IRC : 22-1986

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGESSECTION VI

COMPOSITE CONSTRUCTION

(First Revision)

Published by

THE JNDIAN ROADS CONGRESSJamnagarHouse,ShabjahanRoad,

New Delhi-hO 011

1991

IRC : 22-1986

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGESSECTION VI

COMPOSITE CONSTRUCTION

(First Revision)

Pbli~ht~dby

THE INDIAN ROM)S CONGRESSJamnagarHouse,ShatijahanRoad,

New Delhi-hO Oil

1991

Price Rs. 48(Plus packing& postage)

IRC 22- 1986

First published October,1966

Reprinted March, 1971Reprinted February,1974Reprinted November, 1977 (IncorporatesAmendment

No. 1, February, 1977)

First Revision October, 1986

Reprinted:March, 1991 (Incorporates AmendmentNo. 2, March. 1991)

Reprinted:September,1998

(Rights of Publication and of Tran3la:ion are Reserved)

Printed at Sagar Printers& Publishers,NewDelhi(500 copies)

IRC 22-1986

CONTENTS

SECTION VIComposite Construction

Clause No. Page No.

Introduction .~ I

600 General 2

601 Terminology ,. 4

602 Properties of Materials 7

603 General StructuralRequirement 8

604 Determination of Composite Section 8

605 Differential Shrinkage 9

606 Design Assumptions for CompositeStructures 10

607 Method of Design .. 10

608 Design of Composite Section with SteelBeam and R.C. Slab ,.. II

609 Design of Composite Section with R.C.Girder and R.C. Slab ,,, 13

610 Design of Composite Section with P,S.C.Girder and R.C. or P.S.C. Slab ,,. 14

611 Special Considerations for StructuralElements ,. 15

612 Detailing ... 25

613 Materials and Workmanship 29

614 Maintenance 32

IRC 22-1986

INTRODUCTION

The object of the Standard Specifications and Codes ofPracticepublishedby the Indian Roads Congeressis to establisha common procedure for the design and construction of roadhridgcs in India. This publication is meant to serve as a guidefor engineers,engagedin the desir” and or construction of roadbridges. The provisionsherein shaLt be used with discretion andcareshall be takento ensurethat the stability and soundnessofthe structuresdesignedand/or constructedasper these provisionsare satisfactory.

The desigu’ ‘and construction of road bridges require anextensive and thorough kno ledge of the scienceand techniqueinvolved and should be entrusted only to specially qualifiedengineerswith adequatepractical experiencein ~ridge engineeringand capableof ensuringcareful executionof work.

The Bridges Committee iii their meeting he!d at New Delhian the 16th & 17th September. ~75 constituted a Subcornmittct(personnel given below) to revise IRC 22-1966 ‘StandardSpecificationsand Codeof Practicefor Road Bridges—Section VI(CompositeConstruction)’.

Dr. NS. BahiP.C. BhasinDr. P. RayChaudhuriGouranga GangulyA Ghosal

Ghoshpy NaikUi. KhemanDr. K. SmeenivasaRaoDr. V.K. RainaK.B. SarkarThe President,Indian RoadsCongress(K. TongPangAo)

he Director General (Road Development) and Addi.Secretaryto the Govt. of India (K.K. Sarin)The Secretary,mndian Roads Congress (Ninan Koshi)

COMPOSITE CONSTRUCTION

Arnitava BanerjeeKS. Rakshit

ConvenorMember-Secretary0, VenkatesuluA Rep.of GammonIndia Ltd.Rep.of MIs Stup (Consultants)

(MC. Tandon)Rep. of R.D.S.O. (Satya Rhushan)Rep, of I S.f. (0. Raman)Rep. of D.G.B.R.

(R.V. Ramamurthy)Rep. of SERC, Roorkee

(D.S. Prakash Rao)

-Ex-offic h

-Ex-officlo-Ex-officlo

IRC 22-1986

The Subcommitteeheld fourteenmeetings on 16th and 17thJuly, 8th December,1976, 12th and13th May, 29th and 30th Sep-tember,19fl, 13th and14th March,10thand11th July,26thand27thDecember,1978,6th and 7th July 1979,9th and 10th April, 24thand25thNovember,1980,20thand21st August 1981, 26th August,6th to 8th December,1982 and 2nd and3rd March, 1983.

The Bridge CodeSectionVI as revisedby the Subcommitteewasconsideredandfinalised by the Bridges Committee in theirmeetingheld at New Delhi on the 20th August, 1985. This StandardSpecifications andCodeof Practicefor RoadBridges, Section VI(CompositeConstruction)hasbeenthoroughlyrevisedto copewiththe moderntechnological developmentswhich havetakenplace inthis field of engineeringin variouscountriesof the world.

Later on the draft document was approved by the ExecutiveCommitteethroughcirculation in January, 1986 and was placedbefore the Council in their 115th meetingheld at Rhopal on the1st February,1986. The Council while approvingthe reviseddraft(First Revision)for being publishedby the Indian Roads Congress,aulhorisedthe Convenorof the Bridges Committee to make anychanges which may be considerednecessaryin light of the com-mentsoffered by the members.

As directedby the Council, the draft was reviewed by theConvenor of the Bridges Committee, and editorial correctionswhere considerednecessarywere incorporatedin the text.

600. GENERAL

600.1, Scope

This codewifl apply to simply supported bridges of com-positeconstruction. Whereapproprkite, the requirementsof thisspecificationmay be applied to other typesof bridgeswith amend-ments, as necessary. This code is applicable to Box-Girdersonly when specialconsiderationsbasedon available informationhaveto be made.

600.2. Types

Bridges of composite section coveredby this code includethe following types

(I) Reinforcedconcreteor prestressedconcreteslab with structuralsteelgliders.

(ii) Reinforced concreteor prestressedconcrete slab with pie-castreinforcedconcreteo, prestressedconcretegIrders.

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IRC: 22-1986

600.3, Notations

A Area

Rb =

A,

Ah =

A, =

A, =

A,1 =

A,

b

b, =

c1,c2

d=

d~ =

=

~ (,)E,~(,) =

E~(p) ==

DlameterfEffectivedepth

Depth of haunch

Modulusof elasticityof concreteat 28 days

Modulusof elasticity of’ concreteof in~situslabat 1 days

Modulusof elasticityof pre-castgirderatj days

Modulus of elasticityofconcreteof prefabricatedgirderat 28 days

f~(~)= Modulusof elasticity of concretefor in~situslab at 28days

= Modulus of elasticityof steel(CA = Characteristiccompressivestrengthof 150 mm cubesat

28 days

= Ultimatestrengthof steel

Yield strengthof steel

= Momentof inertia

= Horizontal forces

Area of steelat bottom

Areaof compositegirder

Areaof steelat haunch

Areaof prestressingsteel

Areaof in-situslab,areaof steel

Area01’ steelin longitudinal direction

Areaof steelat top

Width

Width of flange

Width of haunch

Covers

ju

1H. H1, H2,

h,h1

hi

Depth;thickness

Depth of flange

Ageof concreteindays

Coefficient

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IRC 22.1986

L Length

= Lengthof shearplaneUltimate momentof resistanceof compositesection

Modularratio

p Pitchlspacing

Q,. = Allowable rangeof shearresistanceper connector

Q,, Ultimate shearresistanceof eachconnector

V = Vertical shear

Rangeof vertical shear

Longitudinal or horizontalshearperunit lengthRange of horizontalshearper unit length

Y = Distance of thecentroidof theareaunder considerationfrom the neutrala,cisof thecompositesection

Load reductIonfactor.

6004. Units

The units and their symbols shall be adopted as given inAppendix H of IRC :71.

600.5. Referenceto Other RelatedCodes

Apart from design requirements specified herein, for other,~lcvantdesign requirementsin respect of reinforced concrete.structuralsteel or prestressedconcrete, IRC 18, 1R(~: 21 andIRC 24. respectivelyshall be followed.

601. TERMINOLOGY

601. 1. CompositeAction

The actingtogether of the girder andslab as a unit ensuredby the use of mechanicaldevice known asshearconnectors.

601.2. Shear Connectors

There are three main typesof shearconnectors, viz., RigidShearConnector,Flexible Shear ConnectorandAnchorageShearConnector.

4

iItC :22-1986

hlJL2.l, Rigid sheer connector : Rigid shear connectorconsistsof short length bars, stiffened angles, channels or teeswelded on to the ftangeof the steel girders and derivesresistanceto horizontal shear by b~aring agìinst concrete(someof this typeare shown in Fig. II. Such connectors shouldbe provided withanchoragedevicesas shown in Fig. 2,

601.2.2. FlexIble shearconnector: Flexible shear connectorconsists of studs, channels, anglesor teesweldedto steel girdersand derivesresistanceto horizontal shearthroughbending of theconnectors (some of this type are shown in Fig. 3). Wherenecessary,such shearconnectorsshallbe provided with anchoragesdevice(see Clause611,3.2.).

601.2.3. Anchorageshearconnector: This connector is usedto resist horizontal shear and to preventseparation of the girderfrom the concreteslab at the interfacethroughbond, Fig. 4.

601.3. Differential Shrinkage

It is the difference between the shrinkage of the twinclementsfrom the time compositeaction comes into play.

(a) .JM (b) STIFFENED4!~.&L

Ffg. 1. RIgid connectors

~d) CHANNEL

5

IKC: 22-1~6

Hoopeo’ 8av

_T~N~~Q .I9~.TH&

RIGID CONNeCTOR

Fig. 2 Mechanicaldeviceto preventvertical separation

SECTION

[11~BAS~T

e~L

(a) Q~LVICE k’IrftJ~QQPED &AR frIELDED TO TUE’

FLEXiSL~ CONNECTORS

&~y y~gIa’

coni~ecror

A

(b)

V U

DEVICE WITH f-lOOPED BAkS

6

IRC 22-1986

C~) Sruo

—

______ b) ~LQkL

~ _____

Cc) CHANNEL (d) ,ThL

Fig. 3, Flexible connectorsNote : Hoop anchorage to resistvertical separationnot shown in Fig. I

and Fig. 3(b) and (d)

I — -rL~

IFig. 4. Anchorageconnectors

602. PROPERTIES OF MATERIALS

For properties of materials, viz., modulus of elasticityof concreteand steel,creepandshrinkageof concrete,relaxationof steel, IRC :18, !RC : 21 and IRC : 2’+ as applicable, shall bereferred to.

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IRC: 22-1986

603. GENERALSTRUCTURAL REQUIREMENT

Relevantclausesregardingdurability of structuresas provided

in appropriatecodesshall be followed.

Memberswhich are subjectedto cyclic loading shall have tobe examinedfor fatigueeffects. Relevantclausesconcerningfatigueeffect as incorporatedin appropriatecodesshall be referred to inthis regard.

604. DETERMINATION OF COMPOSITESECTION

604.1. EffectiveflangeWidth

604.1.1. For the purposeof design, the effective width ofcompression flange of “T-Beams” (or interior beams)and“EdgeBeams”(or exterior beams)for differenttype of construction mayhe calculatedas per Clause305,12.2.of JRC: 21. For calculationof deilection. however, the full width of slab may be consideredaseffective.

604.2. Equivalent Section

604,2.1. For prefabricatedunits in reinforced concrete orprestressedconcrete, consideration shall be given to the differentmoduli of elasticity of the concreteof pre-castunit and the cast-in-situ unit. The cast-in-situslab shall betransformedinto the corres-pondingequivalentareaof the pre-castgirder.

604.2.2. To determinethe tquivalentareain service condi-tion, the effective flange width as determined underClause604.1.shall he divided by the modular ratio.

in -

Ec(s)

Where,Et (p) Modulus OP elasticityof pre-castgirder at 28 daysEr (s) = Modulus of elasticityof in-situ concreteslabat 28 days

604.2.3. In determining the sectional properties of thecomposite section such asequivalentarea,equivalentmomentofinertia, etc.. at the ageunderconsideration,the effective grossareaof the in-situ slab shall be transformed into the correspondingequivalentareaof the prefabricatedunit.

This shall be done by dividing the effective width of the in-sin b by the modularratio mt which is given by

rn =~ (s)

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IRC: 22-1986

Where Eeg(p) = Modulus of elasticity of pre-cast concrete at j days(J> 28p, and

Eel Is) = Modutusof elasticity of cast-in-situconcreteat i days(1> 28).

604.2.4. For compositesection with prefabricated units insteel, the equivalentareaof concreteslab shall be determinedbydividing the effective width of concretc slab by the modularratios, in as follows

(i) For permanentloads, inK,. E~,(~)

(ii~ i-or transientloads, in — ~—

Er (s)

Where,E, Modulus of elasticity of steelof girder

E1 (.~ Modulus of elasticityof cast-in-situconcreteat 28 days

= Creepfactor which may be takenas0.5

The equivalent at’ca of the concreteslabat any age, however,shall be determinedby dividing the effective width of the concreteslab by the modular ratio,

PH ~ (~)

Where,E, Modulus of eLasticity of steel,andEe . Modulus of elasticity of cast-in-situ concrete at i days

3 :t. 28 days)

605. DIFFERENTIAL SHRINKAGE

605. I. l)ifferenlial Shrinkagein CompositeSectionwith in-situSlabOverPre-castGirder

The effectof differential shrinkage betweenthe prefabricatedgirderand cast-in-situslab shall be duly consideredin the design.However, for common cases, specific assessmentof the stressresultantsmay not be deemednecessary. Clause 605.2. may bereferredto in this connectionfor provision of reinforcement.

For caseswhere stressresultantsdue to differential shrinkageare likely to be significant, specific assessmentof such stressresultants may be made and accounted for in detailing andprovision of reinforcement required. For method of assessment,specia! literature on the subject may be referred to.

605.2. To cater for differential shrinkage stressesminimumtensile reinforcement in . the longitudinaldirection of the cast-in-

9

IRC : 22-1986

situ slab shall not be 1es~than 0.2 per centof the cross sectionalarea(for all gradesof steel).

606, DESIGN ASSUMPTIONS FORCOMPOSITE STRUCTURES

606.1. For the purposeof design,prefabricatedunit shallbeconsideredas sustainingits self-load. Where the load of the formwork andthe in-situ concreteis carried directly by the prefabri-catedunit without adequateprops, it shall also be accounted for.

606,2. Compositeaction shall be consideredto be effectiveonly after the in-situ concretehasattainedat least 75 percent ofits cubestrength(characteristicstrength). in case the compositegirder is requiredto carry imposedloadsin addition to selfweightof girder prior to 28 days,the sectional properties of the girdermay be determinedasperClause604.2.3.or 604.2.’i.

606.3. The compositesectionsshalt be so proportioned thatthe neutralaxis ofthe compositesectionis generally locatedbelowthe in-situ concreteslab.

In caseof steel or concreteprefabricatedunit, if the neutralaxis is located inside the in-situ concreteslab,the portion of theslab below the neutralaxis shall not be consideredeffective forcomputing moment of inertia or resisting moment except fordeflectioncalculations.

607. METHOD OF DESIGN

607.1. Design Load

The designloads shall be in accordancewith that stipulatedin the JRC : 6 Bridge Code Sectionii. The structuresand allelementsshall be designedto sustainsafely the various loads andforces.

607.2. AnalysIsof Structures

The structuresshall be analysed by following analyticalmethod in accordancewith laws of mechanics,recognisedmethodof design and sound engineeringpractice. Structures shall beanalysedto find outmoment, shear,axial force, etc., by usingelastic methodwith designload. The stiffnessof membersshall bedetermined on the basis of an equivalent section as definedinClause604.2.

607.3. PermissIble Stressesof MaterialsPermissiblestressesof different gradesof concreteandsteel

10

IRC: 22-1986

shall be in accordance~ ith the stipulationsmade to this effect inIRC:21 and thoseof structuralsteel shallbe in accordancewith thestipulationsmadeto this effect in IRC:24.

Increasein permissiblestressesfor various load combinationsshall be governedby the corresponding provisionsmadein IRC:21and IRC:24.

607,4. Deflection

The deflectionshall be limited to the relevant provisionsofIRC:21 and IRC:24.

608. DESIGN OFCOMPOSITE SECTION WITH STEELBEAM AND R.C. SLAB

608.1. Design of Section for Flexure

608.1.1. Steelsection

608.1.1.1. Where the unpropped steel sectioncarriestheweight of the concreteslab or any other load during construction,it shall be designed in accordance with IRC:24 andthe resultingstressesaddedto those inducedlater in compositesection.

608.1.1.2. For computationof relief in stressesdue to remo-val of such temporaryloadsaddedduring construction,appropriatesectionalpropertiesof the composite section shall be considereddependingupon the time of removal.

608.1.1.3. The total calculated stressesin the steel sectionshallnot exceedthe appropriateallowable stresses.

608.1.2. Compositesection

608.1.2.1. The stressesin the composite section (steelbeam,concreteslab and longitudinal reinforcement) shall be calculatedin accordancewith elastictheory, ignoring concretein tensionandassumingfull interactionbetweenthe steel beamand concreteslabthroughproperly designe�lshearconnectors.

608.1.2.2. Thc design of compositesectionshall be done inthe samemanneras that of Tee-beam. For this purpose,the pro-perties of the composite section may be computed in accordancewith Clause604.

II

IRC : 22-1986

608,1.3. Deckstab

608.1.3.!. The deck slab shall be designedin accordancewith

elastictheory to resist

(a) The effectsof local bending due to loads acting directlyon it with dueconsiderationof the dispersionof toad in accordancewith provisionsof IRC:2l, and

(b) The effectsof loads acting on the compositememberormembersof which it forms a part, in accordancewith the require-mentsof Clause608.1.2.1.

608.2. DesIgnof Section for Shear608.2.1. Vertical shear

608.2.1.1. The vertical shearshall be assumed to be resisted

by the steel sectionalone.

608.2.2. Longltudinsl shear

608.2.2.1. Longitudinalshear perunit length of the compositebeamshall be calculatedon the basisofthe elastic theory assumingan uncrackedslab of effectivewidth as in Clause604.1.

608.2.2.2. The longitudinal shear Vj. at the interfaceof theprefabricatedunit and in-situ unit shall be determinedfrom thefollo~ingequation

V. Ac. YVi. = _____

Where

VL The longitudinal shear per unit length at the interfacein thesectionunderconsideration.

V The vertical sheardue to deadload andlive load includingimpactactingon the compositesection.

A, Thetransformedcompressiveareaof concreteabovetheneutralaxis of the compositesection.rhe distancefrom theneutralaxis of the composite sectionto thecentroid of theareaA underconsideration.

I The momentof inertia of the whole transformedcompositeSection

P’IoIe: I When the deck slab is cast with the girders supportedbyadequatetemporaryprops,the shearV is the total external sheardueto deadload of the deck including the girder andthe live load

12

IRC 12-1986

with impact. Whenthe deck slab is cast with girdersunpropped,the shearV will be the total externalshear due to deadloud addedafter the concretehasattaineda strength compatible to the com-positeaction assumedand the live load with impact. in the hattercase,whenthe slab is supportedindependentof the girdersystem,the shear V will be the total externalshearincluding the self weightof the slab.

Note 2 The effective flange width of the concreteslabshall be takenas constantover the entirespan.

608.2.2.3. Adequatoshear connectorsand adequatetrans-verse shear reinforcemcnl as perClause611 shall be provided toresist the longitudinal shear. Proper detailing precautionsasmentionedin Clause612 shafl also be taken to supplement thedesign checks.

oo~. DESIGN OFCOMPOSITESECTION WiTHR.C.GIRDER AND R.C. SLAB

609.1. Designof Sectionfor Hexure

609.1.!. Precastsection

609.1.1.1. When the unproppedprecastsectioncarriestheweight of the concreteslab or any other load during construction,it shall be designedin accordancewith IRC:2l and the resultingstressesaddedto those inducedlater in compositesection.

61)9.1 .1 ,:,For computation of relief in stresses due toremoval of such temporary loads added during construction,appropriatesectionalpropertiesof the composite section shall heconsidereddepending upon the time of removal.

609,1.1.3. rhctotal calculatedstressesin the precastsection

shall not exceedthe appropriateallowablestresses.

609.1.2. ComposItesection

609.1.2.1. The stressesin the composite section (precastbeam, concrete slab and longitudtnal reinforcement) shall becalculatedin accordancewith elastic theory, ignoring concrete intension and assuming full interactionbetweenprecastbeamandconcreteslab through properly designedshearconnectors.

609.1.2.2. The designof a precastR.C. Tee.beamand cast-in-situ concreteslab, when actingtogetherasa compositesecti6n,

‘3

1RC 22-1986

shall be done in the same manneras that of a monolithic R.C.Tee-beam. For this purpose, the properties of the compositesectionmay be computedin accordancewith Clause604.

609.1.3. Deckslab

609.1.3.1. The deckslab shall be designedin accordance

with elastictheory to resist

(a) The effects of local bendingdueto loads acting directlyon it with due considerationof the dispersionof loadin accordancewith the provisions of JRC : 21, and

(b) The effectsof loadsacting on the composite member ormembersof which it forms a part, in accordancewith the require-mentof Clause609.1.2.1.

609.2. Designof Section for Shear609.2.1. Vertical shear

609.2.1.1. The vertical shearshall be assumedto be takenup entirely by the rib of the transformedflangedbeam. Theeffectsof the vertical shearare then calculatedby the conventionalmethods for reinforced concrete Tee-beams as envisaged inIRC: 21 and !RC 18.

609.2.2. Longitudinal shear

609.2.21. Longitudinal shear per unit length of the com-posite beam shall be calculated on the basis of elastictheoryassumingan uncrackedslab of effective width as in Chuse604.1.

609.2.2.2. The longitudinal shear,Vi. at the interface of theprefabricated unit and the in-situ unit shall be determinedasstatedin Clause608.2.2.2.

609.2.2.3. Adequate reinforcement in the form of shearconnectorsas well asadequatetransverseshear reinforcement asper Clause 611 shall be providedto resistthe longitudinal shear.Properdetailing precautionsas mentionedin Clause612 shall alsobe takento supplementthe designchecks.

610. DESIGN OF COMPOSITE SECTION WITH P.S.C.

GIRDER AND R.C. OK P.S.C.SLAB

610.1. Designof Section for FiexureDesignof section shall be as indicatedin 1RC : 18.

14

IRC: 22-19g6

610.2. Designof Sectionfor Shear

For designof section for shearthe principles and procedures

as laid down in the IRC: 18 shall be followed.

610.3. Designof Section for Torsion

To safeguardagainst failure of concrete by compression,necessarycheck as envisagedin the IRC : 18 shall be exercised.

Reinforcement for resisting shear resulting from torsionalmomentsshall be providedin addition to reinforcement requiredto resistvertical shearin the mannerspecifiedin the IRC : 18.

611. SPECIAL CONSIDERATIONS FORSTRUCTURAL ELEMENTS

611.1. General

Special considerationsfor structuralelementsin the design ofcompositesection include the following

(i) The longitudinalshearat theinterfaceof the prefabricatedunit andthe in-situ unit shall be transferredfrom one unit to theotherbymeansof specialelementsknownas “Shear Connectors”to ensureinteractionbetweenthe two units.

(ii) The longitudinal shearso transferredfrom the prefabricatedunitto the in-situ unit shall be resisted by the provisionof adequatetransverseshearreinforcementin the in-situ unit.

611.2. 1)esign Requirementsof ShearConnectors

6 11.2.1. The shear connectorsshall be designedto ensureintegral action between the prefabricated unit and the in-situconcreteunit so that the two units act as compositestructure. Theshearconnectorsshall satisfythe following two basic requirements:

(i~ShearalongthecontactsurfaceIs transferredwithout slip, and~ii~Separation of the prefabricatedunit and the in-uitu slab in the

perpendiculardirection is prevented.

611.2.2. The shear connectors shall be of the type whichpermit a thorough compaction of concrete in order to ensureperfectcontactof their entiresurfaceswith concrete.

611,2.3. The shearconnectorswhich are to be welded tothe steel girder shall be of weldable steel. The capacity of the

15

iRC 22-1986

weldsat permissible stressshall not be less than the shear resist-anceof the connectors. Welding shall be in accordancewith therequirements of thc relevant Indian Standards,

611.3. Typesof ShearConnectors

611.3.1. Shearconnectorsshall consistof any or a conibina-tion of the following types.

611.3.2. Shear connectors for deck with R,C. slabover pre-fabricated steel girder

(i) Rigid conr~ectorsconsist of short ength bars,stiffenedanglesofTeesor channelsweldedon the flange of the steel fabricated units(seeFig. I.). With a view to preventingtheseparationof the in-situslab from the prefabricated unit in the directionperpendicularto thecontact surface, some mechanicaldevice must be providedalongwith theseconnectors(seeFig. 2).

(ii) Flexible connectors consist of studs or anglesor channelsor teesweldedon the prefabricatedsteelunit (seeFig. 3). As the head ofthe stud or the horizontal leg of thechannelpreventstheverticalseparationof the two units, no specialdeviceis requiredfor theseconnectorsfor preventingthe vertical separation. But in case ofangle or tee connectors,somespecialdeviceasshownin, Fig, 2 isrequiredfor preventingthevertical separation.

611.3.3. Shearconnectorsfor deck with R,C. or P.S.C. slab:To resistthe longitudinal shearat the interfaceof in-situ slab andprefi~bricatcdgirder, bond or anchorage type shear connectorsconsisting of mild steel or HYSD bars shall be provided (seeFig. 4), The top of the flange shall be made rough for etlectivebonding. Sufficient numberof ties shall be provided to preventseparation of the two units in the direction perpendicularto thccontactsurface.

611.4. Design of Shear Connectors

611.4.1. Shear connectors for deck with R.C. slab and pre-fabricated steel girder Shear connectors may be either of MS. orH.T.S. according to the material specificationsof steelgtrders.

611.4.1.1. High tensileshear connector from fatigue strengthconsideration

611.4.1.1.1. To cater for the effect of repeatedloading, theshearconnectorsshall be designedfor fatigue. The design methodof shearconnectorsfrom fatiguestrengthconsiderationsshall be asgiven in Clauses611.4.1.1.2.and 611.4.1.1.3.

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IRC: 22-1986

611.1.1.1.2. The rangeof longitudinal shear pcr unit lengthat the interfaceis given by the following expression

v -I

Where,V Range of vertical sheari.e. the differencebetweenthe maximumand minimum shearenvelopedueto live loadandimpact.

Vr =. Rangeof horizontalshearper unit length

Ar Areaof transformedsectionon oneside of the interface

V The distance of thecentroidof the areaunderconsiderationfromthe neutralaxisof the compositesection

I Moment of inerti:t of the compositesection

611.4.1.1.3. Basedon the fatigue strengthsof connector andthe range of horizontal shearperunit length,the spacing of shearconnectorsis given by

ZQryr

Where,P •..= Spacingof connectors

Qr The aIlo’~ablerangeof horizontalshearfor eachconnectorevaluatedfrom equationsgivenhereinafter’ (ZQr is theresistanceof all con-nectorsat onetransversecross-sectionof the girder).

V,. Therangeof horizontalshearperunit lengthof beamat the interfaceandmay be determinedfrom equationgiven in611.4.1.1.2.

The fatigue strength of stud connectors, is given by thefollowing expression

A. tO-’ (for ratio of 4 >4)

Where,Qy ..:~ Allowable rangeof horizontalshearper stud connector(kN)

A = Area of stud (mm2)d Diameterof stud connector(mm)

h Height of stud (mm)55 ?s’fPa for 20 10’ cycles

For channel angle or tee shear connectors, the fatiguestrengthshall he calculatedfrom the following formula

Qr = ~ L.l0—3Where,

Qr = Allowable rangeof horizontalshear(kN) perconnectorL Lengthof connector(mm), measuredtransverseto the beam axis

370N/mm for 20 x. 10~cycles

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IP.C : 22-1986

611.4. .2. High tensileshear connector from the considerationof ultimate flexural strength of the compositesection In additionto providing adequatefatigue strength,sufficient numberof connec-tors should be providedso that the flexural strengthof the compo-site member can be reached, Usually the requirementswill besatisfied in most composite beamsbecausefatigueconsiderationsare usually critical except in cases of shoredconstruction. Theflex ural strengthof compositememberscan be achieved if suffi-cient connectorsare provided to resist the maximum horizontalforce in the slab and the connectorscould be spaceduniformly.

611,4.1.2.1. The maximum horizontal force is given by:

H1 An.!, . t0’

H, 0.85fr . bj’ .hf. 10—’Where,

H,, H, = Horizontal force(kN)A.: = Area of tensilesteel(mm’) in longitudinal direetion.4 = Yield stressof steel (MPa)Ic Cube(characteristic)strengthof concrete(MPa)

= Effective widthof flangeof In-situ slabhr — Thicknessof in-situslab

The ultimate flexural strengthof any composite sectionwillbe governedby eitherof the aforesaid equationsdependinguponwhethcr the steel section or the concrete section is large.Therefore, the maximum possible compressiveforce in the slabwould he thesmaller of Ht or ~ and sufficient connectorsshouldbe provided to resist the horizontal force Hi or H2 whichever isthe lesserafter calculatingthe ultimate strength of shearconnec-tors from Clause611.4.1.2.2.

611.4.1.2.2. The ultimate strengthsof shear connectors are

given by the following expressions

(I) NT. Stud connectorsQu — O34Vf~E.X to-a

(ii) NT. Channel/AngleTeeconnectors45 (h + 0.5 h1) Li

1f~ x 10—sWhere,

Qu — Ultimateshear csistingcapacityof oneshearconnector(kN

A Area of studconnector(mm’)* Averagethicknessof channel/Angle/Teeflange(mm)

Thicknessof channel/Angle/Teeweb(mm)

18

IRC : 22-1986

Cube(characteristic)strengthof concrete(MPa)= Modulusof Elasticity of concrete MPa)

To ensurethe developmentof the ultimate flexural strengthof compositebeams,a larger margin of safety against connectorfailure should be providedthan is provided for the beam. Thismargin should be achievedby providing a load reduction factorof A = 0.85 to the ultimate shear strength of connectors. Thenumberof connectorsrequired from fatigue considerationswillusually exceed the requirements for flexural strength. Theminimum numberof shearconnectorsrequired betweenthe pointsof maximum momentandend supportsshall be determinedby

HaxQu

Where,Numberof shearconnecte.rsbetween points of maximummomentand end supports

H Smallervalueof FIL and If, (asper Cl. 611.4.1.2.4.)Load reduction factor 0.83

Qu — Ultimate shearresistingcapadtyor oneconnector

If the numberof shearconnectors given by aboveequationexceeds the number provided by the spacingfrom the formulamentionedin 611.4.1.1.3.,additional connectorsshould be addedtoensure that the ultimate strength of the compositesection isachieved.

611.4.1.3. Mild steelshearconnector

611.4.1.3.1, For mild steel shearconnectors,the safe shearfor eachshearconnectdrshall be calculatedas below

(a) Forweldedstud connectorof steelwith minimum ultimate strengthof 460 MPa, and yield point of 350 MPa and elongationof 20 percent(i) For a ratio of hid less than4.2

Q = 1.49 lid. VF(ii) For a ratio of h/dequal to or greaterthan 4,2

Q = 6.O~d’ v7~TWhere,

Q The safeshearresistanceIn Newtonof oneshearconnectorHeightof stud in mm

d Diä of stud in mm(b~For channnel/ Angle Tee co~nectormade of mild steel with

19

IRC :221986

minimum ultimate strength of 420 to 500 MPa yield point of 230Mra and elongation21 percentQ ,;..: ~ fl f USM I.

Where,Q Thesafeshearresistancein Newton of oneshearconnector

= The maximumthicknessof flange measuredat the faceof the webinmm

/ Thicknessof the webof shearconnectorin mmL Lengthof the shearconnectorin mm

611.4.1.3.2. The spacing of shear connectors shall bedeterminedfrom the formula

pFL

Where,V

1. = The longitudinalshearperunit length asstated in clause611.4.1.33.

Q = Safeshearresistanceof each ShearConnector as statedin clause611.4.1.3.1. above(EQ is the total shearresistanceof all connectorsat one transversecross-sectionof thegirder)

611.4.1.3.3. The longitudinal shear per unit length at theinterface of the prefabricated unit and in-situ unit shall be eva-luated from the expressiongiven below:

v V.A..j’L

WhereV = Vertical shear due to deadload placedafter compositesection is

effective andworking live loadwith impactVt=. Longitudinalshearperunit length

= Areaof transformedsectionon onesideof interface

P Distance of the centroid of the area underconsideration fromthe neutralaxis of the compositesection

M = Moment of inertiaof thecompositesection

611.4.2. Shear connectors for deck with R.C. or P.S.C. slab andR.C. or PS.C.prefabricated girder

611.4.2.1. The load factor for design of shear connectorsunder ultimate load shall be 1.5 for dead load and 2.5 for liveload. The dead load to be taken for calculating the ultimatehorizontal shearshall be the deadload operating after compositeaction is effective.

611.4.2.2. The ultimate longitudinal shearVL per unit lengthat the interfaceshall be evaluatedfrom the expressionas given in

20

IRC 22.1986

Clause 611.4.1.3.3. by calculating ultimate vertical shear withthe above mentionedload factors.

611.4.2.3. The ultimate shear resistance of an anchorageconnectoris given by the following equation

= A1f~x 10—’Where

Q,~= Theultimateshear resistingcapacityof theanchorageconnectorinkN

A, = Thecross-sectionalareaof theanchorageconnectormm’— The ultimate tensile strengthof steel of theanchorconnectorin

MPa. The anchor bars shall be placed either vertical orat anangle of450

611.4.2.4. The spacing of the shearconnectorshall be calcu-lated from the formula

pVL

Where,P = Spacingof shearconnectorsQ~.= Ultimate shearresistanceof eachconnector

= Ultimate longitudinal shearper unit length

611.4.2.5, Notwithstanding the fact that full shearresistancei~provided by anchor bars,,the ultimate bond stress at the inter-lace shall not exceed2.1 MPa, The interfaceshall always be maderough for effective bonding.

611.5. Designof TransverseReinforcement

61 .5.1. The longitudinal shear force Vj. per unit lengthtransferred from prefabricated girder to in-situ slab through anyshear plane shall not exceed either of the following and the re-iriforcement shall be calculated accordingly.

(i) 0,4L,lJ~or

(ii) 0.7 A. i~, ~ 0.08L, %f.Where,

L The length of shearplaneunderconsiderationin mm. Typicalshearplanesareshownin, Fig. 5

fr~’’ Cube(characteristic)strength of concrete (MPa) but not morethan 45 MPa,

A, ~-. The sum áí the cross-sectionalareasperunit length of beam ofall reinforcingbarsintersectedby the shearplane(mm’/mm)

Theyield stressIMPa) of thereinforcingbarsinter-sectedby theshearplanebut not morethan 450MPa.

21

IRC: 22-1986

00

2. i

(ci)

(~)

IolL~

cc)

Fig. 5. Shearplanes (typical)

22

iO

3 3,

(go)

0

(c)

101

(d)

~Jl®I

IRC : 22-1986

611.5.2. 1’rans~ersereinforcement

611.5.2.1. Shearplanesi.e. the surfaceson which longitudinalshear failure can take place in in-situ slab of composite beaminthe process of transfer of longitudinal shearfrom thegirder tothe slab, are of four main types as shownin, Fig. 5. Sufficienttransverse reinforcement shall be provided with a view to trans-fer longitudinal shear from thegirdei’ to the effective width of theslab. The area of transverse reinforcement per unit length ofbeam will be the sum total of all the reinforcement(At, As 1)1’As as shown itt, Fig. 6) which are intersectedby the shearplaneandare fully anchoredon both sidesof the shearplane considered.

611.5.2.2. The total transverse reinforcement, A, per unitlength of beam in case of shearplane1—i which crossesthe wholethickness of the slab will be, the sum of (A5+A~) (see Fig. 6).Area of reintbrcement & and A0 include those provided forflexure. The total transverse reinforcement across plane 2—2in Fig. 6 (a) is A~=2A8 and that acrossplane 3—3 in Fig. 6 (b)is A,2A~s as these planes do not crossthe full thicknessof theslab. In case of shearplane4—4, the total transverse reinforce-rrteilt, A~’=2 (As+As) Fig.6 (c). Some of the above transverser~intorcemeiitsmay be curtailedprovided they satisfythe provisionsas laid down in Clause611.5.2.4.

611.5.2.3. Minimum transverse reinforcement(a) he cr~ss-sectiona1areaof minimum transversereinforcementacross

any shear plane per unit length of beamcalculatedasper611.5.1.shall not be less thanthat determinedfrom the following equation

A, 0,8 L.

Where,A~,L1 and ~ areas defIned in Clause611.5.1.

(b) Acrossshearplane1—1 whereI... = he, not less than50 per cent ofA~should be provided near the bottomof the slabasA~. Wherethe length of shearplanearoundthe connectorI plane2 —2 in Fig.6 (a) J is less than twice the thicknessof theslab,transverserein-forcementin additionto thatrequiredfor flexureshould be providedin thebottomof theslabto preventlongitudinal splitting around theconnectors.

The cross-sectionalarea of this additional reinforcementperunitlengthof beammust not be lessthan 0.8 Sh, / a~.

Thisadditionalreinforcementneednot be provided if the minimumcompressiveforceperunit lengthof beamactingnormal to and overthesurfaceof shearplane is greaterthan 1.4 Sh,,.

(c) Thecross-sectionalareaof transversereinforcement,~,in a haunch

23

II(C 22-1986

(a) Non mi/A UNCHEP SEAM

‘0

(b) LARGE HAIJNCHEO BEAM

Top 4ar~At

2’

8ollom bor,Aa

10 ~,

HAUNCH BAR -

A6

410

(c) SMALL HAUNCHED BEAM

Fig. 6. Transversereinforcementacrossshearplanes

24

tat: 22—1986

per unit length of the beammustnot be less than 0.4 SL~j e~whereL, is the lengthof shearplane3-3 or4—4 in, Fig. 6~.

6) I .5.2.4. Curtailmentof transversereinforcement

The transversereinforcementprovidedto transfer longitudi-nal shearsafely from the girder to the slab acrossshearplane 1 —l(Fig. 6) may be curtailed provided the requirementsof 611,5.1.to611.5.2.3.in respectof all shear planes within the effective widthare satisfied. Forthis purpose,the shearforce VL for such planemay be assumedto vary linearly from the calculated maximumforce on a plane adjacentto the shearconnector to zero midwaybetweenthe centreline of the beamand that of an adjacentbeamor to zero at an adjacentfree edge.

612. DETAILING

612.1. Details of Haunches

612.1 .1. For concrete slab over deel girder

612.1.1.1. The dimensions for haunches to be providedbetweentop of steelgirder andsoffit of slab shall be as indicatedin Fig. 7, the sidesof haunchesbeing located outside ‘a line drawnat 45 degreefrom theoutside edgeof the baseof the connectors.

612.1:1. Wherehaunchesare provided in tue cast in-situslab overprecastconcrete girder, the angle betweenthe haunchline of in-situ slab and the face of the flangeof the precast girdershall be 90 degreesandthe top of the precastgirder shall not behigher than the soffit line of the in-situ slab as shownin Fig. 8.

Fig. 7. Dimensionsof haunches

6 2.1.2. For concreteslabover concretegirder

25

IRC 22-1986

612.2.1. For steelgirder

612.2.1.1. The diameter of stud connectorsweldedto theflangeplate shall not exceedtwice the plate thickness, The heightof the stud connectorsshall not be less than four timestheirdiameter or 10(1 mm. The diameter of the head of the studconnectorsshall not be less than oneandhalf times the diameterof the stud. The leg length of the weld joining othertypesofconnectorsto the flange plate shall not exceed half the thicknessof the flange plate. Channel and angle connectors shall have atleast6 mm fillet welds placed along the heel and toe of thechannelsfangles. The clear distancebetweenthe edgeof a girderflangeand the edgeof the shearconnectorsshall not be less than25 mm (seeFig. 9).

612.2.1.2. The surface of a shear connector which resiststhe separation between the two units (i.e. the undersideof thestud or the inner face of the top flangeof a channel or the insideof a hoop) shall extend not less than 40 mm clear abovethe bottomtransverse reinfotcement, nor less than 40 mm into the compres-sion zone of the concrete flange. Where a concrete haunch isusedbetweenthe steelflange and the soffit of the slab, the surfaceof the connectorthat resistsseparation betweenthe two units shallbe placednot less than 40 mm abovethe transversereinforcementin the haunches (vide Fig. 10) provided this reinforcement isadequate to satisfy the requirement for transfer of longitudinalshear as per Clause611.5. Where the shear connectors are placedadjacent to longitudinal edgeof concreteslab, transverse reinforce-ment provided in accordance with Clause 611.5, shall be fully

Precast girder

Fig. 8

612.2. Dimensionsand Other Detailsof Shear Connectors

26

IRC 22-1986(mm)

d 25 mm ~Automai’IC

L h jsd Stu4 weld

~ 100 mm(ci) STUD CONNE.CTOR

25 mm

h ~oomJ 25 mm (mrn)

— 6mm (mm)fille+ weld

(6) ANGLE/ChANNELC0tJNECTOR

Cc) Lo~4GlTUthNAL SECT~ON

Fig. 9. Details of connectorson steel girders

I

Weld to developThe lensite sfren9+hof The hoop bar

Minimum 6 mm .~IUe+NekL car ~uUwidfti beth a+ heel & toe of charn~elf~n9te

27

1RC 22-1986

anchored in the concrete between the edgeof the slab and theadjacentrow of connectors.

612.2.1.3. The overall height of a connector including anyhoop which is an integral part of the connectorshall be at least100 mm with a clearcover of 25 mm.

612.2.2. For concrete girder

612.2.2.1. In order to resist the longiwdinal shearand theseparationforce all the vertical reinforcementfrom web and flangeof the precast element shall be extended into the cast-in-situconcreteslab and adequately anchored into it. Such reinforce-ment shall not be less than 0.15 percentof the contactareaor130 sq. mm per metreof the spanandshall be evenly distributedas far as possibleoverthe contactarea [seeFig. 11 (e) and 11 (f)~.

612.3. Cover to Sbe~rConnectors

612,3.1. For steel girder612.3.1.1, The clear depth of concrete cover over the top of

the shearconnectorsshall not be less than 25 mm. The horizontalclearconcretecover to any shearconnectomshallnot he less than50 mm (see Fig. 10).

Clear Concrete.~cover 50mm (mm)

CQ STUD CONNECTOR (b) AMGLE/CHANNEL

CONt4~C”TOR

Fig. 10, Cover to connectors

6 ‘~,3.2. For concrete girder

6123.2.1. The cover to be provided for shear connectorsshall c nform the relevant provisions regarding cover toreinibrccmcntsasper IRC: 18 and IRC: 21.

28

IRC: 22-1986

612.4. SpacIng of Shear Connectors

612.4.1. General

612.4.1.1. The shearconnectorsshallbe provided throughoutthe length of the beam and may be uniformly spacedbetweencritical cross-sections.

6 12.4.2. For steelgirder

612.4.2.1, The maximum spacingof shearconnectorsin thelongitudinal direction shalt be limited to 600 mm or three timesthe thicknessof the slab or four timesthe height of the connector(including any hoop which is an integral part of the connector)whicheveris the least.

612,4.2.2. The spacingof the stud connectorsin any direc-tion shall not be less than 75 mm.

6 12.4.3, For concrete girder

612,4.3.1. The spacingof the anchoror bond shear connec-tors shall not be less than0.7 timesthe depth of the slab and shallnot be greaterthan two timesthe depth of the stab.

61 2 5. t)etailing of Transverse Reinforcement

612,5,1, The transversereinforcement shall be placed atlocationsas shownin, Fig. Ii.

612.5.2. The haunch bars shall be extended beyond thejunctionof bottombarsby a length equalto the anchoragelength.Similarly, the anchorage~connectors from the prefabricatedconcrete girders shall be extendedbeyondthe junction of bottombarsby a length equal to the anchoragelength.

613. MATERiALS AND WORKMANSHIP

613.1. Material Specificationsfor Steel Members

613,1,1. Steel for structuralmembers

All structural steel shall comply with the Indian Standardswith latest amendmentsas appropriate.

IS 226—StructuralSteel (StandardQuality)N 2062—StructuralSteel(FusionW~L~ingQuality)IS 961—StructuralSteel(High Tensile)

29

ce) BONOI ANCHORAGECONNECTOR

)- 50 1fl)~~?J~TI~ tC2~ 40mm

[~c / def

Fig. II. Arrangementof transverereinforcement

IRC : 22-1986

(a) STUD CONNSCTOP. tNut~t-HAtJt~tCH~.tDBEAM

(b) C~#w~t.COC~Q~iNUN-HAUNCHt~B~P~M

(C) STUID COMNEC~ORt~4 (c4) ANGLE C0NNEC1O~

HNC~4ED%EAM iN HAUNCHED 8~AM

J I.

(5) SOND/ ANCHORAGECO?’~NECTOR

~ 25 mn or dia of bar

ANCHORAGE LENGrH

30

IRC 22-1986

6! 3.1.2. Steel for shear connectors613.1.2.1. Steel for shear connector of rigid and flexible

type as detailed in clause 611.3.2. shall comply with the IndianStandardsIS 2062 (fusion welding of quality) or IS : 961 confor-tiling to Fe 540 W-1 17 (with latest amendments).

6 13.1.2.2. Steel for anchorage type shear connectors asdefined in Clause611.3.3.shall comply with the following IndianStandardswith latestamendments.

IS 432—Mild Steelgrade1 or Medium TensileSteel Bars15 1786—High StrengthDeformedSteel Bars andWires

613,1.3. Welding electrodes Welding electrodes shallcomply with the requirementsel the follo~tingIndian Standardswith latestamendments.

IS 814—CoveredElectrodesfor Metal Arc Weldingof Mild SteeliS 1442—CoveredElectrodesfor Metal Arc welding of High Tensile

Steel

613,2, Material Specifications for Reinforced Concrete andPrestressedConcrete Members

613.2.1. For reinforced concretemembers,specificationsforconstituentmaterials, strengthof concreteand reinforcementshall

mply s ith the relevant provisionsof I RC: 21

613.2.2. For prestressedconcrete members, specificationsfor constituent materials,strengthof concrete,reinforcementandprestressingsteel, etc.,shall comply with the relevantprovisionsofIRC 18,

613.3, WorkmanshIpfor Steel Structures613.3.1. All structuralsteel membersandcomponentsshall

be fabricated, welded,erectedand protectedagainstcorrosionasspecified in IRC : 24.

613.3.2. The dimensionsandother details of the rigid andflexible type shear connectorsshall be as specifiedin Clause612.2. The welding shall be doneproperly so that shearconnectorsdo not fail dueto defectivewelding. Adequatecover to the shearconnectorsas specified in Clause612.3. shall be provided.

613.4. WorkmanshIpfor Reinforced Concrete and Prestressed

ConcreteMembers

613.4.1. Workmanship in respect of concrete formwork,

31

MC: 22-1986

reinforcement, etc., for reinforced concrete and prestressedconcrete members shall be in accordancewith the relevantprovisions of !RC :18 and IR.C 21 respectively along withIRC : 87,

613.4.2. Prestressingwork shall be done as specified inIBC : 18.

6 13.4.3, The anchorage type shear connectors shall beplaced with adequate cover and requisitebond length. The barsto be used as shear connectorsshall be free from kinks andundesirablebends

614. MAINTENANCE

614,1. General

With a view to ensure the desired life span of a bridgestructurefor which it is designedandto get the maximum servicefront the bridge, routine inspection andperiodic maintenanceshallhe madeas a nile. Any defector damagein the structurenoticedduring routine inspectionshall be rectified forthwith before it cancause arty harmful effect on the bridge structure andtherebyaggravatethe situation,

61 .1,7, Inspection of the Bridge Superstructure

61 47. I , The inspect~onof various componentsof the super-structure shall be made as recommendedin Chapter 4 of theI. R.C. Special Publication:18 Manual for Highway Bridge Main-tenanceInspection.

614.2,2, The inspection report shall consist of the “checktenis’’ as listed in the ‘‘ Proformafor InspectionReport” of the

I RC Special Publication IS.

614,3. Maintenanceof Structural Members

614,3. The 51 ractural menibers shall be checked thoroughlyas indicated ~n Chapter ~4of IRC Special Publication 18 andsuch cot rective and remedial measuresas found necessaryforproper maintenancecf the bridgesuperstructureshall be taken.

1,