1、initiate net vt. (1)開始，著手實(shí)施開始，著手實(shí)施 to initiate a reform to initiate an attack (2)啟發(fā)，啟蒙；傳授（與啟發(fā)，啟蒙；傳授（與in/into連用）連用） to initiate sb. into the game of chess (3)介紹介紹加入（與加入（與into連用）連用） to initiate someone into a club n. 新成員；被傳授

2、了初步知識的人新成員；被傳授了初步知識的人 adj. 新加入的；接受初步知識的新加入的；接受初步知識的 initial nl adj. 開始的，最先的開始的，最先的 initiation ,nen n. 開始；加入開始；加入 initiative ntv n. 主動(dòng)；主動(dòng)性主動(dòng)；主動(dòng)性2、federal fed()r()l adj. 聯(lián)邦的；同盟的聯(lián)邦的；同盟的 federal government/law/court 3、revenue revnju n. 稅收，國家的收入；收益稅收，國家的收入；收益 tax revenue sales revenue revenue and expendi

3、ture fiscal revenue4、survey sve vt. (1)調(diào)查；考察調(diào)查；考察 to survey the will of the people (2)測量，勘測測量，勘測 When a project begins, the site is surveyed and mapped by civil engineers. (Lesson 1) (3)俯視，鳥瞰俯視，鳥瞰 to survey Paris from the top of Eiffel Tower vi. 測量，勘測，測繪測量，勘測，測繪 n. 調(diào)查；測量；審視調(diào)查；測量；審視5、harmony h:mni n.

4、 協(xié)調(diào)；和睦；和諧協(xié)調(diào)；和睦；和諧 in harmony live in harmony in harmony with social harmony6、durability ,djrblti n. 耐久性；耐久力耐久性；耐久力 durable djurbl adj. 耐久的；經(jīng)久的；穩(wěn)定的耐久的；經(jīng)久的；穩(wěn)定的 durability test chemical durability7、accumulation kjumjle()n n. 積累；積聚；聚積物積累；積聚；聚積物 heat accumulation accumulation area8、bump bmp vt. (1)碰，撞，撞擊

5、碰，撞，撞擊 Her car bumped a truck. (2)使碰撞，沖擊使碰撞，沖擊 She bumped the car against a post. (3)把把撞到，撞傷（頭、臂等）撞到，撞傷（頭、臂等） He bumped his arm against the desk. vi. (1)碰，撞（與碰，撞（與against, into 連用）連用） to bump into sb. to bump against the table (2)偶然遇見（與偶然遇見（與 into 連用）連用） I bumped into an old friend in the street. n.

6、 碰撞；撞傷；顛簸碰撞；撞傷；顛簸9、weather we n. 天氣；氣候；處境天氣；氣候；處境 vt. (1)使風(fēng)化；風(fēng)干，曬干使風(fēng)化；風(fēng)干，曬干 They are going to weather the corn in the thrashing field. (2)使退色；使分解；侵蝕使退色；使分解；侵蝕 The wind and waves have weathered the rocks on the shore. (3)渡過（暴風(fēng)雨，困難等）；經(jīng)受住渡過（暴風(fēng)雨，困難等）；經(jīng)受住 Many small firms did not weather the storm of the

7、 recession. vi. 受侵蝕；風(fēng)化；經(jīng)受風(fēng)雨受侵蝕；風(fēng)化；經(jīng)受風(fēng)雨 n. weather forecast weather permitting10、tremor trem n. 顫動(dòng)；震動(dòng)顫動(dòng)；震動(dòng) vi. 發(fā)抖；顫動(dòng)發(fā)抖；顫動(dòng)11、debris debri n. 碎片，殘骸碎片，殘骸 debris flow12、cofferdam kfdm n. （河流、湖泊等的）圍堰；潛水箱，沉箱（河流、湖泊等的）圍堰；潛水箱，沉箱 antiseepage cofferdam earth cofferdam13、caisson kes()n n. 沉井，沉箱沉井，沉箱 caisson pile

8、 open caisson14、hazardous hzds adj. 有危險(xiǎn)的；冒險(xiǎn)的；（化合物）有害的有危險(xiǎn)的；冒險(xiǎn)的；（化合物）有害的 hazardous waste hazardous goods hazard vt. 冒冒的危險(xiǎn)；賭運(yùn)氣的危險(xiǎn)；賭運(yùn)氣 n. 危險(xiǎn)；冒險(xiǎn)危險(xiǎn)；冒險(xiǎn)15、temporary temp()rr adj. 臨時(shí)的；暫時(shí)的；短暫的臨時(shí)的；暫時(shí)的；短暫的 temporary work temporary construction n. 臨時(shí)工；臨時(shí)雇員臨時(shí)工；臨時(shí)雇員16、ingenuity ,ndnjut n. 心靈手巧；獨(dú)創(chuàng)性；精巧；精巧的裝置心靈手巧；獨(dú)創(chuàng)性

9、；精巧；精巧的裝置 originality n. 創(chuàng)意；獨(dú)創(chuàng)性創(chuàng)意；獨(dú)創(chuàng)性 17、derrick derk n. 起重機(jī)；起貨桅桿起重機(jī)；起貨桅桿 v. 用轉(zhuǎn)臂起重機(jī)移動(dòng)或吊起用轉(zhuǎn)臂起重機(jī)移動(dòng)或吊起18、winch wnt vt. 用絞車提升；用起貨機(jī)吊起用絞車提升；用起貨機(jī)吊起 n. 絞車；曲柄；卷揚(yáng)機(jī)絞車；曲柄；卷揚(yáng)機(jī) 19、guardrail drel n. 護(hù)欄；欄桿；護(hù)欄；欄桿；鐵路鐵路護(hù)軌護(hù)軌 guard v. 保衛(wèi)；監(jiān)視保衛(wèi)；監(jiān)視 n. 守衛(wèi)；防護(hù)守衛(wèi)；防護(hù)20、accessory kses()r adj. 附加的；輔助的；附屬的；副的附加的；輔助的；附屬的；副的 accesso

10、ry equipment accessory ingredient n. 配件；附件；附屬品配件；附件；附屬品21、toll tl n. 稅；（橋梁、公路等的）通行費(fèi)，通過費(fèi)稅；（橋梁、公路等的）通行費(fèi)，通過費(fèi) v. 征稅；收通行費(fèi)征稅；收通行費(fèi) road toll toll station22、preliminary design 初步設(shè)計(jì)初步設(shè)計(jì)23、tensile strength 抗拉強(qiáng)度抗拉強(qiáng)度 compressive strength 抗壓強(qiáng)度抗壓強(qiáng)度24 、yield strength 屈服強(qiáng)度屈服強(qiáng)度25、suspension bridge 吊橋，懸索橋吊橋，懸索橋26、com

11、pressed air 壓縮空氣壓縮空氣 Text Bridge Design and ConstructionPlanning The first step leading to the construction of a modern major bridge is a comprehensive study to determine whether a bridge is needed. If it is to be a highway bridge, in the United States for example, a planning study is initiated by a

12、 state bridge authority, possibly in cooperation with local government or the federal government .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. The means for financin

13、g the project, such as public taxes or sale of revenue bonds repaid by toll charges, are considered.If the studies lead to a decision to go ahead with the project, the land needed for the bridge and its approaches is acquired at the selected site. At this point, field engineering work is started. Ac

14、curate land surveys are made.Tides, flood conditions，currents, and other characteristics of the waterway are carefully studied.Boring samples of soil and rock are taken at possible foundation locations, both on land and under the water. The chief factors in deciding whether a bridge will be built as

15、 a girder, 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.Each type of brid

16、ge is most effective and economical only within a certain range of span lengths, as shown in the following table:Selection of bridge design As indicated in the table, there is a considerable overlap in the range of applicability of the various typesIn some cases, alternative preliminary designs are

17、prepared for several types of bridge in order to have a better basis for making the final selection.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.For the Verrazano-Narrows Bridge, for

18、example, the designer used at least seven different kinds of alloy steel, one of which has a yield strength of 50,000 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 corrosionThe designer also can select steel wi

19、res for suspension cables that have tensile strengths up to 250, 000 psi(17, 577 kgsq cm)Selection of materials Concrete with compressive strengths as high as 8, 000 psi (562.5 kgsq cm) can now be produced for use in bridges, and it can be given high durability against chipping and weathering by the

20、 addition of special chemical agents and control of the hardening process.Concrete that has been prestressed and reinforced with steel wires has a tensile strength of 250, 000 psi ( 17, 577 kg / sq cm). Other useful materials for bridges include aluminum alloys and wood.Modern structural aluminum al

21、loy have yield strengths exceeding 40, 000 psi (2, 812 kg / sq cm).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 3, 000 psi (210.9 kg /sq cm). A bridge must

22、 resist a complex combination of tension, compression, bending, shear, and torsion forces.In addition, the structure must provide a safety factor as insurance against failure. The calculation of the precise nature of the individual stresses and strains in the structure, called analysis, is perhaps t

23、he most technically complex aspect of bridge building.The goal of analysis is to determine all of the forces that may act on each structural member.Analysis of forces The forces that act on bridge structural members are produced by two kinds of loads-static and dynamic.The static load - the dead wei

24、ght 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. Although the total weight of the vehicles moving over a bridge at any time is generally a small fract

25、ion 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.For example, the severe impacts caused by irregularities of vehicle motion or bumps in the roadway may momentarily double the effect of the

26、live load on the bridge. Wind exerts force on a bridge both directly by striking the bridge structure and indirectly by striking vehicles that are crossing the bridge.If the wind induces aeroelastic vibration, as in the case of the Tacoma Narrows Bridge, its effect may be greatly amplified.Because o

27、f this danger, the bridge designer makes provisions for the strongest winds that may occur at the bridge location.塔科馬海峽大橋塔科馬海峽大橋塔科馬海峽大橋蛇形共振塔科馬海峽大橋蛇形共振1940年年11月月7日塔科馬海峽大橋倒塌日塔科馬海峽大橋倒塌 Other forces that may act on the bridge, such as stresses created by earthquake tremors, must also be provided for.Spe

28、cial attention must often be given to the design 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 ship. Electronic computers are playing an ever-increasing role in assisting bridge designers

29、 in the analysis of forces.The use of precise model testing, particularly for studying the dynamic behavior of bridges, also helps designers.A scaled-down model of the bridge is constructed, and various gauges to measure strains, accelerations, and deformations are placed on the model. The model bri

30、dge is then subjected to various scaled-down loads or dynamic conditions to find out what will happen.Wind 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 pas

31、t. Construction starts with the foundation, which may cost almost as much as the superstructure.Foundations built in water usually present the greatest difficulties.One of the older methods, which is still used in shallow waters, is to erect cofferdams similar to the ring of closely spaced piles tha

32、t the Romans used.Construction the foundations For constructing foundations in deep water, caissons have long been used.The caisson, which is a huge box closed on all sides except the bottom, is lowered onto the river bed.Workers inside the caisson, which is filled with compressed air to keep out th

33、e water, dig deeper and deeper, and the caisson sinks as the digging proceeds.keep out(1)使留在外面；擋住；不讓進(jìn)來使留在外面；擋?。徊蛔屵M(jìn)來The little girl has never seen him before and so she keeps the stranger out.(2)留下，扣下留下，扣下The company keeps 5% of his salary out each month.When a suitable depth is reached，the caisson i

34、s filled with concrete and becomes part of the foundation itself . Another deep-water method, less hazardous and less costly than the caisson method, uses steel or concrete piles.With modern pile drivers, long heavy piles can be driven even in deep water.The piles can be cut off and capped either ab

35、ove the water level or below it.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 with concrete to form the pier. After all piers and abutments are in place, the erection of the superstructure beginsThe method of

36、 construction used depends largely on the type of bridge being built.There are six construction methods: falsework, flotation, cantilevering, sliding, direct lifting, and suspension.Erecting the superstructure In falsework construction, mainly used in building concrete arch bridges, metal or wood su

37、pports are built temporarily to support the erection.A great deal of ingenuity is often required just to erect the falsework, especially for structures over swift rivers or deep canyons.Temporary piles and trestles are commonly used in wide shallow rivers. In the floatation method, mainly used in bu

38、ilding long bridges , large bridge section are prefabricated on shore and floated out on barges to the bridge site .The sections are then hoisted into place, either by floating derricks or by winches placed on previously constructed sections of the bridge. The cantilevering technique is used not onl

39、y for cantilever bridges but also for steel arch bridges.Construction starts at an abutment and extends toward the center piece by piece.Moving derricks and cranes on the completed portion of the structure handle the heavy material. Sliding construction is used only rarely.In this method, a prefabri

40、cated 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. In the direct lifting method, mainly used for light, short - span highway bridge, a prefabricated bridge unit is lifted by a hoist and swung directly onto the bridge supports. In the construction of suspension bridges, the cables are strung between the bridge towers and used as a support for the bridge deck.The deck erection starts at the ends of the bridge and progresses toward the cent