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SymbolsoftheConquestofSpaceBridgesName：HeZheStudentID：201260101013Guidance：LangYuhuaCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/20241Symbols of the Conquest of SpaContentsCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 1 Bridges4 Girder Bridges5 Arch Bridges6 Cantilever Bridges2 Categories3 Suspension Bridges8/5/20242ContentsCivil Engineering EnglCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges SymbolsoftheConquestofSpaceSymbolsoftheConquestofSpaceBridgesBridges8/5/20243Civil Engineering English（CTGUBridges Bridges are great symbols of mankinds conquest of space.It is a structure that spans obstacles,such 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 aqueduct.1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/20244Bridges Bridges are great symBridgesCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges WaterAqueductBridge1988.7,JunDushan,China8/5/20245BridgesCivil Engineering EngliMaterial Humans have been constructing bridges since ancient times.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 of reinforced concrete to bridge structures was pioneered by Hennebique.2-1Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/20246Material Humans have been conMaterialIn the same period prestressed concrete concepts were being formulated by Jackson and Doehring.There application was not successful 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 EngineeringSection A Bridges 8/5/20247MaterialIn the same period preMaterialPrestressed 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 bridge,but they are not widely used because they are relatively expensive.2-3Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/20248MaterialPrestressed concrete wDivisionThe principal portions of a bridge may be said to be the“superstructure”and“substructure.This division is used here simply for 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 Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/20249DivisionThe principal portionsDivisionIn 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,and are easier to widen if future traffic requires it.3-2Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202410DivisionIn the through type ofLoadsThe 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 refers 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 Bridges 8/5/202411LoadsThe forces that act on brLoadsAll 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 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 8/5/202412LoadsAll three factors must beLoadsIt has been greatly improved by the use of advanced mathematics,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 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 8/5/202413LoadsIt has been greatly improCategoriesGeneral categories of bridges are briefly described in the following paragraphs:5Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202414CategoriesGeneral categories oGirderbridgesGirder 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 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 8/5/202415Girder bridgesGirder bridges6-GirderbridgesGirder bridges come in two basic varieties: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 8/5/202416Girder bridgesGirder bridges cPrestressThe precast-prestressed beam type is a popular bridge type.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 strong 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 8/5/202417PrestressThe precast-prestressGirderbridgesDoubleHelixBridgeCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges LinkingMarinaBaytoMarinaCentre,theHelixBridge,issettobecomeSingaporesnextlandmark.LocatedbesidetheBenjaminShearesBridge,alongsidethevehicularBayfrontBridge,itwasofficiallyopenedon24April2010andistheworldsfirstcurvedbridge.8/5/202418Girder bridgesDouble Helix BArchbridgesArch bridges 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.Reinforced 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 8/5/202419Arch bridgesArch bridges 8CiviArchArches may be grouped into circular,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 elements.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 8/5/202420ArchArches may be grouped intoClassic The arch,with its simple and elegant structures,has become a classic bridge configuration.10Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202421Classic The arch,with its siArchbridges8/5/202422Arch bridges8/19/202322AlternativesCantilever bridges To solve the problem of increasing the span distance,other alternatives to beam and arch bridges included 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 8/5/202423AlternativesCantilever bridgesCantileverbridgeA cantilever bridge is a bridge built using cantilevers,a cantilever 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 wider clearance beneath.12Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202424Cantilever bridge A cantileverTrussesFor 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 girders built from prestressed concrete.13Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202425TrussesFor small footbridges,Cable-stayedbridgeThe 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-stayed bridge will replace it for comparable spanning distances.14Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202426Cable-stayed bridge The cantilCantileverbridgeForthRailwayBridgeTheForthBridgeisacantileverrailwaybridgeovertheFirthofForthintheeastofScotland,totheeastoftheForthRoadBridge,and14kilometres(9mi)westofcentralEdinburgh.Itwasopenedon4March1890,andspansatotallengthof2,528.7metres.8/5/202427Cantilever bridgeForth RailwaSuspensionbridgesSuspension bridges Suspension bridges are used for very long spans or for shorter spans where intermediate piers cannot 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 for cables.15Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges 8/5/202428Suspension bridges Suspension GirderA 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 spans,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 EngineeringSection A Bridges 8/5/202429GirderA typical suspension briFamousSuspensionbridgesMackinacBridge8/5/202430Famous Suspension bridges MTextstructureCivil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges BridgesBridgesGirder BridgesArch BridgesCantilever BridgesSuspension bridges MaterialDivisionLoadsGirder bridgesCategoriesPrestressArch bridgesArchClassicAlternativesCantilever bridge TrussesCable-stayed bridge BridgesGirderSuspension Bridges8/5/202431Text structureCivil EngineerinBridges（在“幻灯片放映”模式中时单击该箭头）8/5/202432Bridges（在“幻灯片放映”模式中时单击该箭头）8/19
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