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STANDARD SPECIFICATIONS

AND

CODE OF PRACTICEFOR

ROAD BRIDGES

Section V

Steel RoadBridges

THE INDIAN ROADS CONGRESS

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STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGES

Section VSteel Road Bridges

Published hiTHEiNDIANROADS CONGRESS

Jamnagar House, Shabjahan Road,NewDelhi-i100il

1984

Price Rs 24(Pluspacking& postage)

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First published : May, 1967Reprinted:August, 1972Reprinted:July, 1976

Reprinted: August, 1984 (IncorporatesAmendment No. 1December, 1982)

(Rights ofPublication and Translation are reserved)

Printed at PRINTAID, New Delhi

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STEEL ROAD BRIDGES

CONTENTS

Clause No. Page No.

introduction ... 1

501. General .,. 2

501.1. Scope ... 2501.2. Clearances .,. 2

502. Materials ,.. 2502.1. Structural Steel ... 2502.2. Rivetand Rivet Bars ... 2

502.3, CastSteel ... 3502.4. CastIron ,,, 3502.5. Steelfor Pins(including KuncklePins)andRollers ... 3502.6. BoltsandNuts .,. 3

502.7. Washers ,,, 3502.8. WeldingElectrodes ... 4502.9. Steel forParallelBarrel Drifts .,. 4502.10. Deleted ,., 4

503. Loads and Stresses ,., 4503.1. LoadsandForces to beTakenintoAccount ,,. 4503.2. CombinationofLoads andForces ... 5503.3. Stresses ... 5

503.4. DeformationStresses ... 6503.5. ReliefofStresses ... 6

504. Permissible Stresses ... 6504.1. AllowableWorking StressforCombination of

Loads andForces ... 6504.2. FluctuationsofStress(Fatigue) ... 7

504.3. Basic Permissible Stresses in Structural Steel ... 9504.4. AllowableWorking Stresses ... 12504.5. Working Shear Stresses in Solid WebPlates ... 19

504.6. Combined Stresses .,, 22504.7. Deleted ... 23

504.8. Deleted ... 23504.9. Deleted 23

504.10. Deleted 23504.11. Deleted ... 23

505. Design ofGeneral Details ... 23505.1. EffectiveSpans ... 23505.2. EffectiveDepth ... 23

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Clause No. PageNo.

505.3. MinimumDepth ... 23505.4. Spacingand Depth ofMain Girders ... 24

505.5. Symmetry ... 24

505.6. Minimum Sections ... 24505,7. Corrosion ... 24

505.8. Drainage ... 25505.9. Deflection ... 2550510. Camber ... 25

505.11. Provision forTemperatureChanges .,. 25505.12. Spacing ofTrusses and Girders ... 25

505.13. Anchorage ... 26505.14. Effective LengthofStruts ... 26505.15. Effective SectionalArea ... 26505.16. FloorBeams ... 28505.17. Joists andStringers ... 28

505.18. Bracing ... 28

505.19. EndCrossGirders ... 28505.20. Plates inCompression ... 29505.21. RivetingandBolting ... 30505.22. Welding ... 32

505.23. Lug Angles ... 33505.24. Clevises and Turnbuckles ... 34505.25. Pins ... 34505.26, CompositeUse ofMild SteelandHighTensile Steel ... 34505.27, Composite Action ofSteelandConcrete ... 34

505.28. Composite Connections 35

506. Solid Web Girders (Plate Girders andRoBed

Beams) ... 35506.1. General ... 35

506.2. Maximum AverageShear Stress ... 36506.3. SlendernessRatio ,.. 36506.4. Flanges .. 36506.5. EffectiveLengthofCompressionFlanges ... 38506.6. Webs ... 41

507. Open Web Girders ... 46507.1. General ... 46507.2. CompressionMembers ... 47

507.3. Tension Members ... 56507.4. Splicing ... 60

507.5. Connections atIntersections ... 60507.6. GussetPlates ... 60

507.7. Diaphragms in Members ... 61507.8. Camber .,. 61

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ClauseNo. Page No.

508. Workmanship ... 61508.1, General ... 61

508.2. Templates ,,, 61508.3. Straightening ... 62

508.4. PreparationofEdgesandF.nds ... 62508.5. Preparationof Holes ,,, 63508.6. RivetandRiveting ... 65508.7. Bolts, NutsandWashers ,,, 66508.8. Drifts ... 68508.9. PinsandPinHoles ... 68

508.10. Deleted

508.11. Welding ... 68508.12. Tie Rods ... 69508.13, Forging ... 69

508.14. BendingandPressing ... 69508.15. ShopErectionand MatchMarking ... 69508.16. Marking and Packing ,.. 70508.17. Protection against Corrosion ... 70

509. FieldErection ,,. 72509.1. General ... 72509.2. Erection ... 72509.3. TemporarySupports ... 73509.4. Joints ... 73

Appendices

Appendix A Deleted 75

AppendixB CriticalCompressionStressC~for Sections ... 75Symmetricalabout theX-Xaxisformula

AppendixC PreparationofCamberDiagramfor Open WebSpans whichare notPredeformedandPrepara-tionofCamber Diagram and RulesforPrede-forming forPredeformed Spans ... 77

Appendix D FieldRequirements ... 80

Tables

Table 1 TotalVariation in AllowableStress ,,

Table 2 Basic Permissible Stresses inStructuralSteel ... 9

Table 3 Values of FforVariousValues offy 13

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Page No.

Table 4 AllowableWorking Stresses P~in kg/sq. mm. onElfective Cross Sectionfor axialCompression ... 13

Table 5 Values of K1 .., 15

Table 6 Values of K2 ,.. 16

Table 7 Values of9 and Bto be used forCalculating ValuesofC~inkgfsq.mm ... 17

Table 8 AllowableWorking Stress P~forDifferentValuesor Critical Stress C~ ... 18

Table 9-A AllowableAverageShearStress(P~in kgper sq. mm)in Stiffened WebofSteelConforming to iS: 226 ... 20

Table 9-B AllowableAverageShearStress(P~in kgper sq. mm)in Stiffened Web ofSteel Conforming to I.S:9 6 1 ... 21

Table 10 MaximumPermissible ValueofEquivalentStressf~in kgpermmforMildandHighTensileSteel ... 22

Table 11 Effective LengthofCompression Members ... 49

Table 12 DiameterofHolesofRivets .,. 64

Table 13 Weight of RivetHeads ... 81

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STEEL ROAD BRIDGES

INTRODUCTION

The Standard Specificationsand CodeofPractice for SteelRoad Bridges was finalised bythe Subcommittee, consistingof thefollowing personnel, attheir meetingheldat NewDelhi onthe9th,10thand 11thJuly, 1965:

K.F. Antia .., ConvenorB. BalwantRao Member-Secretary

S.P.DassD.S. DesaiS.K. Ghosh

NP,MathurN.M.Thadani

P.K. Mukherjee

S.S. Varma

The draft was considered and approved by the BridgesCommittee at their meeting held at New Delhi on the20th Oct.,1965and laterapprovedby the Executive Committeefor publica-

tion as an Indian Roads Congress Standard Specifications andCode of Practice.

Theobjectofissuing theStandardSpecificationsandCode ofPractice for Steel Road Bridgesis to establish a commonprocedurefor the designand constructionofroad bridges inIndia.

This publication ismeant to serve as a guide tobotqthe de-sign engineer andthe construction engineer but compliancewith therules therein doesnot relieve them in any wayoftheir responsibilityfor the stability and soundness ofthe structures designed anderectedby them.

Thedesignand constructionof road bridges require extensiveand thorough knowledgeofthescienceand technique involvedandshould be entrusted only to specially qualified engineers withadequatepractical experiencein bridge engineeringandcapable ofensuring careful execution ofwork.

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~Oi. GENERAL

501.1. Scope

ThisCode dealswith the use ofmildand hightensile steel in

thesuperstructureofsimply supportedroad bridges upto 125 me-tresspan between the centresofbearings. Whereappropriate, therecluirenlentSofthespeciticatioiis nay be appliedto larger spansorothertypesofsteel bridges, butcareshould betaken, inthese circ-umstances, to make necessary amendments for fixity at thesupports,continuity andother indeterminate or specialconditions.

501.2. Clearances

All bridges shall be designed withadequate clearances asspecified in the 1RC : 5 StandardSpecificationsandCodeofPracticeforRoad Bridges Section 1,Cluse 105. Otherfeatures should alsoconformto the standards laid downinother sections.

502. MATERIALS

502.1. Structural Steel

Allstructural steel shall comply withthe following IndianStandards asappropriate

IS:226Structural Steel (standard quality)

IS:2062Struetural Steel (fusionwelding quality)

IS:961Structurai Steel (high tensile)

502.2. Rivet and Rivet Bars

Allrivet andrivet barsshall conformin all respectsto iS1141Specfication for Rivet Bars for Structural PurposesandiS : 1149SpecificationforHigh TensileRivet BarsforStructuralPurposes.

Notes 1. Unless specified, mild steel rivets shall be used with mild steelstructural members and high tensile steelrivets with hightensilesteelmembers.

2 . \Vhere high tensile steel is used for rivets, steps shall betaken toensure that therivels are so manufactured thattheycould bedriven and the heads formed satisfactorily; and thatthephysicalpropertiesofthe steel are not impaired.

3. Generallythecopper content ofthe rivet steel should be inexcessofthe copper contentof the steelmembers with which they comein contact, The ma~drnum permissible percentage ofcopperinrivet steel shall be 0.6.

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502.3. Cast Steel

Theuseof cast steel shall be limited tobearings and othersimilar parts, steel for castingsshallconform to Grade 30-57 oftheIS: 1030Specificationfor Steel Castings for General En~ineeFing

Purposes.

502.4, CastIron

Cast ironshall not be used inany portionofthe stuctureexceptonly whensubject todirect compression. Suchcast ironshallconformto the requirementsofIS:210Specification for GreyIron Castings. The Grade No. of the material shallnot be lessthan 14 and its basic permissible stress shall not exceed the

GradeNo. divided by 2.54.

502.5. Forged Steel for Pins

Forged steel pins shall comply with class 3, 3a or 4 ofIS: 1875-1978andsteel forgingsshallcomplywith class 3, 3A. or 4of IS: 2004-1978.

Steel castings for steel pinsshallconformto Grade 30-57 of

iS: 1030-1974Specification ofSteel Castingfor General Engineer-ingPurposes.

502.6. Bolts andNuts

Allmild steelforbolts andnuts, whentested inaccordancewith the IS: 1608Method for Tensile Testing ofSteel Productsotherthan Sheet, Strip, Wireand Tube,shall have a tensile stre-ngthiofnot less than44kg/mm

2 and a minimumelongation of14per cent on a gauge lengthof5.65s(area.

502.6.1. Hightensile steel (structuralquality forboltsandnuts shall be manufactured from high tensile steelhaving aminimum tensile strength of 58kg/mm2 and other mechanicalproperties in accordance with the IS: 961Specification tbr HighTensileStructural Steel.

1 T o z e . 1-11g b strength friction grip boltsfor bridgeconstructionare not coveredby ths Standard. Their use may be permitted on satisfactory

evidence being produced that theysatisfy the requirements specdledby the Engineer.

502.7. Washers

Plainwashers shall be made ofsteel. Tapered or other

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specially shaped washersshall be madeofsteel or malleablecastiron.

502.8. WeldingElectrodes

Mild steel electrodes shall comply with the requirements ofthe IS: 814 Specification for Covered Electrodes for MetalArcWeldingofMildSteel,andthose forhightensile steel shall complywith IS: 1442 Covered Electrodes for the MetalArcWeldingofHigh TensileSteel.

502.9. Steelfor Parallel BarrelDrifts

Steel for parallelbarrel drifts shall haveatensilestrength of

not lessthan 55.1 kg/mm2 withanelongationofnot lessthan 20 per

centmeasured on a gauge lengthequalto 4iarea.

502.10. Deleted

503. LOADS AND STRESSES

503.1. Loads andForces tobe Taken into Account

For purposes ofcomputing stresses, thefollowingitemsshall,

whereapplicable, be taken into account in accordance withtherequirements of IRC: 5and IRC: 6 Sections IandIIofthe IRCCode of Practice for Road Bridges:

(a)Deadload

(b) Liveload

(C) Impact ordynamiceffec t oflive load

(d)Ceinrifugal force

(e)Longitudinalforces used by tractive~

effort of vehicle or by braking ofvehicles and/or those caused byrestri*int tomovementoffree bearings

(I) Temperature effect

(g) Forceson parapets

(h) Wind load(1 ) Seismic force

(j) Erectione ffec ts

Subjectto the provisions of other clauses, all forcesshall be con-sideredas appliedand all loaded lengths chosen insuch amannerthat the most adverse effect is caused on themember underconsideration. Wind and seismicforces are nottobeconsideredtoactsimultaneously.

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503.2, CombinationofLoadsand Forces

Combinations offorces to be considered are specified below:

(I) The worst possiblecombination ofdead load with liveload,impactandcentrifugal force.

(ii) The worst possible combination of any or allofthe forces listedunderClause 503.1. from (a) to(h;.

~.iii)Theworstpossiblecombinationofany or all of the forces listedunder Clause 503.1. items(a) to (g) and (1).

(iv) Theworst possiblecombinationofforces during erection.

The weight ofall permanent and temporary materials together

with all other forces andeffects ofwhich may operate on any partof thestructureduring erection shall betakeninto account.

503.3. Stresses

503.3.1. Primary Stresses : In the design oftriangulatedstructure,axialstresses inmembers are usually calculated on theassumption that all members are straight and free to rotateat the

joints;all joints lie atthe intersection ofthe centrodial axes of themembers; all loads including the weight ofmembers, are applied atthejoints. These stresses are defined as primary stresses.

503.3.2. In practice, the assumptions made in Clause 503.3.1.are not realisedandconsequently the members aresubject not onlyto axial stress but also to bendingandshearstresses. These stressesarereferredto as deformation andsecondary stresses in section.

503.3.2.1. Deformation stresses are the result of elastic

deformation ofthe structure combined with the rigidityofjoints.

503.3.2.2. Secondary stresses are the result ofeccentricity ofconnectionsandoff joint loading generally, (i.e., the loads rolling,direct on chords, sell-weight of members and wind loads onmembers).

Structures shall be designed,fabricatedanderectedin suchamanneras to minimise, as far as possible, deformation and

secondary stresses.

503.3.2.3. Secondary stresses shall be computedand com-bined with co-existent axial stresses inaccordance with the Clause504.6. but secondary stresses due to self-weightandwind on themembershallbe ignored.

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Note In computing secondary stresses due to loads being carried direct by achord, hechordm ay beassumedto be a c ntinuousgiider supportedatthepanelpoints, the resulting bending moments both atthe centreand atthe supports being takena s equal to three-fo rth ofthe maximum bend-ingmoment in a simplysupported beamofspan equalto panel length..

When desired, exactcalculationsm ay be made and thecalculated bend-ing moments used fordesign. The impact allowanceshallhe based onthe loadedlength equal to one panel length.

503.4. Deformation Stresses

503.4.1. in the case of trussmember, deformationstressesdescribed under Clause 503.3.2.1. shall beeither computedorasstnncd inaccordance with Clause 503.4.2. and added to theexistin axial stress.

503.4.2. in non-prestressed girders, the ratioof width ofthemembers intheplaneofdistortiontotheir length between centresof intersections shall preferably be notgreaterthan 1/12 fbr chordmcmbersand 1/24for webmembers. In the absenceof calculations,the deformationstressesshall beassumed not lessthan 16 per centof the deadand live load stresses.

503.4.3. As the effectiveness ofcomplete removalofdefor-knal ionstressesthroughpredeformation (prestressing) is doubtful

and the extentofrelief in thedeformationstressesthrough prede-lbrmation depends upon several factors, deformation stresses shallbe taken into consideration even when prede farming is resorted to.

503.5. Reliefof Stresses

in deternining the maximum stress in anymember ofabridge, it ispermissibletotakeintoaccountany relief afforded tothe member by adjoining parts. In determining the amount ofrelief, thesecondarystresses, ifany, in the member, shall be taken

into account and considered withother co-existent stresses. Suchreliefmaybetakeninto accountonly if the relieving parts havebeen suitably designed and are effectivelyattached to the member.

In every such case, it is necessary toconsider whether the reliefconsideredwill begiven bytheadjacent member permanently oris liable tovanish owingtoany changeinthesaidadjacentmember.

504. PERMISSIBLE STRESS

504.1. Allowable WorkingStress~for CombinationofLoadsandForces -

504.1.1. For the combination of forces given in Clause

The permissible increase in stresses permiued under this clausewillsupetsede those given under IRC : 6 Section II ofBridge Code, Clause203.

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503.2. (i), the allowableworkingstress shall be those given asbasicstresses under Clause 504.3. When secondary stressesarealsotakenintoaccount in the case of triangulated trusses, allowableworking stressesmay be increased by 16 percent.

504.1.2. For the combination of forces given inClause503.2(ii),the basicpermissible stressesgiven inClause 504.3. maybe increased by 16 percent;where the secondarystresses arealsotakeninto account, inthe case of triangulated trusses, the basicpermissible stresses given inClause 504.3. may be increased by 32

percent.

504.1.3. Forcombination offorcesspecified inClause 503.2.(iii) or 503.2. (iv) viz., for seismic and erection conditions, thestresses may beexceeded by 25 percent;whensecondarystressesarealso takeninto account in the caseof triangulated trusses. thebasicpermissible stresses may be exceeded by 40percent.

504.1.4. Stresses while lifting the spans during maintenance

in the members used for Lifting may exceed the basic permissiblestresses by not morethan2 5 per cent.

504.1.5. In no case the stress inany membershallexceedthe yield stressspecified forthe material,

504.1.6. The total variation in allowable stresses aftercombiningtheprovisionsofClauses 504.1.1 to504.1.4, are given inTable 1. Thevalues given in the table do notallow for the effectoffluctuations instress whichmust be dealtwithaccordingto Clause504.2. whilestresses arisingfromcombinations ofbendingmomentsandsheararesubject toprovisionsofClause 504.6.

504.2. Fluctuations ofStress (Fatigue)

504.2.1. General All detailsshalL be designedto aviod, asfar aspossible, stress concentrations likely to result in excessivereduction ofthefatiguestrength ofmembers or connections. Careshall be taken to avoidsuddenchangesofshapeof a member orpart of a member,especially in regions of tensile stress or localsecondary bending and steps shall betakentoavoid aerodynamicandsimilar vibratfons.

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Note Members subjected to fluctuations of stressesare liablctosuffer fromfatigue failure, this m ay be caused by loads which are very much lowerthan those which would be necessary to cause failureunder asingleapplication, lhe Initiation offatigue cracks is p r i m a r i l y d u e t o s t r e s sconcentrations introduced by the constructional details. Discontinuities

such as bolt or rivetholes,welds and otherlocalor generalchanges ingeometricalformset up suchstress concentrations from which fatiguecracks may be initiated, andthesecracks maysubsequentlypropagatethrough theconnectedorfabricated member.

TABLE t TOTAL VARIATION US Al LOwAaI F STRrSs OVER THOSEOCVEN INCLAUsE 504.3.

( 1 1 For calculatedprimarystress

(ii)Whereprimarystressesare combined with cal-culated deformationand secondarystressesofClauses 503.3.2.tand5033.2.2. (self weightand wind on memberignored)

Increase in allowable stressesfor localcombinationsasperClauses

503.2 (i) 5032.(ii)per cent percent

Noincrease~ 16

No i n c r e a s e I .

16 32

504.2.2 It is notnecessary to reduce thepermissible stressesloallow for the effect of fatigue in the following cases, mainlybecauseofthenumber offluctuations ofdesign stressesbeing smallintheanticipated lifeofthebridge

(i) Mild steel bridges,riveted orwelded;

(it) Hightensile steel bridges,rivetedconstruction,

In the case ofhightensilesteel welded construction,and inthe designofthose membersinwhichheavy reversals ofstress arelikely to occur and the predominatingstressistensile, itmaybenecessarytolower thestress atthediscretion ofthedesigner.

(a) Solid web g i r d e r s

(b) Triangulated trusses

503.2. (iii; 503.2.(iv)per cent percent

25 25

25 2 5

40 40

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504.2.3. Connections, riyetcd or bolted No allowance forfatigue shallnormally be made incalculatingthe required numberofrivetsor boLts in a riveted orboltedconnection except that allrivets orboltssubjected toreversal ofstress during the passage ofthe

liveloadshall beproportionedfor the arithmeticalsum of themaximum load plus 50 per cent of the maximum load oftheopposite sign. In the case ofwind bracing, the connections shallbe designed to resist the greater stress only.

504.2.4. Load-carrying fillet welds: Load carrying ~1lletweldsshall be designedat normalallowable stresses (not reducedon account offatigue)buttheeffective throatdepth offillet weldsshall not be smaller than0.7times thethicknessofthemember

where the connection istransmitting the fullload inthe member.

504.3. Basic Permissiblein Structural Steel: Subject totheprovisions inClause 503.3to 503.5, 504,1, 504.2, 504.4and 504.5,structures shall be so designed that the calculated stresses instructural steel do notexceedthebasicvalues given inTable 2.

TABLE 2 . BASIC PIRM1sSISL.s STRSSSES IN STIWCTUI~ALSr!as.

Mild steelconforming Hightensilesteelconform-toIS: 226 & IS: 2062 ingto IS:961 with yield

with yield stressof stressof

Description 23.6 36.2 33.1 29.9

kg/sq kg!sq kg/sq kg! sq

mm mm mm mm

1 2 4 5

I. Parts in axial tension

(a) On effectivesectionalarea 1 4 . 1 21.2 1 9 3 17.3

( b ) On netsection

bolts and studs

( i ) exceeding38 mm 14.1 19.6

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(Parts inaxialtension conid.)

(ii) exceeding28 mmbut not 38 mm

(iii) exceeding2 2 mmbut not28 mm

(iv) less than 22 mm

(C) Onrivets

2. Parts in axialcompre-session on effectivegross section

3. Parts inbending Iten-sion or compression)on effective sectionalarea forextreme fibrestress

(a)for plates, flats,t ubes, rounds,squ.ares and similarsections

(b) Forrolled beams,channels, anglesandtees,and forplate girders withsingle or multiplewebswith

d1/rnot greater

than 85 for steelconforming to IS:

226d~/znot greaterthan 75 for steelconforming to IS:961

(c)For plategirders with single ormultiple webs, with

d~tgreater than 85 forsteel

conforming to IS: 226egreaterthan 75for steel

conformingto IS: 961

23.6 21.5See a ls o Clause 5044.2.

1 4 . 1 21.2 19,3 1 73

See a ls o Clause 504.4.2.

In the above d1 the clear distance between flange angles or,~ here there areno flange angles, between flanges (ignoringfillets);but where tongue plates having a thickness notless than twice the

2 3 4 5

12.6 18.9

11.0 16.5

9.4 14.1

9.4 14.1

See Clause 504.4.1. ________

15.7 19.5

1 50 18,522.31 20.4

See al so Clause 504.42.

-I

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thickness of the web plate are used,d1 is the depth of the girder

between the flangesless the sumof the depths ofthe tongue platesor eight times the sumof the thicknesses of the tongue plates,

whichever is lesser.

and t = the web thickness

4. Parts inshear

Maximum shear str ess. (Havingregard to the distribution of 10.2 15.7 14,3 13.0stresses in conformity with theelasticbehaviourof the memberin ilexure).

Average shear s tress. (On thegross effective sectional area of 8.5 13.5 12 .2 11.0webs of plate girders rolled See alsoClause 504.5beams,channels,angles and tees). ~---,~.. .. __.._

Onpower driven shoprivet s and

turned andfitted bolts 10.2 14.1

On power driven field rivets 9.4 13.3

Onhand-drivenrivets 8.7

On black bolts 7 .9

On close tolerance bolts andturned barrelbolts 9.4 13.3

Sec also Clauses 505.2 1 .6. and 505.21.7.

5. Parts in bearing

On fiat surfaces 18.9 28.3 25.9 23.6

On powerdriven shop rivetsandturned andfitted bolts 23.6 32,2

On power driven field rivets 22.0 30.7

On hand-driven rivets 18.9

Onblack bolts 15.8

O n close tolerance bolts andturned barrel bolts 22.0 3~.7

See also Clauses 505.21.6.and 505.21.7.

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3 4 5

6. PinsEn shear 10.2 14.1

in bearing 21.2 29.9

In bending(onouter fibres) 21.2 29.9

For turned and titled knuckle pinsandspheres inbearings

On projected area 11.8 11.8

7. Weld. See Clause505.22.

504.4. Allowable Working Stresses

504.4.1. Allowable working stresses for parts in axial com-pression

The calculated average wor~ingstress in compressionmembershall not exceed the value given in Table 4 and derived from theformula given below

P__~_~__I~

i+(0.18+0.0008 -)Sec (~f.._~_._radians)

wIi crc

== allowableworking stresson effective cross section forcompresionmember

p = constant depending upon the yield stressf, ofsteel(SeeTable 3)

in = loadfactor = 1.82

E = Youngs modulus = 21,100 kg/mm2

r = leastradius ofgyration ofthe compression member

I effectivelengthofthecompression member.

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tALE3. V A L U E S 0~ roaV A R aO U S VALUBS 01!, THE YIELD STRUS 1O~MLLD STEEL AND H1GH TSNS!LF ~TUL

Y i el d stressf~ P

kg~sqmm k g / sq mm

23.6 16.5

TABLI4. ALLOWA$LE woRKi

SECT!

NO STRESSES Po.~IN kg/sq. mm ON S F

ON FOP AXIAL COMPRESSION

PECnvEcRoss

P=16.5 P= 2 4 .8 P -~ 2 2 .6 P_20.2

0 14 .00 21.00 19.15 17 .12

20 13.60 20.40 18.60 16.7 0

40 13.00 19.00 17.40 15.70

60 11.80 16.20 15.16 13,913

80 10.10 12.55 12.03 11.35

100 8.05 9.27 9.02 8.70

120 6.30 6.90 6.80 6.62

140 4.94 5.26 5.20 5.12

160 3.90 4.11 4.07 4.01

Steel

Mild steel conforming to IS : 226

FITS. conformingto IS : 9 61 36.2 24 ,8

H.LS. c o n f o r m i n g t o E S :961 33.1 2Z .9

H.T.S. c o n f o r m i n g t o I S : 961 29.9 20.2

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IRC:24-1~67

504.4.2. Allowable working stress in bending: For allsectional shapes the tensile and compressive bending stresses, fb tandf,c, calculatedaccording to Clauses 506.1. and 506.3.shall notexceed the appropriatebasic permissible stresses inClause 504.3.subjectto the provisionin Clause504.4.3. for bending compression.

504.4.3. Bendingcompression: Forsectional shapewith l~smaller than !~

where/~=momcatofinertia ofthe whole sectionabout the axis lying intheplane ofbending (theyy axis),

and 1~.=momentofinertia o(tbe whole section about theaxis normaltothe plane ofbending (the xx axis),

the compressive bending stress, f~shall not exceedthe value Poegiven in Table 8correspondIng to C~,thecriticalstressinthe com-pression element calculated as follows

504.4.3.1. For sections with a single web (including Isectionswith stiffenedor unstiffenededges,channels, angles, tees, etc., butexcluding Isections where thethicknessoftheflange is more thanthreetimes the thicknessof the other flanges)

(a) Wherethe flanges haveequal moments ofinertiaabove y-y axis

267730

(l/r~)2 ~ J [ + ...( ~) ]ic~per sq mm=A

except that the valueofC~calculated above shall be increased by20 per cent for rolledbeamsand channelsandfor plategirdersprovided that:

t~Jtis notgreater than 2

d1 /r isnot greaterthan85,for steelconforming to IS : 226

d2/s is notgreaterthan 75, for steel conforming toIS: 961d1 and t areas defined in Table 2

effective length ofcompressionflange(seeClause 506.5.)

radius of gyration about the y-y axis ofthe grosssectionofthe

wholegirder, at the point ofmaximum bending momentD overall depth ofgirder, at the point ofmaximum bendingmoment

effective thickness ofthecompression flange

K~times mean thicknessofthe horizontal portion of the compres-slon flangeat the point ofmaximum bending moment.

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(For rolled section, t,=K1 timesthe thickness given inreference

books). The co-effi.~ientK1 makes allowance for reduction inthickness of breadth offlangesbetween pointsofeffective lateralrestraint and depends on R~,the ratio of the totalareaofboth

flangesat the point ofleast bending momentto the correspondingareaat the point of greatest bending moment between such pointsofrestraint. (Forflangesofconstant area K1= I).

Flanges shall not bereducedin breadth to give a value ofR~lowerthan0.25.

ValuesofK1 for different ualues O fR~are given inTable 5 below

TABLE 5. VALUESOFK,

Ra 1.0 0.9 0,8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

K, 1.0 1.0 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2

1~fote:Where the value ofRa calculated for the comoression flangealone issmaller than thatwhen both flanges are combined, this smaller valueofRa shall be used.

(b) Where the moment of inertiaofthecompression flange about they~yaxisexoeedsthatofthe tensionflange:

267730 ~ 1 fIt. \1 2677300

(l/ry) ~s.jL 1 +~ j+L~-=A+K~B in kg. persq. mm.

whereF , r~& Dare as defined in (a) above and

effectivethicknessofflange

K, times mean thickness ofthe horizontal portionoftheflange ofgreatermomentofinertiaabout the y-y axis of the girder, at thepoint of maximum bending moment, where K, is obtained fromTable 5 above.

K,=~a coeflIcicnt to allow for inequality of tension and compressionflanges, and dependson Rm, the ratioofthemoment of inertia ofthe compression flanges alone to thatofthe sum ofthe momentsofinertia ofthe compression and tension flanges, each calculatedaboutits ownaxis parallelto they-y axis ofthegirder,at the pointofmaximum bending moment,

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Note: F ~ flangesofequal moment ofinertia

Rm0.5 and KL=0

For teesand angles

R,~=1.0and K,=0.5

Values ofK, fordifferent values ofI?,,,aregiven in Table 6 below:

TABLE 6. VALUES OFK,

R,,, 1.0 0.9 0 8 0.7 9.6 0.5 0.4 0.3 02 0. 1 0.0

K, 0.5 0.4 0.3 0.2 9. 1 0.0 0.2 0.4 0.6 0.8 1 .0

(c) Where the moment of inertia ofthe tensionflange aboul they-yaxis ~ceeds that ofthe compressionflange:

c~=[~/?~9 J[ +J(~~}+K~~ ]x~!= (4 + K,B)1~-inkg/sq.mm.

Where1, r5, D, t~&K, are a s definedin (a) & (b) above,and

y,= distance f-om the neutralaxis ofgirderto extremefibre incompress-sion.

y~=distance from neutralaxisofgirder toextreme fibre in tension.Values ofK.~for differentvaluesofR,,, are given in Table 6 above.Fortees andangles. .R,,,=0and K,=1.

Notes I . Fo r values of A and ~Bfordifferent ratios ofl/ry & DJte tobeusedforcalculatingC, in kg/sq. mm, refer Table 7,

2 Forvalues ofallowable bendig compressive strets Poe for differentvalues ofC,,seeTable 8.

~04.4.3.2. Forsectionsotherthanthosedescribed in Clause504.4.3.1. above:

a ) Where t h e s e c t i on i s sym m et r i ca l about t h ex-xaxis,the valueofC,may beobtained fromthebasicequation in Appendix, 8.

b) Where thesection isnotsymmetricalabout the x-x axis, the exactvalue of C, may becomputed;butvaluesobtainedfrom the formu-lae givenin Clause 504.4.3.1. (b)& (C)can be used with safety.

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TABLE 7. VALLJESA and BTO BE USED FOR C.~LCULATING~ALU~S o~C~in kgsq mm267730 1 1 1 267730

where A= ~ [i + ~ ( ~ ) 1 and B ~j~12Note Whereflanges are equal and ofconstant cross secLion C~=A

A

~ 8 10 12 14 - 16 18 20 25 30 35 40 50 60 80 100

4045

251.0212.5

224.6187.6

208.7 198.6172.6 162+8

191.8156.2

186.9151.5

183.2147.9

117.6142.5

174.7139.5

172.8 171.5 170.1l37~5 136.4 134.7

169.1134.0

168.4133.2

168.01329

167.4132.2

50 184.1 160.6 146-5 137.0 130+7 126.1 122.7 17.3 114.3 1 12.4 111.2 109.8 109.0 108.2 107.7 107.!

5560 t

162.4145.2

140.3124.4

126.8111.5

117.8j03.0

111.797.0

107.292.8

103.8

89.5

98784.4

95.8

81.5

93.9

797

92.6

78.4

91.2

770

90.4

76.2

89.1

75.4

89.1

75.0

88.5

74.3

65 131.5 111.8 99.5 91.3 85.7 81.6 78.3 73.2 70.4 687 67.4 66.0 65.2 64.4 63.9 63.3

70 120.0 101.4 89.8 81.9 76.4 72.4 69.5 64.4 61.6 59.8 58.6 57.3 56.5~ 55.8 553 54.6

75 110.6 93.1 81.7 74.3 69.0 65.0 6 2.0 57.3 54.5 52.8 51.7 5u.2 49.5 48.7 48.2 47.6

80 102.5 85,7 75.1 67.9 62.7 59.1 56.1 51.5 48.7 46.9 45.8 44.4 43.6 42.9 4_.5 41.9

85 95.6 79.5 69.4 62.5 57.5 53.9 51.2 46.6 43.8 42.2 41.1 39.7 38.9 38.1 37.8 37.0

90 89-5 74.3 64.6 58.0 53.1 49.6 46.9 -.2.5 39.8 38.1 37.0 35.6 34.8 34.0 33.7 33.1

95 84.3 69.6 60.3 54.0 49.3 45.8 433 38.9 36.4 34.6 33 5 32.3 31.5 307 30.4 29.6

100110

79.571.5

65.558.7

56.550.4

50.444.7

46.040.6

42,737.5

40.235.1

35.931.0

33.428.7

31.827 .1

30.726.0

29.324.7

28.523.9

27.923.1

27.422.8

26.822.2

120 65.0 53.2 45~5 40.2 36.4 33.4 31.2 27.2 250 23.5 22.4 21.1 20.3 19.7 19.2 18.6

130140150

59.755.151.3

48.744.941.7

41.638.135.4

36.5 32.933.4 30.130.9 27.7

30.127.425.2

28.025.423.3

24.221.920.0

22.019717.8

20.618.316.5

19.517.315.6

18.316.114.3

17 615.413.7

16914.612.9

16.514.312.6

15.913.7

- 12.0

160170180

47.945.042.4

38.936.434.3

32.930.729.0

28.7 25.726.8 23.925.2 224

23.321.620.2

21.419.818.6

18.316.915.6

16.215.013.9

15.013.712.6

14.012.811.7

12.911.710.6

12.111.0

9.9

11.510.2

9.3

11.29.99.0

10.49.38.2

19020021022

I 2302 4 0

40238.036.234.532.931.5

32.430.729.127.726.525.4

27.2j 25.824.623.322 .221.2

23.822.421.320,219.218.4

21.119.818.918.017.016.2

19.118.017.016,1

15.314.6

17.516.415.414.614.013.4

14.613.712.912.311.511.0

12.912.011.310.610 1

9 .6

11.710.910.2

9.69.08 .5

10.910.19.48.8827.7

9.89.08.37.77.26.8

9.18.37.77.16.66.3

8.37.77.16.5605.7

8.0

7.46.86.15.75.4

7.4

6.86.15.5504.7

2 502602 70280290300

30.229.1

28.026.926 025.2

24.423.322.521.721.020.2

20.519.518.9

18.!17.5

- 16.9~

17.6

16.916.215.615.11-.6

15.6

15.014313.713.2128

14.013.4

12.912412.011.5

12.812 I11.711.210.910.4

10.610.196

918.88 .5

9.18 .7

827,9767.2

8 .07.77.46.96.86,4

7.46.96.86.36. 158

6 56.1

585.5

5.25.0

5.85.55.24,94.74.4

5.24.94.64.44.1

3 .9

4 9 4.346 3.943 3.64 .1 3 .43 8 3.236 3.0

c >t.~

P~

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TAI3LE 8. ALLOWABLE WORKING STRESS P~.FO R

CRITICAL STRESS C,

3456789

1012141618

202224262830354045505560

6570758090

100125150200215

(SEETAB~s 2)

1.52.02.53.03.53.84.24.65.36.06.77.2

7.68.08.48.89.29.6

10.511.2

11.912.412.913.3

13.613.914.114.414.915.3

15.815.8

15.815.8

DIPFE1tENT VALUES OF

1.52.02.53.03.53.84.24.65.46.27.07.7

8.49.09.6

10.210.811.412.713.714.615.315.916.5

17.117.417.818.218.819.420.521.222.222.4

C~ P~forsteel conforming P~forsteel conforming

kg/sq. mm

to IS 226 to IS 961

kg/sq. mm kg/sq.mm

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504.5. Working Shear Stresses In SolidWeb Plates

(a) 4verageshear stress: The calculated average shear stress .(. onthe effective section areaoftheweb shall not exceed the value given

In Clause 504.3. Table2 orinthe case of stiffened webs, the valuePq given bythefollowingequations,whicheveri s t h e le s s :

F, i n k g per mm i (i.3_. ~ bK4l+*(~a) }

where

a thegreater dimensionofthe web in a panelnotgreater than 270 t

b = t h e lesserclear dimensionoftheweb in a panel not greater than

1 8 0 :

= thickness ofweb

K, = 9.5 f o r m i l d s t e e l c o n f o r m i n g t o IS : 2 2 6 & 1 3 . 5 f o r H . T . S . conform-

i n g t o I S : 961

K, = 2 5 0 f o r m i l d s t e e l c o n f o r m i n g t oI S : 226 & 200forH.T.S. conform-i n g to IS :961

For stiffened webs,valueofP, for varying ratiosofdepthofpanel d t o thickness ofwebt and v a r i o u sspacingsof stiff~ne~rsaregivenin Table9A for steels conforming to IS : 226and in Table 9Bfor steels conforming toIS: 961 where the depth ofpanel d isdefinedasfollows:

(i) Forw eb s withouthorizontalstiffeners,dis the clear distancebe tweenflange a n g l e s o r , w h e r e there a r e no flangeangles, between flanges~igaoringfillets);but where tongue plates having a thickness notleu than twice the thickness of web pldteare used, disthe depthofth egirderbetweenthe fla n g e s le s s t h e sum o f t h e depths o f t h etongue plates or eighttimes t h e sum o fthe thickness o f t h e tongueplates,whicheveris the less.

iii) For webs with horizontal stiffeners,dis the clear distance betweent h e te nsionflange(anglesor flange plateor tongue plates) and thehorizontalstiffener.

Not. Forthe mjnfmumtWckness ofwebp l a t e s a n d t h e design o f w e b s t i f f e n-era,see Clause506.6.1 to506,6.4.

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TABI.a 9A. ALLOWABLE AVKRAOE SHEAR STRESS

INSTIF~ENBDWsas OFSTEEL, CONFORMING T O IS : 226

hO

130

150

170

1 9 0

200

220

0.4c/ O.6d~ 08d

8.7 87 8.7

8,7 8.7 8.7

8 . 7 8.7 83

8.7 8.7 8,3

8.7 8,7 7.9

8.7 8.5 7.7

8 . 7 8 . 0 7 . 3

8.7 7.7

I .Sd

8.7

8 . 2

~7~5

7.0

dltStress Fqkg/mm

2fordifferent distances betweenstiffeners

d

8.7

8.7

8.5

1 .2d

8.7

8.1

8,0

1.6

l.4d

8.7

8.4

7.7

7.2

7.5

240

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TABLE9 B . Au.owABLa AVERAGESR sA J~STttzssIN

STIFFENED WEBS OF STEEL CONFORMING TOIS : 961

Stress Pgkg!mmfordifferent distances between

dft stiffeners

0.33d 0.44 0 . 6 d 0.8d d l.2d 1.44 1.5d

80 12.6 12.6 12.6 12.6 12.6 112.6 12.6 12.6

100 12.6 12.6 12.6 12,6 12.6 12.5 123 12.0

110 12.6 12.6 12.6 12.6 12.5 12.0 11.5 11.4

1 3 0 12.6 12.6 12.6 12.1 11.7 11.0 10.4 10.3

150 12.6 12.6 12.3 11.4 10.7 9.9 9.4

-~

170 12 ,6 12 .6 11.7 10.6 9.8 9.0

190 12.6 12,6 10.9 9.8 9.0

12.6 12.6 10.6 9.2

12.6 12.0 10.0 8.5

12.4 11.5 93

IRC: 241961

200

220

240

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504.6. CombIned Stresses

504.6.1. BendIng and axialstresses: Members subjected toboth axial and bending stresses (compressive or tensile) shall be

soproportioned thatthe quantity-- + IL does not exceed unity

Fa Fbwhere

fl = calculated axial stress (compressive ortensile)

F. = appropriate allowable working stress in axiallyloaded members

f~= calculated maximum bending ~comprcssive or tensile) stresses aboutbo t h pr i n c i pa laxes including secondaryS tresses,ifany~and

= the appropriateallowableworkingstress inbending(compressive ortensile).Where an increase o r r ed uct i o n in permissiblewor kin g St r e s s i s spec i-fi e d bo t h F~and F~shall be t h e increased or reduced w o r k i n g stressas directed in therelevant Clauses.

504.6.2. shear and bendingstresses: The equivalentstressf~.(see Clause 504.6.4). due t o a combination of shear s t r e s s fbending stress,f,tensile or compressive, is calculated from

fe 3f,2504.6.3. Shear~bearing and bending stresses: The equiva-

lent stress f~(see Clause 504.6.4) due to a combination of shearstressf.,bearingstress!

5andbending stressfb, tensile or conipres-sive iscalculatedfrom

+f5

2+fj,+3f~~

504.6.4, Irrespectiveofthe permissibleincrease of stress inother Clauses the equivalLut stressf~calculated in Clause 504.6.3.above shall not exceed the values given in Table 10.

TABLE 10. THE MAXIMUM PERM ISSIBE.B VALUE 05 EQIJ!VFILBNT$TRE$Sf,pop.MILD AND HIGH TENSILE ETSEL

Qua l i t y o f steel

Mild steel

Y i el d s t r e s s Maxva l ue o f f .

kgjsq. mm kg/sq. mm

23.6 22.0

High tensile steel 36.233.12.99

33.129.926.8

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11W 24.1967

504.7. Deleted

504.8. I)eleted

504.9. Deleted

504.10. D e l e t e d

504.11. Deleted

505. DESIGN OF GENERAL DETMLS

50 5. 1 . E f f e c t ive Span s

The effectivespan shallbe

C i) formain girders t h e d ista nce between the centres ofbearing platesorrockcrpins,

(ii) forcross members, t h e distance between the centresofthe maingirdersor trusses,

(iii) for roud bearers, the distance between the centres ofthe crossmembers,

(iv) for decking, the distance between the centres ofthe road bearers,and

(v) for pins in bending, the distance betweenthecentres ofbearings;butwhere pins pass throughbearing plates having thicknessesgreaterthan halfthe diameter ofthe pins, co sideration may by given tothe ef f ec t ofthe distribution ofbearing pressures on effective span.

Note Where a cross member orbearer terminates onan abutmentor pier,the centres ofthe bearing there n shall be takenasone end o ttheeffe-ctivespan.

505.2. EffectiveDepth

Theeffectivedepth ofplateortrussgirderrhould be taken asthe distancebetween the centres ofgravity of the upperand 1owe~flangesor chord~.

505.3. Minimum Dep%

The minimum depth preferably shall not he less thanthe

following:

tO For trusses 1/10thofeffective spsn

(ii) F o r r olle d steel j oi s t s

and plategriders = I ~25ofeffectivespan(iiij Forcnmpostite steel = as specified in the relevant

and concrete section.

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505.4. Spacing and DepthofM ain Girders

The distanceofcentres between the main girders should besufficient to resist overturing with the specified lateral forces and

loading conditions. Otherwise special provision must bemadeto

prevent this.This distance shall not be lessthan L2Othofthe span.

The depth between the gravity axesofthe topandbottomchordofopen web girders shall not be greaterthan threetimes thedistance between the centresofmaingirders.

505.5. Symmetry

All sectionsshall,asfar as possible, besymmetrical abou tthe line ofresultant stress, andall rivets shall be grouped symme-trically aboutthe sameline.

5 0 5 . 6 . Minimum S e c t i o n s

505.6.1. Noplate or rolledsections less than8mm thicknessshall be used in the main members of the bridgestructurewhenboth sides are accessible for paintingnor lessthan 10 mm whenonly one side is accessibleexcept when it is riveted or welded toanotherplate or rolled section. In floor plates and parapets aminimum thickness of 6mm may be used if both sides are exposedor 8 mm ifonly one side is exposed. For packing plates, thethicknessshall not belessthan 1.5 mm.

505.6.2. No angleless 75x 50 mm shall be used Ibr the maingirders or trusses in riveted construction.

505.6.3, No angleless than65 mmx45 mm nor flatlessthan50mm wide should be used in any part ofthe structure excepthandrailing.

505.6.4. End angles connecting road bearersto crossgirdersor cross girderstomaingirder should be not less inthicknessthanthreequartersofthicknessof the web ofbearer and cross girdersrespectively.

505.7. Corrosion

All the details shall be designed to reduce toa minimumthe incidence of corrosion. All parts should be accessible forinspection, cleaningand painting; otherwise they should be adequa-telyprotected or effectivelysealed.

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505.8. Drainage

Adequate drainage shall be pro v i d e d atall placeswhere

pocketsofdepressions are likely to hold water.

505.9. DeflectIon

505.9.1. Rolled steel beams, p l a t e g i r d er s and la t t i c e girders,shall be designed sothatthetotal deflectiondueto liveload andimpact shall notexceed 1/800thofthespan.

505.9.2. The deflectionof cantilever arms due to liveloadand impact shall not exceed 1/400th ofthe cantilever arm.

505.9.3. In calculating deflection to comply with Clauses505.9.1.and 505.9.2. above, the side-walkLive-loadmay be igno-red. The gross moment of inertia shall be used for calculatingthe deflection of beams or plate girders. In calculating thedeflection of trusses, the gross area of each member should beused.

505.10. Camber

Camber maybe required tomaintain clearanceunderallconditionsofloading or it may be required on accountofappear-

ance. It may also result from prestressing. Beams and plategirders of sptins uptoand including 35 m need not be cambered.In the case ofopen web spans, camber, ifany, shall be provided asrequired under Clause507.8.

505.11, Provision for Temperature Changes

505.11.1. Every span should be provided withmeans so asto permit all longitudinal expansionandcontraction due to change

oftemperature over a range specified in Clause 218.4 (a) of IRC

6Standard Specificationsand Codeof Practice for Road BridgesSection II combined with the greatest extension orcontraction ofthe supported chord due tolive load including impact.

505.11.2. Deleted

505.11.3. Deleted

505.11.4. Deleted

505.11.5. Deleted

505.12. SpacIng ofTrussesand Girders

The distance between the centresoftrusses orgirders shall besufficient to prevent overturing or overstressing due tolateralforces.

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TR C : 24 - 1967

505.13. Anchorage

Anchorand fixing bolts shall be providedwhererequiredtoresistallforces whichmayacton them. Anchorage shall providethestability equivalentto 50per centin excessofanypossible over-

turningmomentofthespan as a whole orofthebearingsdueto allpossibleloadsduring theservice ofthebridge.

505.14. Effective Length ofStruts

For th~puropseof determining allowable axial stress, theeffective length /ofa compression member shall be taken asfollows

(a) Effectively held in position and restrained in direction at bothends, 1 = - 0.7L

(b) Effectivelyheld in positionatbothendsand restrained indirectionat oneend, 1=0,85L

( c ) E ffe c t i v e ly h el d i n p o si t i o n a t both end s but n o t restrained i n directon, 1=L

(d Effectively held in position and restrained in direction at one end, att h e o t h er e n d pa r t i a lly restrained i n d i r ect i o n but n o t h el d i npos i t i on , 1=1.5 L

(c~Effectively held inpositionand restrained indirection at one endbut notheld in position or restrained in direction at theother

end, /=2 Lwhere

L= .. length of strut from c ent re to cent re of intersection withsupporting members or la ter a l s u ppor t s .

For battened strutsthe effective length 1, given above,shallbe increased by 10 ner cent. (See also Clauses 507.3.3. and507.3.4.).

505.15. EffectIveSectional Area505.15.1. The gross sectional area shall be theareaofthe

crosssection ascalculated from specified sizes. (See alsoClause505.21).

505.15.2. Effective sectional areaofa member o f f l a n g e intensionshall be thegrosssection areawiththe following..,deductionas appropriate:

(i) Deductionsforriiet and bolt holes

Except as required by the following paragraph,theareastobededucted sha~1be the sumofthe sectionalareas of the maximumnumber ofholes inanycrosssectionatright angle to the directionofstress in the member.

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lRC: 24-1967

ln the caseof:

all axially loaded tension members,

plate girdersofmild steeL conforming to IS : 2 2 6 or lS : 2062and with d1/tgreaterthan85,

plate girders of steel conforming to IS : 961 and with d1( t greater than 75,

theareato be deducted whentheholesarestaggered shall bethatgivenabove, or ifgreater, thesum ofthe sectional areasof all holeson any zig-zag line extending progressively across the member orpartot the member, less S

2t~4Gfor each gauge space in the chainof holes,

where d1 = the clear distance be tween flange angles or, wherethere a r e no

fla n g e a n g l e s , t h e c l e a r d i s t a n c e betv~eentheflanges

S = t h e s t a g g e r e d p i tc h , ie . , t h e distance, centre tocentre ofholes inc on s e c u t i v e li n es measured parallel tothe direction of stress in themember.

t h e t h i c k n e s s of t h e material,and

C = t h e g a u g e , i . e . , t h e distance,centre to centre ofholes in consecutivelines measured at right angles to the direction of stressin themember.

Forsectionssuch as angleswithholesin both legs,the gauge shallbemeasuredalong thecentre ofthe thicknessofthe section.

in a built-upmember wheretiV~chainsofholes considered in

individual parts do not correspond with the critical chain of holesfor the member as a whole, the valueofanyrivets or bolts joiningt h e pa rt s between such ch a i n s o f h o l es s h a ll be t a k en i n t o accountindetermining thestrength ofthe member.

(ii) Deductions for a tingle angle connectedthrough one leg

To allow for ecentricity ofconnection, the areaofthe un-connected leg shall bemultiplied by

30,3a~+a~

w h er e a t = netarea ofconnected lega 2 = areaof unconnected l e g .

Where lug angles are used, the wholeareaofthe membershall betaken as effective.

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505.16. Floor Beams

All floor beams shall be rolled, riveted or welded steelgirdersrigidly connected to the trusses or may be placed on top

of trusses or the girders. Floorbeams maypreferably be squareto trusses or the girders.

505.17. Joists and Stringers

505.17.1. Stringers shall be of steel. They shall be securelyfastened to cross beams excepting wherearrangements are made topermit ofexpansion. Suitable arrangements for supporting suchstringers shall be designed.

505.17.2 Stringers should have free ends below the expan-sionjoints in decking.

505.17.3. For steel decking over stringers, the limit of spanlengths in which steel stringerscan be riveted continuously to thecross girders fromendtoendofspan, shall be 30metres. Beyondthislimit, sliding bearings should be providedatone or moreinter-mediate points.

505.18. Bracing

505. 18.1. In all spans, bracings shall be provided to trans-mit to the piers or abutments the effectofthelateraland longitudi-nal forces. Wherever theoverhead clearance permits, lateraldiago-nalbracing shouldpreferably be provided in the planes of bothu p p e r and lower chordsofthroughspans.

The floor systemmaybetakenas partofthe bracing system

provided it is designed forthat purpose.

Wherever thedepthofthegirder allows, intermediate swaybracing may beprovided. Ifit isprovided, itshall not betaken asaffording any relief to the lateral system unless the stressesarecalculated for the complete space frame. Sway bracingwhenp r o v i d e d shall be p r o p o r ti o n e d t otransmitto the chord supportedon bearings through the web membersatleast 50 per cent o thepanel lateral load and thevertical membersshallbe designed to

resist the resultingbendingmoment.

505.18.2. Thelateralbracing between compression chordsshall be designed to resist a transverseshearatanysectionequalto2~per cent of the total compressive forcecarriedbyboththe flangeor chords at the sectionunder consideration. This force should beccms~deredin addition to the windand centrifugal forces.

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505.18.3. Where the restraint is provided by members, later-allyconnected to the chord or beam, such members shall be capa-ble ofresisting the above lateral forceapportionedequally to eachpointofrestraintandshall be sobraced or connected to the other

partsofthe structure as to becapableofresisting thislateral force.

505.18,4. Through truss spans shall be provided with portalbracings, as deep astheclearancewillallow. Theportal bracings h a ll be designed to take the full end reactionofthe top chordlateral systemandtheendpostsoftheportalshall be designed totransfer this reaction to the bearings. In addition, the portalsystem shall be designed to resist a lateral shearequal toIf percent of thetotal compressive force in theend posts or in the top

chords i n t h e end p a n el whichever i s greater.

505.19. End Cross Girders

505.19.1. Endcross girders or cross frames shall be providedin all squareendedtrussand girder spansandas far as possible inskew spans. These shallpreferablybe designedto permit the use of

jacks for lifting the superstructure for lubricatingand greasingofbearings. For this,the allowable stress may be increased by

25 per cent. The end cross girders shall bearranged to permitpaintingofthesideof the beam adjacent to the abutment backwall.

505.19.2. in skew bridges, without end girders, the endpanel stringers shall be secured incorrect position by end strutsconnected to the stringersandto the main trusses or girders. Theend panel lateral bracing shall beattachedtothe main trusses orgirdersandalso to the end struts. Adequate provision shall be

madeforexpansion movementofthe stringers.505.19 .3. Whenendcrossgirdersare provided, they shall be

designed to resist forces from the live load taken as not smallerthanthose for which theintermediatecrossgirders aredesigned.

505.19.4. Cross girdersandcross frames shall also be pro-videdatintermediatepoints along the length of girder where thereis a breakin the decking for expansion joints.

505.20. Plates In Compression

505.20.1. The unsupported width of aplatemeasured bet-weenadjacentlinesofrivets, bolts or welds connecting the plate toother partsofthesections shallpreferably notexceed 45twhere t isthe thicknessofa single plate or the aggregate thickness of two or

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more plates provided theseplates areadequatelytacked together.Any excess over this width shall not beincludedin the effectivesectional area in computing the direct compressive stress (Clause507.2.1.4).

505.20.2. The unsupported projection ofany plate measuredirom its edge to the line of rivets or weld connecting the plate toother parts ofthe scctions shall not exceed 16t forsteel conformingto the IS 226Specification forStructural Steel and 14t for hightensile steel conforming to the IS 961 -Specification for HighTensileStructural Steel, t being the thickness of the plate.

505.21. Riveting andBolting

505.2 1.1. Effective diameter of rivets, bolts andpins: incalculating the number of rivets, bolts or pins required, the effectivediameter shall betakenas

(a) for rivets, thediameter ofthe hole,(b) for boltsandpins,thediameter ofthebolt or pin.

Rivets, bolts or pins indoubleshear shall be considered ashavingtwicetheshear areaofthose in single shear.

Theeffectivebearingarea ofapin, rivet orboltshall be thediameter multiplied by the thickness of the part transmitting orreceivingthe load,exccptthatforrivets or bolts with countersunkheadshalfthe depthofthe countersink shall be ignored in arrivingatthelengthinbearing.

505.2 1.2. Deductions forholesforrivets, bolt andpins: In~a1culatingthe area to be deducted for rivets,bolts or pins, thefollowingdiametersofholeshall beused

(i) forshoprivets,the diameterofthehole shall beapplied,

(ii)for coubtersunlcrivetsor bolts, the diameterofthe holeshall betakenas 3 inn:largerthanthatofthe rivetor the bolt, and

(iii) for turned and fitted bolts, the diameter of the h ole shallbe takenasthediam:ter ofthebolt,

505.21.3. Minimum pitch ofrivetsandbolts: Thedistance

hctwecncentresofrivets or boltsshall be not less than 2f timesthe diameter ofthe rivet or bolt hole.

505.2 1.4. Maxinuun pitch of rivets and bolts

(a) Thedistance betweencentresef anytwoadjacentrivetsL

1: boltsconnecting togetherelementsin contactofcompression or

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tension members shall not exceed 32t or 300 mm whicheveris thelesser, where t is thethickness ofthethinner outsideelement.

(b) Thedistancebetween centres oftwo adjacentrivetsorbolts in a line lying inthe direction ofstress shall not exceed 161

or 200mm intension membersand 12 t or 200 mm in compressionmembers. For those compression members in which forces aretransferred through butting facesthis distance shall not exceed 44times the diameter of the rivets or bolts for a distance from theabutting facesequalto Ii times the widthofthe member,

(c) The distance between centresofany two consecutiverivets or bolts in a lineadjacent toand parallelto an edge of anoutside plate shall notexceed 100 mm + 41, or 200 mm whicheveris the lesser, in compression or tension members,

(d) When rivets or bolts are staggeredatequalintervalsandthe gauge does notexceed 75 mm, the distance between centresof rivets or bolts, as specified in (b) and (c) above may be in-creasd by 50 per cent,

505.2 1.5. Edge distance: The minimum distance from thecentreofany hole to the edgeofanelement shall be l~ t i m es t h ediameter of the hole for sheared orhand flame cut edgeand 4timesthe diameter of the hole for a rolled, machine flame cut,sawn or planed edge. Where two or moreparts are connectedtogether, a lineofrivets or boltsshallbe providedata distance ofnot more than38.0mrn+4t from the nearest edge, where t isthethicknessof the thinner outside plate.

505.2 1 , 6 . Rivets or b o l t s throughpackin g The number o f

rivets orboltstransmitting shear through packingshall be increased

above the numberrequired by normal calculations by 2 per centfor each 1.5mmthicknessofpacking, exceptthat forpackings6.0mm or less thick, no increase shall bemade,

For double shear connections packed on bothsides, thenumberofadditional rivetsorboltsrequired shall be determinedfromthethickness ofthe thickerpacking.

The additional rivets or bolts may beplaced in an extensionofthe packing.

505.21.7. Long grip rivets: The grip of rivets carryingcalculated loads shall not exceed eight times the diameter of theholes. Where the gripexceeds sixtimes the diameter of the holes,

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the number of rivets required by normal calculations shall beincreased by not less t h a n one per cent foreach additionaL 1.5 mmofgrip.

505.21.8. Rivets in tension The use of rivets intension

should be avoided whereverpossible, but if their use is unaviod-able, the stress shall notexceed than that specified in Clause 504.3.

505.21.9. Securing! nuts : Where there is a risk ofnuts be-coming loose, they shall besecured.

505.22. Welding : The design of welds in steel shallgenerally be as perIRS s%eldlngcode

505.22.1. Working stresses in weldedjoints: The workingstress shall hebased on thefollowingpermissibe stresses for staticloads

Compression or tension 14.! kg per sq. mm

Sheir in butt or fillet welds other 10.2 kg persq. mmthan in websplicesofbeams &plategirders

Shear in butt or filletwelds in 8.5 kg per sq.m m

web splicesofbeams & plategirders

505.22.2. Paekings in welded construction : Where a pack-ing is used between two parts the pa~kmgandthe welds connecting it to each part shall be capable oftransmittingtheloads betweenthe parts except where the packing is too thin tocarry the lOad orpermit the provision ofadequatewelds,whenit shall be trimmedflush with the edgc of the narrowerpart andthe load shall be

transmitted through the welds abut thewelds being increased insize by an amount equal to the thicknessof thepacking.

505.22.3. Intermittent frau ~~velds: intermittent buttwelds

shallnotbeused.

505.22.4. Fillet weds

505,22.4.1. End returns: Filletweldsbroughtupto acorner

atthe ends orsides ofparts ofmembers shall, where practicable,he continued around the corner for n distance of not lessthantwicethe size olthe weld.

505.22.4.2. End connections bymeans ofsideflflets: Ifsidefillets ilonc are used in endconnections the lennth of each side

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fillet should be not lcssthan thedistancebetween the fillets. Sidefillets may be eitherat theedges of the members or in slots orholes.

505.22.4.3. intermittentfillet welds Intermittentfilletweldsshallnothe used wheretheywould result intheformation of rust

pockets. The distance along an edge of apartbetween effectivelengthsofaconsecutive intermittentfilletwelds,whether the weldsare in line or staggered on alternate sides oftheedge,shallnotexceed 12 timesthethicknessofthe thinner part when in compres-sion or 16 times the thicknessofthe thinnerpartwhen intension,andshall in nocaseexceed 2 00 mm.

505.22.4.4. Where intermittentfilletwelds areused toformT-joints, thethicknessreferred to aboveshall bethat of Ihe tableof the T. In a line of intermittentfilletwelds, thereshall be aweld attheendsofthe partconnected;forwelds staggered alongtwoedges,thisshallapplytobothedges.

505.22.4.5. in built-up members in which platesare con-nected by intermittentfilletwelds,continuous sidefilletweldsshallhe used at the endsfora length not lessthanthe width ofthe plate

concerned.

505.22.5. T - but t j oi n t s : Butt, welds in T-joints shall becompleted by means offilletweldseachhaving aleg length ofnotless than 25 percent ofthethickness oftheoutstanding part.

505.22.6. Testingofwelds

505.22.6.1. X-ray tests or any other non-destructive tests

may also becarried out to ensure soundness of welds. Weldswhichare required tocarrytensile orshear stressesin excessof66~percent ofthoselaid downinClause505.22.1.shall be examinedby means ofX-rays orsomeequally effectivemethod.

505.23. Lug .kngles

505.23.1. Lug angles connecting a channel or similarmember shall, as far aspossible, be disposed symmetrically with

respectto the section ofthe member.

In the case ofanglemembers, the luganglesand their con-nectionto the gussetorother supportingmember, shall be capableof developing astrengthnot Lessthan 20 percent inexcess oftheforce in the outstandinglugofthe angle, and the attachment of

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the lug angles tothe angle member shall becapableofdevelopinga strength 40 per cent in:exCess o f t h a t force.

505.23.2. In the caseofchannel o r s i m i l a r m e m b e r s , t h e lugangles, and t h e i r connection t o t he g usset o r o t h er supportingmember, shall be capable o f developing a st r en g t h no t le s s than 1 0p er cen t i n excess o f t h e force no t accounted for by the directconnection o f t h e member,andtheattachment of the lugangles tothe member shall be capableofdeveloping a strength 20 percentin excess o f t h a t for c e .

505.23.3. In no case, less thantwobolts orrivetsshallbeused for attaching the lug angle to the gusset or other supportingmember. -

505.23.4. The effective connection of the tug angleshall,asfa r a s possible t er m i n a t e a t t h e e nd o f t h e member connected, andt h e f a st en i n g o f t h e lug angle t o t h e member s h a ll p r ef er a bl y s t a r ti n advance o f t h e direct connection o f t h e member t o t h e gusset,etc.

505.24. ClevlsesandTurn Buckles

Clevises and turn buckles s h a ll i n a ll cases dev elo p t h e fu ll

strength o f t h e ba r s of which t h ey f o r m a pa r t .

505.25. Pins

All p i n s o f more than 2 30 mm diameter s h a ll hav e an i n s p e c -tion hole of notless than 50 mm in diameter through the axisunless o t h er means o f i n spect i o n a r e p r o v i d e d .

505.26. CompositeUse ofMildSteelandHighTensileSteelSt e e l c o n f o r m i n g t o I S 2 2 6 an d IS 2062andhightensile steel

conforming to IS:961 may be usedjointly in a structure or in anymember o f a structure p r o v i d e d t h a t t h e maximum s t r e s s i n each

elementdoes not exceed theappropriate permissiblestress.

505.27. Composite Action of SteelandConcrete

Where steel construction is used inconjunctionwith concreteand provision ismadefor adequate interaction between the twomaterials, they shall be treatedas forming a compositememberfor t h e p u r p o se o f calculation.

In such c a s e s , t h e co n st r uct i o n wi ll comply w it h requirementsofthe IRC: 22Standard Specifications&Code of Practice for

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Road Bridges Scetion VI -Composite Construction for RoadCulvertsand Medium Span Bridges.

505.28. Composite Connections

In connections With morethanone typeoffastening, trans-mittin& a forcedirect,thefollowingrequirementshall be compliedwith:

(a) Rhets with close tolerance bolts. The force may beconsidered assharedproportionately betweenthe rivetsandthebolts.

(b) Rivets or close tolerance bolLc with black bolts: Therivetsor closetolerance bolts shall be designed totransmitt h e en ti r e f o r c e.

(c) Welds with anyother tppe ofconnection: The welds shall bedesignedto transmit the entire force.

506. SOLID WEB GIRDERS (PLATE GIRDERS ANDROLLED BEAMS)

506. 1 General

506.1.1, ProportIoning: Solid web girders shall be proport-ioned onthebasis ofthe moment ofinertia ofthe gross sectionwith theneutral axisat the centroid of thesection. Incomputingthe maximum stress, the stresses calculatedon this basis shallbe increased in the ratio of gross to effective,areaofthe flangesection.

506.1.2. The fldngesectional area inrivetedor bolted cons-truction shall betaken to be that ofthe flangeplates,flange anglesandthe portion ofthe web and side plates, ifany, betweenthe

f l a n g e a n g l e s . I n welded co n st r uct i o n , t h e f l a n g e sectional areas h a ll be taken t o be t h a t o f t h e f la n ge p la t es and o f t h e tongueplates (thick vertical plates connecting flange to web) ifany, up toalimitof8timestheirthickness whichshall notbe less than twicet h a t o f t h e web (Clause 506.4 .) .

506.1.3. The e ffe c t i v e sectional area o f compression fla g e ss h a ll be t h e g r o ss area w i t h t h e specified deduction for excessivewidth of pl at es (Clause 505.20.) and t h e maximum deduction for

o p e n h o l es and h o l es for bl a ck bolts occurringi n a section perpend-i c u la r t o t h e a x i s o f t h e member (Clause 505. 21.2.) .

506.1.4, Theeffectivesectional areaof tension flanges shallbe the grosssectional area with deductions for all holes as specifiedfor r i v e t and bolt h o l es i n t en si o n m e m b e r s .

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506.2. MaximumAverage Shear Stress

Maximum shear stress shall be calculated as follows

(a) in case of rolled beamsand channels, it shall beequaltothemaxi-

mumsheardividedbythe productofthe thicknessofthe webandthe overalldepthofsection.

~b) In caseof websof plate girders, it shall be the maxintuntsheardivided by the productofthe thickness ofwebandthe full depthofwebplate.

(c) inthe case of webshaving varied thickness in the depthofthesection byuse oftongue plates andthe like andin thecaseofothersections, the maximum shear stress shall befound bydeterminingthe distribution ofshearstressesover the depthofthesection.

.Vo:c: Webs having openings largerthan those usedfor rivets, bolts or otherfasteningsrequire special consideration and arenot covered here.

506.3. SlendernessRatio

!)r~,ofa girder shall not exceed 300. It shall not exceed 150forcantilevers.

Where / = the effective length ofthe compressionflangeas

specified in Clause 506.5.

p9 the radiusof gyration of the whole girder about

its y-yaxis based on the gross moment of inertiaandthe gross sectional area.

506.4. Flanges

506.4.1. Section

506.4.1.1. SectIon in riveted orboltedconstruction

Flange angles shall preferably form as large a part of the

area ofthe flange as practicable and the number offlange platesshallbekepttoa minimum. Where flange platesareused,theyshallpreferablybe ofequal thicknessandatleast one plateofthetopflange shall extend to the full length ofthe girder unless thetop edge of the web is finished flush with flange angles.

506.4.1.2. Section in weldedconstruction

Eachflange shallpreferably consist ofa single plate unless aplateofsuitablethickness isnot available. Thissingle platemayconsistofmorethan oneplatelaid endto endeffectivelyunited attheir junction.

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ln thc case of welded plates, the ends of the plate shalt betaken to a pointto preventlines ofwelds at anglesto the lines ofstrc ss.

506.4.4. Splices

506.4.4.!. Flange jointsshouldpreferably not belocated atpoints ofmaximumstress.

506.4.4.2. Wherecover plates are used, theircross sectionalareashallbenot lessthan the area oftheflangeelementsplicedand thecalculated working stressin the outer covers shallnotexceed the allowable working stress in the flange. Both in thetensionandcompression flanges,there shall be enough rivets orbolts on each side ofthe splice to develop the effective strength ofthe member spliced. In weldedconstruction, the flange plates shallbejoined by butt welds whereverpossibleand these shall developthe full strength of the sniallerplate.

506.4.5. ConnectIon offlanges toweb: The flanges of plategirders shall be connected tothe web by sufficient rivets, bolts

or welds totransmit the horizontal shear force combined withany vertical loads which are directly applied to the flange.

In case oflocal loading, on the top flange,the rivets, in addi-tion to the stress caused by thetransferring ofweb stresses, are alsostresscd by the vertical action ofthe flange angle beingpresseddown by theload transferring media and the consequentdown-ward pressure on the web should be accounted forby takingthe weightof one of the wheel loads as distributed overa lengthof900mm.

In welded construction, where the web is in close contact withthe flange before welding, vertical loads causing compressionmay be deemed to be resisted by thebearing between the flangeand web.

506.5. Effective Length ofCompression Flanges

The effective length iofthe compression flange forbucklingnormal to the plane of the girder to be used shall be as given inClause 506.5.1. to 506.5.5. except that, when theload is applied tothe compression flange and both the loadand the flange arefree to movelaterally,the values given shall be increased by 20percent.

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506.5.1. Simplysupported girders with no intermediate lateralsupport to compression flange : For simply supported girderswithno lateral bracing between compression flanges and no crossframes,but with each end restrained against torsion (see Clause

506.5,1.1.)(a) with endsofcompression flanges unrestrainedagainst lateralbending

(ic.,freeto r ot a t e inplan atthebearing,..... I=span

(b) withendsofcompression flanges partiallyrestrainedagainst lateral

bending ~e.g.,securely cleatedconnections)..,.,1=0.85span

(c) with endsofcompression flanges fullyrestrainedagainst lateral ben-

ding (i.e.,notfree torotate inplanat thebearing)..,..1=07span

506.5.1.1. Restraint against torsion at thesupports can beprovided byweborflange cleats,bybearing stiffeners,~hyendframesor by lateral supports to the compression flange. The restraintclement shall be designed to resist, in addition to the effectsofwind and other applied lateral forces, the effects ofa horizontalforce F acting normal to the compression flangeofthe girderat

thelevel ofthe centroidofthisflange, where

~~fb

where

Ihasthe valuegiven above, C z thecritical stressin theflangegiven byClauses 504.4.2, and 504.4.3.

= the calculated working stressin flange

thedeflection ofthe flange under the actionofunit horizontal force

as definedinClause506.5.2.

506.5.2. Simply supported girders with compressionflangeslaterally supported byU-frames: For simply supported girderswhere there is no lateral bracingof the compressionflanges, butwhere cross members and stiffeners forming U-frames providelateral restraint

I = 2.5 $(E1a8)

but not less t h a n awhere

== the v i r tu a l la ter a l d i s pla c e m e n t of the compression flangea tt h eframeneare stmid-spanofthegirder,taken as the horizontal deflec-donofthe stilTuers at thepointofits intersection with the centroidofth compressionflange, underthe ac tionofunit horizontal forceapplied at this pOint to theframe only.

This deflection shall be computed assuming that thecrossmember is free to deflect vertically and ~that the tangent to the

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deflectioncurve at thecentre ofits span remains parallel unrc~trai-

ned cross member

a distance between frames

1 maximum moment of inertia o1 compression flangeaboutthe y-y

axis ofthe girder.

(I)When 3 is notgr:ter than ..~

(2) in cases ofsymmetrical U-frameswh&ecrossmembersand stiffeners are each ofconstant moment of inertia throughout

their ownlength,(d~ (d)2b3E1, El,

where

=distance of the centroid of the compresion flangefrom thetop ofthe cross member

= distance of thecentroid of the compression flange from the neutralaxis ofthe crossmember

b=halfthe distancebetw een centres ofthe main girders

I, moment of inertiaof a pair of stitinersabout thecentre of the w ebor ofa singlestiffener aboutthe face of thew eb

1, amoment of inertia of thecrossmember in itsplaneof bending

U-frames shall have rigidconnectionsandshall be designedto resist, inadditionto the effect ofwindandotherapplied forces,

the effect of a horizontal force Facting normal to the compressionflange of the girder atthe level ofthe centroid ofthis flange andhaving a value equal to that given by the formulain Clause506.5.1.1. / having the value 2.5~/(EIa 8)

506.5.3. Girders with laterally supported compression flanges

(a) for all girders where there is effectivelateralbracing tothe com-pressionflange,

thedistinct betweencentres ofintersection of the bracing withthecompressionflange.

(b) for all girderS where the compression flanges are unbraced butsupported laterallyby members controlled by an effectivebracingsystem or anchorage,

/ ~= the distance between centresoflateralsupports.

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506.5.4. Cantilever beams ~ithout intermediate lateral support

Foi cantilever beams ofprojecting length L,

(a Built in atthesupport, free atthe en d 1 0.85 L

(l) Built in at thesupport, restrained against torsion atthe free end by contiguousconstruction I = 0.75 L

(c) Built in at the support, restrained against lateral

deflection and torsion attheen d / = 0.5L(d) Continuous at the support, unrestrained against

torsion atthe support and freeatthe end(e) Continuous at the support with partial r~iaints

against torsion atthesupport and free at the ~t~d 1= 2 L

~f) Continuous atthe support, restrained against torsionatthe support and freeattheen d I L

Wheic in eases (d), (e)and (f) there is a degree offixityatthe ~free end, theeffective length shall be multiplied by 0.75/0.85and 0.5/0.85 f o rdegrees offixity corresponding to cases (b)and(c)respectively.

Restraint against torsion at the supports can be provided asin Clause 506.5.1.1.above.

506 5 5 Compression flange supporl*Ig continuousdeck Acompression flange continuously supporting a reinforced concreteo r s t e e l d e c k s h a ll be deemed t o be e ffe c t i v e ly restrained laterallythroughout i t s l en g t h (i.e.i=0)ifthe frictional or positive connec-tion ofthe deck to the flange iscapableofresisting a lateral fo rceof2~per cent ofthe force in the flangeat the point of maximum

b ending moment, distributed uniformly along i t s l e n g t h , i n addi-t i on t o o t h cr la t e r a l for c e s .

506.6. Webs

506.6.1. Minimum thickness: The thickness t, ofthewebplate shall not be less than 8mmandshall notbe lessthanthefollowing:

(i) for iinstiffened webs:

d,f8 5for steelconforming to IS .: 226

d1/75for steelconforming to IS :961

(ii) forvertically stiffenedwebs11180ofthesmallerclearpanel dimension,

//270 ofthe greater clearpanel dimension, and

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dJ200 for steel conforming to IS :226 or

~1,/I80for steel conforming toIS : 9 6 1

(iii) for webs stiffened, both vertically and horizontally and with the

horizontalstiffener ata distance from the compression flange of 215of thedistance fromthe compression flange t ot h e neutralaxis

i/ISOofthesmallercleardi mensio n i n e a c h pa n e l

1/270ofthe greater clear panel dimension, and

d,/250 forsteelconformingtoIS : 226 or

d~/225for steel conformingto IS : 961

(iv) when th~ is also a horizontalstiffner at the neutral axisofthe

girder:i/ISO ofthe smallerclear dimension ineachpanelor

1/270ofthe greaterclearpanel dimension, and

d,/400forsteel conforming to IS 226 or

d,f360for Steel conforming toIS : 961

lu the above d1 is the clear distancebetween flange angles or

wherethereare no flange angles, betweenflanges(ignoring fillets);but where tongue plateslaying a thickness notlessthan twice thethickness of the web plate are used, d1 is thedepthofthegirderbetween the flanges less the sum ofthe depthsofthe tongue platesor eight times the sumofthethicknessofthe tongue plates which-ever is less;and

d2 is twice the clear distance from the compression flangeangle or plate, or tongue plate to theneutral axis.

506.6.2. Webedges: Forgirders of riveted or bolted con-structionwhich have noflange plates, the topedge ofthewebshallbe flushed with th e angles Thebottomedge oftheweb plate maybe set back from theheels ofthe angles not more than 5 mm Forgirderswhich have flanpplate,theedge oftheweb plate~may besetback from theheels ofthe angles not more than5mm on eachside subjecttotherequirementsfortheedge distanceofholes.

506.6.3. Splices inwebs: Splices inthe websofplate girdersand rolled sections used asbeams shall be designedto resist theshearing forcesandthe~niomentsin the webat the spliced section.

in riveted orbolted construction, splice plates shall be pro-vided oneach sideofthewebs.

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506.6.4. Web stiffeners

506.6.4.1. Rolled I beams andchannels: For rolled 1 beamsandchannels, loadbearing stiffeners shall be providedat points ofconcentrated load (includingpointsofsupport) where the concen-

trated load or reaction exceeds the value ofPa,,x V B

where Pa , , -= theallowable adal stress for struts as giveninClause 504.4. for a

(d ~/3

slenderness ratio of

$ = web thickness

ci, ~- cleard ep t h ofweb between roo t o f fillets

B = the length of the stiff portion of the bearing plus t h e a d d i t i on a llength given by dispersion at 45 tothe levelof the neutralaxis.

The stiff portion of abearing is that lengthwhichcannot deformappreciably in bending,andshall not betakenasgreaterthan halfthe depth of the beam for simply supported beams and the fulldepth of the beam for continuous beams.

506.6.4.2. Plate girders: For plate girders, load bearingstiffeners shalt be providedat po/ntsof support and at points ofconcentrated load, the details oftheseloadbearingstiffeners shallbe as given below:

Load bearing stiffeners shall be symmetricalabout the web,where possible.

Load bearing stiffeners, where the concentrated load causescompression in the stiffener, shall be designed as struts, assumingthe section to consistofa pairofstiffenerstogether with a length ofweb on each side of the centreline of the stiffenersequal,wberepossible,to 20 times the web thickness. The radius of gyrationshall he taken about the axisparallelto the webofthebeamofgirder. Working stress shall be in accordance with the appro-priate allowable value for a strut, assuming an effective lengthequalto 0.7 times the lengthofthe stiffener.

The o ut st a n d i n g le g s o f e ac hpairofloadbearingstiflener sshall be so proportionedthat thebearingstress onthat partof theirarea in contact with the flangeand clearofthe rootofthe flange orflange angles or clearoftheflange welds,does not exceed thebear-ing stressspecified in Clause 504.3.

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Load bc~iringstiffeners shall be provided with sufficient rivets,bolts or weldsto transmit to thewebthe whole ofthe load in the

stiffeners.

Load bearing stiffeners shall be fittedto provide a tightanduniftrrn bearingupon the flange transmitting the load or reactionunless welds are provided between the flangeandstiffener for thispurpose. At points of support thisrequiremen