1、Symbols of the Conquest of SpaceBridgesName：He ZheStudent ID：201260101013Guidance：Lang YuhuaCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/20221ContentsCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 1 Bridges4 Girder Bridges5 Arch Bri
2、dges6 Cantilever Bridges2 Categories3 Suspension Bridges12/19/20222Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges Symbols of the Conquest of SpaceBridges12/19/20223Bridges Bridges are great symbols of mankinds conquest of space.It is a structure that spans obstacles,suc
3、h as rivers,lakes,or gorges,to provide a roadway for traffic.By far the majority of bridges are designed to carry automobile or railroad traffic,but some are intended for pedestrians only.Bridges also support pipes,troughs,or other conduits that transport materials,such as an oil pipeline or a water
4、 aqueduct.1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/20224BridgesCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges Water Aqueduct Bridge1988.7,Jun Dushan,China12/19/20225Material Humans have been constructing bridges since ancient t
5、imes.For a few thousand years the classical form in bridge design has been the vault or arch.This structure,because of its inherent contour,utilized masonry as its material.The use of concrete as a building material,however,was not considered until late in the nineteen century.The first application
6、of reinforced concrete to bridge structures was pioneered by Hennebique.2-1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/20226MaterialIn the same period prestressed concrete concepts were being formulated by Jackson and Doehring.There application was not successf
7、ul because of the high losses in prestress caused by shrinkage and creep of the concrete.It was not until 1926-1928 when Freyssinet was able to control these losses with high-strength steel that prestressing was considered feasible.2-2Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSectio
8、n A Bridges 12/19/20227MaterialPrestressed concrete was widely used for bridges after about 1950.Steel became more useful for bridges with the development of stronger and more corrosion-resistant alloys.Aluminum alloys,which were used in bridges as early as 1933,greatly reduce the dead weight of the
9、 bridge,but they are not widely used because they are relatively expensive.2-3Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/20228DivisionThe principal portions of a bridge may be said to be the“superstructure”and“substructure.This division is used here simply for
10、 convenience,sine in many bridges there is no clear dividing line between the two.Bridges may also be classed as“deck”or“through”types.In the deck type of bridge,the roadway is above the supporting structure,that is,the load carrying elements of the superstructure are below the roadway.3-1Civil Engi
11、neering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/20229DivisionIn the through type of bridge,the roadway passes between the elements of the superstructure.Deck structures predominate:they have a clean appearance,provide the motorist with a better view of the surrounding area,a
12、nd are easier to widen if future traffic requires it.3-2Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202210LoadsThe forces that act on bridge structural members are produced by three kinds of loads:the dead load,the live load,and the occasional load.Dead load re
13、fers to the weight of the bridge itself-is usually the greatest load.Live load refers to traffic that moves across the bridges as well as normal environmental factors such as changes in temperature,precipitation,and winds.4-1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridge
14、s 12/19/202211LoadsAll three factors must be taken into consideration in the design of a bridge.The design of bridges requires the collection of extensive data and from this the selection of possible options.From such a review the choice is narrowed down to a shortlist of potential bridge designs.A
15、sensible work plan should be devised for the marshalling and deployment of information throughout the project from conception to completion.4-2Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202212LoadsIt has been greatly improved by the use of advanced mathematics
16、,electronic computers,and test model,with these techniques,designers can obtain precise calculations of stresses and strains under both static and dynamic conditions.The designer of each medium and long-span bridge tries to devise a structure that is best suited to the conditions encountered at that
17、 particular location.The result is an almost bewildering variety of structures that differ either in basic design principle or in design details.4-3Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202213CategoriesGeneral categories of bridges are briefly described i
18、n the following paragraphs:5Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202214Girder bridgesGirder bridges A girder bridge is perhaps the most common and most basic bridge.A log or a piece of other material across a creek is an example of a girder bridge in its
19、 simplest form.That piece of material called a girder or beam rests directly on the ground on each side or is supported on heavy foundations known as piers.6-1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202215Girder bridgesGirder bridges come in two basic varie
20、ties:plate and box girders.Simple or continuous beam-type bridges can be made of timber,steel,concrete,prestressed concrete or other materials.6-2Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202216PrestressThe precast-prestressed beam type is a popular bridge ty
21、pe.These bridges can be founded both as overpasses and as bridges.This type of bridge became popular in the 1950s.Prestress indicates that the reinforcing is stressed before loading,thereby placing the entire concrete beam section in compression or at a low value tension stress.Since concrete is str
22、ong in compression and relatively weak in tension,this procedure creates a more effective concrete section.7Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202217Girder bridgesDouble Helix BridgeCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A B
23、ridges Linking Marina Bay to Marina Centre,the Helix Bridge,is set to become Singapores next landmark.Located beside the Benjamin Sheares Bridge,alongside the vehicular Bayfront Bridge,it was officially opened on 24 April 2010 and is the worlds first curved bridge.12/19/202218Arch bridgesArch bridge
24、s A strong point in favor of arch bridges in their pleasing appearance and aesthetic elegance.Arch bridges can be made of bricks or stone blocks that are held together by the compressive force characteristic of the arch because tensile strength is not necessarily required for arch construction.Reinf
25、orced concrete and steel arches are altogether much lighter structures.The structure consists basically of the arch,the deck and usually some supports from the arch to the deck.8Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202219ArchArches may be grouped into ci
26、rcular,parabolic and catenary arch in terms of the shape of arch.With regard to structural articulation the arch can be fixed or hinged.Three types of arches are used:the fixed arch,the two-hinged arch,and the three-hinged arch.The main supporting structure in an arch bridge is one or more curved el
27、ements.The dead and live forces that act on the arch bridge are transmitted along the curved line of the arch into abutments or supporting structures at either end.9Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202220Classic The arch,with its simple and elegant s
28、tructures,has become a classic bridge configuration.10Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202221Arch bridges12/19/202222AlternativesCantilever bridges To solve the problem of increasing the span distance,other alternatives to beam and arch bridges inclu
29、ded suspension and cantilever bridges.Among the largest cantilever bridges in the United States is the Commodore John Barry Bridge.11Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202223Cantilever bridge A cantilever bridge is a bridge built using cantilevers,a ca
30、ntilever is a structure or beam that is unsupported at one end but supported at the other,like diving boards.When anchored firmly,a cantilever is a very strong structure.It consists of three parts:the outer beams,the cantilevers,and the central beam.This configuration made longer spans possible and
31、wider clearance beneath.12Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202224TrussesFor small footbridges,the cantilevers may be simple beams;however,large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel,or box
32、girders built from prestressed concrete.13Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202225Cable-stayed bridge The cantilever bridge was a popular type of bridge in the first half of the twentieth century,but at present,some commentators believe that the cable
33、-stayed bridge will replace it for comparable spanning distances.14Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202226Cantilever bridgeForth Railway Bridge The Forth Bridge is a cantilever railway bridge over the Firth of Forth in the east of Scotland,to the eas
34、t of the Forth Road Bridge,and 14 kilometres(9 mi)west of central Edinburgh.It was opened on 4 March 1890,and spans a total length of 2,528.7 metres.12/19/202227Suspension bridges Suspension bridges Suspension bridges are used for very long spans or for shorter spans where intermediate piers cannot
35、be built.Of all the bridge types in use today,the suspension bridge allows for the longest spans.The principal structural elements of a suspension bridge are:flexible main cables,towers,anchorages,hangers,deck and stiffening girder.Some primitive examples of suspension bridges use vines and ropes fo
36、r cables.15Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 12/19/202228GirderA typical suspension bridge is a continuous girder with one or more towers erected above piers in the middle of the span.The girder itself is usually a truss or box girder though in shorter span
37、s,plate girders are not uncommon.At both ends of the bridge large anchors or counter weights are placed to hold the ends of the cables.Suspension bridges,when well designed and proportioned,are clearly the most aesthetically pleasing of all bridges.16Civil Engineering English（CTGU）Chapter 8 Bridge E
38、ngineeringSection A Bridges 12/19/202229Famous Suspension bridges Mackinac Bridge12/19/202230Text structureCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges BridgesBridgesGirder BridgesArch BridgesCantilever BridgesSuspension bridges MaterialDivisionLoadsGirder bridgesCategoriesPrestressArch bridgesArchClassicAlternativesCantilever bridge TrussesCable-stayed bridge BridgesGirderSuspension Bridges12/19/202231Bridges（在“幻灯片放映”模式中时单击该箭头）12/19/202232
