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1、Symbols of the Conquest of SpaceBridges,Name：He ZheStudent ID：201260101013Guidance：Lang Yuhua,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,1,Contents,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1 Bridges,4 Girder Bridges,5 Ar
2、ch Bridges,6 Cantilever Bridges,2 Categories,3 Suspension Bridges,1/18/2023,2,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,Symbols of the Conquest of SpaceBridges,1/18/2023,3,Bridges,Bridges are great symbols of mankinds conquest of space.It is a structure that spans
3、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 pipeli
4、ne or a water aqueduct.,1,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,4,Bridges,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,Water Aqueduct Bridge1988.7,Jun Dushan,China,1/18/2023,5,Material,Humans have been constructing brid
5、ges 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
6、 first application of reinforced concrete to bridge structures was pioneered by Hennebique.,2-1,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,6,Material,In the same period prestressed concrete concepts were being formulated by Jackson and Doehring.There appli
7、cation 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.,2-2,Civil Engineering English（CTGU）Chapter 8
8、 Bridge EngineeringSection A Bridges,1/18/2023,7,Material,Prestressed 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 re
9、duce the dead weight of the bridge,but they are not widely used because they are relatively expensive.,2-3,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,8,Division,The principal portions of a bridge may be said to be the“superstructure”and“substructure.This d
10、ivision 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
11、below the roadway.,3-1,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,9,Division,In 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 be
12、tter view of the surrounding area,and are easier to widen if future traffic requires it.,3-2,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,10,Loads,The forces that act on bridge structural members are produced by three kinds of loads:the dead load,the live lo
13、ad,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.,4-1,Civil Engineering English（CTGU）Cha
14、pter 8 Bridge EngineeringSection A Bridges,1/18/2023,11,Loads,All 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
15、 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.,4-2,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,12,Loads,It has been grea
16、tly 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 be
17、st 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.,4-3,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,13,Categories,Ge
18、neral categories of bridges are briefly described in the following paragraphs:,5,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,14,Girder bridges,Girder bridges A girder bridge is perhaps the most common and most basic bridge.A log or a piece of other material
19、 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.,6-1,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/20
20、23,15,Girder bridges,Girder 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.,6-2,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,16,Pre
21、stress,The 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 com
22、pression 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.,7,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,17,Girder bridgesDouble Helix Bridge,Civ
23、il Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,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
24、 the worlds first curved bridge.,1/18/2023,18,Arch bridges,Arch 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 te
25、nsile 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.,8,Civil Engineering English（CTGU）Chapter 8 Bridge En
26、gineeringSection A Bridges,1/18/2023,19,Arch,Arches 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 arc
27、h.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.,9,Civil Engineering English（CTGU）Chapter 8 Bridge Engineering
28、Section A Bridges,1/18/2023,20,Classic,The arch,with its simple and elegant structures,has become a classic bridge configuration.,10,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,21,Arch bridges,1/18/2023,22,Alternatives,Cantilever bridges To solve the proble
29、m 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.,11,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/
30、2023,23,Cantilever bridge,A 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,t
31、he cantilevers,and the central beam.This configuration made longer spans possible and wider clearance beneath.,12,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,24,Trusses,For small footbridges,the cantilevers may be simple beams;however,large cantilever bridg
32、es designed to handle road or rail traffic use trusses built from structural steel,or box girders built from prestressed concrete.,13,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,25,Cable-stayed bridge,The cantilever bridge was a popular type of bridge in th
33、e first half of the twentieth century,but at present,some commentators believe that the cable-stayed bridge will replace it for comparable spanning distances.,14,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,26,Cantilever bridgeForth Railway Bridge,TheForth B
34、ridgeis acantileverrailwaybridgeover theFirth of Forthin the east ofScotland,to the east of theForth Road Bridge,and 14kilometres(9mi)west of centralEdinburgh.It was opened on 4 March 1890,and spans a total length of 2,528.7 metres.,1/18/2023,27,Suspension bridges,Suspension bridges Suspension bridg
35、es 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 s
36、tiffening girder.Some primitive examples of suspension bridges use vines and ropes for cables.,15,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,28,Girder,A typical suspension bridge is a continuous girder with one or more towers erected above piers in the mid
37、dle 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
38、aesthetically pleasing of all bridges.,16,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,1/18/2023,29,Famous Suspension bridges Mackinac Bridge,1/18/2023,30,Text structure,Civil Engineering English（CTGU）Chapter 8 Bridge EngineeringSection A Bridges,Bridges,Bridges,Girder Bridges,Arch Bridges,Cantilever Bridges,Suspension bridges,Material,Division,Loads,Girder bridges,Categories,Prestress,Arch bridges,Arch,Classic,Alternatives,Cantilever bridge,Trusses,Cable-stayed bridge,Bridges,Girder,Suspension Bridges,1/18/2023,31,Bridges,（在“幻灯片放映”模式中时单击该箭头）,1/18/2023,32,
