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Student Guide Steel Bridge Design

Description
Outil indispensable aux étudiants pour assurer le calcul des ponts métalliques. Ce document fournit des notions essentielles en vue de comprendre les principes qui gouvernent les ponts.
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  Student guide to steel bridge design Corus Construction Services & Development  02 Contents 1Introduction 1.1General1.2Basic features of bridges 2Forms of steel bridge construction 2.1Beam bridges2.2Arch bridges2.3Suspension bridges2.4Stayed girder bridges2.5Advantages of steel bridges 3Composite plate girder highway bridges 3.1General layout3.2Girder construction3.3Girder erection and slabconstruction3.4Scheme design3.5Design code checks 4Material properties andspecifications5Corrosion protection6Concluding remarks7References and further reading Corus gratefully acknowledges the assistance given by the Steel Construction Institute in compiling this publication.  Introduction 1 Introduction Bridges are an essential part of thetransport infrastructure. 03 1.1 General  A bridge is a means by which a road,railway or other service is carried overan obstacle such as a river, valley, otherroad or railway line, either with nointermediate support or with only alimited number of supports atconvenient locations.Bridges range in size from very modestshort spans over, say, a small river tothe extreme examples of suspensionbridges crossing wide estuaries. Appearance is naturally less crucial forthe smaller bridges, but in all cases thedesigner will consider the appearance of the basic elements, which make uphis bridge, the superstructure and thesubstructure, and choose proportionswhich are appropriate to the particularcircumstances considered. The use of steel often helps the designer toselect proportions that are aesthetically pleasing.Bridges are an essential part of thetransport infrastructure. For example,there are more than 15,000 highwaybridges in the UK, with approximately300 being constructed each year asreplacements or additions. Many ofthese new bridges use steel as theprincipal structural elements because itis an economic and speedy form ofconstruction. On average, around 35,000 tonnes of steel have been usedannually in the UK for the constructionof highway and railway bridges.The guide describes the general featuresof bridges, outlines the various forms ofsteel bridge construction in commonuse, and discusses the considerationsto be made in designing them. Itdescribes the steps in the designprocedure for a composite plate girderhighway bridge superstructure,explaining how to choose an initialoutline arrangement and then how toapply design rules to analyse it anddetail the individual elements of thebridge. Reference is made to simplifiedversions of the Structural Eurocodes forbridge design, which are available forstudent use (see Ref.1 on page 31). Inaddition, the guide outlines materialspecification issues and the variousapproaches to corrosion protection.  Above: Renaissance Bridge (Photo courtesyof Angle Ring Co.), Bedford, England Opposite: Clyde Arc Bridge, Glasgow,Scotland Front cover: Hulme Arch, Manchester,England  04 1.2 Basic features of bridges Superstructure The superstructure of a bridge is thepart directly responsible for carrying theroad or other service. Its layout isdetermined largely by the disposition of the service to be carried. In mostcases, there is a deck structure thatcarries the loads from the individualwheels and distributes the loads to theprincipal structural elements, such asbeams spanning between thesubstructure supports.Road bridges carry a number of trafficlanes, in one or two directions, and mayalso carry footways. At the edge of thebridge, parapets are provided for theprotection of vehicles and people. Thearrangement of traffic lanes andfootways is usually decided by thehighway engineer. Traffic lane andfootpath widths along with clear heightabove the carriageway are usuallyspecified by the highway authority.Whilst the bridge designer has littleinfluence over selecting the layout andgeometry of the running surface, hedoes determine the structural form ofthe superstructure. In doing so, he mustbalance requirements for thesubstructure and superstructure, whilstachieving necessary clearances aboveand across the obstacle below.Rail bridges typically carry two tracks,laid on ballast, although separatesuperstructures are often provided foreach track. Railway gradients are muchmore limited than roadway gradientsand because of this the constructiondepth of the superstructure (from raillevel to the underside or soffit of thebridge) is often very tightly constrained.This limitation frequently results in ‘half through’ construction (see Section 2.1). Railway loading is greaterthan highway loading and consequently the superstructures for railway bridgesare usually much heavier than forhighway bridges.Footbridges are smaller lighterstructures. They are narrow (about 2mwide) and are usually single spanstructures that rarely span more than40m. There are a number of forms ofsteel footbridge (see Ref.4 on page 31),although they are outside the scope ofthis guidance publication. Substructure The substructure of a bridge isresponsible for supporting thesuperstructure and carrying the loads tothe ground through foundations.
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