IRC 6-1966

STANDARD SPECIFICATIONSAND

CODE OF PRACTICEFOR

ROAD BRIDGESSECTION 11

LØADS AND STRESSES

AN ROADS CONGRESS

IRC 6-1966

c1X .~~tk1STANDARD SPECIFICATIONS

AND

CODE OF PRACTICEFOR

ROAD BRIDGESSECTION II

LOADS AND STRESSES

S.

PublishedbyTHE INDIAN ROADS CONGRESS,

JamnagarHouse,SbahjahanRoad,New Deihi-ilOOl I

1974

PriceRs 5+00(Packing & F ostageexfta)

~

IRC 6-1966

First publishedin December,1958Reprinted:May, 1962Reprinted:September~19632nd Edition: October,19643rd Edition in Metric Units: October,1966Rcpri~t~Reprinted:March, 19t2 (incorporatesAmendmentNo. 1—Nov.1971)Reprinted:February1974 (IncorporatesAmendmentNo. 2—Nov.

1972)Reprinted: August 1974 (Incorporates Amendment No. 3—April

1974)

(Rightsof Publicationandof Translationare reserved)

Printedat PRINTA1D, Eastof Kailash, New Delhi

ER( 61966

CONTENTS

~ectionII

LOADS AND STRESSES

Clause No, Page No.

201 Classification .. 4202 Loads, Forces and Stresses ., 5203 Pcrmissihk Increase in the Workmg Stresses ui

any Structural Member under Variqus Combi-nations of Loads, Forces and Stresses given inClause 202 6

204 Deleted ~... 6205 Dead Load 6206 Traffic Lanes ..,, 8207 Live Loads 8208 Reduction in the Intensity of Live L9ad Stress-

es on Bridge.s accommodating more than twoTraffic Lanes 12

209 Footway, Kerb, Railings and Parapet Loading 13210 TraMway Loading .. 15211 impact 16212 Wind Load . 19213 Horizontal Forces due to Water Currents ,., 22214 Longitudinal Forces 25215 Centrifugal Forces ... 27216 Buoyancy . 27217 Earth Pressure 28218 Temperature Effects 31219 Deformation.. Stresses 32220 .. Secondary Stresses ~.. 32221 . Erection Stresses ~., 32222 Seismic Force 33

Platt F — Curves showing Fqunahnt Heights olSurcharge of Barth 35Appendix I—Hypothetical Vehicles Rn Classifi-cation of Vehicles and Bridges (Revised) 37

IRC :6-1966

INTRODUCTION

The briefhistory of the Bridge Code given in the in..troductionto Section1 ‘GeneralFeatures ofDesign’ applies to Section H also.generally. The draft of SectionIi for “LoadsandStresses”asdis-cussedat the Jaipur Session of theIndian RoadsCongressin 1946was consideredfurther at a numberof meetingsof the BridgesCom—

mittee for linalisation, in the years 1957 and 1958, the work ofhnahsingthe draft was pushed on vigorouslyby the BridgesCorn-mittee constitudedas follows

Shri S.L. Bazaz ~.,, ConvenorShri M,P, Nagarsheth + ... Member-Secretary

(i) Location, Laynut and Hydraulics Division

Shri H.P. Sinha+ Brig. S,K, Bose..Representative,E-in-C’s Branch, AHQ.

Shri ‘U.J. BhattShri Baleshwar Nath Rcprestntingthe C B I & PDr. K.L. Rao .,,Representipgthe C.W.& P.C.

(ii) Substructureand Superstructure Division

~+hriH.P. Sinha Shri MV. Jogiekar Shri~S,I.JoshiShri K,F, Antia , Shri S.K. Ghosh Shri P.C. PoonenShri D.S. Desai Shri K.K. Nam’biar Shri S’.S. Varma

2...At the Bridges Committee meeting heldat BombayinAugust 1958,all the con,mentsreceived till then on the differentclausesof this Sectionweredisposedoil fnaily anda Drafting Com-mittee consistingof SarvashriS.B. Joshi, K.K. Nambiar, K.F AntiaandS,K. Ohoshwas appointedto work in conjunction with theofficers of the RoadsWing ihr finalising this Section.

This Cornmittceat its meetingheld at New Delhi in September 1958 and later through correspondence finalise4 Se9tion II ofthe Codewhich wasprinted in1958, reprintedin 1962 and 1963.

hi second editionot Section ¶1 of the Code(1964 edition)included all the amendments,additions& alterations madeby theBridges Committeein their meetingsheld from. time to time.

IRC : 6~1966

The Executive Committee of the indian Roads Congressapprovedthe publicationof the third edition in metricunits, in 1966.

The Bridges. Committee at its meetingheld in 1971 approvedcertain amendmentsip. the light of the Fourth Revision of Section1and the publication of Section lEE. These amendments, videAmendmentNo. I of November 1971 ‘(amending clauses 204, 207,209, 212 and 216) andNo. 2 of November 1972, (regarding sub-clause201.1) havebeenincluded in thisEdition. The presentreprintalso incorpori~tesAmendment No. 3, April 1974, regarding sub-clause211.2anderratumto sub-clause209.4(c).

3

i sc : 6—1966

LOADS AND STRESSES

SCOPE The. objectof the StandardSpecificationsand Codeof Practiceis to establish a cpmm.on procedurefor the designandconstruction of road’ bridges in India. This publication is meantto serve as a. guide to ‘both the design engineerandthe constructionengineerbut compliancewith the rules thereindoesnot relieve themin any way of their responsibility fOr the stability andsoundnessofthe structure designed~’anderectedby them. The designan’d con-struction of’ road bridgesrequire an extensiveandthoroughknow-ledge o’f the scienceandtechniqueinvolved and shouldbe entrustedonly to spcciallyqualified engintirs s~ith idcquatt. pr ictical cxperience in bridgeengineeringand capable of ensuringcareful execu-tion of work.

201. CLASSIFICA TION

201.1. Road bridgesandculverts shall be divided into classesaccordingto the loadingsthey aredesignedto carry.

LR.C, Class AA Loading :.—This loading is to be adoptedwith-in certain municipal limits, in certain existingor contemplatedindus-trial areas,in otherspecifiedareas,and along certain specifiedhigh-ways. Bridges designed for ClassAA Loading shouldhe checkedfor Class.A Loadingalso, asundercertainconditions,heavierstress-es may be obtainedunderCk.iss..A ‘Loading.

NOTE, : “Where Class 70-5. is sp~cffled,ii shall he usedin placeof IRCClassAA loading’’,

I,R.C. ‘Class A Loading i—This loading is to be nornmlly adopt-ed on all roadson which permanentbridges andculvertsare cons-tructed.

LR.C. ClassB Loading ‘This loading is to be normallyadopt-ted fin temporary structures and for bridges in specifiedareas.Structures‘with timber spansare to be regardedas tem’porarystrdc—turestir the purposeof this Clause.

For particularsof the abovethreetypesof Icading, see Clause207.

4

IRC : 6-1966

201,2. Existing bridgeswhich were not originally constructedor later” strengthenedto take one of the above specified l.R.CT+Loadings will he classified by giving eacha numberequal to thatof the highestslandard load class whose effecti it cansafely with-stand.

Appendix I gives the essentialdataregardingthe limiting loadsin each bridge class, ‘and forms the’ basisfor the classificationofbridges.

201.3. individual bridges and culvertsdesignedto take elec-tric tramways or otherspecialloadingsand not constructedto takeany of the loadings described in Clause201.1 shallbe classifiedinthe appropriateload class indicatedin Clause201.2.

202. LOADS, FORCES AND STRESSES

202.1. The loads, forces and stressesto be consideredindesigningroad bridgesandculvertsare

I. Dead load,2. Live load,

3. lmpact or dynamiceffect of the. live load,

4. Wind load,5. Horizontalforces due to water currents,

6. Longitudinal forces causedby the tractiveeffort ofvehiclesor by braking of vehiclesand/orthosecausedby restraintto movementof free bearings,

7. Centrifugal forces, +

8. Buoyancy,

9. Earth pressure,

10. Tcmperaturestresses,

I. Deformation stresses,12. SecondaryStresses,

13. Erection stresses.

14. seismic forces.

202.2. All membersshall be designed‘to sustain safely thevariousloads,forcesand stressesthat can co-exist, and all calcula-tions shall tabulatedistinctly the various comibinations of the aboveloadsand stressescoveredby the design.

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IRC :6-1966

*203 PERMISSIBLE INCREASE IN THE WORKINGSTRESSESIN ANY STRUCTUREMEMBER UNDER

VARIOUS COMBINATiONS OF LOADS, FORCES ANDSTRESSESGIVEN IN CLAUSE 202

203.1. The permise.ihleworking stressesshaltnot be exceedelfur any combinationof the loadsand forces,’specifiedin items I to 9of Clause202.1, thatvan co-exist.

203.2. When the effectsof temperaturestressesarealsoadd-ed, the permissibleworking stressesmay be increasedby 15 percent.

203.3. When the combinedeffectsof any combinationsof anyof the forcesspecifiedin items 10 to 13 are added, the permissibleworking stressesmay be exceededby 25 per cent,and

203.4.. When the effectsof seismic forces are also consideredin addition to those from any combination of the loadsandforcesspecified in items I to 3 and5 to 13 of Clause 202.1 that canoccur,the permissible working stressesmay be exceededby 50 percent,providedalways that (i) under the combined effects of loadsandtbrces specified in items 1 to 13 of Clause 202.1, the permissibleworking siressesshall not exceedby more than 25 per cent, and (ii)this excess does not result in the stresses in any steel memberincreasingbeyondthe yield point.

Pio:~’: Theconditions laid down for different combinationsshould besimultaneouslysatisfied.

**204 DELETED

205+ DEAD LOAD

The dead load carried by a girderor membershall consistofthe portion of the weight of the superstructure(and the fixed loadscarried thereon)which is supportedwholly or in part by the girderor memberincluding its own weight.’ The following tin it weightsofmaterialsshall be usedin dermining loads,.+unlessthe unit weightshavebeendeterminedby actual weighing of representativesamples

tProvisions made under Clause 203 shall not be applicablein caseofcoocreate,masonryor steel structuresfor which a referenceshall be madeto therelevantclausesof I S.C. StandardSpecificationsand Code of Practice forRoadBridges SectionslIE, IV & V

**Deleted, as relevant provisions are covered in tRC : 5-1970,StandardSpecificationsandCodeof Practicefor RoadBridges-Section1.

6

IRC 6-1966

of the materialsin question,in which casethe actual weightsas thus

determinedshall be used

Weight perMaterials cu. m. in

tonnes

1. Ashlar (granite) ‘ ... 2.72. Ashlar (standstond) ... 2.43. Stonesetts

(a) Granite ... 2.6(h) Basalt ... 2.7

4. Ballast(stonescreened,broken, 2.5cmto 7.5cm gauge,loose):(a) Granite .,, 1.4(b) Basalt ,,, 1 .6

5. Brickwork (pressed)in cement mortar ... 2.2

.6. Brickwork (common)in cementmortar .,. 1.97. Brickwork (common)in lime mortar ... 1 .~

8. Concrete(asphalt) ... 2.2

9. Concrete (breeze) ‘ ... r.410. Concrete(cement—plain) , ... 2.2

11. Concrete(cementplain with plums) ... 2.3

12. Concrete(cement—reinforced) ... 2.4

13. Concrete (cement—prestressed) ... 2.5

14. Concrete(lime—brick aggregate) ,,, is15. Concrete (lime- stoneaggregate) ,,, 2.1

16. Earth(compacted) . , ,,,

17. Gravel ‘ i.s

18. Macadam (h~nderpremix) ... 2.2

19. Macadam (rolled) ,~, 2.6

20. Sand (loose) ... 1.4

21. Sand(wet compressed) ,,, I .9

22. Coursedrubblestonemasonry(cementmortar) .2.6

7

IRC :6~i966

Weight perMaterials cu.m. in

tonnes

23. Stonemasonry(lime mortar) 2.4

24.. Water ,,; 1.0

25. Wood .., 08

26. Castiron ... 7.2

27. Wrought iron

28 Steel (rolled or dast) ,,, 7.8

206. TRAFFIC LANES

The numberof traffic laneson a bridge shall be determined bythe maximum intqgralnumberof trains of standardClassA vehiclesdescribedin Clause207, which can be accommodatedon the clearitin tgt~sa~s~idthof tho hi idgt w nh thc vU ides ti a~ethngparslIdto the length of the bridge and leaving the minimum clearancesspecifiedin Clause207.

All new bridges shall be of either one-lane,two-lane, or ibur-lanewidth. Three_ian:e:ihridges shall not he co~structed.in thecaseof four-laneor multiples of two-lanebridges,at least l.2ni widecentral vergeshall be provided.

207. LIVE LOADS

207.! Details of LR.C. Loadings

207,1.1. For bridgesclassifiedunderClause20!.1 the design-ccl live load shallconsistof standardwheeled or tracked~vehiclO ortrains of vehiclesas illustrated in Figs. I to 3 and Appendix I. Thetrailers attached to the driving unit are not to he considered~asdetachable.

207 12 Within the herb to kerb width of tht. roadssay thestandardvehicleor train shallbe assumedto travel parallel to the

TRACKED VEHIcLEFig. ~h Class AA tracked and wheeled vehicles (Clause207,1)

8

l:g 1 1’ (‘ontd,) ‘IRC : 61966

l—~——COUIACS WAY WIDTH ‘~~S’~S

3Si’ONNES ~I5TONNES1

ii it~~p“~‘ii’L I

TRAdED VEHICLE~— CARRIAGEWAY WIDTH ———*‘-—s~’

m Hits ——~“*4

It t~—~I,I$m—~4

~ I ( ~r~cgnnh ‘

.*+,__:uIi,HSl O,H_~lL:Hl~

~ Et

S..

PlanWHEELED VEHICLE

Fig. 1. ClassA’~trackedand wheeledvehicleslClaus~207.1)

NotvI . “1’ he sin ye to

tail cpa~ing bet%s’i en iwo r,iIcein’r,i;n’,’vi’chiele,,i yh;:ill notlii;r linri

Iv it I,, i.’

whiv,,ticner ei~’i.nico

~h~yll(dl L’.lr1~nLlereLll~sCl Ii

1 Li iitt SL

No flhiyr lis Cnhvill be cmion

vIe red 0 0 9 liviiII II’iii 5,5

olecarriagewaYofthe bridge whyabove merit i oii cittrain or ychiclys IIIcrossing the hridee.

3 niasimum buds rrrsvliceleui vcltiolvshall he SI) tinoncufor ii iiflr 5: aisle

hi’gi~of m’’’:m asIc’sstaaceLl nthan 1.2 r ceimimesL

4. The con or ormucbearanc:e b”uu~ccnthc’ vinyl face i:nl ihekerl:i and tIne oumoredge iii’ tIie wIsedor track, ( sh::iibthe as tinder

Carriageisa~ %Iinhnuniss’id th 55~toe or t’

Single l.,ane Bridges

3.8 in arid (1.3 rnahou’ e

MW il~L,aneBridges

Lessshari

5,5 10

5~5sri or 1,2 niabove

625 TONNES 625 TONNES

fr,.~,.~ iii ,..,f,,,

:!E~:4

ac:.. 6~t9Yi

I... lIhdflI~J~I’I

-‘i”——’ “Ifl ifiC H 7

ii’ Si’ A UI h’W ~ U ‘Ii it

No t~t’,sthe T’iOtitl to tiiit dustance hilti%iIle’ri

si,i.cgesiiisetrains shall irot he less sharii,,~i1ni,

W ‘2( No cithei’ liae boast shunt! crlverany part cif the crirria~ewr’iy when atrain ci vehicles br trainsi:ik’ vehicles’

multi—lane hridge)I is crossing thebridge,

3. The irroaisd cnrit:ict area cit tinesiheebsstiutil be. ascinder:

c:iroonci contcict area1\mule loan:!

lvi nrtn:’ sirniri runt

11.4 250 5006.8 2011 3802,7 ISO 200

4, The minirniunt cteararnt:e, /~bet-weenouter edge ot’ the wheel arid theroadway lace of the kerb, and therninirriurn clearance, g, between theouter edges of passing or crossingvehicles sun multi lane bridges shall beasgiven betow

eMS iItrwAs

itoowoC _______is 550’~

ericII carriigeway I

width

IJnitomm l3~ineneas- ~f-ing rrom 0.4 sri ~ —

to [2 in1.2 ni

— ‘I

class A train of vehicles

IN

B

4Hw

Pln~Drising selsicle

Fig. 2(‘lass ‘A’ trisin of selsicles

i,(:’Itittse 207, I)

5,5 ni to

7.5 rn

Ahove 7 5 rn

‘Ii I II II

ii iiIO”I LIII ‘“ I ,, NIiIIli’aiiI~~II

a iJ ~ H1IiI~1IIE, a 1:1 $ ,,11J 1

(‘las’s’ Ft tririni or3’IIIui’ r

I. I’l’in,:i’’: rI’s,:’ Ii rail .H’~:’ri’:’,,ii’c:ril s’n:L::L:u:s’,ii y: ii’~iimu’, ::Iu,iII ii ‘u ii,’

I 8.4 as2 ‘Ni otiul,”n’ H,,: Ii”: ii

I..’In In of ri::’ Ii iud,’s (In r ira iuiii iii in-Ian .:‘ Ic’ ]iIIL~di 1.1 ~ ii:,

in:! en’.7, Thu: ilI,VinIb CiII’[,,I.:’: dliii

is !se’i::I ‘r sun II tin: uu.s

a, I,ii nI’’II’I’’Li’ ~

‘gsa,,

I [Ilki [~{I

4 Thu ntininucnscle,.tvanr,e,.I’ll ihIc’ i’’hi:,~l eeL I ii

i’irai:Ii’rui’i’ (‘a,:n:: rd thy’ icc—it’n, niH h,’

asil I I il I lIlt 5i I ii IL ill I II

on :nnuW-Iani,:’ hr it:..:,:’.i., I: ithens

Ii::Iu[irridismei,s’ as’ ii’

il: tu I

udnullu IiiriliIIIiIl till iiii sii’i~n, I’ri.’:’i’r it i Ii~: n::

‘

AI.uiusc’ 7:5 us1.2. no

1.2 ri,

::

wfl

nun iii,’01:91 mit

:1’ Li .:i~:ii

PierFIr i’sml, s’t’hicle

Fig, 3(‘tuis~,93’ train of velui.’ies

(f~Iuuuisi.2i.i?.l i

I ~ (“ + (.~+ ~

lcngll’h of the bridge, and to occul~any posit~onwhich WdI producema simu’rn sti’esses’provided that the ‘minirn’un. clearances betweena. vehicle and tIi e road way face of k.erb and between two tUt5 Stor c:rossing vehicles, shown in Figs. I to 3, are not encroachedU polL

2(17, 1.3. For each sta ndard vehicle or train, all the axles of aunit of vehicles shall he considered as acting simultaneously in aposition causing maximum stresses.

207.1.4. Vehicles in adjacent lanes shall be taken as headed inthe direction producing maximum stresses.

207.1.5. The spaces on the carriageway left uncovered by thestandard train of vehicles shall not be assumed as subject to anyadditional live load.

~2072 DELETED

207.... Dispersion of Load through Fills on Arch Bridges

The dispersion of toads through the fills above the arch shall beassumed at 45 degrees both along and perpendicular to the span inthe case of arch bridges.

208. REDUCTION IN THE INTENSITY OF LIVELOAD STRESSESON BRIDGES ACCOM-

MODATING MORE THAN TWOTRAFFIC LANES

208.1. The position and number of loaded lanes used shall besuch as to produce maximum stresses in all cases.

208.2., Where maximum stre.sses are produced in any memberby simultaneously loading more than two traffic lanes, the intensitiesof the resultant live load stresses shall be reduced by 10 per cent foreach additional loaded traffic lane in excess of the two lanes subjectto a maximum red uci ion of 20 per cent, and subject also ‘ to thecondition that the stresses as thus reduced are not lower than thestresses resulting from a simultaneous loading on two traffic lanes.

~Ddeiedas retevantprovisionsare covered in IRC 2l~l972 StandardSpecifIcationsand Code of Practicefor Road Bridges—SectionIII.

MII4iMUM ‘‘ II’, a’iuaiii’5tIa~fl,’, ---—‘-ar ~ ami, ~ ..~‘k i,,’ifl’--”-?

~iau5I,tqIaIu~II M~ti~I ~ ~na~9~ 1I~’,I ~ /ii1u1

1

i~ ~ ‘t’—r -‘——-—‘u---—~-a ii ft liii

-II, au maiM a,i a,

ClassB train cif sehucles‘

NonesI, The nose t_u nail du’il,sntc,:

wren successivetiniirua r,hall iu,:’i tin:’

w W tl’uanu 18.4 in.2~ No other live Inunui:I ‘-hal1 y:iii yr

an çuaui of the eninniaeesu,as ‘.sI’’,:uutrains of s’c—hiclcus (ian’ tnaiius iii’ si_I’ t:’ ia—in n’ui,,ilti—lntruy: buidgnu~ is, ini’nnssiuu,y ds,ubr ids~e,

3, ‘rIce’ i;niuanuil c:onln:,ny’I tiTian ii’

sshee,Is stso II hum’ as uuu d~n

(iroLin I con[act a un’ :1Astir load

ma ,tonnes , :mu rem inn an

68 21.104j 150 3titi1,6 125 Ii)

CLaSS caniser’Siss auuunin’l

a ‘ a

25 tn)

4, The.mninsinu,mnl cleaununce, . 101-ween outenetlge of Ihe sshe,e I and isrnuadway rraue nil’ the kerh_ uanni:Iin ins i~stinsselcci no nice, ç’ - betsincen n lucouten edges of passing’ or cnnim’,’uini[n:velcucleson nusult,i—tane bridges si’stucu:i s gi senbelow

C leancanninigewn[y g

idth -

5.5 in to k,.,Inifoun’nly incnca-27.5 n’s sing fnon’n 0.4 io

- 1,2 inAbove 7,5 1-2 an ~

PisraDrising schick

Fig, 3(lass ‘B’ 1mm of seisicles

(Onmuse2071:1

l~~

1RC 6.1966

209. FOOTWAY, KERR, RAILINGS AND PARAPET LOADING(the provisions under this Clausedo not apply to Foot-Bridges)

209,1, For all parts of bridge floors accessible only to pedes-trians and anin~als~’andfor all footways the loading shall he 400 kgper m2. Where crowd loads are likely to occur, such as on bridgeslocated near towns, which are either centres of pilgrimage or wherelarge congregational fairs are held seasonally, the intensity of foot-way loading shall be increased from 400 kg per m~to 500 kg per m2.

209.2. K.erbs, 0.6 m or more in width, shall be designed forthe above loads and for a local lateral force of 750 kg per metre,applied horizontally at the top of the kerb. if the kerb width is lessthan 0.6 m, no live load shall he. applied in addition to the lateralload specified above.Note The horizontal force neednot t~econsidet’ed in the design of the main

structural members of thehrfdgtt.

209.3. In calculating stresses in members of structures withcantilevered footways, the footways shall be considered as loaded onone side or on both sides, or unloaded, whichever condition givesthe maximum stresses.

209.4. in bridges designed for any of the loadings described inClause 207.1, the main girders, trusses, arches, or other memberssupporting the footwaysshall be designed for the following live loadsper square metre of’ footway area, the loaded length of footway takenin each case being such as to produce the worst effects on the mem-ber under consideration:

(a) For effective span of 7.5 in or less, 400 kg per in2 or500 kg per m2 as the case may be, based on sub-clause209.1

(b) For effective spans of over 7,5 m but not exceeding 30 m,the intensity of load shall be determined according to theequation

p~. _____

(c) For effective spans of over 30 m, the intensity of load

shall be determined according to the equation:

P==(P’_260~L4800 16:!H

where .P”— 400 kg per m’2 or 500 kg per rn2 as the caseniay be, based on sub-clause 209.1,

13

TI.2

Nc c .s

Clearance between passingsingle deck b,ogic cars on~tr~ight tracks laid at~ndai~.l 2,75 in trackccnLies shall be 300 mm.

2. Clearance t~ctwcen passingdouble hogie cars onstraight tracks laid at$tarL b;ird ~:75 :51: trackcentresshall be 450 nm.

~i.fnl,tHth~~~~____hq— ~ — 4.6~_—~

S~NGLt‘~iC~CSfl’JGIE DECK~

tROLLEr Wa~r

I

I 1 (III I [~~

E-H’”h ___

6~4m p

—‘~2,25rn —ao~asCA~(5NCiI D~C’~

sO~1~EC~R (DoueuD(c~~

ROL LING STOCK WEIGHTS

DescriptionLoadedweighttonnes

Unloadedweighttonnes

Single truck(single deck)

9,6 7,9

Bogie car(single deck)

15.3 122

:~gi:tcar 21.5(Double deck)l

16.0

Fig, 4~A~erngedlmensions~sf tramway rolling stock(Clause 210J)

1RC : 6-1966

Pr,: the live load in kg per ni2,

L. t=the effective span of the main girder, truss orarch in m, and

Wzzr:width of the footway in m.

209.5. Each part of the footway shall be capable of carrying awheel load of 4 tonnes, which shall be deemed to include impact,distributed over a contact area 300 mm in dcameter; the permissibleworking strcsses shall b.c increased by 25 per cent to meet thisprovision. This provision need not be made where vehicles cannotmount the footway as in the case of a. .ioot~~ayseparated from theroadway by means of an insurmountable obstacle, such as truss or amain girder.’

Note A footway kerb shall be consideredmountableby vehicles.

209.6. The bilings and parapets shall be designed to resist alateral horizontal force and a vertical force each of 150 kg per metreapplied simultaneously at the top of the railing or parapet. Thesetorces need not he considered in the design of the main structuralmembers if fool paths are provided. In cases where footpaths areprovided, the effect of these threes shall be considered in the designof the structural system supporting tile railings and the footpath up—to the face of the footpath kerb only.

210. TRAMWAY LOADING

210.1. When a road bridge carries tram lines, the live loaddue to the type of tram cars sketched in Fig. 4 shall be computedand shall be considered to occupy a 3 in width of roadway.

2i0.2. A nose to tail sequence of the tram cars or any othersequence which produces the heaviest stresses shall be considered inthe design.

210.3. Stresses shall be calculated for the following two con-ditions and the maximum thereof considered in the design:

(a) Tram loading, followed and preceded by the appropriatestandard loading specified in Clause 207.1 together withthat standard loading on the traffic lanes not occupied bythe tram car lines.

(b) The appropriate standard loading specified in Clause207.1 without any tram cars.

15

IRC :6-1966

211~IMPACT

211.1 . Provision br impact or dynamic action shall be madeby an increment of the live load by aii impact alIo~anceexpressedas a fraction or a percentage of the applied live load.

211.2. For Class A or Class B Loading:—ln the members ofany bridge designed either for Class A or Class B loading (sideClause 207.1), this impact percentage shall be determined from thecurvas indicated in Fig. 5. The impact fraction shall be determinedIrom the lollowing equations which are applicable for spa as het~seen3 in and 45 in.

(i) Imçaet factor fraction for reintht’eed

concrete bridges ~‘~‘~L

(ii) Impact factor fraction for steel bridges. ~

For spans simply supported or continuous or for arches—— the‘L’ shall be the effective span of tile member under consideration.

211.3. For Class AA Loading and Class 70 R Loading —Thexalue of the impact percentage shall be taken as follovss:

(a) For spans less than 9 ni

(i) For tracked vehicles : 25 per cent for spans upto 5 mlinearly reducing to 10 per centfor spans of 9 m

iii) For wheeled vehicles: 25 per cent

(b) For spans of 9 m or more:

(i) Reinforced concrete bridgesTracked vehicles : 10 per cent upto a span of 4Dm

and in accordance wiih thecurve in Fig. 5 br spans in ex-cess Qf 40 ni

Wheeled vehicles : 25 per cent for spans upto 12 mand in accordance with thecurve in Fig. 5 for spans in cx- It

cess of 12 m

(ii) Steel. bridgesTracked vchiclcs : 10 per cent for all spans

16

IRC

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~l9

66

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9961-93)11

IRC: 6.1966.

(c) Ft:r calculating the pressure on theportion ‘f the structure. mote tha ii

3 in heloss die bedblI,ick zero

2.11.8. In lie design of members subject, among other stresses,In direct lensiun, such as hangers in a hos¼string.girder bridge, andin the design of members subject to ditect cL’mprrs sion. such assi~andreIcol ~tmns or ss ails in an open spand rd arch, the impact

pore c nUme shall he taken the same as that applicable to the ci esignof the correspond np member or rue mhcrs of the floor system5¼hich tea nsfer. loads to the tensile or cosnpressis e inembers in(Ittestion.

211,9. These CIa uses on Impact do not appI~to the design ofsuspension bridges.

212.. WIND LOAD

21 2.1. All structures shall be designed for the follos’~ing lateralwind forces. These forces shall be considered to act horizontally and

itch a direction that the resultant stresses in the member underconsideration are iii emaxitnum.

212.2. The ss intl force on a structure shall be assumed as altorizorttal force of the intensity specified in (,.‘lause 212.3 and :tctingon an area caleitlatecl as follows

(a) For a clecic st ucturc

The area of’ the strnc~itreas seen in elevation includingthe. Ibm 5 stem and railing, less area of perforations ~nthe hand—railing or parapet wails,

( b) For a through or half—through structure

ihe area of the elevation of the windward trassas speci—fled at (a) above pIns half the. area of elevation abose thedeck level pf all other trusses or girders.

212.1. The intensity of tile 55 mcI force shall be based on thetable of si md pressures a nd wind velocities given on page 21. andshall be allowed for in the design. The presstires given tIm erein sl~all,howes er. be doubled for bridges situated in areas such as theKa thiawar Peninsutla arid the i3c’ngal arid Orissa coasts shown hatch-ed in Fig, 6.

19

IRC: 6-1966

As given in the Table in Clause 212,3

Double the values in the Table in Clause 212.3

INTENSITY OF WIND PRESSURE

Fig. 6

20

IRC: 6-1966

TABLE OF WIND PRESSURES AND WIND VELOCITIES

H. )“. P. H. V. P.

0 80 40 30 147 1412 91 52 40 155 157

4 100 63 ‘ 50 162 171

6 107 73 60 168 1838 113 82 70 173 193

10 118 91 80 177 20215 128 107 90 180 21020 136 119 100 ‘ 183 21725 142 130 110 186 224

where, H=the average height in metres of the exposed surfaceabove the mean retarding surface (ground or bedlevel or water level).

V=horizontal velocity of svind in kilometres per hour atheight H.

F—horizontal wind pressure in kg per sq. m. at heightH.

212.4. The lateral wind force against any exposed moving liveload shall be considered as acting at 1.5 m above the roadway andshall be assumed to have the following values

While calculating the wind force on live load, the cleardistance between the trailers of a train of vehicles shall not beomitted.

212.5. The bridges shall not be considered to be carrying anylive load when the wind velocity at deck level exceeds 130 km perhour.

212.6. The total assumed wind force as calculated accordingto Clauses 212.2, 212.3, 212.4 and 212,5 shall, however, not be less

Highway bridgis~ ordinary’Highway bridges, carrying tram way

300 kg/linear m450 kg/linear rn

21

LRC 6~1’tt~6

than 450 kg per linear metre in the i4ane of the burled chord and

225 kg per linear rtietre in I lte plane of umtloaded chord on through orhalf—through truss, l:.itticed or other similar spans, amid not less than450 kg per linear metre on deck spans.

21 2,7. A wind ~ressure ot 240 kg per m~on the unloadedstructure, applied as specified in Clauses 212.?, and 212,3 shall heused if it produces greater stresses than those prod need by the coin—bined winrl fbrces as per (Tlau~es212,2, 212.3, 212.4 and 212.5 or b~time wind force as per Clause 21 2.6.

212.8. in calculating the uplift in the posts and rtnchorages ofhigh latticed towers due to the above nientionecl lateral forces, stress-es shall also be investigated tbr the condition of decking, beingloaded on a traffic lane or lanes on the leeward side only.

213, HORIZONTAL FORCES DUE TO WATER CURRENTS

213. 1 , Any part of a road bridge which may be submerged inrunning water shall he designed to sastain safely the horizontal pres—sure due to the force of the current.

213.2. On piers parallel to the direction of the water current,the mt ensity of pressure shall be calculated from the follosc i ngequation

P=52 KV2where P inlensity of pressure due to the water current, in kg per

sq m.1”:.:rihe velocity of the current at the point svhere the

ressure intensity is being calculated, in metres persecond, and

K::::::::a constant having the following values for differentshapes of piers illustrated in Fig. 7

(ii Square ended piers (and for the superstructure): 1.50(ii) Circular piers or piers with semi-circular ends: 0,66

~iii) Piers with triangular cut and ease waters, theangle included between the faces being 30degrees or less: 0.50

(iv) Pcers with triangular cut and ease waters,the angle included between the faces beingmore than 30 degrees but less than 60degrees: 0.50 to 0,70

(v) ---do -—60 to 90 degrees : 0.70 to 0.90

1,

IRC: 6.1966

Piers with square ends

(CCircular piers or piers with

semi-circular ends

Piers with triangular cut andease waters, the angle includedbetween the faces being 30degrees or loss

Piers with triangular cut andease waters, the angle includedhetweerit he faces being morethan 30 degrees but less than60 degrees

Piers with triangular cut andease waters, the angle includedbetween the faces being 60 to90 degrees

Piers with cut and ease watersof equilateral arcs of circles

Fig. 7

Piers with arcs of the cut andease waters intersecting at 90degrees

SHAPES OF BRIDGE PIERSClause (213.2)

23

1I4C 6-1966

(vi) Piers with cut and ease waters of equilate-ral arcs of circles : 0.45

(vii) !iers with arcs of the cut and ease watersintersecting at 90 degrees : 0.50

213 1 The value of P in the equation given in Clause 213 2shall be assumed to vary linearly from zero at the point of deepestscour to the squ ire ol the maximum s elocity at the free suilace ofwater. The maxim uni velocity for the purpose of this sub-clauseshall be assumed to he ~/2 times the maximum mean velocity ofthe current.

~ Square of max. Square of velocityi at a height

~ r ~ x from the. point of deepest~ L—u’.-~./ ve1ocity~2c~ 172X

scour”.- U2=2X , where V is the maximum

mean velocity.nary DF DhP*ST SCOUR

213.4. When the current strikes the pier at an angle, the velo-city of the current shall be resolved into two components—oneparallel and the other normal to the pier.

(a) The pressure parallel to the pier shall he determined asindicated in Clause 213.2 taking the velocity as the com -ponent of the velocity of the current in a direction parallelto the pier.

(b) The pressure of the current, normal to the pier and actingon the area of the side elevation of thç pier, shall becalculated similarly taking the velocity as the componentof the vehocity of the curreht in a direction normal to thepier, and the constant K as 1,5, except in the case of circu -lar piers where the constant shall be taken as 0.66.

213.5. To provide against possible variation of the directionof the current from the direction assumed in the design, allowance~hali be made in the design of piers for an extra variation in thecurrent direction of 20 degrees; that is to say, piers intended to beparallel to the direction of current shall be designed for a variationof 20 degrees from the normal direction of the current and piersoriginally intended to be inclined at & degrees to the direction of thecurrent shall be designed for a current direction inclined at (20±8)degrees to the length of the pier.

24

tRC: 6-1966

213.6. in case of a bridge having a pueca floor or having aninerodible bed, the effect of cross~currents shall in no case he takenas less thea that of a static force due, to a difference of head of 250mm between the opposite faces of a pier,

213.7. When supports are made with two or more piles ortrestle columns, the group shall he treated as a solid rectangular pierof the same overall length and width and the value of K taken as1.25 for calculating pressures-due to water currents both parallel andnormal to the pier.

213.8. The effects of the lbrce of water currents shall be dulyconsidered upto the level indicated in Clause 2 P 4.7.

214. LONGITUDINAL FORCES

214.1. In all road bridges, provision shall be made for longi-tudinal forces arising from any one or more of the following causes.

(a) l’ractive effort caused through acceleration of the drivingwheels

(b) Braking effect resulting from the application of the brakesto braked wheels ; and

(c) Frictional resistance offered to the movement of freehearings due to change. of temperature or any oTher cause.

Note : Braking etfect ~sinvariably greater Than the tractive-effort.

214.2. The braking effect on a simply supported span or acon tinuous unit of spans or on any other type of bridge unit shall beassumed to have the following value

(a) In the case of a single lane or a two~lanebridge : twentyper cent of the first train load plus ten per cent of the loadof the succeeding trains or part thereof, the train loads inone lane only being considered for the purposes of thissub-clause. Where the entire lirst train is not on the fullspan, the braking force shall be taken as equal to twentyper cent of the loads actually on the span.

(h) In the case of bridges having more titan two lanes~:’. as in(a) above for the first two lanes plus five per cent of theloads on the lanes in excess of two.

Note Tue loads in this CIa use sli~li not be increased on accounl ofiii i~~ct.

25

IRC 6-1966

214.3, The force dueto brakingeffect shall be assumedto actalong a line parallel to tht roadway and 1.2 m aboveit, Whiletransferring the force to the hearings, the change in the verticalreaction at the bearingsshouldhe taken into account.

214.4. The longitudinal force at any free bearingshall belimited to the sum of dead and live load reactionsat the bearingmultiplied by the appropriateco-efficient of friction. The co-efficientof friction at the beating shall be assumed to have the followingvalues.

For rofler bearings ... 0,03

Fbr sliding bearings of hardcopper alloy ... 0.15

For sliding bearings of steel oncast irorror steel on steel , .,. 0.25

For sliding bearingsof steelonferro asbestos . ... 0.20

For other types of bearingsof As may be permittedproved utility if permitted by the Engineer-in-at the discretion of the chargeon exaniina-Engineer-in-charge tion of the available

data.

For simply supportedreinforcedconcrete andprestressedcon-crete superstructure,the spanuptowhich plate bearingscan be usedshallhelimited to 15 metres.

214.5. The longitudinal force at the fixed bearing,shall betakenas the algebraic sum of the longitudinal forces at the freebearingsin the bridge unit underconsiderationandIhe force duetothe braking effect on the wheelsas mentioned in Clause214.2.

214.6. The effectsof braking force on bridge structureswith-out bearings,such as arches, rigid frames, etc., shall be calculatedin accordancewith opproved methods of analysisof indeterminatestructures.

2i 4.7. The effects of the longitudinal forces andall otherhorizontalforcesshouldhe calculateduptoa level where the result-ant pas.siveearth resistanceof the soil below the deepestscourlevel(floor level in case of a bridge having pucca floor) balancestheseforces.

26

IRC :6-1966

215. CENTRIFUGAL FORCES

215.1. Where a road bridge is situated on a curve, all portionsof the structure affected by the centrifugal action of moving vehiclesare to be proportioned to carry safely the stress induced by thisaction in addition to all other stress to which they may be sublect-ed.

215.2. The centrifugal force shall be determined from thefollowing equation

WV8127R

where Cr centrifugal force acting normally to the traffic(I) at the point of action of the wheel loads or(2) unifbrmly distributed over every metrelength on which a uniformly distributed loadact~,in tonnes,

live load (I) in case of wheel loads, each ssheeload being considered as acting over the gro-und contact length specified in Clause 207, inton nes, and (2) in case of a uniformly distri-buted live load, in tonnes per linear metre,

1’—-the design speed of the vehicles using thebridge in km per,hour, and

R=the radius of curvature in metres.

215.3. The centrifugal tbrce shall be con sidèred to act at aheight of 1.2 in above the level of the carriageway.

215.4. Nc) increase for impact effect shall he made on thestress due to centrifugal action.

215.5. The overturning effect of the centrifugal force on thestructure as a whole shall also he duly considered.

216. BUOYANCY

216.1. The effects of buoyancy indicated in Clause 122.5.6 ofIRC: 5-l970~shall be considered in the design if there is any possi-bility of a combination of forces whereby the stability of the bridgefoundation considering buoyancy may be compromised,

2.16.2. In the design of ahutments, especially those of sub-mersible bridges, the effects of buoyancy shall also be considered

* Standard Specilications and Code of Practice for Road BridgesSection 1—General Features of Dcsign

27

IRC:6-1966

assuming that the till behind the abutments has been removed by

scour,.**216.3, Deleted216.4. To allow for full buoyancy a reduction is made in the

gross weight of th,e member affected, in the fOllowing manner

(a) When the member under consideration displaces wateronly, e.g., a shallow pier or abutment pier founded at ornear the bed level, thc reduction in weight shall be equalto that of the volume of the displaced water,

(b) When the member under consideration displaces water andalso silt or sand, e.g., a deep pier or abutment pier passingthrough strata of sand and silt and founded on similarmaterial, the upward pressure causing the reduction inweight shall be considered as made up of two factors(i) Full hydrostatic pressure due to a depth of water equal

to the difference in levels between the free surface ofwater and the foundation of the ipember under con -sideration, the free surface being taken for the worstcondition ; and

(ii) Upward pressure due to the submerged weight of thesilt or sand cakulated in accordance with Rankine’stheory, for the appropriate angle of internal friction.

216.5. in the design of submerged masonry or concrete strue-‘tures, the buoyancy effect . through pore pressure may be limited to

1 5 per cent of full buoyancy.

216,6. In case of submersible bridges, the full buoyancy effecton the superstructure shall he taken into consideration.

217. EARTH PRESSURE

217.1. Structures designed to retain earth fills shall be propor -tioned to withstand pressure calculated in accordance with anyrational theory. Coulomb’s theory shall be acceptable, subject tothe modification that the centre of pressure exerted by the backfill,when considered dry, is located at an elevation of 0.42 of the height

*soeieted, as relevant provisions are covered in IRC : 5-1970, StandardSpecifications and Code of Practice for l~oad Bridges Section 1 (FourthRevision).

28

IRC 6-19~l6

of the ‘vail above the base instead of 0.33 of that height. No structureshall, however, be designed to withstand a horizontal pressure lessthan that exerted by a fluid weighing 480 kg per cu. m.

217.2. (a) The distribution of normal pressure on a retainingwall due to a concentrated surface load on thebackfill shall he obtained by any rational methodof design, the one using Spangler’s equation, whichis giVen below, being acceptable

KP X~x~r

in which Ii =.r. normal unit pressure on the wall at anypoint, in kg per sq. m.,

Pr.rzr applied wheel load in kg.,.

X:rr.:distance from load to back face of wal’ in m,subject to a minimum of 150 mm,

Y,::,~lateral distance from any point on the wall tothe normal vertical plane containing the load,in m,

Zr:::::: vertical distance from any point on the wallin the horizontal plane containing the load,mm,

R::.~r:radius vector measured from the wheel load tothe point at which the pressure is to be calculat-ed,zn m,

zz~Xtf Y2+Z2, and

K and ii are emptrical constants equal to 1 .0 and0.25 respectively.

(b) in the particular case of bridge abutmen’ts; theconcentrated surface loads due to the wheel or f rackloads of any of the i.R.C. standard vehicles ortrains described in Clause 207.1 placed on the back-fill, shall be considered to have the same effect asthe equivalent heights of surcharge of earth shownin the~Table given on page 30 and curves in Plate 1which are based on the Spangler’s equationgiven in Clause 217.2 (a). These heights of surchargeshall be assumed to act over the entire length of theabutment.

29

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9961-9:

IRC: 6-1966

21 7,4. All designs shall provide for’ the thorough drainage ofback-filling material by means of weep holes and crushed rock orgravel drains, or pipe drShs, or perforated drains.

217.5, l’he pressure of submerged soils (not provided withdrainage ifrrangements) shall he considered as made up of twocomponents

(a) pressure due to the earth calculated in accordancewith the method laid down in Clause 217.1, the unitweight of earth being reduced for buoyancy, and

(b) full hydrostatic pressure of water.

217.6. in the design of return walls, live load surcharge shall

be taken for loads placed beyond the length of the approach slab.

218. TEMPERATURE EFFECTS

218.1. Provision shall he made for stresses or movementsresulting from variations in temperature (see also Clause 214).

2 18-2. The rise and fall in temperature shall be fixed fo~thelocality in which the structure is to be constructed and shall befigured from an assumed temperature at the time of erection.

218.3. Due consideration shall be given to the lag betweenair temperature and the interior temperature of massive concretemembers of structures.

218.4. Except where stated otherwise, the following range oftemperature shall generally be assumed in the design

(a) Metal StructuresModerate climate : from minus 18 degrees C. to 50

degrees C.Extreme climate : From minus 35 degrees C. to 50

degrees C.

(b) Concrete StructuresTemperature Temperature

rise fallModerate climate 17 degrees C. 17 degrees C.Extreme climate 25 degrees C. 25 degrees C.

But in both cases, i.e. in (a) and (b\ intermediate valuescan he allowed at the discretion of the engiiieer responsi-ble for the design,

3’

I1kC: 6-1966

218.5. The co-efficient oF expansion per degree centigrade shallhe taken as 0.0000117 for steel and reinfoj~çed concrete structuresand 0.00(0108 for plain concrete structures S

219. DEFOF3MATION STRESSES (‘for steel bridges only)

219.1. A. deformation stress is defined as the bending stressin any memher of an open web-girder caused by the vertical deflec-lion of the girder combined with the rigidity of the joints. No otherstresses are included in this definition,

219.2. All steel bridges shall he designed, manufactured anderected in a manner such that the deformation stresses are reducedto a minimum. In the absence of calculations, deformation stressesshall he assumed to be not less Ihan 16 per cent of the dead andlive load stresses.

219.3. In prestressed girders of steel, deformation stresses maybe ignored.

220. SECONDARYSTRESSES

220.1. (a~Steel sti-uctures :—Secondary stresses are additionalstresses brought into play due to the eccentricity of connections,floor beam loads applied at intermediate points in a panel. crOss gir-ders being connected away from panel points., lateral wind loads onthe end-posts of through girders, etc., and stresses due to the move-ment of supports. I

(b) Reinforced concrete structures :--~Secondary stressesare additional stresses brought into play due either to the movementof supports or to the deformations in the geometrical shape of thestructure or its member, resulting from causes such as rigidity of endconnection or loads applied at intermediate points of trusses or rest-rictive shrinkage of concrete floor beams,

220.2. All bridges shall be designed and constructed in a man-ner such that the seconda)’y stresses are reduced to a minimum andthey shall be allowed for in the design.

220.3. For reinfbrced concrete members, the shrinkage co-efficient’for ~urposesof design may be taken as. 2x l0’~.

221. ERECTION STRESSES

Allowance shall be made in the design for stresses set up inany member during erection; such stresses ;iay be different fromthose which the member will be subjected to during actual working.

32

1RC :6-1966

222. SEISMIC FORCE

222.1. If a bridgeis situated in a region subject to earth’-quakes,allowanceshallbe madein the design for seismic force andearthquakeresistantfeatures shall be embodied in the structuraldetailsof design.

222.2. The seismicforce shall hetakenas a horizontal forceequal to the appropriatefraction specified in Clause 222.3 of theweigh.tof the deadandthe live loadsacting above thesectionunderconsideration. (Partsof the structureembeddedin soil shall not beconsideredto produceany seismicforces).

2223 The country is divided into threeregions as shown inFigS and the seismic forcesin the regions shall he taken as nil,

Map of India and neighbourhood showing zones liable to damagebyearthquakeswith eplcentral regionsol the important earthquakes

Fig .8

Sfl~rE~OUP4DARIE$

EPICINTRAL TP&CTS

LIABI4~’OSEVERE

flIED LIA8LE To MOOZRATE

uau TO MainsDAM&* oct iat.

33

IRC 6-1966

o 20 and C/IC) for the regions shown therein as “Liable to minordamage or nil”, “Liable to moderate damage”, and “Liable to severedamage” respectively. For bridges situated in epicentral Iractswhere large devastations have occurred in the past, clue to earth-quakes the percentage shall be fixed by the engineer responsible forthe design, ssith due regard to the local conditions regarding theintensity of earthquakes generally experienced in these regions.

222.4. These horizontal forces due to the seismic effect shallhe taken to act through the centre of gravity of all the loads underconsideration. The direction of these forces should be such thatthe resultant stresses in the member under consideration are tli.ein a xiinum.

222.5. Seismic and wind lhrces shall not be considered to actsiniultaneou si y.

222.6. The magnitude of the seismic force shall not he reduc-ed on account of reduction in the weight due to buoyancy obtainedon a submerged mass.

34

EQUiVALENT HEIGHTS (Metres)

OF

SI.JRCHARGEOF EARTH

WHICH WOULD GIVE OVERTURNING MOMENT AT THE BASE

OF

BRIDGE ABUTMENTS

EQUAL TO THE MAXIMUM MOMENT CALCULATED BY SPANGLERSEQUATION UNDER CONCENTRATED SURFACE LOADS DUE TO

THE WHEEL OR TRACK LOADS OF

I,R.C. STANDARD VEHICLES OR TRAiNS

IEC 5.1-n

PLATE

Vole —The‘~aiue\of heightsof ‘ui chargegiven in this Plateare basedon the foHo~vingsaIue~for the eon’,tanisfor theabutniunts...A ~L-. Li 4~t1aijcj LIIC t;acKlIll

il) Lengh of abutment (LI 4.5 m for ~ingic lanebridges and 7.6 m für multilane bridges.

(2) Angie of iniernal friction of the backfill (4) 3(3

(3) Weight 0f backfill ( IV)—1600 kg per cu. m.(4) The resultantearth pressureacts in a horizontal

direction.For different values, say. L1.

4i and W1 for the constants. the

valuesobtainedfrom their curves should bemultiplied by the fo1low~ing factors

L (4,5 or 7.6 as the easemaybej (~5i~~)L1 3 (I—sin ~i)

1500respectively

I.R.C. CLASS ‘A’ LOADiNG MULTI-LANE BRIDGES

DEPTH OF ABUTMENT IN METRES(b)

Li ~c -

~ 7:

o Lii -~

U~ a ~9~~

CO