standard specifications and code of practice...

C:83 (PartI)-1999

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGES

SECTION : IX

BEARINGS

PART!: METALLIC BEARINGS(FirstRevision)

THE INDIAN ROADS CONGRESS1999

IRC:83(Part I)-1999

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGES

SECTION : IX

BEARINGS

PART!:

METALLIC BEARINGS

(First Revision)

Publishedby

THE INDIAN ROADS CONGRESSJamnagarHouse,ShahjahanRoad,

NewDelhi-hO0111999

Price(Pluspacking& postage)

IRC:83(Part-I)-1999

First published : December,1982Reprinted: June, 1990Reprinted: April, 1994First Revision: December,1999

(Rightsof PublicationandofTranslationare reserved)

Printedat DeeKay Printers,5/16,Kirti Nagarindi.Area, NewDelhi.110015(1000Copies)

IRC:83 (PartJ)-1999

CONTENTS

PageNo.Membersof BridgeSpecifications& StandardsCommittee (i) to (iii)

Introduction

900. Scope

901. Definitions 2

902. Typical Arrangementof Sliding, Rocker,Roller~~cum-RockerandSingleRollerBearings,ShowingvariousComponentsof theBearings 8

903. SpecialRequirements 8

904. MaterialsandSpecifications 9

905. LoadsandForces 10

906. Basic PermissibleStressesin Steel 10

907. Design Considerations 13

908. WorkmanshipandTolerances 18

909. AcceptanceCriteria andTesting 18

910. PlacingandPositioningthe Bearings 21

911, Inspection,MaintenanceandReplacementofBearings 22

Appendix~1: HorizontalForcesat BearingLevel 23

Appendix-2: PermissibleStresses 25

Appendix-3: GuidelinesregardingprocedureforUltrasonicTestingof ForgedSteelRollersConformingto IS-2004Class3 andits AcceptanceStandard 27

IRC:83(PartI)-l999

MEMBERS OF THE BRIDGE SPECIFICATIONS ANDSTANDARDS COMMITTEE

(As on 27.9.97)

AD, Narain* DG(RD) &AddI. Secretary to the Govt.of India,(Convenor) Ministryof Surface Transport(RoadsWing),

TransportBhawan, New Delhi-I 10001

~. The ChiefEngineer(B) S&R Ministry of Surface Transport (Roads Wing).(Member-Secretary) TransportBhawan, New Delhi-I 10001

3 SS.Chakraborty Managing Director, Consulting Engg.Services(1) Pvt.Ltd., 57, NehruPlace,New Delhi-I 10019

4. Prof. D.N. Trikha Diieuor, Structural Engg.Res.Centre,Sector-19, CentralGovt. Enclave, Kamla NehruNagar, PB No.10. Ghaziabad-201002

5 Ninan Koshi DG(RD)& Add!. Secretary (Retd.),56, NalandaApartments, Vikaspuri,New Delhi

6, AG, Borkar Technical Adviser to Metropolitan Commr.A-i, Susnehi Plot No. 22, Arun Kumar VaidyaNagar, Bandra Reclamation,Mumbai-400050

7. N.K. Sinha ChiefEngineer(PlC), Ministry ofSurfaceTransport(RoadsWing), TransportBhawan,New Delhi-i 10001

8. A. Chakrabarti Director General(Works) Central Public WorksCE, CPWD, representing Department, Nirman Bhavan, New Delhi

9. M.V.B. Rao Head,BridgesDivision, Central RoadRes.Institute,P.O. CRRI, Delhi-Mathura Road,New Delhi-I10020

10. CR.Alimchandani Chairman& Managing Director, STUPConsultantsLtd., 1004-5,RahejaChambers,213,NarimanPoint,Mumbai-400021

Ii. Dr. S.K.Thakkar Professor, DepartmentofEarthquakeEngg.,UniversityofRoorkee, Roorkee-247667

12. M.K. Bhagwagar Consulting Engineer, Engg.Consultants(P)Ltd., F-14115,Connaught Place,InnerCircle,2ndFloor, New Delhi-i 10001

13. P.D. Wani Secretaryto the Govt.of Maharashtra,P.W.D.,Mantralaya,Mumbai-400032

* ADG(B) beingnot in position. The meeting was presidedby Shri AD. Narain,DG(RD) & AddI. Secretaryto the Govt.of India, Ministry of Surface Transport

(i)

IRC:83(Part [)-1999

4, S.A. Reddi

15, Vijay Kumar

16. CV. Kand

17, M.K. Mukherjee

IS. MaheshTandon

19. Dr. TN. SubbaRan

20. AK, Harit

2 I PrafullaKutnar

22. S yR. Parangusam

23 B.C. Ran

24. P.C. Rhasin

25. P.K. Sarruah

26, The Secretary to the Govt.ofGujaral

27 The ChiefEngineer(R&B)

25 The Chief Engineer (NH)

29. TheEngineer-in-Chief

Dy. Managing Director, Gammon indiaLtd.,Gammoni-louse,VeerSavai-karMarg,Prabbadevi,Mumbai-400tJ25

General Manager, UPState BridgeCorpn. Ltd.486, Hawa Singh Block, Asiad Village,New Delhi-l 10049

Consultant,E-21136,MahavirNagar,Bhopal-4.62016

40/182. CR.Park,New Delhi-I 10019

Managing Director. Tandon Consultants (P)Ltd.. 17, Link Road,JangpuraExtis., New Delhi

Chairman, Construma Consultancy (F)Ltd.,2nd Floor, Pinky Plaza, 5th Road, Khar (West)Mumbai-4000S2

Executive Director(R&S), Research Designs& Standards Organisalion, Lucknow-22601I

Member (Technical), NationalHighwaysAuthority of India, I, EasternAvenue,Maharani Bagh.New Delhi-i 10065

ChiefEngineer(B) South,Ministry of SurfaceTransport (Roads Wing). TransporlBhawan,New Delhi

011g. DDG(Br.(, Dy. Director General (B). DGBR,WestBlock-1V,Wing I. R.K. Purarn,New Delhi-I 10066

324. Mandakini Enclave, Alkananda,New Delhi-1I00l9

ChiefEngineer,PWD (Roads) Assam,P.O.Chandmari,Guwahati-781003

(H.P.Jamdar)R&BDepartment,Block No. 14. New Sachivalaya,2nd Floor,Gandhinagar-3820l0

(D. SreeRamaMurthy), NationalHighways.Irrum Manzil, Hyderabad-500482

(D. Cuba), Public Works Department,Writers’ Building, Block C,Calcutta-70000l

(KB. Lal Singal), Haryana P.W.D.. B&R,Sector-19 B,Chandigarh-l600l9

(ii)

IRC:83(PartI)-1999

30. The ChiefEngineer(R)S&R

31. The Director

32. The Director& Head

33. The ChiefEngineer(NH)

34 The Chief Engineer (NH)

35. The ChiefEngineer(NH)

36. President.IndianRoadsCongress

37. DirectorGeneral(RoadDevelopment)

38, Secretary,Indian RoadsCongress

I NV. Merani

2 Dr.G.P.Saha

3. ShitalaSharan

4. Dr. MG. Tamhankar

(InduPrakash),Ministry ofSurfaceTransport(RoadsWing),TransportBhawan.New Delhi-I 10001

(N. Ramachandran)HighwaysResearchStation.76,SarthatPatelRoad,Chennai-600025

(VinodKumar),BureauofIndian StandardsManakBhavan,9, BahadurshahZarfarMarg,New Delhi-I 10002

M.P. Public Works Department,Bhopal-462004

(PD.Agarwal), UP. PWD, PWDQuartersKabir Marg ClaySquare,Lucknow-22600I

PunjabPWD, B&R Branch,Patiala

Ex-Officlo Members

H.P.Janidar.Secretaryto theGovt. of Gujarat,R&BDepartment,Sachivalaya,2ndFloor,Gandhinagar-382010

AD. Narain,DG(RD) & Addi.Secretaryto theGovt. of India,Ministry ofSurfaceTransport(RoadsWing),TransportBhawan,New Delhi

S.C.Sharma,ChiefEngineer,Ministry of SurfaceTransport(RoadsWing),TransportBhawan,New Delhi

CorrespondingMembers

PrincipalSecretary(Retd.),A-47/l344,AdarshNagar,Worli, Mumbai-400025

ChiefEngineer,HindustanConstructionCo. Ltd.,Hincon House.Lal BahadurShastnMarg,Vikhroli (W), Mumbai-400083

AdvisorConsultant,ConsultingEngg.Services(1) Pvt.Ltd., 57,Nehru Place,NewDelhi- 110019

EmeritusScientist.StructuralEngg.Res.Centre399, PcrketE,MayurVihar, PhaseII, Delhi-I 10091

(iii)

IRC:83 (PartI)-1999

BEARINGS

PartI : METALLIC BEARINGS

INTRODUCTION

The Standard Specificationsand Code of Practice for RoadBridges Section: IX-Bearings-PartI: Metallic Bearings was initiallypreparedby theSub-CommitteeforBridgeBearingsandExpansionJointsand approvedby the Bridge Specifications& StandardsCommittee,ExecutiveCommitteeandthe Council. This was subsequentlypublishedas IRC:83-1982- Part Tin December,1982. Therequirementof revisingthe IRC:83-1982- Part Ito copeup with thetechnologicaldevelopmentswhich havetakenplace in this field of engineeringhasbeenfelt for quitesome time. The first draft revision was preparedby the TechnicalCommitteeon Bearings,Joints& Appurtenanceduring 1991-93 withShriB.J. Daveas the Convenor.ThisCommitteewas reconstitutedinJanuary,1994consistingof the following personnel:

N.K, Sinha Convenor

KB. Thandavan Member-Secretary

MEMBERS

D.K. Rastogi S.F.ChakrabartiA. Chakraharti S.S.SaraswatAK. Saxena P.Y. ManjureP.L. Manickani Ajay KumarGupta[).K Kanhere Achyut GhoshSM. Sant S. SenguptaM.V.B. Rao Rep.of R.D.S.O.LucknowR.K. Dutta Rep.of Bureauof IndianG.R. Haridas Standards(VinodKumar)

A.R. Jambekar

EX-OFFICJOMEMBERS

President,IRC M.S. Guram,ChiefEngineer,PunjabPWD B&R, Patiala

DG(Ri)) AD. Narain,DirectorGeneral(RoadDevelopment.)& Addi. Secy.MOST, New Delhi

Secretary,IRC S.C.Shanna,ChiefEngineer,MOST, New Delhi

CORRESPONDINGMEMBERS

B .J Dave Prof. PremKrishnaMaheshTandori M.K. Mukherjee

SuprioGhosh

IRC:83 (Part1)-1999

ThereconstitutedCommitteediscussedthe draft during numberof meetingsheldbetweenJanuary,1994andJanuary,1997. Thedraftwasfinalisedby this Committeeaftermaking necessarymodifications.

The draft was consideredand approvedby the BridgeSpecifications& StandardsCommitteeattheir meetingheldatNewDelhion 27.9.97andapprovedby theExecutiveCommitteeon 29.11.97andthenby the Councilin their meetingheld on 5.1.98 atBhopal.

Theprovisionsof this Codeshallsupersedethe following clausesof IRC:24-l967. “StandardSpecificationandCodeof Practicefor RoadBridges.SectionV: SteelRoadBridges”.

ClauseNos. 502.10,504.7, 504.8, 504.9, 504.10,504.11, 505.11.2to505.11.5and 508.10,Appendix 1, S.No.8th and9th of Table 2 givingreferenceto clauseNo. 504.7 and504.11.

900. SCOPE

ThisCodedealswith thedesign,manufacture,testingpositioningand maintenanceof Metallic Bearings.onroadbridges.Theprovisions ofthis Codeare meantto serveasa guide toboththedesignandconstructionengineers,butmerecompliancewith the provisionsstipulatedhereinwillnot relieve them in any way of their responsibility for the stability andsoundnessof the structuredesignedand erected. This code coverslongitudinal movement(mainly for monoaxialmovement)only, specialhearingslike sphericalbearingsareexcluded,

901. DEFLNITIONS

For thepurposeof this Code,the following definitionsshallapply:

901 . I. Bearings

Thepart of thebridgestructurewhich bearsdirectly all the forces

Irom the structureaboveandtransmitsthe sametothesupportingstructure.

901.2. SlidingBearing

A type of hearingwheresliding movementis permittedbetweentwo surfaces,Fig. 1.

2

TRC

:83(P

artI)-1999CVICC,,

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IRC:83 (Part!)-1999

901.3. RockerBearing

A type of bearingwhereno sliding movementis permittedbut

which allows rotationalmovement,Fig. 2,

901.4. Sliding-cum-RockerBearing

A type of bearingwhere, in additionto the sliding movement,eitherthetoporbottomplate isprovidedwith suitablecurvatureto permitrotation. ‘Sliding-cum-Rocker’bearingshouldconformto GeneralDesignFeatures.

901.5. Roller-cum-RockerBearing

A typeof bearingwhichpermitslongitudinalmovementby rollingandsimultaneouslyallows rotationalmovement,Fig. 3.

901.6. Top Plate

A plate which is attachedto the undersideof the structureand

which transmitsall the forcesfrom it to theothermembersof thebearing.

901.7. SaddlePlate

A platewhich is positionedbetweenthetopplaeandtheroller(s).

901.8. RollerA part of bearingwhich rolls betweena topplateanda bottom

plate,or betweena saddleplate and a bottom plate.

901.9. BottomPlate

A plate which rests on the supportingstructureand transmitsforcesfrom thebearingto the supportingstructure.

901.10. KnucklePin

A cylindricalpin providedbetweenrecessesof thetopandbottompartsof a bearingfor arrestingrelativesliding movementof the top andbottompartswithout restrictingrotationalmovement,

901.11. KnuckleA recessin the surfaceof the bottom/saddleplate or top plate

housinga knucklepin preventingrelativemovementbetweentwo plateswithoutrestrictingrotationalmovement.

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IRC:83 (PartI)-1999

901.12. Rocker Pin

A lug on thesurfaceof the bottomplateorsaddleplate which fitsinto correspondingclear recessmadein the top plate to preventrelativemovement of the two plates without restrictingrotationalmovement,Fig. 3.

901.13. Guide

A Guide is a device providedto maintain the alignmentof theroller duringmovement.

901.14. Stopper

A Device/arrangementprovided in the bottom plate, to arrestmovementbeyondthe specifiedlimit.

901,15. AnchorBolts

A rag bolt orordinaryboltanchoringthe topandbottomplatestothestructure,

901.16. SpacerBar

A bar looselyfixed ateachendof aroller assemblyforconnectingthe individual rollers in a nest and to facilitatemovementof rollers inunison.

901.17. FreeSupport/FreeBearing

A support/bearingwhich permits the free relativemovementofthepartsof thestructure.

901.18. FixedSupport/FixedBearing

A support/bearingwhich preventsthe translationalmovementoftherelativepartsof the structure.

901.19. BearingAxis

The symmetricalaxisof thebearing.

901,20. EffectiveDisplacement

Thetotalrelativemovementbetweenthestructuresincontactwiththe bearing.

7

IRC:53 (Part 1)-1999

902. TYPICAL ARRANGEMENT OF SLIDING, ROCKER, ROLLER-CUM-ROCKERAND SINGLE ROLLERBEARINGS, SHOWINGVARIOUS

COMPONENTSOFTHEBEARINGS ARE INDICATED INFIGS. 1,2,3, &4

NOTE: STOPPERS ARE REQUIRED TO BE PROVIDED TO PREVENT ROLLERS FROMROLLING AWAY FROM THE BOTTOM PlATE.

Fig. 4. Single Roller Bearing (Typical)

903. SPECIAL REQUIREMENTS

903.1. Roller Bearings

Only full cylindericalroller ispermitted. Adequatewidth of baseplateshallbeprovidedto caterfor anticipatedmovementsof thesupportingstructure.

8

IRC:83 (PartI)-l999

903.2. For Seismic Areas(Zone IV andV only)

The roller and rocker bearingcomponentsshall havesuitablehearingguidesto preventthem from beingdisplacedduring earthquakes.The componentsshall allow formovementas calculated.

903.3. SkewBridges

For bridgeswith skew angleless than 20° the bearingsto beprovidedshallbeplacedat right anglestothe longitudinalaxisof thebridge.Forbridgeswith skewanglegreaterthan200, verywidebridgesandcurvedbridgeswheremulti directionalmovementsare expected,specialtype ofbearingsare to beprovided.

904. MATERIALS AND SPECIFICATIONS

904.1. Mild Steel

904.1 .1. The mild steel to be usedfor the componentsof the

hearingsshall comply with the following Indian Standardsii IS:2062-1992 Steel for General Structural Purposes

-Specification

ii) For all componentsexceeding50 mm in thicknessrequiringwelding,the carboncontentsfor such platesshallbeascertainedand suitable welding procedurelike pre-heating.use of lowhydrogenelectrodesetc., beadoptedafterapproval.

904.2. ForgedSteel

904.2.1. Thesteel for forging to beusedfor the componentsof the bearingsshall comply with Class3, 3A or 4 of IS: 1875 andsteelforgingsshallcomply with Class3, 3A or 4 of IS:2004.

904.2.2. All slabs should be normalisedafter forging. Ifwelding is involved,andif the slabsaremorethan20mmthick, preheatingof the slabupto 200°Cshouldbe done.

904.3. High TensileSteel

High Tensile steel for bearingsshallcomply with IS: 961.

904,4. StainlessSteel

The stainlesssteel shall be austenitic Chromium-nickelsteel,possessing,rust,acidandheatresistingpropertiesgenerallyasperIS: 6603

9

IRC:83 (Part I)-1999

and IS: 6911. Mechanicalproperties/Gradefor suchstainlesssteelshallbeas specifiedby the acceptingauthoritybut in no casebe inferior to mildsteel.

904.5. CastSteel

904.5.1. Caststeel usedin bearingsshall conformto Grade280-520Nof IS: 1030-1989‘Specificationof SteelCastingsfar GeneralEngineeringPurposesSpecifications’. In casewheresubsequentweldingis unavoidablein the relevantcaststeelcomponent,the letterN at theendof the gradedesignationof thesteelcastingshallbereplacedby letter ‘W’.

Note: GradeW is difficult to producein comparisonto gradeN

904.5.2. Forthe purposeof checkingthesoundness,castingsshall beultrasonicallyexaminedfollowingproceduresasp~rIS: 7666withacceptancestandardasperIS: 9565. Thecastingsmay alsobe checkedbyany otheracceptedmethodof non-destructivetestingas specifiedin IS:1030.

904.6. Welds

Weldingof steelconformingtoTS: 2062,shall beas perIS: 1024,usingelectrodesasperIS: 814.

905. LOADS AND FORCES

905. I. The loadsand forcesto be consideredin designingbearings for bridges shall be in accordancewith the requirementsofIRC: 6. Horiiontal forcesat hearinglevel shall beas given inAppendix-I.

905.2. The movementof supportingstructure shall be

assessedandcateredfor.

906. BASIC PERMISSIBLE STRESSESIN STEEL

906.1. The basic permissiblestressesin steel shall be asgiven in Appendix-2.

906.2. Basic PermissibleStressesin StainlessSteel

The basic permissible stressesin stainlesssteel shall be asspecifiedby the acceptingauthority,but in no caseless than that for mildsteelspecificationClause906.. 1.

10


906.3. BasicPermissibleStressesin Concretein Contactwith Bearings

The basic permissible stresses in concreteshallbe asspecifiedinIRC: 21.

906.4. Allowance Working Stresses in WeldedJoints

906.4.1. The allowableworking stressshall bebasedon thefollowing stresses

I) Butt Welds - Stressesin butt welds shall not exceed thosepermittedin theparentmetal. Butt welds shall be treatedas parentmetal with a thickness equal to the throat thickness.

ii) Fillet Welds- The permissible stress in fillet welds based on itsthroat areashall be110 MPa.

iii) Plug Welds - The permissible shearstresson plug weldsshall be110 MPa.

906.4.2. Where welds arenot subjected to radiographic or anyother equallyeffective methodsof testing,but theacceptingauthority isotherwisesatisfiedwith the quality of work, the allowableworking stressspecifiedin Clause906.4.1 shallbe multiplied by a factorof 2/3.

906.5. Allowable Working Loadson Cylindrical RollerBearings

(Length of rollers worked out on the basis of formulasgiven below shall be exclusive of width of groove.)

906.5.1, Cylindrical rollerson a flat surface : The allowableworking load for a single or double roller in Newton permmlength of rollershall be as follows:

Roller material Flat surfacematerial

CastSteel ForgedSteel Mild Steel

(‘ast SteelForgedSteelMild Steel

lId lid 8dIi d 11 d 8 d

Mild steel rollers are not permitted

whered is thediameterof the roller in mm.

II


For threeor more rollers the valuesof working load shall betwo-thirds of the abovementionedvalues.

Thebasicformulafor allowableworking load in Newtonpermmlength of roller for singleor doubleroller is

9d ~‘u2

E

where °u = Ultimate tensilestrengthof the softermaterialin N/mm2

F = Modulusofelasticityof steel in N/mm2

The allowableworking loadwhenboththeroller andthematingsurfaceareof hightensilesteelor anyotherhighgradesteelmay befoundoutusingtheaboverelationship.

906.5.2. Cylindrical rollers on a curved surface Theallowableworking load for a singleor double roller in Newtonper mmlength of roller shall he asfollows

Rollermaterial

Curvedsurfacematerial

CastSteel ForgedSteel Mild Steel

Cast Steel

ForgedSteel

Mild Steel

I I(ddi)/(d~—d) I l(ddt)/(di—d) 8(ddi)/(di-d)

ll(ddt)/(di-d) Il(ddi)/(di-d) 8(ddi)/(dt-d)

Mild steel rollers are not permitt.’d

Where, d isthediameterof theroller in mm

di is the diameter of the concave surface in mm

For threeor more rollers the values of working load shall beIwo-third of theabovementionedvalues.

Thebasicformulafor allowableworking load inNewtonpermm

length of roller for singleor doubleroller is

9ddt auz

E (d-dt)

12

IRC:83(Part 1)-l999

906.5.3. Spherical or cylindrical,,knuckle : The basic

permissiblepressureshall not exceed120 N/mm’, The working pressure

shall hecalculatedon theprojectedarea ofthemating surface.

907. DESIGN CONSIDERATIONS

907. I. General

907.1.!. The hearings shallbe designed towithstand themaximumvertical reactionsand longitudinal force under the most criticalcombination of loadsandforces. Provisionshall alsobemadeagainstanyuplifi to whichthe hearingsmayhe subjectedunderthe actionof theabovetorces.

907.1.2. The allowable bearingpressureon the loaded areaof

a base under a hearing shallbe given by Clause307 of IRC: 21.

907.1.2.1. The loaded areashall be calculatedas below:

i) For plateswith rocking line of contactthe width shall be theavailable dispersedwidth (max. dispersionbeinglimited to 2horizontaltoonevertical).

and

ii) Forplateswith rolling linesof contactthe widthforanyparticularpositionshallbe thecentreto centredistanceofoutermostrollersplus the availabledispersedwidth beyondtheoutermostlines ofcontact (max. dispersionbeinglimited to 2 horizontalto onevertical).

907.1.3. Where the eccentricity of loads and longitudinalforcesare considered alongwith directcompressiveforces, the calculateddirect bearingstressand the flexural stress, shallsatisfy the followingequation

oc0, cal tyc, cal+

csco oc

Where, ~c0, cal= the calculateddirectbearingstress= the allowabledirect bearingstressasperclause907.1.2.

~c, cal = the calculated flexural stresscc = thepermissible flexural stressin concrete or ~c0

whicheveris higher.

13

IRC:83 (Part l)-l999

907.2. Rockerand Rofler-cum-Rocker Bearings

907,2.1. Top, saddleandbottom plates

907.2.1.1. The platesshall besymmetricalto the bearingaxis.They shall he of mild steel/caststeel/forgedsteel/hightensilesteel.

907.2.1.2. Thewidth of platesshallnotbe lessthaneitherof thefollowing:

i) 100mm

or

ii) Thedistancebetweenthecentreto centredistanceof outermostrollers (whereapplicable)plus twice theeffectivedisplacementduringserviceor twice the thicknessof the plateplus 10 mm asmargin for error in siting. (The centre to centredistanceofoutermostrollers if these are two or more. For single rollerbearingsit shall betakenas zero),seeFig. 5.

907.2.1.3. Thethicknessof theplateshallnotbe lessthan(i) 20mm or (ii) 1/4th the distancebetweenconsecutivelines of contact,whicheveris higher.

907.2.1.4. Thethicknessof theplateshallalsobechecked,basedon thecontactstressesarrived ataccountingfor theactualwidthof theplateprovided, to satisfy therequirementsof structuraldesignandpermissiblestressesaslaid down in Clause906.

907.2.2. Rollers

907.2.2.1. Forgedsteelrollers maybe preferredover caststeelrollers,Mild Steel rollersshallnotbeused,Theminimumdiameterof rollershall be 75 mm.

907.2.2.2. The ratio of the length of the roller to its diametershall normally notbe morethan 6.

907.2.2.3. The effectivecontactlength with the plateshall beusedfor arrivingat the length of the rollersto beusedin theformulagivenin Clause906.5.

907.2.2.4. Thegapbetweentherollersshall notbelessthan 50mm in caseof multiple rollers.

14

ROt.LER AXIS

MAXIMUM S~lWTorDCCXING FROM I

POSITION IN

OIR~CTIDN

Fig. 5 . Maximum Shifts ofTop Plate and Rollersdueto Movementsof Deck

The minimum width of various plates shall be calculated from thefollowingformulae (Clause 907.2.1.2)

W1 ~. 100or2tl whicheveris greater

W2 >, 100 or [(n-l) C + 2~Ior [(n-i) C + 2t~)whicheveris greatestW3 >_. 100 or [(n-i) C + 2~or [(n-i) C + 2t3Jwhicheveris greatest

= Effectivedisplacementn = No. of roller

tI,tzandt3asin,Fig.3

IRC:83 (PartI)-1999

MEAN AXIS OF PLATE

MAXIMUM SHIFT OF

DECKING FROM MEANPOSITION

15

IRC:83 (Part l)-l999

907.3. SlidingBearings

907.3.1. The top plates shall project on all sides over the

bottom plate by atleast 10 mmfor anyextremeposition of thehearing.

907.3.2, The thickness of the plate shall satisfy therequirementsof structural design and permissible stresses laid down inClauses 906 and 907.2.1.4, but shall not be less than 20 mm.

907.4. MiscellaneousComponents

907.4.1. Design of knuckle : The knuckle pins shall be sodesignedas to he safe in bearingandresist thehorizontalsheardueto themaximum longitudinal forces acting on the bearing. The permissiblehearingstressshall be limited to the valuespecified in Clause906.

907.4.2. Rockerpin

907.4.2.1. The pins providedin bearingsshall be designedtoresist the maximumlongitudinal force actingon the bearings. The pinsshall be driven force fit in the saddleor bottom plate and shall havecorrespondingrecessesin thetopplatewith adequatetoleranceto allowforroeking.

907.4.2.2. The rocker pin and the correspondingrecessshall

satisfy the following

i) Thediameterof the rockerpin ~d’shall notbe lessthan 16 mm.

ii) Thepin shallbe force fit to adepthof0.5d.

iii) Thepin shallproject0.5d and have a taperin the projectedportion

to accommodate the rotation of the structure.

iv) Thediameterof thecorrespondingrecessshallbe1.1 d or d + 2.5

mm,whichever is less.

v) The minimumclearanceabovethe topsurfaceof the rockerpin

shall be 2.5 mm.

907.4.3. Spacer bars : To ensuremovement of multiplerollersin unison,spacerbarsmaybeprovidedbut thearrangementshallhesuchthat the rollers canrotatefreely,Fig. 3.

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IRC:83 (Part E)-1999

907.4,4. Guide lugs and grooves

907.4.4.1. To prevent transverse displacement ofthe bearingcomponentssuitable guide lugs in plateswith corresponding grooves inrollersshall he provided.

907.4.4.2. The guide lugs and the corresponding grooves shallsatisfy Ihe fbllowing

i) The numberof guides and lugs shall be 2 for eachcase andincreasedto 3 wheretheratio of roller lengthto diameterexceeds6.

ii) The width ~b’of the lug shallnotbelessthan 10mm.

iii) Theguide lug shall he force fit to a depthof 0.5 b.

iv) Theguidelug shall project0.5 b.

v) Thecorresponding groove shall havea clearanceof 1.00mm onthesidesandtopof the guide lug.

907.4.5. Stoppers : To prevent rollers from rolling off thebottom plate, suitable stoppers shallbe provided.

907.4.6. Anchor bolts

907.4.6.1. The top and bottom platesshallbe suitablyanchoredto the girder and the pier abutment cap or pedestalsby means of anchorbolts.

907.4.6.2. The anchorbolts shall be designed to resist themaximumhorizontalforce actingon thebearing.

907,4.6.3, Theminimum length of the anchor bolts inconcretemay bekeptequal toits diametersubjectto a minimum of100 mm.

907.4.7. Anchoringof deckto substructure: The anchoringarrangementshall be designed forsuchaforceso as toprovide for astabilityequivalent toI .1 timesthe overturningmoment due to permanent load (or0.9 times iftheeffectis moresevere) and1.6timestheoverturningmomentsdue to temporaryloadsor live loads.

17


907.4.8, Pendulum guides : An arrangementwith slots topreventthedisplacementof the rollerunit dueto siesmicor otherdynamicvibrationsshallbe provided.An exampleof suchan arrangementis shownin, Fig. 4.

90& WORKMANSHIP AND TOLERANCES

908.1. All surfacesof themajorcomponentslike topplates,saddle plate, base plates,rollers of the bearingsshall be machined all overfor correctalignment,interchangeability,proper fitting, etc.

908.2. Plates

908.2.1. The plate dimensions shall be in accordance with theapproveddrawing. Toleranceon the lengthandwidth of the plate shall notexceed+ 1 .0 mm, toleranceon the thicknessof theplateshallnot exceed+ 0.5 mmand no minus tolerance shall be allowed.

908.2.2. All rolling, rocking andsliding surfacesshallhaveamachinesmooth finish to 20 micron maximum meandeviation as perTS:3073.

908.3. Rollersand Curved Surfaces

908.3,1. The toleranceon the diametersof both rollers and

convexsurfacesshallconformto K 7 of IS:9l9.

908.3.2. The toleranceon the diameterof concavesurfaces

shall conformto D8 of IS:919.

908.4. Castings

908.4.1. No minustolerancewill be allowed in the thicknessof any part of the castings.The edgeof all ribs shallbe parallelthroughouttheir length.

909. ACCEPTANCE CRITERIA AND TESTING

909.1. AcceptanceCriteria:Unlessagreeduponotherwisebetween theEngineerandtheManufacturer,theManufacturershallfurnisha complete Quality Assurance Programme (QAP) comprising the processof quality control, raw material testing, various stagesof manufacture,testingon hearingcomponentsas well as testing on completebearingetc.in conformity with relevantcodalstipulationsprior to thecommencementof manufacture,The saidquality assuranceprogrammeshall be approved

18


by the Engineer/Accepting Authority. Manufacturing process, qualityassurance, testing, documentation, etc. shall be carried out in conformitywith the approvedquality assuranceprogramme~PrOperdocumentation,records and certificates shallbemaintained atall stagesof manufactureandinspection by manufacturer to ensure to the conformity with the approvedQuality Assurance Programme.

The Engineer may appoint an authorised inspection agency on hisbehalf br the purposeof inspectionas perapproved QualityAssuranceProgramme to certify the acceptance or otherwise of the bearings.

909.1.1. Test certificates of reputed testing laboratories for allraw materialsshall be submitted. If suchtest certificatesare not availablethen bearing manufacturer shallperform the necessary confirmatory testsas perrelevantcodes of practiceand shallfurnish the test results. Engineeror his representative may carry out independently tests on raw materialsand witness the manufacturing process.

909.1.2. All casting and forgings shall beannealedlnormalised and the heatcycle record shallbe submitted totheInspectingOfficer/Engineer for scrutiny. InspectingOfficer/Engineermayensurethe proper reduction ratio. Suitable weld data record shall bemaintainedand submitted.

909.1.3. The Engineer shall reserve the right to witness suchinspection at manufacturer’s workshop. For this, bearing manufacturer shallhavein-plantminimumtestingfacilities as follows

ii Fully equipped chemical test laboratory to find out Carbon,Sulphur,Phosphorous,Manganese,Silicaandotherelementsasrequired.

ii) UTM of minimum 40 MT capacity

iii) BHNtesting equipment of 3000Kg!. (Hydraulic type)

iv) Ultrasonic flawdetector

v) Metalography for checking of microstructure of differentmaterials

vi) Load testing machine of required capacity having facilities ofrotationandlateral loading.

19

IRC:83 (Part I)-l999

909,1,4. Bearing manufacturer shall maintain a list ofconsumption of rawmaterialsincludingtestrecords,for aperiodof at leastprecedingtwo years.

Testcertificatesof bearingsmanufacturedduringprecedingtwoyearsshall be made available to the Inspecting Officer(s)/Engineeratmanufacturer’s works.

909.1.5. Bearing manufacturershall employ full timesufficientgraduateEngineeringstaff for manufactureandquality controlof hearings and shall have full time trained Scientist in chemical andphysicaltestingandalsohavequalified person for ultrasonic testing.

Bearingmanufacturershallhavequalified/certifiedwelders.

909.2. Testing

909.2.1. The manufacturer has to produce test certificate fromoriginalproducersof rawmaterialsusedin themanufactureof thebearings.Irrespectiveof the producerstestcertificates,the manufacturerwill carryout the detailed tests on raw materials (both physical and chemical) fordifferent types of raw materials used in the manufactureof thebearingsasper relevant codes for such raw materials, For this purpose they willidentify stock materials with certain batchnumberanddrawsamplesfromsuch stock materials and mark the same with same batchnumbers.Foreachhatch, 3 sets of samples will be drawn separately for testsof physicalandchemical properties on samples. The manufacturer will carry out tests onchemical and physical properties on one set of samples and keep theremaining 2 sets of samples duly identified with the batch number forverification by the Engineer and/or his authorised representatives forconb’ormatory tests with respect to the results obtained by the manufacturer,Such tests can be carried out on a few samples selected at random by thediscretionof the Engineerand/or his representatives. The following ISCodes may be referred for carrying out such tests (both physical andchemical)

IS : 1030 for castingIS : 2062 for Mild SteelComponentsIS : 2004 for forging

Otherspecialmaterialsshall beasperrelevantIS/BS/AISICodes.

909.2.2. All machined cast steel components shall be testedfor ultrasonic testing to level Ilird of TS:9565. Critical surfaceshallalsobechecked by Dye Penetration Test (DPT) and/or magnatic particle test fordetecting presence of surface defects.

20

IRC:83 (Part 1)-l999

909.2.3. All forged steelcomponents after machining willbesubjectedto ultrasonictesting. Guidelines givenin Appendix-3 could bereferred to. To ensure the reduction ratio, macro-etching testwill heconducted on the integral test piece (per heat) attached to anyoneof theforging.

909.2.4. All bearings shall be tested to1.25timesdesignload.Recovery shouldbe 100 percent. Contactsurfaces andwelding shall beexamined by illumination source/ultrasonic test/DPI for any defects/cracksetc.

909.2.5. All welding shall be checked by Dye PenetrationTest. If specifically required by Engineer, the X-ray test may also be done.

909.2.6. Engineer may carryout the destructive testing of anycomponenticomponentsof bearings supplied forconformity of testresultssubmitted.

909.2,6.1. In case there is any major discrepancy regarding

materials, Engineer may declare the whole lot of bearings as unacceptable.

910. PLACING AND POS~ONINGTHE BEARINGS

910.1. General Considerations

910.1.1. On supporting structures, pocketsshall be providedto receive the anchor bolts. Appropriate methodfor levelling/grouting ofthe bearing to both beamsand pedestal structure shall be adopted.Thepocket shall he filled with mortar of mix 1:1 and the concretebearingareaalso shall be finished level by a thin mortarpad of mix 1:1 just beforeplacing of bearing assemblies orbottom plateon theconcreteseat.

910.2. Positioning of Bearings

910.2.1. During installation the bearings shall be pre-set withrespect to the bearing axis to account for the movements due to thefollowing:

i) Temperature variation between the average temperatureprevailing at the time of installation and the mean designtemperature.

ii) Shrinkage, creepandelastic shortening.

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9 10,2,2. For bridges in gradient the bearingplatesshall beplacediii a horizontalplane.

910.3. Precautionsduring Construction

910.3.1. In prestressed construction where launching ofgirdersis employed, in order to avoid slipping or jumping of rollers due tovibrationsor jolts, it is suggestedthat the roller bearingsbe providedafterlaunching operations or otherwise adequate measures taken to ensure thatthe roller assembly is notdisturbed. It is normal practice to provide rockerbearings on the iaunching end and place the beam on the rockerendslightlyin advance of placing on the roller.

9 10.3.2. During concreting of girders, the bearings shall heheld in position securely by providing temporary connection between thetop and bottom platesin case of fixed bearings, and between top plate,saddle plate and base plate in case of a roller-cum-rocker bearing or by anyother suitable arrangement which preventstherelativedisplacementof thecomponents. The bearing plate shall be kept level duringconcreting.

910.3.3. In pre-stressed pre-casi girders where recesses are lefton the undersidd ofgirders to receive the anchorholts, grout holes extendingto the beam sides or to the deck level shall be provided. The grout shallhave a mix of 1:1.

911. INSPECTION, MAINTENANCE AND REPLACEMENT OF BEARINGS

911.1. Suitableeasyaccessto the bearingshallbeprovidedfor inspectionandmaintenance.

911.2. Provision shall be made for jacking up of thesuperstructure so as to allow for adjustment repair/replacement of rollers ofthe hearings.

911.3. Each bridge bearing assemblyand the adjacentmembers in contact shall be inspected at leastonceayearto ascertaintheiractual condition and suitable remedial measures taken immediately ifdefects are noticed including replacement in the event of irrepairabledamage. However, the bearings shall also be examinedcarefully afterunusual occurrences like heavy traffic damage, earthquakes, and batteringsfrom debris in high floods. Necessary records of inspection shall bemaintained.

22


Appendix-i(Clause 905.1)

HORIZONTAL FORCES AT BEARING LEVEL

Thedesignhorizontal forces at the bearings shallbe the maximumof the following combination

(I) For simply supported bridge with afixedand freebearing (other

than elastomerictype on stiff supports)

Fixed Bearing Free Bearing

(i) Fh-~.t(Rg+Rq) ~i(Rg+Rq)or (ii) Fh/2+p.(Rg+Rq)

whichever is greater.

Where:

Fh Braking or seismic force* on the length of deckingeffective for the bearing

Rg Reaction at thefreeend dueto dead loadRq Reaction at the freeend due to live load

= Coeff. offriction at the movable bearings, which shall beassumed to have the following values:

(a) ForSteelRollerBearings- 0.03(b) ForSliding Bearings:

(i) Steelon Steelor castiron - 0.5 (unlessotherwiseprovedby testsorother supportingdata)

(ii) Meehanite andGreyIron Castingsonsimilar metal - 0.40

In seismicareas,the fixed bearing shall alsobe checked for full seismicforce.

(2) Slab typebridges of spanlessthan 10 m

The force at the bearing shall he Fh/2or j.tRg whichever is greater.

Where:

Rg = Reaction due to Dead Loadon thebearing

Note: *Thecomponentin the directionoftrafficofseismicorwind forceon the structurecausedby the live load, neednot be consideredalong with braking force.

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(3) Continuing Bridge with onefixed bearingand other free bearings

(other than elastomerictype onstiff supports)

FixedBearing FreeBearing

CaseI

(l.LR-IIL) + ye and Fh acting in .~yedirection

(a) IfFh>21.tR

Fh-(MR+p.LL) j.tRx

(h) lfFh<2j.sR

Fh_______-. - (~tR-jaL)1 + EnR

CaseII

(jiR-~.tL)+ ye and Hi acting in — ye direction

(a) IfFh>2~tL

Fh-(J.LR+IIL) ~xRx

(b) Fh <2pL

Fh______ - (~tR-3~L)I + EflL

whichever is greater

where

l.~Lor n~ = number of free bearings to the left or right of fixedbearings, respectively.

Pt or ~R = the total horizontal force developed at the freebearings to the left or right of the fixed bearingrespectively.

~aRx = the net horizontal force developed at any one of thefreebearingsconsideredto the left or rightof thefixedbearings.

24

JRC:83 (Part I)-1999

PERMISSIBLE STRESSES

Appendix-2(Clause 906.1.)

Table 1. Basicpermissiblestresses inMPain membersi.e.plate, flats,squares,rounds etc.other than rocker pin, knucklepin, anchor bolts,screws,etc.

S.No~Description High Cast Forged MildTensile Steel Steel SteellS:961- IS:l030- IS:2004- IS:226-1975 or sp steel 1989 1978 75/ 2062-84

1. Max, axial tensilestresson effectivesectionalarea(ay~

O.6Oay, 160 160 140

2 Max. bendingtensile or compressivestressoneffectivesectionalarea for extremefibre (al/ac)

O.66oy, 180 180 150

3, Max. shearstress(~ra)

0.45 ay. 120 120 105

4. Max.bearingstress on non-sliding surface(ap)

0.8Oay, 215 215 186

5 Max. combinedbendingshear& bearing, stress(abc)

0.92 ay, 250 250 210

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Table2. PermIssiblestressin MPa In knucklepin, rockerpin

Max. axialtensiles~ress(at)

Max. shearstress ttra)

Max. hearingstress (cryt)

Permissiblestressesin a boltofanyotherproperty classwill beasper Ci. 8.9.4.3of IS:800-1984which is reproducedbelow forconvenience:

“Thepermissiblestressin abolt(otherthana highstrengthfrictiongrip bolt) of propertyclass higherthan4.6 shall be those given inTableS.! multiplied by theratioofitsyield stressor0.2per cent proofstressor 0.7 timesl’s tensile strength,whichever is the lesserto 235MPa.”

S.Nc. Description HighTensileIS:96l-l975orspsteel

CastSteelIS:1030-1989

ForgedSteelIS:2004-1978

I.

2.

3

Max. axial tensilestressoneffectivesectionalarea(ayt)

Max. shear stress(tra)

Max, hearingstresson non— slidingsurface (ap)

0.60 cry.

(3.37 cry,

0.87 cry,

160

100

235

160

100

235

Table3. Permissible stressesin MPa in anchor bolts and screws

S Nc , Description Black BoltsconformingtopropertyCl.4.6ofIS:l367~!961

120

80

250

Note : Coniponentsofhearingsshouldhedesignedfor theworstcombinationofloadswith no increasein permisiblestresses.

26

IRC:83 (Part I)~1999

Appendix-3(Clause909.2.3)

(;uIDEL!NEs REGARDING PROCEDURE FORULTRASONICTESTINGOFFORGED STEEL ROLLERS CONFORMING TO IS:2004CLASS3 AND ITS

ACCEPTANCE STANDARD

Type ofEquipment KrantakrammerlEClL/EEC orultrasonic flow detector

Vibronics make

Test Method Pulse echo direct contact method

Test 2-2.5 MHz, 24mm

FrequencyProbe Straight beam (normal) probe

SizeCouplant

Text

Oil/Grease

Scanning by hand probing

Direction

Calibration

Throughoutthe length of the body of forgedproof-machine rollers inall possible direction at leastcoveringthe surfacearea upto 1800.

Calibration of the machine (UFD) is to be done using11W block/standard calibration block fora range of2.00mm.

Sensitivity setting The sensitivity shall be set on a 3.0 mmdia. Flatbottom (FB) hole drilled upto a depth of 25 mmon a200 mmlength x 10 mmdia. Class 3 forged barhaving reflection of screen height of 75% from theFB hole.

AcceptanceStandard

i) Forged rollers shall not contain harmful defectlike shrinkage,cavities, porosities, pipingcracksetc. Any type of surface crackis notacceptable.

ii) Flaw signal more than 70% height at onelocationshallbe a cause forrejectionincasetheflaw is along thecentralaxis zone ofthe roller(i.e. 12.0 mmeither side of the axis line).

27

IRC:83(Part I)-!999

iii) Flaw signals equal or more than 50% heightshall be a cause of rejection in case twoconsecutive flaw echos are within 200 mmdistance at thecentral axis zone.

iv) At no point the length of the central axis zonedefect shall exceed2 probe position.

v) The defectssodetected,shall not bespacedlessthan 200mmat theroller ends(within 100mm).

vi) Total number of defectsshall not exceed3 inoneroller.

vii) Connected discontinuities shall not bepermitted.

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standard specifications and code of practice...

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