1RC 24-1967

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGES

SectionV

Steel RoadBridges

THE INDIAN ROADS CONGRESS

1984

IRC 24-1967

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGES

SectionVSteelRoadBridges

PublishedhiTHE iNDIAN ROADS CONGRESS

JamnagarHouse,ShabjahanRoad,New Delhi-i100il

1984PriceRs 24

(Plus packing& postage)

IRC 24-1967

First published: May, 1967Reprinted:August, 1972Reprinted:July, 1976Reprinted:August, 1984 (IncorporatesAmendmentNo. 1—

December,1982)

(Rightsof Publication and Translationare reserved)

Printed at PRINTAID, New Delhi

IRC: 24-1967

STEEL ROAD BRIDGES

CONTENTS

Clause No. PageNo.introduction ... 1

501. General .,. 2501.1. Scope ... 2501.2. Clearances .,. 2

502. Materials ,.. 2502.1. StructuralSteel ... 2502.2. Rivet andRivet Bars ... 2502.3, CastSteel ... 3502.4. CastIron ,,, 3502.5. Steelfor Pins (including KuncklePins)andRollers ... 3502.6. Bolts andNuts .,. 3502.7. Washers ,,, 3502.8. Welding Electrodes ... 4502.9. Steel for ParallelBarrelDrifts .,. 4502.10. Deleted ,., 4

503. LoadsandStresses ,., 4503.1. LoadsandForcesto be Takeninto Account ,,. 4503.2. Combinationof LoadsandForces ... 5503.3. Stresses ... 5503.4. DeformationStresses ... 6503.5. Reliefof Stresses ... 6

504. PermissibleStresses ... 6504.1. Allowable WorkingStressfor Combinationof

LoadsandForces ... 6504.2. Fluctuationsof Stress(Fatigue) ... 7504.3. BasicPermissibleStressesin StructuralSteel ... 9504.4. Allowable Working Stresses ... 12504.5. Working Shear Stresses in Solid WebPlates ... 19504.6. Combined Stresses .,, 22504.7. Deleted ... 23504.8. Deleted ... 23504.9. Deleted 23504.10. Deleted “ 23504.11. Deleted ... 23

505. Designof General Details ... 23505.1. EffectiveSpans ... 23505.2. EffectiveDepth ... 23

IRC: 24-1967

Clause No. PageNo.

505.3. Minimum Depth ... 23505.4. SpacingandDepthof Main Girders ... 24505.5. Symmetry ... 24505.6. Minimum Sections ... 24505,7. Corrosion ... 24505.8. Drainage ... 25505.9. Deflection ... 2550510. Camber ... 25505.11. Provisionfor TemperatureChanges .,. 25505.12. Spacingof TrussesandGirders ... 25505.13. Anchorage ... 26505.14. Effective Lengthof Struts ... 26505.15. Effective SectionalArea ... 26505.16. Floor Beams ... 28505.17. JoistsandStringers ... 28505.18. Bracing ... 28505.19. End CrossGirders ... 28505.20. Platesin Compression ... 29505.21. Riveting andBolting ... 30505.22. Welding ... 32505.23. Lug Angles ... 33505.24. ClevisesandTurnbuckles ... 34505.25. Pins ... 34505.26, CompositeUseof Mild SteelandHigh TensileSteel ... 34505.27, CompositeAction of SteelandConcrete ... 34505.28. Composite Connections 35

506. Solid Web Girders(PlateGirdersandRoBedBeams) ... 35

506.1. General ... 35 —

506.2. Maximum AverageShearStress ... 36506.3. SlendernessRatio ,.. 36506.4. Flanges .. 36506.5. Effective Lengthof CompressionFlanges ... 38506.6. Webs ... 41

507. Open Web Girders ... 46507.1. General ... 46507.2. CompressionMembers ... 47507.3. Tension Members ... 56507.4. Splicing ... 60507.5. Connectionsat Intersections ... 60507.6. GussetPlates ... 60507.7. Diaphragmsin Members ... 61507.8. Camber .,. 61

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ERC: 24-1967

ClauseNo. PageNo.

508. Workmanship ... 61508.1, General ... 61508.2. Templates ,,, 61508.3. Straightening ... 62508.4. Preparationof EdgesandF.nds ... 62508.5. Preparationof Holes ,,, 63508.6. Rivet andRiveting ... 65508.7. Bolts, Nuts and Washers ,,, 66508.8. Drifts ... 68508.9. ‘ PinsandPin Holes ... 68508.10. Deleted508.11. Welding ... 68508.12. Tie Rods ... 69508.13, Forging ... 69508.14. BendingandPressing ... 69508.15. ShopErectionandMatch Marking ... 69508.16. Marking andPacking ,.. 70508.17. ProtectionagainstCorrosion ... 70

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

Appendices

Appendix A Deleted 75

AppendixB Critical CompressionStressC~for Sections ... 75Symmetricalaboutthe X-Xaxis formula

AppendixC Preparationof CamberDiagramfor OpenWebSpans whicharenot PredeformedandPrepara-tion of Camber DiagramandRulesfor Prede-formingfor PredeformedSpans ... 77

Appendix D Field Requirements ... 80

Tables

Table 1 Total Variationin Allowable Stress ,,

Table 2 Basic Permissible Stresses inStructuralSteel ... 9

Table 3 Valuesof ‘F’ for VariousValuesoffy 13

It’

IRC; 24-1961

PageNo.Table 4 Allowable WorkingStressesP~in kg/sq. mm. on

ElfectiveCrossSectionfor axial Compression ... 13

Table 5 Valuesof K1 .., 15

Table 6 Valuesof K2 ,.. 16

Table 7 Valuesof 9 andB to be usedfor CalculatingValuesofC~inkgfsq.mm ... 17

Table 8 Allowable Working StressP~for Different ValuesorCritical StressC~ ... 18

Table 9-A Allowable AverageShearStress(P~in kg persq. mm)in StiffenedWeb of SteelConformingto iS: 226 ... 20

Table 9-B Allowable AverageShearStress(P~in kg persq. mm)in StiffenedWeb of Steel Conformingto I.S: 961 ... 21

Table 10 MaximumPermissibleValueof EquivalentStressf~in kg permm’ for Mild andHighTensileSteel ... 22

Table 11 EffectiveLength of CompressionMembers ... 49Table 12 Diameterof Holesof Rivets .,. 64

Table 13 Weight of Rivet Heads ... 81

iv

IRC: 24-l~67

STEEL ROAD BRIDGES

INTRODUCTION

The Standard Specificationsand Code of Practicefor SteelRoad Bridges wasfinalised by the Subcommittee,consistingof thefollowing personnel,at their meetingheld at New Delhi on the 9th,10th and 11thJuly, 1965:

K.F. Antia .., ConvenorB. BalwantRao Member-SecretaryS.P.DassD.S. DesaiS.K. GhoshNP, MathurN.M. ThadaniP.K. MukherjeeS.S.Varma

The draft was considered and approved by the BridgesCommittee attheir meetingheld at New Delhi on the20th Oct.,1965 andlater approvedby the Executive Committeefor publica-

tion as an Indian Roads Congress Standard SpecificationsandCodeof Practice.

The objectof issuingthe StandardSpecificationsand CodeofPracticefor Steel Road Bridgesis to establishacommonprocedurefor the designandconstructionof roadbridgesin India.

This publication is meant to serveas aguideto botqthe de-sign engineerandthe constructionengineerbut compliancewith therulesthereindoesnot relievethem in anywayof their responsibilityfor the stability and soundness ofthe structures designedanderectedby them.

Thedesignandconstructionof road bridgesrequire extensiveand thoroughknowledgeof thescienceandtechniqueinvolved andshouldbe entrusted only to specially qualified engineers withadequatepracticalexperiencein bridgeengineeringandcapableofensuringcarefulexecutionof work.

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(RC: 24-19b7

~Oi. GENERAL

501.1. ScopeThis Code dealswith the use of mild and high tensile steel in

the superstructureof simply supportedroad bridgesupto 125 me-tresspanbetweenthe centresof bearings. Whereappropriate,therecluirenlentSof the speciticatioiis nay be appliedto larger spansorother typesof steel bridges,but careshould be taken, in thesecirc-umstances,to make necessaryamendmentsfor fixity at thesupports,continuity andother indeterminateor specialconditions.

501.2. Clearances

All bridges shall be designedwith adequateclearancesasspecified in the 1RC : 5 StandardSpecificationsandCodeof Practicefor Road BridgesSection 1, Cluse105. Otherfeaturesshould alsoconformto the standardslaid down in other sections.

502. MATERIALS

502.1. StructuralSteel

All structural steel shall comply with the following IndianStandardsasappropriate

IS:226—StructuralSteel (standardquality)

IS:2062—StrueturalSteel (fusion welding quality)

IS:961—StructuraiSteel (high tensile)

502.2. Rivet and Rivet Bars

All rivet andrivet barsshall conformin all respectsto iS1141—Specfication for Rivet Bars for StructuralPurposesandiS : 1149—Specificationfor High TensileRivet Bars for StructuralPurposes.

Notes 1. Unless specified, mild steel rivets shall be usedwith mild steelstructural members and high tensile steelrivetswith high tensilesteelmembers.

2. \Vhere high tensilesteel is usedfor rivets, stepsshall be takentoensure that the rivels are so manufacturedthattheycould bedriven and the headsformedsatisfactorily;andthatthe physicalpropertiesof thesteelarenot impaired.

3. Generallythecoppercontentof the rivet steelshould be in excessof thecopper contentof the steelmemberswith whichthey comein contact, The ma~drnumpermissible percentageof copperinrivet steelshall be0.6.

2

IRC 24-1~67

502.3. Cast Steel

The use of caststeel shall be limited to bearingsand othersimilar parts,steel for castingsshall conformto Grade30-57 of theIS: 1030—Specificationfor Steel Castingsfor GeneralEn~ineeFingPurposes.

502.4, CastIron

Cast iron shall notbe used in any portionof the stuctureexceptonly when subject to direct compression. Suchcast ironshall conform to the requirementsof IS: 210—Specificationfor GreyIron Castings. The Grade No. of the material shallnot be lessthan 14 and its basic permissible stress shall not exceed theGradeNo. divided by 2.54.

502.5. Forged Steel for Pins

Forged steel pins shall comply with class 3, 3a or 4 ofIS: 1875-1978andsteelforgingsshall comply with class3, 3A. or 4of IS: 2004-1978.

Steel castings for steel pins shall conformto Grade30-57 ofiS: 1030-1974Specificationof Steel Castingfor GeneralEngineer-ing Purposes.

502.6. Bolts and Nuts

All mild steelfor bolts andnuts, whentestedin accordancewith the IS: 1608—Method for Tensile Testingof Steel Productsother than Sheet, Strip, Wire and Tube,shall havea tensilestre-ngthi of not less than44kg/mm2 and a minimum elongationof 14per centon a gaugelengthof 5.65s(area.

502.6.1. High tensile steel (structuralquality’ for bolts andnuts shall be manufactured from high tensile steelhaving aminimum tensile strength of 58 kg/mm2 and other mechanicalpropertiesin accordance with the IS: 961—Specificationtbr HighTensileStructuralSteel.

1”Toze . 1-11gb strengthfriction grip boltsforbridgeconstructionarenot coveredby ths Standard. Their use may be permitted on satisfactoryevidence being produced that theysatisfy therequirementsspecdledby the Engineer.

502.7. WashersPlain washers shall be made of steel. Tapered or other

3

IRC: 24-1967

specially shapedwashersshall be madeof steel or malleablecastiron.

502.8. Welding Electrodes

Mild steel electrodesshall comply with the requirementsofthe IS: 814 Specification for Covered Electrodes for Metal ArcWelding of Mild Steel,andthose for high tensile steel shall complywith IS: 1442 Covered Electrodesfor the Metal Arc Welding ofHigh TensileSteel.

502.9. Steelfor Parallel Barrel Drifts

Steel for parallelbarrel drifts shallhavea tensilestrengthofnot lessthan55.1 kg/mm2with an elongationof not less than20 percent measuredon a gaugelength equalto 4iarea.

502.10. Deleted

503. LOADS AND STRESSES

503.1. Loads and Forces to be Taken into Account

For purposesof computing stresses,the following items shall,whereapplicable, be taken into accountin accordancewith therequirementsof IRC: 5 and IRC: 6 Sections I andII of the IRCCode of Practicefor RoadBridges:

(a) Deadload

(b) Live load

(C) Impactor dynamiceffect of live load(d) Ceinrifugalforce(e) Longitudinalforcesused by tractive~

effort of vehicle or by braking ofvehicles and/or those caused byrestri*int to movementof freebearings

(I) Temperatureeffect(g) Forceson parapets(h) Wind load(1) Seismicforce(j) Erectioneffects

Subjectto the provisionsof other clauses,all forcesshall be con-sideredas applied and all loadedlengths chosenin sucha mannerthat the most adverse effect is caused on the member underconsideration. Wind and seismicforces arenot to be consideredto actsimultaneously.

4

IRC: 24-196~

503.2, Combination of Loadsand Forces

Combinationsof forcesto be consideredarespecifiedbelow:

(I) The worst possiblecombinationof deadload with live load, impactandcentrifugalforce.

(ii) The worst possiblecombination of any or all of theforceslistedunderClause503.1. from (a) to (h;.

~.iii)Theworst possiblecombinationof any or all of the forces listedunder Clause503.1. items (a)to (g) and(1).

(iv) Theworst possiblecombinationof forcesduring erection.

The weight of all permanentandtemporarymaterialstogetherwith all other forcesandeffectsof which may operateon any partof the structureduringerectionshall be takeninto account.

503.3. Stresses

503.3.1. Primary Stresses: In the design of triangulatedstructure,axial stressesin membersare usually calculated on theassumption that all membersarestraight and free to rotateatthejoints; all joints lie at the intersectionof the centrodial axes of themembers;all loadsincluding theweight of’ members,are applied atthejoints. Thesestressesaredefined asprimary stresses.

503.3.2. In practice,the assumptionsmadein Clause503.3.1.arenot realisedandconsequentlythe membersaresubjectnotonlyto axial stressbut alsoto bendingandshearstresses.Thesestressesarereferredto as deformationandsecondarystressesin section.

503.3.2.1. Deformation stresses are the result of elasticdeformationof the structure combinedwith the rigidity ofjoints.

503.3.2.2. Secondarystressesare the result of eccentricityofconnectionsandoff joint loadinggenerally,(i.e., the loads rolling,direct on chords, sell-weight of members and wind loadsonmembers).

Structures shall be designed,fabricatedanderectedin sucha manneras to minimise, as far as possible, deformation andsecondarystresses.

503.3.2.3. Secondary stressesshall be computedandcom-bined with co-existentaxial stressesin accordancewith the Clause504.6. but secondarystressesdue to self-weightandwind on themembershallbe ignored.

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IRC: 24-1967

Note In computing secondarystressesdueto loadsbeingcarried direct by achord, hechordmay beassumedto be a c ntinuousgiider supportedatthe panelpoints, the resulting bendingmomentsboth at the centreandatthesupportsbeingtakenasequal to three-fo rth of themaximum bend-ing moment in asimply supportedbeamof span equalto panel length..When desired,exactcalculationsmay be madeand thecalculated bend-ing moments used for design. The impact allowanceshallhe basedonthe loadedlength equal to one panel length.

503.4. Deformation Stresses503.4.1. in the case of trussmember,deformationstresses

described under Clause 503.3.2.1. shall beeither computedorasstnncdin accordancewith Clause 503.4.2. and added to theexistin axial stress.

503.4.2. in non-prestressedgirders,the ratio of width of themembersin the planeof distortion to their length between centresof intersectionsshallpreferablybe not greaterthan 1/12 fbr chordmcmbersand 1/24 for web members.In the absenceof calculations,the deformationstressesshall be assumednot less than 16 per centof the deadand live load stresses.

503.4.3. As the effectivenessof completeremovalof defor-knal ion stressesthroughpredeformation (prestressing)is doubtfuland the extentof relief in the deformationstressesthrough prede-lbrmation dependsupon several factors,deformation stressesshallbe taken into considerationevenwhenpredefarming is resortedto.

503.5. Relief of Stressesin deternining the maximum stress in anymemberof a

bridge, it is permissibleto takeinto accountany relief afforded tothe member by adjoining parts. In determining the amountofrelief, the secondarystresses,if any, in the member,shall be takeninto account andconsideredwith otherco-existentstresses. Suchrelief may be takeninto accountonly if the relieving parts havebeensuitably designedandareeffectively attachedto the member.

In everysuch case,it is necessaryto considerwhetherthe reliefconsideredwill be given by the adjacentmember permanentlyoris liable to vanish owing to any changein the said adjacentmember.

504. PERMISSIBLE STRESS

504.1. Allowable Working Stress~for Combination of Loadsand Forces -

504.1.1. For the combination of forces given in Clause

The permissible increase in stressespermiued under this clausewillsupetsedethose given under IRC : 6 SectionII of Bridge Code, Clause203.

IRC 24-1967

503.2. (i), the allowableworking stressshall be thosegiven asbasicstressesunder Clause 504.3. When secondary stressesarealsotakeninto accountin the case of triangulated trusses, allowableworking stressesmay be increasedby 16 per cent.

504.1.2. For the combination of forces given in Clause503.2(ii), the basic permissiblestressesgiven in Clause 504.3. maybe increasedby 16 per cent; wherethe secondarystressesarealsotakeninto account, in the case of triangulated trusses,the basicpermissible stressesgiven in Clause504.3. may be increasedby 32per cent.

504.1.3. For combinationof forcesspecified in Clause503.2.(iii) or 503.2. (iv) viz., for seismic and erection conditions,thestressesmay be exceededby 25 percent; whensecondarystressesare also takeninto accountin the caseof triangulated trusses. thebasic permissible stresses maybe exceededby 40 per cent.

504.1.4. Stresseswhile lifting the spansduring maintenancein themembersused for Lifting may exceed the basic permissiblestressesby not morethan25 per cent.

504.1.5. In no case the stress inany membershall exceedthe yield stressspecified for the material,

504.1.6. The total variation in allowable stresses aftercombiningthe provisionsof Clauses504.1.1 to 504.1.4, aregiven inTable 1. The valuesgiven in the tabledo not allow for the effect offluctuationsin stress whichmust be dealtwith accordingto Clause504.2. while stressesarising from combinationsof bendingmomentsand sheararesubject to provisionsof Clause504.6.

504.2. Fluctuationsof Stress(Fatigue)

504.2.1. General All details shalL be designedto aviod, asfar as possible,stress concentrations likelyto result in excessivereduction of the fatigue strengthof membersor connections. Careshall be taken to avoid suddenchangesof shapeof a memberorpart of a member,especiallyin regions of tensile stressor localsecondary bending andstepsshall be takento avoid aerodynamicand similar vibratfons.

7

ERC: 24-1967

Note Memberssubjectedto fluctuations of stressesare liablc to suffer fromfatiguefailure, this may becausedby loads which are very much lowerthan those which would be necessaryto cause failure undera singleapplication, ‘l’he Initiation of fatiguecracksis primarily due to stressconcentrationsintroducedby the constructionaldetails. Discontinuitiessuch as bolt or rivet holes,welds and otherlocal orgeneralchangesingeometricalform setup suchstressconcentrationsfrom which fatiguecracks may be initiated, andthesecracksmay subsequentlypropagatethroughtheconnectedor fabricatedmember.

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

(11 For calculatedprimarystress

(ii) Whereprimarystressesarecombinedwith cal-culated deformationand secondarystressesofClauses503.3.2.tand5033.2.2. (self weightand wind on memberignored)

Increase in allowablestressesfor localcombinationsasperClauses

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

Noincrease~ 16

No increase I.

16 32

504.2.2 It is not necessaryto reducethe permissiblestresseslo allow for the effect of fatigue in the following cases, mainlybecauseof thenumberof fluctuationsof design stressesbeing smallin the anticipatedlife of the bridge

(i) Mild steel bridges,riveted or welded;

(it) High tensile steel bridges,riveted construction,

In the case of high tensilesteel weldedconstruction,and inthe designof thosemembersin which heavyreversalsof stress arelikely to occur and the predominatingstressis tensile, it maybenecessaryto lower the stressat the discretionof the designer.

(a) Solid web girders

(b) Triangulatedtrusses

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

25 25

25 25

40 40

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mc : 24-1967

504.2.3. Connections,riyetcd or bolted No allowance forfatigueshall normally be madein calculatingthe required numberof rivets or boLts in a rivetedor bolted connection except that allrivets or bolts subjectedto reversalof stressduring the passageofthe live load shall be proportionedfor the arithmeticalsum of themaximum load plus 50 per cent of the maximum load oftheopposite sign. In the caseof wind bracing, the connectionsshallbe designed to resist the greater stressonly.

504.2.4. Load-carrying fillet welds: Load carrying ~1lletweldsshall be designedat normal allowablestresses(not reducedon accountof fatigue)but the effective throat depthof fillet weldsshall not be smaller than0.7 timesthethicknessof the memberwherethe connectionis transmittingthe full load in the member.

504.3. Basic Permissiblein StructuralSteel: Subject to theprovisions in Clause 503.3to 503.5,504,1, 504.2, 504.4and 504.5,structures shall be so designed that the calculatedstressesinstructuralsteel do not exceedthe basic valuesgiven in Table 2.

TABLE 2. BASIC PIRM1sSISL.sSTRSSSESIN STIWCTUI~ALS’r!as.

Mild steelconforming High tensilesteelconform-to IS: 226 & IS: 2062 ing to IS: 961 with yieldwith 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. Partsin axialtension

(a) On effectivesectionalarea 14.1 21.2 193 17.3

(b) On netsectionboltsandstuds

(i) exceeding38 mm 14.1 19.6

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IRC : 24-1967

(Parts in axial tension conid.)(ii) exceeding28 mm

but not 38 mm(iii) exceeding22 mm

but not28 mm(iv) less than 22 mm(C) On rivets

2. Parts in axial compre-sessionon effectivegross section

3. Parts in bending Iten-sion or compression)on effective sectionalarea for extremefibrestress

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

(b) For rolled beams,channels, anglesand tees,and forplate girderswithsingle or multiplewebswithd1/r not greaterthan 85 for steelconformingto IS:226

d~/znot greaterthan 75 for steelconformingto IS:961

(c) For plategirderswith single ormultiple webs,withd~tgreaterthan 85 for steelconformingto IS: 226

e greaterthan 75 for steelconformingto IS: 961

23.6 21.5See also Clause 5044.2.

14.1 21.2 19,3 173See also Clause 504.4.2.

In the above d1 the clear distancebetweenflange anglesor,~ here there areno flange angles, betweenflanges(ignoring fillets);but where tongue plateshaving a thicknessnot lessthan twice the

2 3 4 5

12.6 18.9

11.0 16.5

9.4 14.19.4 14.1

See Clause504.4.1.________ —

15.7 19.5

150 18,522.3‘1 20.4

See also Clause 504.42.

-I

10

tRC~24.1967

thicknessof the web plate are used,d1 is the depth of the girderbetweenthe flangeslessthe sum of the depthsof the tongue platesor eight times the sumof the thicknesses of the tongue plates,which ever is lesser.

and t =— the web thickness

4. Partsin shear

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

Average shear stress. (On thegross effective sectional area of 8.5 13.5 12.2 11.0webs of plate girders rolled Seealso Clause504.5beams,channels,anglesand tees). ~—--———-,~.. .. __.._

Onpowerdriven shoprivets andturned andfitted bolts 10.2 14.1

On power driven field rivets 9.4 13.3

On hand-drivenrivets 8.7

On black bolts 7.9

On close tolerance bolts andturned barrel bolts 9.4 13.3

Secalso Clauses505.21.6. and505.21.7.

5. Parts in bearing

On fiat surfaces 18.9 28.3 25.9 23.6

On power driven shop rivets andturnedandfitted bolts 23.6 32,2

On power driven field rivets 22.0 30.7

On hand-driven rivets 18.9 —

On black bolts 15.8

On close tolerance bolts andturned barrel bolts 22.0 3~.7

Seealso Clauses505.21.6.and 505.21.7.

11

Il~.C:24.1907

3 4 5

6. Pins

En shear 10.2 14.1

in bearing 21.2 29.9

In bending(on outer fibres) 21.2 29.9

For turned andtitled knuckle pinsand spheresin bearings

On projectedarea 11.8 11.8

7. Weld. SeeClause505.22.

504.4. Allowable Working Stresses

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

The calculatedaveragewor~ingstressin compressionmembershall not exceedthe value givenin Table 4 and derived from theformula given below

P__~_~__I~

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

wIi crc

== allowableworking stresson effective crosssection forcompresionmember

p = constantdepending upon the yield stressf,of steel(SeeTable 3)

in = loadfactor = 1.82

E = Young’s modulus = 21,100kg/mm2

r = leastradiusof gyrationof the compressionmember

I effectivelengthof the compressionmember.

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!RC: 24-1967

tALE 3. VALUES 0~ roa VARaOUS VALUBS 01’!, THE YIELD STRUS 1’O~

MLLD STEEL AND H1GH TSNS!LF ~TUL

Yield stressf~ P

kg~sqmm kg/sq mm

23.6 16.5

TABLI 4. ALLO WA$LE woRKiSECT!

NO STRESSES Po.~IN kg/sq.mm ON SFON FOP AXIAL COMPRESSION

PECnvE cRoss

•± P=16.5 P=24.8 P-~22.6 P_20.2

0 14.00 21.00 19.15 17.12

20 13.60 20.40 18.60 16.70

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 steelconformingto IS : 226

FITS.conformingto IS : 961 36.2 24,8

H.LS. conforming to ES :961 33.1 2Z.9

H.T.S. conforming to IS : 961 29.9 20.2

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IRC:24-1~67

504.4.2. Allowable working stress in bending: For allsectional shapesthe tensile and compressivebendingstresses,fbtandf,c, calculatedaccordingto Clauses506.1. and 506.3.shall notexceed the appropriatebasic permissiblestressesin Clause504.3.subjectto the provision in Clause504.4.3.for bendingcompression.

504.4.3. Bendingcompression: For sectionalshapewith l~smaller than !~

where /~=momcatof inertia of the whole sectionabout the axis lying inthe plane of bending (the y—y axis),

and 1~.=momentof inertia o(tbewhole section about the axis normalto the plane of bending (the x—x axis),

the compressivebending stress,f~shall not exceedthe value Poegiven in Table 8 correspondIngto C~,the critical stressin the com-pressionelementcalculatedas follows

504.4.3.1. For sectionswith asingle web (including I sectionswith stiffenedor unstiffenededges,channels,angles,tees,etc., butexcludingI sectionswherethe thicknessof the flange is more thanthreetimesthe thicknessof the otherflanges)

(a) Where the flangeshave equal momentsof inertia abovey-y axis

267730

(l/r~)2‘~J[ + ...( ~) ]ic~per sqmm=A

exceptthat the valueof C~calculatedabove shallbe increasedby20 per cent for rolled beamsandchannelsandfor plategirdersprovidedthat:

t~Jtis notgreaterthan 2

d1/r is not greaterthan85, for steelconforming to IS : 226

d2/s is not greater than 75, for steelconforming to IS: 961—d1 and t are as defined in Table 2

effectivelength of compressionflange (seeClause506.5.)

radius of gyration about the y-y axis of the grosssectionof thewhole girder, at the point of maximum bending moment

D over all depth of girder, at the point of maximum bendingmoment

effective thicknessof the compression flange

K~times meanthicknessof the horizontal portion of the compres-slon flange at the point of maximum bending moment.

14

IRC 24-1967

(For rolled section, t,=K1 timesthe thicknessgiven in referencebooks). The co-effi.~ientK1 makes allowance for reduction inthicknessof breadth of flangesbetweenpointsof effectivelateralrestraint and depends on R~,the ratio of thetotal areaof bothflangesatthe pointof leastbendingmomentto the correspondingareaatthe point of greatestbendingmomentbetweensuch pointsof restraint. (For flangesof constantareaK1= I).

Flangesshall not bereducedin breadthto give avalue of R~lowerthan0.25.

Valuesof K1 for different ualuesOf R~are given in Table 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 of Ra calculated for the comoressionflange alone issmaller than thatwhen both flanges are combined, this smaller valueof Rashall be used.

(b) Where the moment of inertia of the compressionflangeabout they~—yaxisexoeedsthat of the tensionflange:

267730 ~ 1 f It. \‘ 1 2677300

(l/ry)’ ~s.jL 1 + ~ j+L~-

=A+K~B in kg. per sq. mm.

where F, r~& D are as defined in (a) aboveand

effectivethicknessof flange

K, times mean thickness of the horizontal portion of the flange ofgreatermoment of inertia about 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 ratio of the moment of inertia ofthe compression flanges alone to that of the sum of the momentsof inertiaof the compressionand tension flanges, each calculatedabout its own axis parallel to they-y axis of the girder,at the pointof maximum bending moment,

15

IRC 24-1967

Note: F ~flangesof equal moment of inertia

Rm0.5 and KL=0

For teesand angles

R,~=1.0and K,=0.5

Values of K, for different values of I?,,, are given inTable 6 below:

TABLE 6. VALUES OF K,

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 of thetensionflangeaboulthey-yaxis ~ceedsthat of the compressionflange:

c~=[~/?~9J[ +J(~~}+K~’~ ]x~!

= (4 + K,B)1~-inkg/sq.mm.

Where 1, r5, D, t~& K, areas definedin (a) & (b) above,and

y,= distance f-om the neutral axis of girder to extremefibre in compress-sion.

y~=distancefrom neutral axisof girderto extremefibre in tension.Valuesof K.~for different valuesof R,,, aregiven inTable 6 above.For teesandangles. .R,,,=0 and K,=—1.

Notes I. For values of A’ and ~B’for differentratiosof l/ry & DJte to beusedfor calculatingC, in kg/sq.mm, referTable7,

2 For values of allowable bendig compressivestrets Poe for differentvaluesof C,, seeTable 8.

~04.4.3.2. For sectionsother than thosedescribedin Clause504.4.3.1.above:

a) Where the section is symmetrical about the x-x axis, the value ofC, maybe obtainedfrom the basicequationin Appendix,8.

b) Wherethe sectionis not symmetricalaboutthe x-x axis, the exactvalue of C, may becomputed;but valuesobtainedfrom theformu-lae givenin Clause 504.4.3.1.(b) & (C) can be usedwith safety.

16

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~12

Note Whereflangesareequaland of constantcrosssecLion 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 17.3 114.3 112.4 111.2 109.8 109.0 108.2 107.7 107.!

5560 t

162.4145.2

140.3124.4

126.8111.5

117.8j03.0

111.797.0

107.292.8

103.889.5

98784.4

95.881.5

93.9797

92.678.4

91.2770

90.476.2

89.175.4

89.175.0

88.574.3

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 62.0 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

12.111.09.9

11.510.29.3

11.29.99.0

10.49.38.2

19020021022

I 230240

40238.036.234.532.931.5

32.430.729.127.726.525.4

27.2j 25.8

24.623.322’.221.2

23.822.421.320,219.218.4

21.119.818.918.017.016.2

19.118.017.016,115.314.6

17.516.415.414.614.013.4

14.613.712.912.311.511.0

12.912.011.310.610 1

9.6

11.710.910.29.69.08.5

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

8.07.46.86.15.75.4

7.46.86.15.5504.7

250260270280290300

30.229.128.026.926025.2

24.423.322.521.721.020.2

20.519.518.918.!17.5

- 16.9~

17.616.916.215.615.11•-.6

15.615.014313.713.2128

14.013.412.912412.011.5

12.812 I11.711.210.910.4

10.610.196918.88.5

9.18.7

- 827,9767.2

8.07.77.46.96.86,4

7.46.96.86.36.158

6 56.1585.55.25.0

5.85.55.24,94.74.4

5.24.94.64.44.13.9

4 9 4.346 3.943 3.64.1 3.43 8 3.236 3.0

c>t.~

P~-.1

IBC : 24 1967

TAI3LE 8. ALLOWABLE WORKING STRESSP~.FORCRITICAL STRESSC,

3456789

10121416182022242628303540455055606570758090

100125150200215

(SEETAB~s 2)

1.52.02.53.03.53.84.24.65.36.06.77.27.68.08.48.89.29.6

10.511.211.912.412.913.313.613.914.114.414.915.315.815.815.815.8

DIPFE1tENT VALUES OF

1.52.02.53.03.53.84.24.65.46.27.07.78.49.09.6

10.210.811.412.713.714.615.315.916.517.117.417.818.218.819.420.521.222.222.4

C~ P~for steelconforming P~øfor steelconforming

kg/sq. mm

to IS 226 to IS 961

kg/sq. mm kg/sq.mm

18

IRC: 24.1961

504.5. Working Shear StressesIn Solid Web Plates

(a) 4verageshear stress: The calculatedaverage shear stress .(. onthe effectivesectionarea of theweb shall not exceedthe valuegivenIn Clause504.3.Table2 or in thecase of stiffened webs, the valuePq given by thefollowing equations,whicheveris the less:

F, in kg per mm’ i (i.3_. ~ bK4l+*(~a) }

where

a thegreaterdimensionof the webin a panel not greaterthan 270t

b = the lesserclear dimensionof the web in a panel not greater than

180:

= thickness of web

K, = 9.5 for mild steel conforming to IS: 226 & 13.5 for H.T.S. conform-ing to IS : 961

K, = 250 for mild steel conforming to IS : 226& 200 for H.T.S. conform-ing to IS :961

For stiffened webs,valueof P, for varying ratios of depth ofpaneld to thicknessof webt and various spacingsof stiff~ne~rsaregivenin Table9A for steelsconformingto IS : 226 and in Table 9Bfor steelsconforming to IS: 961 where the depth of panel d isdefinedas follows:

(i) For webswithout horizontalstiffeners,d is the cleardistancebetweenflange angles or, where thereare no flangeangles,betweenflanges~igaoringfillets); but where tongue plates having a thickness notleu than twice the thickness of webpldte areused,d is the depthof the girderbetweenthe flanges less the sum of the depths of thetongueplatesor eight timesthe sum of the thickness of the tongueplates,whichever is the less.

iii) For webs with horizontal stiffeners,d is the cleardistance betweenthe tensionflange(anglesor flange plate or tongue plates) and thehorizontalstiffener.

Not. For themjnfmum tWcknessof web plates and the design of web stiffen-era, seeClause506.6.1 to 506,6.4.

19

lkC: 24-1967

TABI.a 9A. ALLOWABLE AVKRAOE SHEAR STRESS

IN STIF~ENBDWsasOF STEEL, CONFORMING TO IS : 226

hO

130

150

170

190

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

dl tStressFq kg/mm2 for differentdistancesbetween

stiffeners

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

20

TABLE 9 B. Au.owABLa AVERAGE SRsAJ~STttzssIN

STIFFENED WEBSOF STEEL CONFORMING TO IS : 961

StressPg kg!mm’ for different distances betweendft stiffeners

0.33d 0.44 0.6d 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

130 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

21

IRC: 24-1967

504.6. CombIned Stresses

504.6.1. BendIng and axial stresses:Members subjected toboth axial and bendingstresses(compressiveor tensile) shall beso proportionedthatthe quantity

-- + IL does not exceedunityFa Fb

wherefl = calculated axial stress(compressiveor tensile)F. = appropriateallowable workingstressin axially loadedmembersf~’= calculated maximum bending~comprcssiveor tensile) stressesabout

both principal axesincluding secondaryStresses,if any~and= theappropriateallowableworkingstressin bending(compressiveor

tensile).Where an increase or reduction in permissible working Stress is speci -fied both F~and F~shall be the increasedor reducedworking stressasdirectedin therelevant Clauses.

504.6.2. shear and bendingstresses: The equivalent stressf~.(see Clause 504.6.4).due to a combination of shear stress fbendingstress,f,tensileor compressive,is calculated from

fe 3f,2

504.6.3. Shear~bearing and bending stresses: The equiva-lent stressf~(see Clause 504.6.4) due toacombinationof shearstressf.,bearing stress!

5 andbending stressfb, tensile orconipres-sive is calculatedfrom

+f52+fj,+3f~~

504.6.4, Irrespectiveof the permissibleincreaseof stress inotherClausesthe equivalLutstressf~calculatedin Clause 504.6.3.aboveshall notexceedthe valuesgiven in Table 10.

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

Quality of steel

Mild steel

Yield stress Max value off.

kgjsq. mm kg/sq.mm

23.6 22.0

High tensile steel 36.233.12.99

33.129.926.8

22

11W 24.1967

504.7. Deleted

504.8. I)eleted

504.9. Deleted504.10. Deleted

504.11. Deleted

505. DESIGN OFGENERALDETMLS

505.1. Effective Spans

Theeffectivespan shall be

Ci) for main girders the distance between the centresof bearingplatesor rockcr pins,

(ii) for cross members, the distance between the centresof themaingirdersor trusses,

(iii) for roud bearers, the distance between the centres of thecrossmembers,

(iv) for decking, the distance between the centresof theroadbearers,and

(v) for pins in bending, the distancebetweenthe centres of bearings;but wherepins passthroughbearingplateshavingthicknessesgreaterthan half the diameter of thepins, co siderationmay by given tothe effect of the distributionof bearing pressureson effective span.

Note Where a cross member or bearer terminates on an abutment or pier,the centresof the bearingthere n shall be takenasoneendot’ theeffe-ctive span.

505.2. Effective Depth

The effective depth of plate or trussgirder rhould be takenasthe distancebetweenthe centresof gravity of the upperand 1owe~flangesor chord’~.

505.3. Minimum Dep%The minimum depth preferably shall not he less than the

following:

tO For trusses 1/10th of effective spsn

(ii) For rolled steel joists

and plategriders = I ~25of effectivespan(iiij For cnmpostite steel = asspecified in the relevant

andconcrete section.

23

IRC: 24-1967

505.4. Spacing and Depth of Main Girders

The distanceof centresbetween the main girdersshould besufficient to resist overturingwith the specifiedlateral forces and

loading conditions. Otherwise specialprovision mustbe madetopreventthis. This distanceshall not be lessthan L’2Oth of the span.

The depth between the gravity axesof the top andbottomchordof openweb girdersshall not be greaterthanthreetimesthedistancebetweenthe centresof main girders.

505.5. Symmetry

All sectionsshall, as far as possible, be symmetrical abou tthe line of resultant stress, and all rivets shall be grouped symme-trically about the sameline.

505.6. Minimum Sections

505.6.1. No plateor rolled sectionsless than8 mm thicknessshall be usedin the main membersof the bridgestructurewhenboth sides are accessiblefor paintingnor lessthan 10 mm whenonly one side is accessibleexceptwhenit is rivetedor weldedtoanotherplateor rolled section. In floor plates and parapetsaminimum thicknessof 6 mm maybeusedif both sidesareexposedor 8 mm if only one side is exposed. For packing plates, thethicknessshallnot belessthan 1.5 mm.

505.6.2. No angleless75 x 50 mm shall be used Ibr the maingirdersor trussesin riveted construction.

505.6.3, No angleless than65 mm x 45 mm nor flat lessthan50 mm wide should be used in anypart of the structure excepthandrailing.

505.6.4. End anglesconnectingroad bearersto crossgirdersor crossgirdersto main girder should be not less in thicknessthanthreequartersof thicknessof the web of bearerand crossgirdersrespectively.

505.7. Corrosion

All the details shall be designed to reduce to a minimumthe incidenceof corrosion. All parts should be accessibleforinspection,cleaningandpainting; otherwisetheyshould be adequa-tely protectedor effectivelysealed.

24

IRC: 24-1967

505.8. DrainageAdequate drainage shall be provided at all placeswhere

pocketsof depressionsarelikely to hold water.505.9. DeflectIon

505.9.1. Rolled steelbeams, plate girders and lattice girders,shall be designed sothat the total deflection due to live load andimpact shall not exceed1/800th of the span.

505.9.2. The deflectionof cantileverarms dueto live loadand impactshallnot exceed1/400th of the cantilever arm.

505.9.3. In calculating deflection to comply with Clauses505.9.1.and 505.9.2. above,the side-walkLive-loadmaybe igno-red. The grossmomentof inertia shall be used for calculatingthe deflection of beams or plate girders. In calculating thedeflection of trusses, the grossareaof eachmember should beused.

505.10. Camber

Camber maybe required to maintain clearanceunderallconditionsof loadingor it maybe requiredon accountof appear-ance. It may alsoresult from prestressing. Beams and plategirdersof sptinsupto and including 35 m need not be cambered.In the caseof openweb spans,camber,if any,shall be provided asrequiredunderClause507.8.

505.11, Provision for Temperature Changes

505.11.1. Every span should be providedwith meanssoasto permit all longitudinalexpansionandcontractiondueto changeof temperatureoverarangespecifiedin Clause218.4(a) of IRC6 StandardSpecificationsand Code of Practicefor RoadBridgesSectionII combined with the greatestextensionor contractionofthe supported chord due to live load including impact.

505.11.2. Deleted505.11.3. Deleted

505.11.4. Deleted

505.11.5. Deleted

505.12. SpacIng of Trussesand GirdersThe distancebetweenthe centresof trussesor girdersshall be

sufficient to prevent overturing or overstressingdueto lateralforces.

25

TRC: 24-1967

505.13. Anchorage

Anchor andfixing bolts shall be providedwhererequiredtoresistall forceswhich may act on them. Anchorageshall providethe stability equivalentto 50 per centin excessof any possibleover-turning momentof thespanas a whole or of the bearingsdue to allpossibleloadsduring the serviceof the bridge.

505.14. Effective Length of Struts

For th~puropseof determining allowable axial stress,theeffective length / of a compression member shall be takenasfollows

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

(b) Effectively held in positionat both endsandrestrainedin directionat one end, 1’=0,85L

(c) Effectively held in position at both ends but not restrained in directon, 1=L

(d Effectively held in position and restrained in direction at oneend, atthe other end partially restrained in direction but not held inposition, 1=1.5 L

(c~Effectivelyheld in positionand restrained in directionat one endbut not held in position or restrained in direction atthe otherend, /=2 L

whereL=.. length of strut from centre to centre of intersection withsupportingmembersor lateral supports.

For battened strutsthe effective length1, given above,shallbe increased by 10 ner cent. (See also Clauses507.3.3. and507.3.4.).

505.15. EffectIveSectionalArea

505.15.1. The gross sectional areashall bethe areaof thecrosssectionascalculated from specifiedsizes. (Seealso Clause505.21).

505.15.2. Effective sectional areaof amember of flange intensionshall be the grosssectionareawith the following.., deductionas appropriate:

(i) Deductionsfor riiet and bolt holes

Except as required by the following paragraph,the areasto bedeductedsha~1be the sum of the sectionalareas of the maximumnumberof holesin anycrosssectionat rightangleto the directionof stressin the member.

26

lRC: 24-1967

ln the caseof:

all axially loadedtensionmembers,

plategirdersof mild steeLconformingto IS : 226 or lS : 2062and with d1/t greaterthan85,

plate girders of steel conforming to IS : 961 and with d1(tgreaterthan 75,

the areato be deducted whenthe holesarestaggeredshall be thatgivenabove,or if greater,thesum of the sectionalareasof all holeson any zig-zag line extendingprogressivelyacrossthe memberorpartot the member,less S

2t~4Gfor eachgaugespacein the chainof holes,

whered1 = the clear distance between flange angles or, wherethereare no

flange angles, the clear distance betv~eenthe flanges

S = the staggered pitch, i e., the distance,centreto centreof holesinconsecutive lines measured parallel to the direction of stress in themember.

the thickness of the material,and

C = the gauge, i.e., the distance,centre to centre of holes in consecutivelines measured at right angles to the direction of stressin themember.

For sectionssuchas angleswith holesin both legs, the gauge shallbe measuredalong the centreof the thicknessof the section.

in abuilt-up memberwheretiV~chainsof holesconsideredinindividual parts do not correspondwith the critical chain of holesfor the memberas a whole, the valueof anyrivets or bolts joiningthe parts between such chains of holes shall be taken into accountin determiningthe strengthof the member.

(ii) Deductionsfor a tingleangle connectedthroughone leg’

To allow for eécentricity of connection,the areaof the un-connectedleg shall bemultiplied by

30,3a~+a~

where at = netareaof connectedlega2 = areaof unconnected leg.

Where lug angles are used, the wholeareaof the membershall be takenas effective.

27

IRC: 24-1967

505.16. Floor Beams

All floor beams shall be rolled, riveted or welded steelgirdersrigidly connectedto the trusses or may be placedon topof trussesor the girders. Floor beamsmaypreferablybe squareto trusses orthe girders.

505.17. JoistsandStringers

505.17.1. Stringers shall be of steel. They shallbe securelyfastenedto crossbeamsexceptingwherearrangementsare made topermit ofexpansion. Suitable arrangementsfor supportingsuchstringers shall bedesigned.

505.17.2 Stringersshould havefree ends below theexpan-sionjoints in decking.

505.17.3. For steel decking over stringers, the limitof spanlengthsin which steelstringerscan be riveted continuously tothecrossgirdersfrom endto endof span, shall be30 metres. Beyondthis limit, sliding bearingsshould be providedat one or moreinter-mediatepoints.

505.18. Bracing

505.18.1. In all spans,bracings shall be provided totrans-mit to thepiersor abutments theeffect of the lateral and longitudi-nal forces.Wherever theoverhead clearancepermits, lateraldiago-nal bracingshouldpreferablybe provided in theplanes of bothupper and lower chordsof throughspans.

The floor systemmaybe takenas part of the bracing systemprovided it is designedfor thatpurpose.

Wherever thedepthof the girder allows, intermediateswaybracing may beprovided. If it is provided,it shall not betakenasaffording any relief to the lateral systemunless thestressesarecalculated for the complete space frame. Swaybracingwhenprovided shall be proportioned to transmitto the chord supportedon bearings through the web membersat least50 per cent o thepanel lateral load and the vertical membersshallbe designedtoresist the resultingbendingmoment.

505.18.2. The lateralbracing between compression chordsshall bedesignedto resist atransverseshearat anysectionequalto2~per cent of the totalcompressiveforce carriedby both the flangeor chords atthe sectionunderconsideration. This force should beccms~deredin addition tothe wind andcentrifugal forces.

28

IRC: 24-1967

505.18.3. Wherethe restraintis providedby members,later-ally connectedto the chordor beam,suchmembersshall be capa-ble of resistingthe above lateral force apportionedequally to eachpoint of restraintandshall be so bracedor connectedto the otherpartsof the structureas to be capableof resistingthis lateral force.

505.18,4. Throughtrussspansshallbe providedwith portalbracings,as deepas the clearancewill allow. The portal bracingshall be designed to take the full end reactionof the top chordlateral systemandthe endpostsof the portalshall be designed totransfer this reaction to the bearings. In addition, the portalsystem shall be designed to resista lateral shearequalto If percentof the total compressiveforce in the end posts or in the topchords in the end panel whichever is greater.

505.19. End CrossGirders

505.19.1. Endcrossgirdersor crossframesshall beprovidedin all squareendedtrussandgirder spansandas far as possibleinskew spans.Theseshall preferablybe designedto permit the useofjacks for lifting the superstructurefor lubricatingandgreasingof bearings. For this, the allowable stress may be increasedby25 per cent. The end cross girders shall be arrangedto permitpaintingof theside of the beam adjacent to the abutmentbackwall.

505.19.2. in skew bridges, without end girders, the endpanel stringers shall besecuredin correctpositionby end strutsconnectedto the stringersandto the maintrussesor girders. Theend panel lateral bracingshallbe attachedto the main trussesorgirdersandalsoto the endstruts. Adequate provision shall bemadefor expansionmovementof the stringers.

505.19.3. Whenendcrossgirdersareprovided,theyshall bedesignedto resistforces from the live load taken as not smallerthanthosefor which the intermediatecrossgirdersaredesigned.

505.19.4. Crossgirdersandcrossframesshall also be pro-vided at intermediatepointsalongthe lengthof girder where thereis abreakin the deckingfor expansionjoints.

505.20. PlatesIn Compression

505.20.1. The unsupportedwidth of a platemeasuredbet-weenadjacentlinesof rivets, bolts or weldsconnectingthe plate toother partsof thesectionsshallpreferablynot exceed45t where t isthe thicknessof asingle plateor the aggregatethicknessof two or

29

IRC: 24-1967

more plates provided theseplatesare adequatelytackedtogether.Any excess over this width shall not be includedin the effectivesectionalareain computingthe direct compressivestress (Clause507.2.1.4).

505.20.2. The unsupportedprojectionof anyplate measuredirom its edge to the line of rivets or weld connectingthe platetoother partsof the scctionsshall not exceed16t for steel conformingto the IS 226—Specificationfor StructuralSteel and 14t for hightensile steel conforming to the IS 961 -—Specification for HighTensile StructuralSteel, t beingthe thicknessof the plate.

505.21. RivetingandBolting

505.21.1. Effective diameter of rivets, bolts andpins: incalculatingthe numberof rivets, bolts or pins required,the effectivediametershall be takenas

(a) for rivets, thediameterof thehole,(b) for boltsandpins, the diameterof the bolt or pin.

Rivets, bolts or pins in doubleshearshall be consideredashavingtwice the shearareaof thosein single shear.

The effectivebearingareaof a pin, rivet or bolt shall be thediameter multiplied by the thickness of the parttransmittingorreceivingthe load,exccptthat for rivets or bolts with countersunkheadshalf the depthof the countersinkshall be ignoredin arrivingat the length in bearing.

505.21.2. Deductionsfor holesfor rivets, boltü and pins: In~a1culatingthe area to be deducted for rivets,bolts or pins, thefollowing diametersof hole shall be used

(i) for shoprivets, thediameterof the holeshall be applied,(ii) for coubtersunlcrivets or bolts, the diameterof the holeshallbe

taken as 3 inn: largerthan thatof therivet or thebolt,and(iii) for turned and fitted bolts, the diameter of thehole shallbetakenas

the diam:terof the bolt,

505.21.3. Minimum pitch of rivets andbolts: The distancehctwecncentresof rivets or boltsshall be not less than 2f timesthe diameterof the rivet or bolt hole.

505.21.4. Maxinuunpitch of rivets andbolts

(a) The distancebetweencentresef anytwo adjacentrivetsL

1: bolts connectingtogetherelementsin contactof compressionor

30

LRC: 24-1967

tension membersshall not exceed32t or 300 mm whicheveris thelesser,where t is the thicknessofthe thinneroutsideelement.

(b) The distancebetweencentresof two adjacentrivets orbolts in a line lying in the directionof stressshall not exceed 161or 200mm in tensionmembersand 12t or 200 mm in compressionmembers. For thosecompressionmembersin which forces aretransferred through butting facesthis distanceshall not exceed44times the diameter of the rivets or bolts for adistancefrom theabuttingfacesequalto Ii timesthe width of the member,

(c) The distance between centresof anytwo consecutiverivets or bolts in a line adjacentto andparallelto an edge of anoutsideplate shallnot exceed100 mm + 41, or 200 mm whicheveris the lesser,in compressionor tensionmembers,

(d) When rivets or bolts arestaggeredat equalintervalsandthe gaugedoesnot exceed75 mm, the distancebetweencentresof rivets or bolts, as specified in (b) and(c) abovemaybe in-creasdby 50 per cent,

505.21.5. Edge distance: The minimum distancefrom thecentreof anyholeto the edgeof an elementshall be l~ times thediameter of the hole for shearedor handflame cut edgeand 4times the diameterof the hole for a rolled, machine flame cut,sawn or planed edge. Where two or more partsareconnectedtogether,a line of rivetsor bolts shallbeprovided ata distance ofnot more than38.0 mrn+4t from the nearestedge, wheret is thethicknessof the thinneroutsideplate.

505.2 1,6. Rivets or bolts through packing The number ofrivets or bolts transmittingshearthroughpackingshallbeincreasedabovethe numberrequiredby normal calculationsby 2 per centfor each 1.5 mm thicknessof packing, exceptthat for packings6.0mm or lessthick, no increaseshall be made,

For double shear connections packed on bothsides,thenumberof additionalrivets or bolts requiredshall be determinedfrom the thicknessof the thicker packing.

The additional rivets or bolts maybe placedin an extensionof the packing.

505.21.7. Long grip rivets: The grip of rivets carryingcalculatedloadsshallnot exceedeight times the diameter of theholes. Where the grip exceedssix times the diameterof the holes,

31

IRC 24-1967

the number of rivets required by normal calculations shallbeincreased by not less than one per cent for each additionaL 1.5 mmof grip.

505.21.8. Rivets in tension The use of rivets in tensionshould be avoided whereverpossible,but if their use is unaviod-able, the stress shall not exceed than that specified in Clause 504.3.

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

505.22. Welding : The design of welds in steel shallgenerallybe asper IRS s%eldlngcode

505.22.1. Working stressesin weldedjoints: The workingstressshall he basedon the following permissibestresses for staticloads

Compressionor tension 14.! kg per sq.mm

Sheir in butt or fillet welds other 10.2 kg per sq. mmthan in web splicesof beams&plate girdersShear in butt or fillet weldsin 8.5 kg per sq. mmwebsplicesof beams& plategirders

505.22.2. Paekings in weldedconstruction: Wherea pack-ing is used betweentwo parts the pa~kmg andthe welds connecting it to eachpart shallbe capable oftransmittingtheloadsbetweenthe parts exceptwhere the packingis too thin to carry the lOad orpermit the provisionof adequatewelds, whenit shall be trimmedflush with the edgc’ of the narrowerpart andthe load shallbetransmittedthroughthe welds abut the welds being increased insize by an amount equal tothe thicknessof thepacking.

505.22.3. Intermittent frau ~~velds: intermittentbutt welds

shall not be used.

505.22.4. Fillet we’ds

505,22.4.1. End returns: Fillet welds broughtuptoa cornerat the endsor sides of parts ofmembersshall, where practicable,he continuedaround the corner for n distanceof’ not less than twicethe size olthe weld.

505.22.4.2. Endconnectionsby meansof sideflflets: If sidefillets ilonc areused in endconnections the lennth of each side

32

IRC 24-1967

fillet should be not lcss than the distancebetweenthe fillets. Sidefillets may be eitherat the edges of the membersor in slots orholes.

505.22.4.3. intermittentfillet welds Intermittentfillet weldsshall not he usedwherethey would result in the formation of rustpockets. The distancealong an edgeof a part betweeneffectivelengthsof a consecutiveintermittentfillet welds,whether the weldsare in line or staggeredon alternatesidesof the edge,shall notexceed12 timesthe thicknessof the thinnerpart when in compres-sion or 16 timesthe thicknessof the thinnerpart when in tension,andshall in no caseexceed200 mm.

505.22.4.4. Where intermittentfillet welds areusedto formT-joints, the thicknessreferredto aboveshall be that of Ihe tableof the T. In a line of intermittentfillet welds, thereshall be aweld at theendsof the part connected;for welds staggered alongtwo edges,this shall apply to both edges.

505.22.4.5. in built-up members in which platesare con-nectedby intermittentfillet welds,continuousside fillet weldsshallhe usedat the endsfor a length not less than the width of the plateconcerned.

505.22.5. T-butt joints : Butt, welds in T-joints shall becompleted by meansof fillet weldseachhavinga leg length of notless than 25 percentof the thicknessof the outstandingpart.

505.22.6. Testingof welds

505.22.6.1. X-ray tests or any other non-destructive testsmay also be carried out to ensure soundnessof welds. Weldswhich are required to carry tensile or shearstressesin excessof 66~percentof those laid down in Clause505.22.1.shall be examinedby meansof X-rays or someequally effectivemethod.

505.23. Lug .kngles

505.23.1. Lug angles connecting a channel or similarmembershall, as far as possible,be disposed symmetrically withrespectto the section of the member.

In the case of anglemembers,the lug anglesand their con-nectionto the gussetor othersupportingmember,shall be capableof developing a strengthnot Less than20 percent in excess of theforce in the outstandinglug of the angle, and the attachment of

33

IRC: 24-1967

the lug angles tothe angle member shall becapableof developinga strength40 per cent in:exCess of that force.

505.23.2. In the case of channel or similar members, the lugangles, and their connection to the gusset or other supportingmember, shall be capable of developing a strength not less than 10per cent in excess of the force not accounted for by the directconnection of the member,andthe attachmentof the lugangles tothe member shall becapableof developingastrength20 percentin excess of that force.

505.23.3. In no case, less than two bolts or rivets shallbeused for attaching thelug angle to thegusset or other supportingmember. -

505.23.4. The effective connectionof the tug angleshall,asfar as possible terminate at the end of the member connected, andthe fastening of the lug angle to the member shall preferably startin advance of the direct connection of the member to the gusset,etc.

505.24. Clevlsesand Turn Buckles

Clevises and turn buckles shall in all cases develop the full

strength of the bars of which they form a part.

505.25. Pins

All pins of more than 230 mmdiameter shall have an inspec -tion hole of notless than 50 mm in diameter throughthe axisunless other means of inspection are provided.

505.26. Composite Use of Mild SteelandHigh TensileSteel

Steel conforming to IS 226 and IS 2062andhightensilesteelconformingto IS: 961 may beusedjointly in astructureor in anymember of a structure provided that the maximum stress in eachelementdoesnot exceedthe appropriatepermissiblestress.

505.27. CompositeAction of Steeland Concrete

Where steelconstructionis usedin conjunctionwith concreteand provision is madefor adequate interactionbetweenthe twomaterials, theyshall be treatedas forming a compositememberfor the purpose of calculation.

In such cases, the construction will comply with requirementsof the IRC: 22—StandardSpecifications&Code of Practice for

34

IRC: 24-1967

Road Bridges Scetion VI - Composite Construction for RoadCulvertsandMedium SpanBridges.

505.28. CompositeConnectionsIn connectionsWith morethanonetypeof fastening,trans-

mittin& a force direct,thefollowing requirementshall be compliedwith:

(a) Rhets with close tolerance bolts. The force may beconsideredassharedproportionatelybetweenthe rivetsandthe bolts.

(b) Rivetsor close tolerance bolLc with black bolts : Therivets orclosetolerance bolts shall be designed to transmit the entire force.

(c) Weldswith anyother tppeof connection: The weldsshall be designedto transmit the entire force.

506. SOLID WEB GIRDERS (PLATE GIRDERS ANDROLLED BEAMS)

506.1 General

506.1.1, ProportIoning: Solid web girdersshall be proport-ioned on the basis of the moment of inertia of the grosssectionwith the neutral axis at the centroidof the section. In computingthe maximum stress, the stressescalculatedon this basisshallbe increased in the ratio of gross to effective,areaof the flangesection.

506.1.2. The fld’nge sectionalareain riveted or bolted cons-truction shall be takento be that of the flange plates,flangeanglesandthe portion of the web and side plates, if any, betweentheflange angles. In welded construction, the flange sectionalareashall be taken to be that of the flange plates and of the tongueplates(thick vertical plates connecting flangeto web)if any,up toa limit of 8 times their thickness which shall not be less than twicethat of the web (Clause 506.4.).

506.1.3. The effective sectional area of compression flagesshall be the gross area with the specified deduction for excessivewidth of plates (Clause 505.20.) and the maximum deduction foropen holes and holes for black boltsoccurringin a section perpend-icular to the axis of the member (Clause 505. 21.2.).

506.1.4, The effective sectionalareaof tension flangesshallbe the grosssectionalareawith deductionsfor all holesas specifiedfor rivet and bolt holes in tension members.

35

IRC: 24-1967

506.2. Maximum Average Shear Stress

Maximum shearstressshall be calculatedas follows

(a) in caseof rolled beamsand channels,it shall be equalto themaxi-mumsheardivided by the productof the thicknessof theweb andthe overall depthof section.

~b) In caseof websof plate girders, it shall be themaxintuntsheardivided by the productof the thickness of webandthe full depthof web plate.

(c) in the case of webshaving varied thickness in thedepthof thesectionby useof tongueplatesandthelike andin the caseof othersections, themaximum shear stressshall be foundby determiningthedistribution of shearstressesoverthedepthof the section.

.Vo:c: Webshaving openingslarger than thoseusedfor rivets, bolts or otherfasteningsrequire special consideration and are not coveredhere.

506.3. SlendernessRatio

!)r~,of a girder shall not exceed 300. It shallnot exceed150for cantilevers.

Where / = the effective length of the compressionflangeasspecified in Clause506.5.

p9 the radiusof gyrationof the whole girder about

its y-y axis basedon the gross momentof inertiaandthe grosssectionalarea.

506.4. Flanges

506.4.1. Section

506.4.1.1. SectIonin riveted or bolted constructionFlange anglesshall preferably form as largeapart of the

areaof the flangeas practicable and the numberof flange platesshall be kept to aminimum. Where flange platesareused,theyshall preferablybe of equal thicknessandat leastoneplateof thetop flange shallextend to the full length of the girder unlessthetop edgeof the web is finished flush with flangeangles.

506.4.1.2. Sectionin weldedconstruction

Eachflangeshallpreferably consistof a singleplate unlessaplateof suitablethicknessis not available. This single platemayconsistof morethan oneplate laid endto end effectivelyunited attheir junction.

36

IRC: 241967

506.4.2. Compression flange

506.4.2.1. In riveted or bolted construction, the flange plates,unless stiffened at the edges,shallnot project beyondthe outerlinesof connectionsto the flange angles by more than 16t, formild steelor 14t for high tensile, where r is the thickness of thethinnestflange plateor aggregatethickness of two or moreplates,when the projecting portionsof theseplates areadequatelytiedtogether.

506.42.2. Compressionflangein ‘nelded construction: Theflange plates, unless stiffened at their edges, shall not projectbeyondthe line of connectionsto the web or tongue platesbymorethan l2t, were z is as defined in Clause506.4.2.1.

506,4.2.3. Tension flange plates: In all cases, the flangeplates stiffened or unstiffened at their edges,shall not projectbeyond the outer line of connections to the flange anglesor (whereno flange anglesto the web or tongueplates)by morethan 20 r.

506.4.2.4. For the flangesof girderswith vertical stiffeners,only (see Clause 506.6.4.3.) where d1(t is greaterthan 130 in thecaseof mild steelor 110 in the caseof high tensile steel,and whenthe average shearstress in the web is greaterthan 0.6 of the per-missiblestress given for mild steel in Tables 9A and 9B, thequantity J/b

3t shallnot be less than2.Sx10”~in the caseof mildsteel,and 3x 10’s in the caseof high tensilesteel,

WhereI=the momentof inertiaof the compression flange aboutitsaxis normalto the web taken asthatof flange anglesandplates and the enclosed portion of web in caseot’ rivetedconstructionandasthe flange plate togetherwith a depth ofweb adjacent to the flange plate equal to 16 times the webthickness in caseof weldedconstruction,

d,=effectivedepthof girderas definedin Clause506.6.1.

b spacingof stiffeners

V ==thicknessof web

506.4.3. Curtailment of lunge plates: Each flange plateshall be extended beyond its theoretical cut-off point, aS theextension shall contain sufficient rivets,bolts or welds to developthe loadin the plate calculated from the bending moment andgirdersection (takento includethe curtailedplate)at the theoreticalcut-off point.

37

lItC: 24~1967

ln thc caseof welded plates, the endsof the plateshaltbetaken to a point to preventlines of welds at anglesto the linesofstrcss.

506.4.4. Splices

506.4.4.!. Flange joints shouldpreferablynot be located atpoints of maximumstress.

506.4.4.2. Wherecover platesare used,their crosssectionalareashall be not lessthan the area of the flange elementsplicedand the calculated working stressin the outer covers shall notexceedthe allowable working stressin •the flange. Both in thetensionandcompressionflanges,there shall be enough rivets orbolts on eachsideof the spliceto developthe effective strengthofthe memberspliced. In weldedconstruction,the flange platesshallbejoined by butt welds whereverpossibleandtheseshall developthe full strengthof the sniallerplate.

506.4.5. ConnectIonof flangesto web: The flanges of plategirdersshall be connectedto the web by sufficient rivets, boltsor welds to transmit the horizontal shear force combined withanyvertical loads which are directly applied to the flange.

In caseof local loading,on the top flange,the rivets, in addi-tion to the stresscausedby the transferring of web stresses,are alsostresscdby the vertical action of the flange anglebeingpresseddown by theload transferring media andthe consequentdown-ward pressure on the web should be accounted for by takingthe weightof oneof the wheel loadsas distributed overalengthof 900mm.

In weldedconstruction,wherethe web is in closecontactwiththe flange before welding, vertical loads causing compressionmay be deemedto be resistedby the bearing betweenthe flangeand web.

506.5. Effective Lengthof CompressionFlanges

The effective length i of the compressionflangefor bucklingnormal to the planeof the girder to be usedshall be as given inClause506.5.1.to 506.5.5. exceptthat, whenthe load is applied tothe compression flange and both the loadand the flangearefree to movelaterally,the values given shall be increasedby 20percent.

38

IRC 24-1967

506.5.1. Simply supportedgirderswith no intermediatelateralsupportto compressionflange : For simplysupportedgirderswithno lateral bracing between compression flanges and no crossframes,but with each end restrained against torsion(seeClause506.5,1.1.)

(a) with endsof compressionflanges unrestrained against lateral bending(i c., free to rotate in plan at thebearing,.....I=span

(b) with endsof compressionflangespartially restrainedagainstlateralbending~e.g.,securelycleatedconnections)..,.,1=0.85span

(c) with endsof compressionflangesfully restrainedagainstlateral ben-ding (i.e., not freeto rotatein planatthe bearing)..,..1=07 span

506.5.1.1. Restraint against torsion at the supportscan beprovidedby web or flangecleats,by bearingstiffeners,~hyendframesor by lateral supports to the compressionflange. The restraintclementshall be designed to resist, in addition to the effectsofwind and other applied lateral forces,the effectsof ahorizontalforce F acting normal to the compressionflangeof the girder atthe level of the centroidof this flange, where

~~fb

whereI hasthevaluegivenabove,Cz the critical stressin the flange given by

Clauses504.4.2,and504.4.3.

= thecalculated working stressin flange

the deflection of the flange under the action of unit horizontal force

as defined in Clause 506.5.2.

506.5.2. Simply supported girders with compressionflangeslaterally supported by U-frames: For simply supportedgirderswhere there is no lateralbracingof the compressionflanges,butwhere cross members andstiffeners forming U-frames providelateral restraint

I = 2.5 $‘(E1a8)

but not less than awhere

== the virtual lateral displacement of the compressionflangeat theframenearestmid-spanof thegirder, takenasthehorizontal deflec-don of the stilTuers atthepointof its intersection with the centroidof thç compressionflange,undertheactionof unit horizontal forceappliedat thispOintto theframeonly.

This deflection shall be computed assumingthatthecrossmember is free to deflect vertically and ~that the tangentto the

39

tRC :24-196?

deflection curve at the centre of its span remains parallel unrc~trai-

ned cross member

a distance between frames

1 maximum moment of inertia o1 compression flangeaboutthey-y

axis of the girder.

(I) When3 is not gr:ter than ..~

(2) in casesof symmetricalU-frameswh&e crossmembersand stiffenersareeachof constant moment of inertia throughouttheir own length,

(d’~ (d)2b3E1, El,

where

= distance of the centroid of the compresion flange from the top ofthe cross member

= distance of the centroid of the compression flange from the neutralaxis of the cross member

b = half the distance between centres of the main girders

I, — moment of inertia of a pair of stitiners about the centre of the webor of a singlestiffener about the face of the web

1, a moment of inertia of the cross member in its planeof bending

U-framesshall haverigid connectionsandshall be designedto resist, in addition to the effectof wind andotherapplied forces,the effect of a horizontalforce F acting normal to the compressionflange of the girder at the level of the centroid of this flangeandhaving a value equal to that given by the formula in Clause506.5.1.1./ havingthevalue 2.5~/(EIa 8)

506.5.3. Girders with laterally supportedcompressionflanges

(a) for all girders where there is effective lateralbracingto thecom-pressionflange,

the distinct betweencentres of intersectionof the bracing withthecompressionflange.

(b) for all girderS where the compression flanges are unbraced butsupported laterally by members controlled by an effectivebracingsystemor anchorage,

/ ~= thedistancebetweencentresof lateral supports.

40

IRC : 24-l9~

506.5.4. Cantileverbeams~ithout intermediatelateral support

Foi cantileverbeamsof projecting length L,

(a Built in at the support, free at the end 1 0.85 L

(l) Built in at the support, restrained against torsion atthe free end by contiguous construction I = 0.75 L

(c) Built in at the support, restrained against lateraldeflection and torsion at the end / = 0.5 L

(d) Continuous at the support, unrestrained againsttorsion at the support and free at the end

(e) Continuous at the support with partial r~iaintsagainst torsion at the support and free at the ~t~d 1= 2 L

~f) Continuous at the support, restrained against torsionat the support and free at the end I — L

Wheic in eases(d), (e) and(f) thereis a degreeof fixity atthe ~free’ end, the effective length shall be multiplied by 0.75/0.85and 0.5/0.85for degreesof fixity correspondingto cases(b) and(c)respectively.

Restraintagainsttorsion at the supportscan be provided asin Clause506.5.1.1.above.

506 5 5 Compressionflangesupporl*Igcontinuousdeck Acompressionflange continuouslysupportinga reinforcedconcreteor steel deck shall be deemed to be effectively restrained laterallythroughout its length (i.e.i=0) if the frictional or positive connec-tion of the deck to the flange is capableof resistinga lateral forceof 2~per centof the force in the flangeatthe point of maximumbending moment, distributed uniformly along its length, in addi-tion to othcr lateral forces.

506.6. Webs

506.6.1. Minimum thickness: The thicknesst, of the webplate shall not be lessthan 8 mm and shallnot be lessthanthefollowing:

(i) for iinstiffened webs:d,f85 for steelconformingto IS .: 226d1/75for steelconformingto IS :961

(ii) for vertically stiffenedwebs11180of the smallerclearpaneldimension,

//270of thegreaterclearpaneldimension,and

41

IRC 24-1967

dJ200 for steel conforming to IS : 226 or

~1,/I80for steel conforming to IS : 961

(iii) for webs stiffened, both vertically and horizontally and with thehorizontal stiffener at a distance from the compression flange of 215of the distance from the compression flange to the neutral axis

i/ISO of the smaller clear dimension in each panel

1/270 of thegreaterclearpanel dimension,and

d,/250for steelconformingto IS : 226 ord~/225for steel conforming to IS : 961

(iv) when th~ is also a horizontalstiffner attheneutralaxis of thegirder:

i/ISO of the smaller clear dimension in eachpanelor

1/270of the greater clear panel dimension, and

d,/400for steelconformingto IS 226 or

d,f360 for Steel conformingto IS : 961

lu the above d1 is the clear distance betweenflange anglesorwherethereare no flangeangles, betweenflanges(ignoring fillets);but where tongue plateslaying a thickness notlessthan twice thethicknessof the web plate are used,d1 is the depthof the girderbetween theflangeslessthe sum of the depthsof the tongueplatesor eight times the sumof thethicknessof the tongue plateswhich-everis less;and

d2 is twice the clear distancefrom the compressionflangeangle or plate, or tongue plate to theneutralaxis.

506.6.2. Web edges: For girders of riveted or boltedcon-structionwhich have no flange plates, the topedgeof the web shallbe flushed with the angles The bottomedgeof the webplate maybe setback from the heelsof the angles notmore than 5 mm Forgirders which have flanp plate, the edgeof the web plate~may besetback from the heelsof the angles notmore than 5 mm on eachside subject to the requirements for the edgedistanceof holes.

506.6.3. Splicesin webs: Splicesin the websof plate girdersand rolled sections used as beamsshall be designedto resist theshearingforcesandthe~niomentsin the webatthe spliced section.

in riveted or bolted construction, splice plates shall be pro-vided on each sideof the webs.

42

1RC 241967

506.6.4. Web stiffeners

506.6.4.1. Rolled I beamsandchannels: For rolled 1 beamsandchannels,load bearingstiffenersshall be providedat points ofconcentratedload (including pointsof support)wherethe concen-trated load or reactionexceedsthe value of

Pa,,x V B

where Pa,, -= the allowable a’dal stress for struts as given in Clause504.4. for a

(d ~/3slenderness ratio of

$ = webthickness

ci, ~- cleardepth of web between root of filletsB = the length of the stiff portion of the bearingplus the additional

length given by dispersion at 45’ to the level of the neutralaxis.

The stiff portion of a bearingis that length which cannotdeformappreciablyin bending,andshallnot be takenas greaterthanhalfthe depth of the beam for simplysupportedbeamsand the fulldepthof the beamfor continuousbeams.

506.6.4.2. Plate girders: For plate girders, load bearingstiffenersshaltbe providedat po/ntsof support and at points ofconcentratedload, the detailsof theseloadbearingstiffenersshallbe as given below:

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

Load bearing stiffeners, wherethe concentratedload causescompressionin the stiffener, shall be designed as struts, assumingthe sectionto consistof apair of stiffenerstogetherwith a lengthofweb on each side of the centreline of the stiffenersequal,wberepossible,to 20 times the web thickness. The radius of gyrationshall he taken about the axis parallelto the webof the beamofgirder. Working stressshall be in accordance‘with the appro-priate allowable value for a strut, assumingan effective lengthequal to 0.7 times the length of the stiffener.

The outstanding legs of each pair of load bearingstifl’enersshall be so proportionedthat the bearingstresson thatpartof theirareain contactwith the flangeandclearof the root of the flangeorflange anglesor clearof theflangewelds,doesnot exceedthe bear-ing stressspecifiedin Clause504.3.

43

IRC : 24-1967

Load bc~iringstiffenersshall be provided with sufficient rivets,bolts or welds to transmit to the web the whole of the load in thestiffeners.

Load bearing stiffeners shall be fitted to provideatight anduniftrrn bearingupon the flangetransmittingthe load or reactionunless welds are provided betweenthe flangeandstiffenerfor thispurpose. At points of supportthis requirementshallapply at bothflanges. Wherethe endsof stiffenersarenot fitted o~connectedtothe flangetheyshalt be kept well clearof theflange.

Load bearing stiffners shall not he joggled and shall besolidly packedthroughout.

When load bearing stiffeners at support are the sole meansofproviding restraintagainsttorsion(Clause 506.5.), the moment ofinertia 1 of the stiffenershall riot be tessthan

D’T RX

where / moment of inertia of the pair of stiffeners about thecentreline of theweb plate

0 overalldepthof girderT maximumthicknessof compressionflangeR reactionon thebearing

tott~lload of girder

In addition, the baseof the stiffenersin conjunction with the bear-ing of the girder shall be capableof resistinga momentdue to thehor/zontal force F spec/fiedin Clause506.5.1.1.

506.6.4.3. Intermediatestiffeners: Vertical stiffenersto limitweb buckling shall be providedthroughoutthe lengthof the girderat a distanceapartnot morethanl~di whenthe thicknessof theweb is less than that specified for unstiffened webs in Clause506.6.1. The spacing of the stiffenerwebsshall be madecloserwhenso requiredaccordingto the allowableaverageshearstressinthe web.

where c1~— depth of web as defined inClause5O6.6.I. Thesestiffenersshall bedesignedso that

(It, t~1 is not less than 1.5 x

where 1 ‘--- themomentof inertiaof apairof stiffenersaboutthecentreofthe web, or of asinglestiffeneraboutthefaceof theweb

t minimum requiredthicknessof web

44

IRC 24-1967

S . :‘..: maximumpermittedcleardistance betweenstiffenersfor thickness t.

Note Where on the basis of requirementsof strength,the webthicknesspro-vided is greaterthanthe,minimumrequired, or the stiffener spacingismade closerthan themaximumpermissible,the momentof inertia of thestiffenersneednot be correspondingly incrcased.

Intermediatc vertical stiffeners, when not actingas load bearingstiffeners,may be joggled and maybc in pairs placedoneon eachside of the web or single, and shallextendto thefull depth of theweb, Unless theyareconnectedto the flanges, they shall be keptwell clear of them.

506.6.4.4. Horizontal stiffeners: Where horizontalstiffenersare used in addition to vertical stiffenersthey shall be as follows

When the thickness of the web is less thand2/200for steelconformingto IS: 226 or d2/lSO for steel conforming to , 15:961where d2 == depth of web as definedin Clause506.6.1.one hori-zontal stiffener, on oneor both sidesof the web, shallbe placed ata distancefrom the compressionflange equal to 2/5 of the distancebetweenthe compressionflange andthe neutralaxis. This stiffenershall havea moment of inertia I not lessthan 4 St~whereI and 1areas definedin Clause506.4.3.above,and S is the actual distancebetweenstiffeners.

A secondhorizontal stiffener, on one or both sidesof the web,shall be placed on the neutralaxis of the girder when the thick-ness of the webis lessthan d2/250for steelconforming to IS: 226and d2f225 for steel conforming to iS: 961. This stiffener shallhave a momentof inertia I not lessthan d2 t

3 whereI and r areasdefinedin Clause506.4.3.aboveand d

2 in Clause 506.6.1.

Horizontal stiffeners shall extend betweenverticalstiffenershut neednot be continuousoverthem, or coni*ted to them.

5Q66 45 Externalforceson intermediatestiffeners Whenvertical intermediatestiffeners are subject tobending momentsandshears due tothe eccentricityof vertical loads,or the actionoftransverseforces, themomentof inertia I of the. stiffenersgiven byClause506.6.4.3.above shall be increasedas follows:

Bending moment on stiffener due to eccentric/tv of vertical load-ing with respect to 1/ic vertical avis of the web:

1.5 MD’Increaseof I

45

IRC : 24-1967

Lateral loadingon stiffener:

3 PlYIncrease of I —

whereM = the applied bending momentP = the lateral force to betakenby stiffeneranddeemedto be

appliedat thecompressionflangeof thegirderD overall depth of girder

t = thicknessof web

E = Young’s modulus

506.6.4.6. Connection of intermediate stiffeners to web:Intermediatevertical and horizontal stiffeners not subjected toexternal loads, shall beconnectedto the web by weldsor rivets.in orderto withstand a shearing fotce in kg per mm2 betweeneach component of the stiffener and the web, of not lessthan

12.6 wheret equalsweb thickness/n mm andh equalsthe pro-jection in mm of the stiffener componentfrom the web.

506.6.4.7. Outstandof all stiffeners: Unlessthe outer edgeof eachst/ffener /s continuouslystiffened,the outstandof all st/fe-nersfrom the web shall not exceedthe following

For steelsections—16t for steelconformingto IS: 22614 t for steelconformingto IS: 961

For flats —12 t for all steelswheret is thethicknessof the sectionor flat.

507. OPENWE~GiRDERS

507.1. General

For triangulate4 frames designed on the assumptionof pinjointed connections,mmbers meeting at a’ joint should, wherepracticable, have their centroidal axes meeting at a point; andwhereverpracticablethe centreof resistanceof aconnection shalllie on the line of actionof the load soasto avoid amomentdue,toan eccentricityon the ‘connections.

Where the designis basedon non~/ntersectingmembersat ajo/nt, all stressesarising from the eccentr/cityof the members shallbe calculated and the stressseskeptwithin the limits specifiedinthe appropriateclausesof this code.

46

IRC: 24-1967

507.2. CompressionMembers

507.2.1. General

507.2.1.1. The top chord and endposts shall normally be ofthe inverted trough sectionconsistingof two side segmentswith oneflange plate at top andwith tie plate andlacing or battens on theopn side. In chordsof light section,tie plates,lacings or battensmaybe usedin place of the flangeplates.

507.2.1.2. The top chordsandend postsshouldbe stiffenedwherenecessaryby diaphragms. The overall width of top chordsshould preferably be not lessthan 1/15th of the unsupporteddis-tancebetweenthe pointsof intersectionof the lateralbracingor ofsubstantial side brackets where lateral bracing is omitted, norshould the total length of the chord exceed45 times its width unlesseffectivelateral staysareprov/ded.

507.2.1.3. if the shapeof the trusspermits,chordsshould becontinuous,top andbottomchord splices should be as near thepanelpoints aspracticableandpreferablyon the sideof the panelpoint where the smallerstressoccurs.

507.2.1.4. The unsupportedw/dth of a plateforming anypart of a compress/onmember,measuredbetweenadjacentlinesofrivets, bolts or welds connecting the plate to otherpartsof thesection,unlesseffectively stiffened,shallnot exceed 90 t for mildsteel conforming to IS: 226 and80 1 for H.T. steelconformingtoIS: 961,

where I is the thicknessof theplatein thecaseof asingleplate,or the total thicknessof two or moreplateseffectively tackedtogether~seealsoClause505.20).

507.2.1.5. The opensid~sof bui1t~upcompression-membersof U or I sectftinsshall be connectedby lacing, battening or per-lorahd plaic’s where the length of the outstandtowardsthe openside exceeds16 times the meanthicknessof the outstand

507 2 1 6 1 a~rng and batt~ning shall bedesignedm aLLorlance with Ciausc507.2.6.and507.2.7. andshall be propqrtionedtoresista total tran~verseshearforce Q at any point in the length ofthe member ~qual to at least2~percentot the axial foic~ein themembertogetherwith all sheardue to externalforces,if any, in thep1 mc of lacing Fh. shearforLe Q shall be conside-edas dividedamoneall transversesystemandplating in parallel planes,

47

IRC 24-1967

507.2.1.7. Compression members composedof two or morecomponentsconnected,as describedin Clauses 507.2.5.to 507.2.7.may be des/gnedas homogeneousmembers.

507.2.1.8. All bu/lt-up compression members should be

stiffenedby batteningor lacing as specified in this code. Whenthe

componentpartsarejo/nedtogetherto form a unit, the ratio -i-- for

any component partbetweenthe connectionsof lacingshouldnotbe morethan0.7 times the slendernessratio of the member as awhole.

507.2.1.9. At the endof rivetedstrutsfor alength equaltoat least 4 times the w/dth of the member,the pitch of the rivetsshall not exceed4~d/ameter.

507.2.2. Effective sections

507.2.2.1. The properties of the crosssectionshall be com-putedfrom the effectivesectionalarea. When platesare providedsolely for the purposesof lacingor batteningtheyshallbe ignoredin computingthe radiusof gyrationof the section.

507.2.2.2. The effective sect/onal area shall be the grossarealessthe specifieddeductionsfor excessivewidthsof plates(seeClause 505.20.) and the maximumdeductionsfor openholes,in-cluding holes for pins and black bolts (see Clause 505.15.2.)occurringin a sectionperpendicularto the axis of the member.

507.2.2.3. The ratio of effectivelengthto the leastradiusofgyrationshall not exceed

120 for main members,and140 for wind bracingandsubsidiarymembers.

507.2.3. Effectivelengths

507.2.3.1. In riveted,boltedor weldedtrussesthe compres-sion membersact in acomplexmannerandthe effectivelengthItobe used/n Clause504.4. shallbe takenas givenin Table 11,exceptthat, for battenedstruts,all valuesgiven shallbe increasedby 10per cent.

507.2.3.2. For single-angle discontinuous struts conne.ted to gussetsor to a section either by riveting or bolting by notlessthantwo rivetsor bolts in line along the angleat eachend,orby their equivalentin welding, the eccentricity ofthe connection

48

IRC 24-1967

TAQLE 11. EF~Ecr1vEL~NOTKOFCOMPRESSION MEMURS

~%4ember

Effectivelength I of member

For bucklingin the plane

of truss

‘

For buddingnormal to theplaneof truss

~Compressionchord or compres- Compressionsine member chord or corn-effectively pressionmemberbracedby lateral unbrncedsystem

0.85 x distancebetweencentresof intersection

Chords with thewebmembers

0.70 x distanceSingle betweencentres

triangulated of intersectionsystem with main

chords

Multiple in-Webs tersection 0.85 x greatest

system where distance betweenadequate centresof anyconnections two adjacentare provided intersectionsat all pointsof intersec- ‘tions

0.8 x distancebetweencentres SeeClauseof intersection 507.2.4with lateralbracisigmembersor rigidlyconnectedcrossgirders

085 ~ distance distancebetweenbetween centres centresofof intersections intersections

~~

0.70x distance 0.85 x distancebetween centres between centres01’ intersection of intersectionwith the main with mainchords chords

‘~

Note : The intersectionsreferredto arethose of the centroidal axes of themembers.

49

IRC 24~i967

with t’cspe~to the centroid of the strut may be ignored andthestrut designedas an axially-loaded member providedthat thecalculated averagestress doesnot exceed the allowable stressesgiven in Table4 of Clause 504.4. in which I isthe length of thestrut, centre to centre of fasteningsat eachend,and r is the mini-mum radiusof gyration.

507.2.3.3. For single angle discontinuousstrutsintersectedby, andeffectively connectedto anotherangle in cross bracing, theeffective length /n the plane of the bracing shall be taken as inTable II in Clause507.2.3.1. In the plane normal to the plane ofthe bracing, the effective length shall be taken as the distancebetween the points of intersection and the centroidsof the mainmembers. In calculating thc ratio of slenderness,the rad/us ofgyration aboutthe appropriaterectangular axis shall be taken forbuckling normal to the plane of the bracing and the leastradiusof gyrationfor buckling in the planeof the bracing.

507.2.4. Effective length of unbracedcompressionchordsFor simply supported trusses with ends restrained at thebearingsagainsttorsion, the effective length I of the compressionchord for buckl/ng normal to the planeof the truss,to be used inthe equationgiven /n Clause504.4,shall be takenas follows

507.2.4.1. WIth no lateral support to compression chord:Where there is no lateral bracingbetween compressionchordsand no cross frames,

1= span

507.2.4.2. With compressionchord supported by U-frames:Where there is no lateral bracing of the compressionchord,but wherecrossmembersandverticals forming V-framesprov/delateral restraint:

but notJess than a

whereS =the virtual lateraldisplacementof thecompression‘chord attheframenearest mid span of thetruss takenasthehonzontal deflectjon of the verticalmemberatthepointsof itsintersectionwith thecentroidof thechordsundertheactionof aunit horizontal force appliedat this pOint ‘to the frameonly.

This deflection shall be computedassumingthat thecrossmemberis free to deflect verticallyandthatthetangenttothedeflectioncurveat the centreof its spanremainsparalledto the neutralaxisof theunrestrainedcrossmember~

50

IRC: 24-1967

a~=distancebetweenframes

I maximummomentof inertia of compressionchord about

the p—i’ axis of the truss

when S is not greaterthan —--——————,

40Ff

in caseof symmetrical U-frames wherecrossmembersandvcrticals are eachof constantmomentof /nertia throughout theirown length.

(d’)3 (d”)1b

~:: ~__-~*

3Ff, El,

where

distanceof the centroidof thecompressionchordfrom the top of thecrossmember

d”= distanceof thecentroidof the compressionchordfrom the neutralaxis of thecrossmember

b = half the distancebetweencentresof the main trusses

I, = moment of inertia of the vertical in its planeof bendingI moment of inertia of thecro.qsmemberin itsplaneof bending

U-framesshallhaverigid connectionsand shall be designedto resist,in addition to the eff.~ctof wind, andotherapplied forces,the effect of a horizontal force F acting normal to the compress-ion chord of the truss at the level of the c~ntroidof this chordwhere,

1.4xI0~l--

(C,

fb

In theabove formulaF

C~=Eiilerckitical stressin thechord==(l!r)5

where(hasthevalue2 5

f~--the calculatedworking stress in the chord

S =—the deflectionof thechord undertheactionofunit’

horizontal forceasdefinedabove,

Si

IRC 24-1967

507.2.5. Compressionmembers composedof two componentsbackto back

507.2.5.1. Compression members composedof two angles,channelsor tees, back-to-back,andseparatedby a distancenotexceeding50 mm shall be connectedtogether by riveting, boltingor welding, so that maximum ratio of the slendernessFir of eachcomponentof the memberbetweensuch connectionsis not greaterthan 50 or 0.5 timesthe maximum ratio of slendernessof thememberas a whole, whichever is less, whereI is the distancebetweenthe centresof connections.

The numberof connectionsshallbe such thatthe memberisdivided into not lessthanthreeapproximatelyequalparts.

507.2.5.2. Where the members areseparatedback-to-backthe rivets or bolts in these connections shall pass through solidwashersor packings,andwherethe connectedangles,legsor tableofteesare 125 mm wide or over, or where websof channelsare150mm wide or over, not lessthan two rivets or boltsshall beused in eachconnection,oneon the line of eachgaugemark.

507.2.5.3. Where these connectionsare madeby welding,solid packings shallbe usedto effect the jointing unlessthe mem-bers aresufficiently closetogetherto permit but welding,andthemembersshallbeconnectedby welding along bothpairsof edgesof the main components.

507.2.5.4. The rivets, bolts or welds in these connectionsshall be sufficient to carry the shearforcesand the momentsspeci-fied for battened struts, and in no caseshall the rivets or boltsbe lessthan 16 mm.

507.2.5.5. Compressionmembersconnectedby such riveting,bolting or weld/ngshall not be subjectedto transverseload/ngina plane perpendicular to the riveted, bolted or welded surfaces.

507.2.5.6. Where the components arein contactback-to-back riveting, boltingor interm/ttent welding shall be in accor-dancewith clausesapplicable.

507.2.6. Lacing of compressionmembers

507.2.6.1. As far as practicable,the lacingsystemshallnotbe variedthroughoutthe lengthof the compressionmember.

507.2.6.2. Lacing barsshall be inclined at an angleof 50 to70 degreesto the axis of the member wherea single intersection

52

IRC 24-1967

system is used,and at an angleof 40 to 50 degreeswherea doubleintersectionsystemis used.

507.2.6,3. Except for tie plates as specified in Clause507.2.6.9. below, double intersection lacingsystemsshallnot becombined with membersof diaphragms perpendicular to thelongitudinal axis of the main member,unlessall forcesresultingfrom deformationarecalculatedand provided for in the lacingand its fastenings.

507.2.6.4. Lacing barsshallbe soconnectedthat thereis noappreciableinterruptionof the triangulationof thesystem.

507.2.6.5. The maximumspacing of lacing bars whetherconnected by welding, riveting or bolting shallbe suchthat themaximumslendernessratio 1/r of the componentsof the compres-sion memberbetweenconsecutiveconnectionsof the lacing bars toone componentis not greaterthan50 or 0.7times the maximumratio of slendernessof the memberas a whole, whichever is thelesser, where 1 is the distance betweenthe centresof the connec-tions of the lacing barsto onecomponent.

507.2.6.6. The required section of lacing ‘bars shall bedetermined by using permissible stressesfor compressionandtensionmembersgiven in Clauses504.3. and 504.4.subject to therequirementsin Clause507.2.6.7. The ratio fir of the lacing barsshall not exceed140. For this purpose,the effective length I shallbe takenas follows

(a) In riveted or boltedconstruction,the lengthbetweentheinner end r/vets or bolts of the lac/ng bar in single intersectionlacing,and0.7 times this length for double intersection lacingeffectively connectedat intersect/ons.

(b) In weldedconstruction,the distancebetween the innerendsof effectivelengthsof weldsconnectingthe bars to the com-ponents in single intersectionlacingsand0.7 timesthis lengthfordouble intersect/onlacing effectivelyconnectedat intersections.

507.2.6.7. In riveted or bolted construction, the minimumwidth of lacing bars shall not be lessthandoublethe edgedis-tance.

507.2.6.8. The riveting,bolting or weldingof lacing bars tothe main members shall be sufficient to transmitthe loadto thebars. Whereweldedlacingbars overlap the main components,

53

1RC 24-1967

the amountof lap shallbe not iC5S than four times the thickness ofthe bar or four timesthe meanthicknessof the flangeor the corn-pOnLnt to which the barsar~attached,whicheveris the lesser. Thewelding shall be provided at leastalongeachside of the bar forthe full lengthof the lap and returnedalong the endsof the platefor a length equalto at least4 timesthe thicknessof theplate.

Where lacing barsarefitted between the main components,they shall be connectedto eachcomponentby fillet weldson bothsidesof the bar or by full penetrationbutt welds.

507.2.6.9. Lacedcompressionmembers shall be providedwith tie platesat the endsof the lacingsystemsatpointswhere thelacing systemsare interruptedandwherethememberis connectedto anothermember.

The ltngthof endtie platesmeasuredbetweenend fasteningsalong the longitud/nal axis of the member shall he not less thanthe perpendicular distance between~thelinesof rivets connectingthem to the flangesor the verticalside plates of the main chordswhicheveris greaterandshallbe at leastequalto the depth of thecross girderswheretheseare directly attachedto the strutsand thelength of intermediatetie platesshall be not less than ~ of thisdistance.

507.26.10. The thicknessof tie platesshall benot less than1f50 of the distancebetweenthe innermostlinesof rivets, bolts orwelds except when effectivelystiffenedat the free edges,in whichcase the minimum thickness may be 8 mm; for this purpose theedgestiffenershall havea slendernessratio not greaterthan 170.

507.2.6.11. Tie plates and their fastenings(calculated inaccordancewith the methoddescribedfor battens)shallbecapableof carrying the forces for which the lacing systemis designed.

507.2.7. Batteningof compressionmembers: Battenedcom-pressionmembersshallcomply with the following requirements.

507.2.7.1. The battensshall be placed opposite each otherat each end of the member and at pointswhere the memberisstayedin its length, and shall, as far as practicable,be spaced andproportioneduniformly throughout. The numberof batt ns shallbe suchthat the memberis divided into not less than 3 bayswithinits actuallength centre-to-centreof connections.

507.2.7.2. In battenedcompressionmembers in which theratio of slendernessabout the y-y axis (axisperpendicularto the

54

mc : 24.1961

battens)is not morethan0.8 timesthe ratio of slendernessaboutthe x-x axis, the spacing of battens centre tocentreof endfasten-ings shall be suchthat the ratio of slendernessI/r of the lessermaincomponent over thisdistance shall be not greaterthan50 orgreaterthan0.7 timesthe ratioof slendernessof the member as awhole, about its x-x axis(axis parallelto the battens).

In battenedcompress/on membersin which the ratio ofslen-dernessaboutthe y-y axis is more than0.8 times,the ratioof slen-dernessabout the x-x axis, the spacirkgof battenscentreto centreof end fasteningshall be suchthat the ratioof slenderness f/rofthelessermaincomponent over thisdistanceshallnot be greaterthan50 or greaterthan0.7 timesthe ratio of slendernessof the memberas awhole aboutits weakeraxis.

507.2.7,3. Battensshall beplates,channels orI sectionsandshall be riveted, bolted or welded tothe main components.Battensand their connections shall beso designed that they resist

simultaneously a longitudinal shear force equal to and a

momentequalto where:

1) = thelongitudinal distancecentreto centreof battensa= the minimum transversedistance betweenthecentroidsof rivet

or bolt groups,or weldingQ = the transverse shear force as defined in Clause507.2.1.6.anda == the number of parallel planesof battens.

507.2.7.4. The effective length of a batten parallel to theaxis of the membershalt betakenas the longitudinal d/stancebet-ween the end fastenings. End batt~nsshall havean effectivelength of notlessthanthe perpendiculardistancebctweenthe linesof rivets connectingthem to components,or theverticalside platesin the case of chords whichever is greater and intermediatebattens shall have aneffective length of not less than~of tb/sdistance, but inno case shall thelength of any batt~nbe less thantwice the width of the smaller component in theplaneof thebattens.

507.2.7.5. The thicknessof battenplates shall not belessthan 1/60 of the minimum distancebetween theinnermostlines ofconnecting rivets,bolts or welds,except wheneffectively stiffenedat the free edges, in which case the minimum thickness may be8 mm, for this purpose the edgestiffenersshallhave a slendernessratio notgreaterthan 170.

55

lkC: 4-1961

507.2.7.6. The lengthof weld connecting each longitudinaledge of the battenplateto a componentshall in the aggregatebenot lessthanhalf thelengthof the battenplate,and at least one-third of the weld shallbe placed at eachend of the longitudinaledge. In addition,the welding shall be returned along the endsof the platefor a lengthequalto at leastfour timesthe thicknessofthe plate.

Wheretie or battenplates are fitted between main compo-nents they shall be connectedto eachcomponenteitherby filletwelds on eachsideof the plate, at least equal in length to thatspecified in the precedingparagraph,orby completepenetrat/onbuttweldsalongthe whole lengthof the plate.

507.2.7.7. Battened compressionmembers not complyingwith theserequirements,or thosesubjectedto bendingmoments inthe plane of the battens,shalt bç designedaccord/ngto the exacttheoryor elast/cstability, or empirically with verification by tests,so that they have a load factorof not lessthan1.7in the actualstructure.

507.2.7.8. Battenedcompressionmemberscomposedof twoangles forming a cruciform cross-sectionshall conform to theaboverequirementsexceptas follows:

(ii thebattensshall be in pairs placedin contactoneagainstthe other,

unlesstheyareweldedto form cruciformbattens.

(ii) a transverseshearforceoi~?jz shall be taken as occurring

separatelyabouteachrectangularaxis of the whole member.

(iii) a longitudinal shear force of a and the moment shall

betakenin reSpectof eachof thetwo planes,exceptwherethemaxi-mumvalueof l/r can occur about a rectangularaxis, In which caseeach batten shall be designed to resista shearforceof 2~percentofthetotal axialforce. Q, D and a areas defined in Clause507.2.7.3.

507.3. TensionMembers507.3.1. Gener*1

507.3.1.1. Tens/onmembersshould preferably be of rigidcross section, and when composedof two or morecomponents,theseshallbe connectedas describedin Clauses507.3.4.to 507.3.6.

For main members,the ratioof unsupportedlength to theleast ratio of gyrationshallnot exceed300.

IRC : 24-1967

507.3.1.2. Theopensides of built-up tens/on members ofU or I section shall be connectedby lac/ngor batteningwhenthelength of the outstandtowardsthe open side eiceeds 16 times themeanthicknessof the outstand.

507.3.1.3. Lacing andbatteningshall be designedin accor-dancewith Clauses507.3.5.and5073.6.andshallbe proportionedto resist all shearforcesdueto externalforces,if any, in the planeof lacing. The shearshall be consideredas divided equallyamongall transversesystemsandplating in parallelplanes.

507.3.2. Effective-sectionalarea: The propertiesof the crosssectionshall be computedfrom the effectivesect/onalarea. Whenplatesarc provided solely for the purposesof lacing or battening,they shall be ignored in computingthe radiusof gyrat/onof thesection.

507.3.2.1. The end sectional area of a bolt or screwedtensionrod shallbetakenas the areaat root of the thread.

507.3.3. Deductions: The effective sectional area of themembershall be the grosssectionalareawith the following deduc-tions as appropriate

(1) Deductionsfor rivet and bolt holes(SeeClause505.21.2).Exceptas requiredby Clause505.15.2.

the arcasto be deductedshall be the sumof the sectionalareasofthe maximumnumberof bolesin anycrosssectionat right anglesto the directionof stressin the member.

(ii) Deductionsfor a single angle connectedthroughone leg

To allow for eccentricityof connection,allowanceshould bemadeas per Clause505.15.

507.3.4. Tensionmemberscomposedof two componentsback

to back507.3.4.1. Tensionmemberscomposedof two anglàs,tees,or

channelsback to back,either in. contactor separatedby adistancenot exceeding50 mm shallbe connectedtogetherin their lengthatregularintervalsby riveting,bolting or welding so spacedthat themaximum ratio of slendernessof eachelementis not greaterthanthat specifiedfor main membersin Clause5073.1.1.

507.S.4.2. Where the components are in contactbacktobach,riveting, bolting or intermittent weldingshall bein accor-dancewith Clauses505.21.3. to 505.21.5. as applicable.

57.

IRC: 241%?

507.3.4.3. Whenthe componentsareseparatedtheyshall beconnectedthrough solid washersor packings, riveted, bolted orwelded.

507.3.5. Lacing of tensionmembers

5073.5.1.As far as practicablethe lac/ngsystemshall not bevaried throughout the lengthof tensionmember.

507,3.5.2, Lacingbarsshall be inclined at an angleof 50 to70 degrees to the ax/s of the memberwhena s/ngle intersection.system/s usedand at an angleof 40 to 50 degreeswhen a doubleintersectionsystemis used.

507.3.5.3. Except for tie as specified in Clause507.3.5.8,doubleintersect/on lacing systemsshall not be combined withmembersor diaphragmsperpendicularto the longitudinal axis ofthe member, unless all forces result/ngfrom deformationof themember are calculated and provided for in the lacinganditsfastenings.

507.3.5.4. Lacing bars shallbe so connec~tedthat thereis noappreciableinterruptionof the triangulationof the system.

507.3.5.5. The required Section of lacing bars shall bedeterminedby us/ngthe permissiblestressestbr compress/onandtens/onmembersgiven in Clauses504.3. and 504.4.subject to therequirementsof Clause 507.3.5.6. The rat/o If r of the lacing shallnot exceed170. For this purpose, the effective lengthshall betaken as follows:

(i) In riveted or bolted construction, the length between the inner endrivets or bolts of the lacing bar in single intersection lacing and 0.7times this length for double intersection ladingeffectively connectedat intersection.

(ii) In welded construction,the distance between the inner endsofeffectivelength of welds connecting bars to the components forsingle intersection lacing, and 0.7 times this length for double inter-sectionlacing effectivelyconnectedat intersections.

507.3.5.6. The rivet/ng, boltit~gor weld/sigof lacing bars tothe mainmembersshallbe sufficient to transmit the load to thebars. Wherewelded lacingbars overlapthe main components,theamountof lap shallbe not lessthanfour timesthe thicknessof thebar or 4 timesthe meanthicknessof the flangeor the componentto which the barsareattached,whicheveris the lesser. The weld-ing shallbe providedatleastalongeachsideof the bar for the fulllengthof the lap.

58

IRC; 24-1967

Where lacing bars are fitted between main components, theyshall be connected to each component by fillet welds on both sidesof the bar or by full penetrat/onbutt welds.

507.3.5.7. Lacedtensionmembersshall be prov/ded withtie plates at the ends of the lacing systems, at points where thelacingsystemsareinterruptedandwherethe memberis connectedto anothermember.

The length of end t/e plates, measured between end fasteningsalongthe longitudinalax/sof themember,shall be not less thanthe perpend/cular distance b~tween the centro/ds of the maincomponents,and the lengthof the intermediatetie platesshallbenot less than ~ of this distance.

507.3.5.8. The thicknessof all t/e platesshallbe not lessthan 1 60 of the distance betweenthe innermostlinesof r/vets,bolts or welds attaching them to the main components,exceptwhen effectively stiffened at the edges,in wbi~hcasethe minimumthicknessmay be 8 mm; for th/s purpose,the edge‘sI/ifeners shallhavea slendernessratio not lessthan 170.

507.3.6 Battening of tension members

507.3.6.1. The spacingof battens,measuredas the distancebetweenthe middlesof adjacentendpit :hesof rivets or bolts or,for welded construction, the clear distance betweenthe battens,shall be such that the maximum ratio of slendernessof eachelementis not greaterthan that specified for main members inClause 507.3.1.1.

507.3.6.2. The effective lengthof the batten,parallel to theaxis of the member, shall be taken as the longitud/nal distancebetweenendfastenings.

End battensshallhavean effective lengthof not lessthantheperpendiculardistancebetweenthe centroidsof the ma/n compo-nents and intermediate battens shall have an effect/ve length of notless thanone-halfof this d/stance.

507.3.6.3. Batten plates shall have a thicknessofnot lessthan 1/60 of the minimum distancebetweenthe connectingrivet orbolt groups or welds except where they are stiffened at the/r edges.

507.3.6.4. Wherebattensareattachedby rivets or bolts, notless than two r/vets or bolts shall be usedin eachconnection.

59.

IRC : 24-1967

Wherebattensare attachedby welds, the lengthof welds connect-ing each longitudinal edge of the battenplate to the componentshall, in the aggregate,benot less thanhalf the lengthof the battenplate, andat least 1/3 of the weld shall be placedat each end ofthe longitudinal edge. In addition, welding shall be returnedalongthe baseof the plate for a lengthat leastequalto four timesthe thicknessof the plate.

Wherethe tie or battenplatesarefitted between ma/n com-ponentstheyshallbe connectedto each member either by filletweldson eachside of the plateequalin lengthto at leastthatsped-fled in the precedingparagraphsor by full penetrat/onbutt welds.

507.4. Splicing

507.4.1. Spliceswhether in tens/on, compress/on,bendingor shear shall be designed to transmitthe requiredforce in themember.

507.4.2. Covermaterial: All covermaterialshall,as far aspracticable,be so disposedwith respectto the crosssection of thememberas to communicatethe proport/onalloadin the respectivepartsof the section.

507.4.3. Both surfacesof the partsspl/cedshallbe coveredor othermeanstakento mainta/nthe al/gnmentunderload of theabuttingends.

507.4.4. Rivets,bolts or welds shall developthe full load inthe covermaterialcalculatedon the coverarea.

507.5. Connectionsat Intersections507.5.1. Connections of members at an intersectionshall

developat leastthe des/gnloadsandmomentscommun/catedby themembers. Due regardto the natureand distr/butionof stressoverthe crosssectionof the membersshall be given in determining thed/str/butionof the fastenings. All membersshall, wherepossible,be soconnectedthat the load is appropriatelydistributedover thecrosssection;otherwise,considerationshallbe given to the distri-bution of stress through the materialto thosepartsof the sectionnot directlyconnectedandfor this purpose,the angle of distribu-tion maybe takenas45°.

507.6. GussetPlates

The gusset plates must not be lessthan9 mm th/ck and

60

mc: 24-1967should be of ample thickness to resist shear, d/rectstressand

flexuresactingon the weakestor critical sectionof max/mumstress.

Re-entrantcutsshould beavo/dedas far asposs/ble.

507.7. Diaphragmsin Members

In addit/on to d/aphragmsrequiredfor the properfunctioningof the structure,diaphragmsshall be providedas necessary forfabricat/on,transport anderection.

507.8. Camber

507.8.1. In unprestressedopenweb spans, which are notpredeformed, the camberof the main girders and thecorrespondingvariationsin lengthof membersshall besuchthatwhen the girdersare loadedwith full deadload plus75 per centof live load with-out impact produc/ngmaximum bend/ng moment, they shall takeup the true geometrical shape assumed in the/rdesign. Thecamber diagram shallbe preparedas ind/catedin AppendixC.

507.8.2. In open web spanswhich arepredeformed, camberchange shall be based on full deadloadandlive-load includingimpact. Under this load, the girders will assume the truegeometr/calshape. Predeformationshall becarriedout in accor-dancewith AppendixC.

507.8.3. For provisionsregarding portal swayand lateralbracings,see Clause505.18.

508. WORKMANSHIP

508.1. General

All woik shall be /n accordan’~ewith the drawings andclauses of this code. Care shall b~takenthatalt partsof anassemblyfit accurately together.

508.1.!. Interchangeability of parts: Unless speciallyrequ/redunderthe contract, corresponding partsneednot beinter-changcabte. Whenthe parts are not interchangeable,the partsshall beniatchmarkedas requiredunderClause508,16.

508.2. Temptate~

Templates, jigs and other appliances used to ensure theaccuracy of the work shall be ofmild steel; where speciallyrequired these shall be bushedwith bardsteel. AU. measurements

61

IRC: 24-1967

shall be made by meansof steeltape or otherdev/ceproperlycalibrated. Wherebridgematerialshavebeen used as templatesfor drilling, theseshall be inspectedandpassedby the EngineerorInspect/ngOfficer beforetheyareused as parts of the fin/shedstructure.

508.3. S~raIgb1en1ng

All structuralsteelmembersand parts shall have straightedgesandblunt surfaces. If necessary,theyshallbe straightenedor flatt nedby pressurebeforebe/ngworkedor assembledunlessthey are reqwred to be of curv/l/ntar form, They shallalsobefree from twist. Pressureapplied for straigbtcning or flatteningshallbe suchas would not /n~urethe materials so that adjacentsurfaces or edgesshallbe in closecontactor atuniform d/stancethroughout.

508.4. Preparaion of EdgesandEnds

508.4.1. All structuralsteel partswhere required shall beshearedcropped, sawnor flame cut andgroundaccuratelyto therequiredd/mensionsandshape.

508.4.1.1. In the caseof h/gh tensile steelconforming to IS:961 Specification for High TensileStructuralSteel, at least6 mmof the material from the flame cut edge and at least 3 mm ofthe mater/al from the shearededge shall be removed bymatching.

508.4.2. Cutedgesof plates

508.4.2.1. Longitudinaledgesof all platesandcover platesform/ng plate girders and built up membersshallbe mach/nedexceptin the following cases:

(a) Rollededgesof singleuniversalplatesor fiats maynot bemachined.(bl Covers to single flange plates may be left unmaóhined.(c) Machine flame cutting instead of machining is acceptable for edges

of single platesin compression and for edges of singleplates,25mmor less thick, In tension.

(d) Edgesof singleshapedplatesover 25mm thick notcapableof beingmaehmedby ordinarymethodsmaybe machineflamecut andtheend surfaceground,

(e) Edgesof universalplatesor flats of thesamenominalwidth used intiers maybe left unmachined,if soauthorisedby theEngineer.

508.4.2.2. All edgesof st/tchandgussetplates 12 mm thick

62

IRC : 24-1967and over shallbe mach/nedand thoselessthan 12 mm thick may

be shearedandground.

508.4.3. Ends of plates and sections508.4.3.1. The endsof platesandsectionsforming the main

components of plate girders or of bu/lt up membersshallbemachined,machine flame cut, sawn, or hand flame cut andground.

508.4.3.2. In joints and splices of compression members,and girder flanges andof tensionmemberswheresospec/fiedonthe drawings,the abuttingsurfacesshallbe faced and brought toan even bearing. A tolerance of 0.5 mm may be permittedlocally.

Whereclosefitting is not specified,any clearancesshall notexceed3 mm.

508.4.3.3. Whereendsof stiffeners are requ/red to be fitted,they shall be machined,machine flame cut, sawn,shearedandground,or hand flame cut andground.

508.4.3.4. LacIng bars: The ends of lacing bar shall berounded unlessotherwiserequired.

508.4.4. Other edgesandendsof mild steel parts may be

sheared.

508.4.5. Any burrsof edgesshall be removed.

508.5. PreparatIon of Holes

508.5.1. Drilling and sub-punching: All holesfor r/vets shallbe drilled or drilled smallandreamed.If however,it is preferred,the holes maybe sub-punchedto adiameterof 6 mm lessthan thefinished size andthenreamedto the propersize.

508.5.1.1. Whereseveralplatesor sectionsfrom a compoundmember, they shall, where practicable, be firmly connectedtogether by clampsor tacking bolts andthe holes drilled throughthe whole th/cknessat a one operat/onor alternatively,andin thecaseof repetitionwork, the plates and sections may be drilledseparately from jigs andtemplates. Thejigs andtemplatesshallbe checkedat leastonceafter every25 operations. All burrsshallbe removed.

63

lRC �4-i9c~7

508.5.2. in the caseof the repetition spans the erection ofC\ cry span shallnot be insistedupon exceptwhereclosetoleranceor turned bolts are used,providedthat methodsareadoptedtocnsurcstr/ct interchangeability. In suchcases,onespanin ten orany numberless thanten of eachtype shallbe erectedfrom piecesselectedat randomby the Engineer and should there be anyfa/lure of the pieces to fit, all s/milar spansshallbe erectedcomplete. In the eventof the spans being provided completelyinterchangeable,all correspondingpartsshallcarrythe samemarksothatsortingof the materialsat the s/temay be facilitated.

508.5.3. Block drIlling: Wherethe numberof plates to beriveted exceeds three or the total is 90 mm or more, the rivetholes,unlesstheyhave been drilled through steel-bushedjigs,shall bedrilled out in place3 mm all round, after assembling. insuch cases,the work shallbethoroughly boltedtogether.

508.5.4. Sizeof hoies

508.5.4.1. Thesizes of holes in mill/metre are given inTable 12.

TaLE 12. DtatsrutOF HOLES FOR RIVETs

Nominaldia. of rivets Dia. of holesmm mm

12 13.5

14 1.5.5

t6 .17.5

18 19.5

20 21.5

22 23.5

24 25.5

21 29.0

30 - 32.0

33 35.0

64

IRC 24-1967

508.5.4.2. Closetolerance bolts and barrel bolts

The diameter of the holesshallbe equal to thç nominaldiameterof the bolt shank orbarrelsubject to a toleranceof+0.125 mm and—0mm.

Preferably,partsto be connected withclosetolerance or bybarrel bolts shall befirmly heldtogetherby tack/ng bolts orclampsandthe holesdrilled throughall the th/cknessat one operationandsubsequently reamedto size,if necessary,in order to providetrue holes within the specifiedlimits of accuracy. All holes notdrilled throughall thicknessat oneoperationshallbe drilled to asmaller size and reamed out after assembly.Wherethis is notpracticable,the separateparts shall be drilled through hard-bushed steel j/gsandreamed,if necessary.

508.5.5. Removalof burrs: The work shall be taken apartafter drilling and all burrs left by drilling and thesharpedgesofall rivet holescompIetel~tremoved.

508.6. Rivet and Riveting

508.6.1. The diameterof rivets shownon drawingsshall bethe sizebeforeheating. Each rivet shall beof sufficient length toform a head of thestandarddimensionsas given /n I.S. Hand-book on Steel SectionPart 1. it shall be free from furs on theundersideof the head.

508.6.2. When countersunkheads are required,the headsshall fill the countersink, The included angleof the head shall beas follows

(a) For platesover 14 mm . 90’

(b) For plates upto andincluding 14 mm thick 120°

508.6.3. The tolerance on the d/ameterof rivets shallbe inaccordancewith the IS: 1148—Specificationfor Rivet Ears forStructural Purposesand the IS: 1149—Specification for HighTensile Rivet Bars for StructuralPurposesand, unless otherwisespecified, the toletanceshall beminustolerance, ‘When specialplus andminustolerances arerequiredby the purchaser,the sumof suchtolerances shall not bespec/fiedas lessthanthe tolerancesspecified in the IS: 1148— Specificationfor R/vet Bars for Struc-tuctural Purposesandthe IS: 1149—Spec/ficationfor High TensileRivet Bars for StructuralPurposes.

508.6.4. Rivets shall be heateduniformly to a l/ght cherryred andshall be at red heat fromhead to point when inserted,

65

1RC 24-1967

and shaltbe upsetin its entire lengthsoas to fill the hole as coin-pletelyas possiblewhenhot. Rivets afterbeing heatedandbeforebeinginsertedin the hole shall be free from scale by strik/ng thehot rivet on a hardsurface.

508.6.5. Wherever possible, the rivets shall be machinedriven,preferablyby direct act/ng rivets. The driving pressureshallbe maintainedon the rivet for ashorttime after the upsettingis completed.

508,6.6. Where flush surface is required, any project/ngmetal shallbe chippedor groundoff.

508.6.7. Before riveting is commenced, all work shall beproperly bolted up so that the various sections and plates are in

close contact throughout. Drifts shall be used only for drawingthe work into position and shall not be used to such an extent asto distort the holes.Drifts of a largersize thanthe nominald/ameterof the holeshallnot be used.

508.6.7.1. Driven rivets, when struck sharplyon the headwith a quarter-pound rivet resting hammer, shall be free frommovementandvibration. -

508.6.8. All loose or burnt rivets and rivets with crackedorbadly formed defective heads or with headswhich are undulyeccentric with the shanks, shall be removedandreplaced. Inremoving rivets, the head should be shearedoff’ andthe rivetpunchedout soas not to /njure the adjacentmetal and, if neces-sary, they shall be drilled out, Reeupping and caulking shall notbe permitted.

508.7. Bolts,NutsandWashers

508.7.1. Black bolts (blackall over): Black boltsareforgedbolts in which the shanks, heads and nuts do not receive anyfurther treatment exceptthe cuttingof screwthreads. They shallbe trueto shapeandsizeandshallhavethe standard dimensionsas shown in draw/ngs.

508.7.2. ClosetoleranceboltsClose tolerance bolts shall be faced under the headand

turnedon the shank.

508.7.3. TurnS barreibolts: The d/ameterof the screwedportionof turnedbanelbolts shall be 1.5 mm smaller than the

66

IRC: 241967

diameter of thebarrelunlessotherwisespec/fledby the eng/neer.The diameterof the bolts as given on the draw/ng shall be thenominal diameterof the barrel. The lengthofthe barrel shall besuchthat it bears fullyon all the parts connected. Thethreadedportion of each bolt shall projectthroughthe nutby at least onethread. Faces ofheadsandnutsbearingon steel work shall bemachined.

508.7.4. Washers

508.7.4.1, General: In all caseswherethe full bearingarea- of the bolt is to be developed,the bolt shall be providedwith asteel washer under the nut of sufficient thicknessto avo/danythreaded portion of the bolt be/ng w/th/nthethicknessof the partsbolted together and to prevent the nut whenscrewedup frombearingon the shankof the bolt.

508.7.4.2. For close tolerance orturnedbarrelbolts, steelwasherswhose facesgive a truebear/ngshall be prov/ded underthe nut. The washershallhaveahole d/ameternot lessthan 1.5mm largerthanthe barrelanda thicknessof not less than 6 mmso that the nut, when screwedup, will not bearon the shoulderofthe bolt.

508.7.4.3. Taperwashers: Taperwashers of the correbtangle of taper shall be provided under all headsandnuts bearingon bevelled surfaces.

508.7.4.4. Springwashers: Spr/ngwashers may beusedunder nuts to prevent slackening of the nuts whenexcessivevibration occurs.

508.7.4.5. Washers fortimber: Where the heads or nutsbear on timber, square washers havinga lengthof eachsidenotlessthanthreetimes thediameterof bolt or roundwashershav/ng34 times the diameter of bolt and thickness notlessthanI ofdiameterof the bolt should be provided.

508.7.5. Studs: Ordinarystuds may be usedfor holdingparts together,the holes in oneof the partsbeing tappedto takethe thread of the stud. Countersunk studsmay be usedformaking connectionswhere thesurfacesare requ/redto beclear ofall obstructions such as protruding heads of bolts or rivets.S.uds may also be weldedon the steel work in the positionsrequired.

67

IRC 24-1967

508.7.6. Servicebolts: Servicebolts shallhave the sameclearanceas black bolts and, where it is importantthat thereshall be no movementprior to final riveting, sufficient drifts orclosetolerancebolts shallbe usedto locate thework.

508.8. Drifts

The barrelshall be drawn or mach/ned to the requ/reddiameter for a length of not less thanone diameterover thecombinedthicknessof the metalthrough wh/ch the dr/fts have topass. The diameter of the parallelbarrelshall beequalto thenominal diameter of the hole subjectto a toleranceof + 0 mmand—0,125mm. Bothendsof thedrift for a length equal tofl times the diamettr of the parallelportionof thebar shall beturneddown with a taperto a diameterat the end equal to one-halfthat of parallelportion.

508.9. PinsandPin Holes

508.9.1. Pins: The pins shallbe parallel throughout andshall have a smooth surface free from flaws. Theyshallbeofsufficient length to ensurethat all parts connectedthereby shallhaveafull bearingon them. Wherethe ends are threaded, theysh~allbe turnedto asmallerd/ameterat the ends for the threadand shall be providedwith a pilot nut,wherenecessary,to protectthe threadwhen beingdrawnto place.

508.9.1.1. Pinsmorethan 175mm in length or diametershall be forged andannealed,

508,9.2, Pinboles: Pin holesshallbe bored trueto gauge,smooth,straightatright anglewith the axis of the member andparallelwith eachother,unlessotherwiserequired. The tolerancein the lengthoftensionmembersfrom outsideto outsideofpinholesandof compressionmembersfrom inside to insideofpinbolesshallbe one mill/metre. in bu/lt-up members,the boringshallbedoneafter themembershavebeenrivetedor welded.

508~9,2.1.The specifieddiameterof thepin hole shallbe itsminimum diameter. The resultingclearancebetweenthe p/n andthe hole shall be not less than0.5 mm andnot morethan1.0mm.

508.10. Deleted508.11. WeldIng

508.11.1. Welding shall only be perm/tted on weldingquality steelsuch as mild steel conformingto IS : 226 and2062or

68

lRC 24-1967

high tensile steel, conforming to IS : 961. Workmanship willconformto IRS weldingcode.

508.11.2. When the mater/al is 20 mm thick, specialprecautions like preheat/ng may be taken aslaid down in theIS : 823.

508.11.3. Electrodes: In all cases,the electrodesusedshallbe to the Indian Standardlaid down andalsosuit the quality ofmaterial andthe work in hand.

508.11.4. The workmanshipshallgenerallycomply with the

appropriateIndian Standard.

508.12. Tie Rods

Tie rodswith the upsetendsandplus threadsand- tie rodswith forged eyes shall be formedby be/ngpressedup in a die.Whereagreedby the engineer,su/tablydesignedflamecutor forgedeyesor machinedstubendsmaybe metal-are welded or resistanceweldedto the rods. Steel which has been worked above thetransformation temperature shall be air-cooled. Steelwhich hasbeen hot worked below this temperature shall be subsequentlynormalised.

508.13. Forging

Forgingshallbe carr/edout in such a manner as not toimpair the strength of the metal. Steelwhich hasbeenworkedabovethe transformationtemperatureshall be air-cooled. Steelwhich has been hot worked below this temperatureshallbesubsquentlynormalised.

508.14. BendingandPreüsing

Bending and pressing may be by either the hot or coldprocess. All joggles and knees shall be formed by pressure. Inno case shall the internal radius of bends in cold-bent plates belessthan twice thethicknessof the metal.

508.15. ShopErectionandMatch Marking

Beforebeingdespatched,the steelwork shall be temporarilyerectedin the fabrication shopfor inspectionby the Engineerorthe Inspector either wholly on in such portion as the Engineer orthe Inspector may require so that he may be sat/sfiedboth as toalignment and fit of all the connections. For th/s purpose,

69

IRC: 24-1967

sufficient numberof paralleldrifts andservicebolts tIghtly screwedup shall be employed. All parts shall fit accurately and be inaccordance w/th draw/ngs and specifications.

508.15.1. After the work has been passedby the Engineerand before it is dismantled, eachpart shallbe carefullymarkedfor re-erection w/th dist/ngu/shingmarks andstampedw/th durablemarkings. Draw/ngs correctlyshowing these markings shall besupplied totheEngineer.

508.15.2. Where closetoleranceor turnedbarrel bolts areused for thosecaseswhereinterchangeabil/tyis not /nsistedupon,eachspan shallbe erectedand membersof each span markedd/stinctly.

508.16. MarkIng and Packing

508.16.1. All work shall be protected from damage intransit, particular care••be/ng taken to stiffen freeends,preventdistortion,andadequatelyprotectall machined surfaces.

508.16.2. Eachpackageor bundleshall be clearly markedwith the shipp/ngmarksandits weight.

508.16.3. All rivets, bolts, nuts,washers,screws,small platesand small articles, shallbe suitablypacked. Largerplatesandbars wherebundledshall be securely fastenedtogether.

508.16.4. Long piecesandgirders shall be so loadedandmarkedthat theymay bedeliveredat the bridge s/te in positionfor erection without turning. Instructionsfor suchdel/very shallbe givento the receivingcarrier.

508,17. ProtectionagainstCorrosion

508.17.1. General steel work shall be protected againstcorrosion by:

(i) am/nimumof threecoatsof paints,or -

(ii) a metalcoatingfollowed by two coatsof paint.

508.17.2. Unless otherw/sespecified,all painting andprotec-tive coating work shall generallybe donein accordancewith theIS: 1477—.(Pt.I) Code of Practice for Painting of FerrousMetalsin Buildings,andall/edfin/sites—Pretreatment.

508.17.3. Surfacepreparation. Steel surface to be paintedeitherat the tabricatingshop orat the siteof work shall be prepa-

70

IRC : 24-1967

red in a thorough manner with a view to ensuring completeremoval of mill scaleby one ofthe following processesas agreedto betweenthe fabricatorandthe Engineer

(a) Grit and sandblasting;(b) Picklingwhich shiaid berestricted

to singisplates,barsand sections;(c) Flamecleaning;(d) Scrapingandwire brushing.

508.17.3.1. Primary coat shalt be appliedas soon aspractic-able after cleaning and in caseof flame cleaning,primarycoatshall be appliedwhile the metal is warm.

508.17.3.2. All slag from welds shall be removed beforepainting. Care shall betakento brushthe surfaceclean prior topainting. Surfacesshall be maintaineddry andfree from dirt andoil. Work out of doors in frosty or humid weather~shallbeavoided.

508.17.4. Coatings

508.17.4.1. Prime coat to be usedshall conform to thespecificationof primersapprovedby the Engineer. Metal coatingsshall beregardedas priming coatings.

508.17.4.2. All coatsshallbe compatible with eachother.When metalcoatingsare used,the undercoatshall be compat/blewith the metalconcerned. The undercoatand the finishing coatshall preferably be from the samemanufacture. Successivecoats of paint shall beof different shades orcoloursandeach shallbe allowedto dry thorduglybeforethenext is applied. Particularcareshall be takenw/th thepriming andpaintingof edges,corners,welds,and rivets.

508.17.5. P~tntiigin the shop

508.17.5.1. All fabricatedsteelshallbe paintedwith at leastone priming coat inthe.:~~~iiops,unlesstheexposedsuffac~sare sub-sequently to be cleanedat site or unlesstheyare metalcoated.

508.17.5.2. Shop contactsurfaces,if specifically required tobe painted,shall be brought togetherwhile the paint /s still wet.

508.17.5.3. Surface not incontact but inaccessibleaftershopassemblyshallreceive-the fullyspecifiedprotective treatmentbefore assembly. .

71

IRC 24-1967

508.17.5.4. Wheresurfacesareto be welded,the steel shallnot be painted or metal coatedwithin asuitabledistanceof anyedge to be weldedif thepaintspec/fiedor the metalcoatingwouldbe harmful to weldersor would impair the quality of site welds.

508.17.5.5. Exposedmachinedsurfacesshall be adequatelyprotected.

508.17.6. Paintingat site

508.17.6.1. SurfacesWhich will be inaccessible after siteassembly shall receive the full specifiedprotectivetreatmentbe-fore assembly.

508.17.6.2. Surfaces which will be /n contact after siteassembly shall receive a coat of paint ~/naddition to any shoppriming) andshall be broughttogetherwhile the paintis still wet.

a508.17.6.3. Damagedor deterioratedpaintsurfacesshaHftrst

be madegood with the sametype ofcoatas theshopcoat.

508.17.6.4. Wheresteelhasreceived ametal coatingin theshop,thiscoating~hailbe completedon site soas.to be continuousover anywelds,bolts ands/te rivets.

508.17.6.5. Sped/fledprotectintrStms:sbe1ltecompletedaftererection.

~39.FIELD :EEECflOPI

509.1. General

The bridge work shall . be setout to the requirc4lines andlevelsand the stakesandmarktThef~ofltSft~becaretilly preser-vet. Theiridgc.:steelwork sbat1beero~td,adjusted and com-pietcd-in,;therequiredposit/ontothespSfied~1ines::nndMvels.

509.2. ErectIonThemethodoferection,thedrawings of~tenqSrarywork,rand

the erectionequipmentshallbe subjectto approvalby theEng/neerbutsudhapprovalSit not: telien theconfletOr of any responsi-bility. AliteiniporarjrWor.k:shill bedetignet:afld constructed%rtheloadswhich it will be calledupon to support.

IRC : 24-1967

509.3. Temporary Supports

Spans erected upod staging shall be supportedon suitablepacking to ensure that the bridgewill beat the correctcamber,elevationandalignmentwhen completed. In addition, sufficientdrifts and bolts shall beinsertedto maintainthis condition.

509.4. Joints

509.4.1. Any connection to be riveted or bolted shall besecured inclosecontactby serv/cebolts or a suffIcient number ofpermanentbolts before the rivets aredriven or beforethe connec-tions arefinally bolted. Jointsshall normally be made by fillingnot less than50 per centofthe holesw/th servicebolts and barreldrifts in the ratio of 4.1. The serv/cebolts are to be fully tightenedup assoonasthejo/nt /S assembled. Connectionsto be made byclose tolerance or barrel bolts shall be completedas soonas practi-cable after assembly.

509.4.2. Any connectionsto be site weldedshall besecurelyheld in position by approvedmeansto ensure accuratealignment,camber andelevationbeforeany welding is commenced.

509.4.3. In caseof prestressedgirders,the membersshall bestrainedby meansof internal forcesin sucha way that the holesare as far apartas possible. Drifting of thejoints shall be avo/dedand when necessaryshould be donew/th greatcareand underexpertsupervisionso that the edgesof the holes donot get dama-ged. The methodof erection to befolowed is given /n AppendixCwhich does not apply when the cant/levermethod/s usedbutshouldbe followed when erectionis doneby supportingthe girderson panel points.

73

LkC 24-1967

APPENDIX A(Deleted)

APPENDIX B(504.4.3.2)

CRITICAL COMPRESSION STRESSC, FOR SECTIONSSYMMETRICAL ABOUT THE X-X AXIS FORMULA

B-i. The criticalcompressionstressc, for sectionsabout thex-x axismay be calculated from:

rr Ely GK/ ~W \1C,~ ~ L ~ ‘~ .~ kg/sq.mm

whereZ~=grosssectionmodulus aboutx-x axis

1= effectivelengthof compressionflangeI,.— Is,

____Jr1,= momentofinertia ofthe wholesectionaboutx-x axistv= momentof inertiaof thewholesectionabouty-y axisE= Youngismodulustakenas21,100kg/sq.mm

modulusof rigidity takenas0.4E

K— appropriatetorsionconstant

w= warping constant= for I sections

h= distance betweenflangecentroidsI~=moment of inertia of the compressionflange only about y-y

axis of the girder

B-i.!. For 1 sectIonsthis formulareducesto:

c,= :. _Af[!~~(1+12.3 ~~:)JkaPers~.mm

L~orsectionsof approximately rectangular elements

- (bt~~ approximately, whereb and t are the breadth and\ T) averagethicknessof eachelement.

13-1.2. For channelandZ sections, the formula inB-i.!. abovegivesconservativevalues.

75

IRC : 24-1967

13-1.3. For box members, conservative values of t~are obtained bysubstitutingin the formula B—I.! above.

4,42

it = approxui.atelywhere

A = total enclosedareaof section

S = lengthof eachClementof the periphery

— thicknessof eachelement(m the caseof curtailed flanges theeffectivethlckaCss)e.g.for a box Of depthd, width b, anduniform thicknesst

2b’d~tJC = approximately

B.i.4. Foraplateor flat in bendingin a plane parallel to its surface

(substitutingappropriatevaluesof K, etc.)C’, =4220O~-kg/sq.mm

wherethickness

D depth

effectivelength of partincompression.

76

iRC: 24-1967

APPENDIX C(507.8.and509.4.3.)

METHOD OF ERECTION

C-I. Preparationof camberdIagramfor girders which are not predefornkedAll bridgetrussesshah beerectedsuch that thepanel points of the truss

are raised a certain distance abovethehorizontal line throughthe supports.Thiseffect shall be obtained by increasing length of top chord memberswhile retaining the nocilinal lengths of thebg;pmchord andweb members.Thenecessaryfiguresshall besoworkedGut that the camberat the centre isequal to the calculated deflection specified inClause507.8.1, Thetotal in-crease inthe length of thechord should be uniformly distributed over all thepanels.

C-2. Predeformedopen web girder spaas

C-2.I. Preparationofcamberdiagram: Working drawingsshallbedimen-sioned for the main girder without camber and in orderto ensurethat itsfabrication and erection shall be such as toeliminatedeformationstressesin theloadedspan,acamberdiagram shall be prepared on which shall beclearly indicated the amountsby which thenominallengthstthatis the lengthwhich will give no camber)of membersshall be increasedor decreasedinorder that the outline of thegirderunder fullload (deadload,live load andimpact) shall be the nominal outline. A further change as indicatedin(Clause C-2.l.3 maybemadewhentheoutline of the girder shall be normaloutline enlarged(I +K) times in the vase of a through spanand reduced1-K), times in the case of a deck span(seeClauseC-2~1.3 for definitionof K).

C-2. 1.1. Thestresscamberchangein eachmember shallbe equal to thechange of length of the memberdue to the aboveloading,butof oppositesign.

C-2.[.2. Forthe purposeof calculatingthechange in length of membeEsunderstress, themodulus of elasticity for both hightensileandmild steel shallbe takenas20,470kgImm~.The effective length shall be taken between thetheoretical intersectionpointsof adjacentmembersandareasof membersshallbe the grossareas.

C-2.i.3. To ensurethatthe length of the floor systemof a span shallbeconstructed to its nominal dimensions,that is, to avoidchangesin lengthsoffloor and loadedchord lateralsystem,a furtherchangein lengthmay be madein the lengthsof all membersequalto:

LoadedchordextensionorcontractionLoadedchord length x lengthof member==KxL

in through spans,this change shall be an increase in the length of allmembers while in the deck spans it will beadecreasein the lengthsof allmembers.

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Cl. 1.4. Thenominalgirderlengths alteredin accordancewith Clauses(>2.1 andC-2.l.3 abovegive a correctlystresscamberedgirderbutwith loadedchord length identical with that shownon theworking drawings, thus requiringno modificationsto floor andloadedchordlateral systems.

C-2.l.5. The nominal lengthsandcamberlengths shall berounded off tothe nearest0.5 mm.

C-2.l.6. The difference betweennominallengthsandcamberlengths thusmodified is the practicalcamber change.

C-2.t.7. A Williot diagram shallbedrawn for thepracticalcamberchangesto obtain ordinatesof theerection packingsnecessaryto producetherequiredcamber.

C-2.l.S. Adjustmentsof the lengths shall bemadeto toplateralbracingmembers to suit camberlengthsof the top chordsin thecasesof throughgirderspansand to thebottom lateral~racingmembersin thecaseof deck spans. Theaveragevalueof the predefortiledlengthof top orbottom latetal memberr, asthe casemay be, may be adopted throughout.If adjustmentsof ClauseC-2.l.3.havenot beenmade,the lengthof the floor andloaded chords lateralsystemsmay havcto beadjusted.

C-2.2. Fabrication

C-2.2.I. The actual manufacturedlengthsof themembersare to be thelengthswith cambergiven onthecamberdiagram,

C-2.2.2. The positionsandangularsetting outlinesof all connection holesin themain gussetsandalso theposition of theconnectionholes in the chordjoints andthemachiningof theends shallbe exactlyas shown on the workingdrawings. This will permit the buttsIn the chord segmentsto be exactly asshownon the working drawings.

C-2.2.3. The groupsof connection holesat theendsof all themembersareto be as shown onthe workingdrawings,i.e., withoutanyallowancefor camberbut the distancebetweenthegroupsat theendsof eachmembershall be alteredby the amountof thecamberallowancein themember.

C-2.3. Erection

C-2.3.l. The joints of thechordsshall bedrifted, boltedandpreferablyrivetedto their geometricoutline.

C-2.3.2. All other members shall be elasticallystrained Intopositionbyexternal forces, so that as many holesaspossiblearefair whenfilled withrivets.

C-2.33. Drawingin themembersby drifting ofjoints shall be avoided asfar as possible and, when necessary,shallbedonewith greatcareandundercloseexpert supervision.HarnmersnotexceedingonekilogramIn weight shallbe used with turnedbarreldriftsand a numberof holesdrifted simultaneously,theeffectof the drifting being checkedby observation of adjacent unfilledholes.

C-2.3.4. The first procedureduring erectionshallconsistof placing camberjacks in position on whichthestructureIs to be supported. The camber jacksshall be set with their top levelandwith sufficientrun-out to allow for thelowering of panelpoints except by the necessaryamounts to produce the

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requiredcamberIn the main girders. It is essentialthat the camber is accura-tely maintained throughoutthe processof erectionandit shallbe constantlychecked. Thejacks shallbespacedsothat theysupportthe ends of the maingirders and the panelpoints. The bottomchordmembersshall thenbe placedon thecamberjacks, carefully levelled and checkedfor straightnessand thejoints madeandriveted up.

C-2 3.5, The vertical and diagonal web members,excepttheendposts,shall thenbe erectedin their properpositionson the bottomchords. It is reco-mmendedthat temporary top gussets,the positions of the holes inwhich arecorrectedfor thecamberchangeof the lengthin themembers,shall be used toconnect the top ends of themembers;this will ensurethat theanglesbetweenthemembersat thebottomjpints are as given by the nominal outline of thegirders. Theverticalsenddiagonalashalltheaberivetedto thelower chords.

C-2.3.6. The temporary top gussets,if used, shall then be replacedby the permanentgussets,whichshall berivetedto themembersafter thesehavebeenstrainedinto their correctrelativepositions.

C-2.3.7. All panel points, except the centre, shall then beloweredbyamountsto producethe correct camberin the main girders as shownon thecamber diagram.

C-23.8. The top chord shall be erectedin itsuncamberedposition andsupporiedat the panel points by suitable means,thecentrebeingat its finalposition, It is essentialthat the centre of this length of top chord shallalsobe thecentreof this span, Thebutt joints shallthenbe made and rivetedup.

C-2.3.9. Theendsof the upperchordshallthenbe loweredto the cambe-red position and the holes brought into eorrectregistrationby strainingthewebmembers,

C-2.3l0 Theend postsshall beerectedlast. The upper end connectionshall preferablybemadefirst, andif thereis no splicein theendraker,the finalclosure made at the bottom end connection. If there is a splice,the finalclosureshall bemadeatthesplice.

C-2.3.lI Whencantilevermethodof erectionis used,theproceduregivenin ClausesC-2.3.4. to C-2.3.lO.doesnot apply.

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IR.C: 24-1967

APPENDIX ID

FIELD REQUIREMENTS

D-1. LinesandlevelsAll lines and levels shall be specified by theengineeror thepurchaser.

Thecontractorshall be respOnsiblefor all setting out and shall give allnecessaryassistanceand. facilities for checking by the Engineer orthepur-chaser.

Any stakes or marks set out by the Engineeron siteshallbecarefullypreserved.

D-2. Unless otherwise provided in the contract, the contractor shallsupply anderect allnecessaryfalseworkandstagingandshall supply all labour,tools, erection plant, drifts, service bolts, nuts and washers and othermaterialsnecessaryto carry out thework.

D-3, DespatchingThecontractorshouldsOpply all rivets, bolts,nuts,washers,etc., required

to completeerectionat site with anallowancefor wastage,etc.,of 121 per centof the net numberof field rivets,bolts, washersrequired,or a minimumof fivenumberof eachitem,

Serviceboltsandnuts,ordinary platters,washersanddrifts for useIn theerectionof thework shall besuppliedat60 per cent~45percentboltsand 15 percentdrifts) of thenumberof field rivets per span in each size (this Includeswastage).The purchasermay,however,specifya reductionin thequantities ofservicebolts,etc.,if morethan onespanofeachtypeIs ordered.

D-4. Measurementfor paymentof weightNormally the basis of payment shall be computed by weightbasedon

the nominal weight of materials. When specially agreedupon betweenthepurchaserand the supplier, the basis of payment may be the weighbridgeweight.

D-5, The weightof rolled and caststeeland cast iron shall determinedfrom thedimensionsshownon thedrawingson thefollowing basis:

Rolledox caststeel: 1,84>~10’ kgjm’CastIron: 7,21x 10’ kg/m’Weight of structuralsectionsshallbenominalweight.

Theweightof castingsshall becomputedfrom the dimensIonsshown onthe drawingswithan additionof S per centfor fillets andoverrun.

Theweightof weld fillets andtheweightof protective coatings shallnotbe included,

D-6. The weight of rivet headsshall becomputedby taking the weightof 100 snapheadsasgivenin Table13.

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When specially agreed upon, theallowancefor snapheadsmaybetakenas a flat percentageof the total weight. This percentagemaybetakenas 3percentor modified by mutualagreement.

TABLE 13. WuosirOP RIVET Hs4ws

Dia. of rivet as manufactured Weightof 100snap heads

mm

12

, kg,

1.314 • 2.116 3.418 4.4520 6.122 8.124 10.527 15.030 20.533 27,2

Detailedcalculatedweightsheetsshall besupplied.No addition shall be made for the weight of protective coatingsor

weld fillets,D-7. Where computed weight is to bethebasisof payment,the weight

shallbecalculatedfor the exact cut sizes of membersused in thestructure,deductionsbeing made for all cuts. Additions shall be madefor the rivetheadsasin theClauseabove.

When payment is basedon weigh bridge weight, no deductionshallbemadefor theweight of weld fillets or theweightof anyprotectivecoating.

D-8, InspectionThe Engineer or his representativeshallhaveaccessto the contractor’s

premisesat all reasonabletimesfor the purposeof Inspectingthework, and nowork shall be painted orpackeduntil it hasbeeninspectedandpassed. Anywork found to be defective shall be liableto rejection. Thecontractorshallsupplyall facilities includinglabourandtoolsrequired in connectionwith theinspectionof thework.

D-9. TracIngsThe contractor shall supply free of charge, one setof neatlyexecuted

tracingson linen and threesetsof prints on strongpaperdoneby an approvedprocessshowingthework asconstructed. They shall be fully dimensioned andcontainall erectionmarks,

D-lO. LIstsThe contractor shall also supply, without charge,threecompletelists of

the rivet andbolts,oneof which shallbeon tracing linen required for erectingthe work at site,showingthepartsof the work to whichthevariousrivetsandboltsbelongandhavingeachitem markedso asto indicate the particular casein which it will be found.

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