IRC 058 1988+Design+Rigid+Pavements
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CRC: 58-1988 GUIDELINES FOR THE DESIGN OF RIGID PAVE MENTS FOR HIGHWAYS (First Revision) THE INDIAN ROADS CONGRESS 1991
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Transcript of IRC 058 1988+Design+Rigid+Pavements
CRC: 58-1988
GUIDELINESFOR
THE DESIGN OF RIGIDPAVEMENTS
FOR
HIGHWAYS(First Revision)
THE INDIAN ROADS CONGRESS1991
~RC 58~l98S
GUIDELINESFOR
THE DESIGN OF RIGIDPAVEMENTS
FOR
HIGHWAYS(First Revision)
Pubtishedby
THE INDIAN ROADS CONGRESS.Jaiinsgar House, Sh!kjahan Road,
New Delhi-I 10 011P~91
Price Rs, ~2tiL(Phis Packing& Pui~age)
IRC: 54N$
First published: July 1974First Revision : June 1988Reprinted:March. 199%Reprinted:October,2000
(Rights ofPubllcadoa and q( Translationare reserved)
PrintedatDee KayPrinters,NewDelhi(1000copies)
itC: $$4SS
CONTENTS
Clause No. Page No.1. Introduction ... 1
2. General ... 2
3. Design Parametersand Assessmentof
their Design Value ... 24. DesignofSlab Thickness ... 9
5. DesignofJoints ... 17
6. DesignofReinforcement ... 22
AppendIces1. Extract froth IRC: 15-1981“Standards
Specificationsand Code of Practicó forConstruction of Concrete Roads”—Preparationof Sub-gradeand Sub-base ... 25
2. Logarithms’ ... 29
3. An IllustrativeExample of DesignofSlab
Thickness ‘ 384. An Illustrative Example ofDesign ofDowel
Bars and TieBars 40
lkC :58-1988
GUIDELINES FOR THE DESIGN OF RIGIDPAVEMENTS FOR HIGHWAYS
INTRODUQION
Guidelines for the Design of Rigid Pavementsfor High-ways wereapprovedby the Cement Concrete Road SurfacingCommittee in their meeting held at Chandigarh on the 11thMarch, 1973. These were approved by the Specificat.~ons&StandardsCommitteein their meetingheld on 31stJanuary and:1st February, 1974. The Guidelineswcre then approvedby!~~heExecutiveCommitteeand the Council in their meetings held onthe 1stMay and 2nd May, 1974 respectively.
In view of the recentupwardrevision of the legal limit onthe maximum laden axle-loads of commercialvehicles from8160 kg, to 10200kg. (new legal maximum wheel load 5100kg.), appropriate modifications havebecomenecesaryin somesectionsof the Guidelines.
Accordingly, the Cement Concrete Road SurfacingCommittee of the indian RoadsCongressin their 17th reetingheld at Nagpuron 8th January, 1984 (personnel given below)considered and approvedcertain changes
1. ShivalingaiahN. SivaguruK, SuryanarayanaRaobirector (Civil) 1.5.1.
(G. Raman)D.G.B.R. (Maj. Gen. J.M. Rai)B.T. UnwallaDirector General CementResearchInstituteof India
(Dr. H C. Visvesvaraya~Director, U.P. P.W.D. ResearchInstitute(P.D. Agarwal)City Engineer(Roads),MunicipalCorporationof BombayA Rep. of C.P.W.D.D 0. (RD.) —tx-officio
ConvenorMember-Secretory
K K. NambiarYR. Phull
H.S. BhatiaD.C. ChaturvediNC. DuggalOP. GuptaPlC. Issac’P.J. .lagusD.P. lainRS. lindalMaj. Can. R.K.KairaP,V. KamatDr. S.K. KhannaP.J. MehtaC.B. MathurD.C. Panda
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IRC : 58-1988
The amendmentswere consideredby the Specifications &StandardsCommittee inthcir meetingheld at New Delhi on the21st August, 1985 and werereturnedback to CementConcreteRoad SurfacingCommitteefor further consideration, The draftwasthenfinalisedby Dr. M.P. Dhir ConvenorandShri S.S. SeehraMember- Secretary of the reconstitutedCommittee. The draftreceivedfrom the CementConcreteRoad Surfacing Committeewas reconsideredby the Highways Specifications & StandardsCommittee in their meeting held on 25th April, 1988 at NewDelhi andapproved. Theseamendmentsreceived the approvalof the Executive Committee andthe Council in their meetingsheld on 26th April and 7th May, 1988 respectively.
2. GENERAL
Rigid pavement design commenced with the classicalanalysis of Westergaardin 1926. Mostof the subsequent work,till recently,aimed at modifications and adaptationsof West-ergaard’s work either with a view to match better with theactual performance andtest data, or simplify the analysisfor easierdesign. Of late, thereis a noticeable trend towardsthe development ofultimate load analysis in this field, andconsequentupon the AASHO Road Test, attemptshavebeenmadealso to apply the ‘serviceability-performancecriteria torigid pavementdesign. ihey are, however,still in a developingstage.
Someof thesemethods take onlytraffic loads intoaccount,ignoring suchenvironmentalfactors as temperaturechanges inthe pavement,which may substantially limit its load-carryingcapacity. There areother factors, like inipact, load repetitions,etc., the effects of which thoughunderstoodqualitatively, arenot yct conclusively established quantitatively. Nevertheless,for a rational design,their effectsshould be incorporated to theextent possiblewith the existingknowledge.
It is with the objectiveof simplifying this task and to pro-in ote thescientific designof rigid pavementsthat these guide-lines havebeen drawn,
3. DESiGN PARAMETERS AND ASSESSMENTOF THEIR DESIGN VALUE
3. 1. Traffic Parameters
.3.1.1. Design wheel load: The design wheel load shouldhe the maximum wheel load of the predominant heavy vehicle
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1R.C 58-1988
likely to usethe pavement in the normal course. In case ofpublic highways,it will obviously be governedby the prevailinglegal limits on the maximum laden weight of commercialvehicles. It is currently taken at 5100 kg,
in addition to the design wheel load, the maximum tyreinflation pressuresfor the vehiclesshould alsobe ascertained,seas to enabledeterminationof tyre contact area through whichthe load is transmittedto the pavement. For most commercialhighway vehicles,this rangesfrom about 5.3 to 7.3 kg/cm2.
.i.i.2. Traffic intensity : Passage of traffic results in re-petitive loading of the pavement,therebyinducingfatigue effectsin the concrete, Theseeffects,while not of much consequencein caseof low traffic intensitiesbecauseof considerabletime lagbetweensuccessivepasses,assumegreaterimportancein ease ofheavily trafficked pavements,as the fatigue strength of concretereduceswith increasein the tiumber of load repetitions it isrequiredto sustain.
While a rigorousapproachwould requirethe assessmentoftotal numberof design load repetitions during intended designlife of a pavement including due allowance for lighter andheavierloads throughthe useof appropriateequivalencyfactors,a more practicalapproachis to classifythe pavements,for thepurposeof making fatigueallowance,accordingto traffic inten-sity rangeexpected.
Sincetraffic intensity is a growingphenomenon,the heavi-est intensity will occur at the endof the designlife of a pave-rnent. However, it is generally consideredadequateif the trafficis projectedto a periodof 20 years after construction, since inthe initial stagesthe traffic intensitywill be much less than thatat the endof the designlife.
For traffic prediction on main highways, the followingcorrelationmay be adopted
T=F(I+rr2° ... (1)
with T=designtraffic intensityin termsofnumber of commer-cial vehicles(ladenweight )‘ 3 tonnes)per day,
Pr traffic intensityat last traffic count,~annualrateof increaseof traffic intensity,and
‘nrsnumber of years since last traffic count andcommis-sioningthe new concretepavement.
3
lRC 58-1988
The traffic intensity P for assessmentof design traffic inten~sity T should normally be a sevenday averagebasedon 24-hourcounts,in accordancewith 1RC 9-1972 Traffic Censuson Non-Urban Roads(First Revision). However, in exceptional cases,where such data are not available, an averageof threedaycounts may be usedas an approximation. Basedon growth ratcof traffic over the past few years, a value of 7.5 per cent i~suggested for br~ for rural roads for the time being, whereveractual dataare not available.
in c:ase ~of new highway links, whereno traffic count datawill he available, data from highwaysof similar elassifieatic.~nond~mportance may he used to predict the design trafficin teii sity.
The pavementclassification basedon design traffic intensity,suggested for adoption for rigid pavement design, is given inTable I
EARL F t , TRAFfiC (‘LssslricATrON FOR RiGiD j’AvFMFNT L)LSic,N
Trafficclassification
Design Traffic ntensityVehicles(ladenweightthe end or design life
:>3 tonnes) pcrday ai
A 0-ISB i5~45(1 45-ISO1) 150450F::. 4504500F 1500-4500C; Abovc 4500 and aU cxprcssway
.3,2. EnvironmentalParameters
3.2.1. :reml!eratilre differential Tcntperature differentialbetween top and bottom of concretepavementsis a function: ofsolar radiation receivedby the pavementsurfaceat the location,lossesdue to wind velocity, etc., and thermal diffusivity, of con-crete, and is thus affected by geographical features of thepavementlocation,
As fat as possible,valuesof actuallyanticipatedtempera-ture differentials at the location of the pavement should he
4
IRC 58-1988
Temp. differential in ‘C in
slabsof thickness
10cm 15cm 20cm 25cm 30cm
I. Punjab, UP., Rajasthan,Gujarat, Haryana and NorthMP., excluding hilly regionsand coastal areas
H. Bihat, West Bengal, Assam andEastern Orissa, excluding hillyregionsand coastal areas
lii. Maharashtra, Karnataka SouthM,P., Andhra Pradesh,WesternOrissa and North Madrasexcluding hilly regions andcoastalareas
lv. Kerala and South Madras,excluding hilly regionsandcoastal areas
V. Coastalareas bounded by hillsVI, Coastal areas unbounded by
hills
10.2 12.5 13.1 14.3 15.8
14.4
14.75
15.6 16,4 16.6 16.8
17.3 l~,0 20.3 21.0
13.2 15.0 16.4 17.6 18,1
12,8 14.6 15,8 16.2 17,013.6 15.5 17.0 19.0 19,2
Note The above mentioned table has been prepared on thebasis of actualobservationsby Central Road ResearchInstitute, New Delhi.
3.2.2. Mean femperaturecycles:Mean temperaturecycles-daily and annual of concrete pavementsaffect the maximumspacingof contractionandexpansionjoints in thepavementanddesignvalues for thesefactorswould be requiredif it is desiredto adopt the maximum safe spacing of expansionjoints.However, these factors are dependent upon the geographicallocationof the pavement,and data thereon are generally notavailable readily. Somewhat conservativerecommendationsfor maximum expansionjoint spacing have, therefore, beenframed as guidelineson the basis of actual temperaturedatacollectedat selectedlocations in different partsof the country.
3.3, Foundation Strength and Surface CharacterIstIcs
3.3.1. Strength: The foundation strength, in caseof rigid
adopted for pavement design. For this purpose, guidance may
be had from Table 2.
TaLE 2. RIc0MMOWID TrMrraA’suaE DIFIFRENTIALS tN~oNCRLT&RoADS
Zone States
5
lit : S1
pavements,Is expressedin terms of modulus of subgrade reac-don, A’, which I. defined as pressureper unit deflection of thefoupdation as determinedby plate bearingtests.As the limitingdesigndeflectionfor concretepavementsis taken at 1.25 mm,theK-value is determined from the pressure sustained at thisdeflection. As K-value is influenced by teat plate diameter, thestandard test is run with a 75 cm dia. plate, beyond which theeffect ofdiameterhasbeenfound to be negligible. A frequencyofone test perkm per lane is recommended for assessmentofK value, unlessfoundation changeswith respectto subgradesoiltype, ofsub-baseor the nature offormation (IA. cut or fill) whenadditional testsmay be conducted.
In caseof’ homogeneous foundation, test values obtainedwith plates of smaller diametermay by convertedto thestandard75 cm plate value by experimentally obtainedcorrelations, e.g,
with K~5and Ks. as theK valuesobtained on 75 cm and 30 cmdia. plates respectively. However, in caseof layered construc-tion, as in thecaseof sub-base,the testswith smaller plates givegreater weightageto the stronger top layer, and direct conversionto 75 cm plate valuesby theabovecorrelations somewhat over-estimatesthe foundation strength, and such conversionmust beregardedasvery approximate only.
The subgradesoil strength, and consequentlythestrengthofthe foundation as a whole, is affected by its moistuit content.The designstrength obviously must be the minimum that will beavailable under the worst moisture conditions encountered. Theideal period for testingthe foundation strength would thus beafter the monsoonswhenthe subgradewould have attained itshighest moisture content.
In casethe testshaveto be conductedat some other time.especially during thedrypart ofthe year, allowancefor loss instrength due to increasein moisture must be made. For this pur-pose,an ideaof theexpectedreduction in strength on saturationof the subgrade may be had from laboratory CBR testsonsubgrade soil samples compactedat field density and moisturecontent and testedbeforeand after saturation. An approximateidea of K value of a homogeneoussoil subgrademay be haddirectly from its CER valueusing Table 3. A more elaborate
• procedure involves correlation through consolidation tests onunsoakedand soakedsamples.
6
IRC: 58-1988
Tai. 3 APn0XLMATE K VALUE CORRESPONDiNG To CBR VALUES 10*HoMOGENEoUS Soit SUBORADn
CBRvatue(%) 2 3 4 5 7 10 20 50 100
K-valve (kg/cm’) 208 2.77 3.46 4.16 4.84 5.54 6.92 13,85 22.16
The recommendationsof IRC 15-1981 shall be followedand a K-value of less than 5.5 kg/cm3 tested on the subgradeshall not be permitted. In case of rocky subgrades withaK-value of 5.5 kg/cm3 and higher, ,the pavementmay be laiddirectly thereonor after providinga levelling course,if required.In caseof problematicsubgradessuch as clayey ar’l expansivesoils, etc., appropriate provisionsshalt be made for a blanketcourse in addition to the sub-baseas perthe relevantstipulationsof IRC: 15-1981, reproducedin Appendix!.
3.3.2. Foundationsurfacecha1acterlstics The foundation
surfacecharacteristics,viz., its smoothnessor roughness, deter-mine the extent of resistanceto slab movementduring expansionand contractionon account offoundation restraint, and affectjoint.spacings.The maximum safespacingincreaseswith increasein surface roughnessof the foundation in caseof expansionjoints, and decreasesin case of contractionjoints.
For the purpose ofdeterminationof joint spacings, diffe-rent types of foundations generally adopted may be classifiedinto threecategories,viz., very smooth,smoothandrough,accor-ding in their surfacecharacteristics,as given in Table4. As the,foundationsnormally adoptedin the country fall within the lasttwo categories,only thesetwo categories have been consideredin formulating recommendationsfor expansionjoint spacings.
TABLE 4. CLASSInCATION op Dunnwr Tyris o~RiolDPAVEMENT FouNDATIoNs ACCORDING TO THEIRSURFACE CHARACTERISTICS
Surface roughnesscharacteristics
Very Smooth
Type of foundation
Compactedsand andgravel. Smooth foundationcoveredwith waterproof paper
Smooth Compacted sand,gravel and clinker, ,a’tabilisedsoil. Rough foundationcovered with waterproofpaper
Rough Water-bound macidam, soil-gravel mix, rolledleanconcrete,lime-pozzolanaconérete,etc.
I
IRC: 58-1988
3•4. Concrete Characteristics3.4.1. Design strength As stressesinduced in concrete
pavements are due either to bending or its prevention,theirdesign is necessarilybasedon the flexural strengthof concrete.For economicaldesign, the design value adopted for fiexuralstrengthof pavementconcreteshould not be less than 40 kg/cm2.This strengthvalue, however, should not be confusedwith themix designstrength. The mix hasto be sodesignedas to ensurethe minimum structural strength requirementsin the field withthe desiredconfidencelevel. Thus if:
a = structuraldesignvalue for concretestrength,
$ = mix design valuefor concretestrength,= tolerajicefactor for thedesiredconfidencelevel,
o = expectedstandarddeviationof field test samples,basedon a know-ledgeof thetype of control, viz, very good, good or fair, feasibleatsite.
then s=s+t.a ‘~ (3)
sothat to achievethe desiredminimum structural strengths inthe field,the mix design in the laboratory has to be madeforsomewhathigherstrength,s making due allowancefor the typeand extent of quality control feasible in the field.
For pavementconstruction,the concretemix shouldprefer-ably be designedand controlled on the basisof flexural strength.if that is not possible,correlation betweenflexural andcompres-sive strengthsshouldbe establishedon the basis of actual testson additional samplesmade for the purposeat the time of mixdesign. Quality control can then be exercised on the basisofcompressivestrength,so long as the mix materialsand propqr-tions remainsubstantially unaltered. Even though it is custo-mary to assume280kg/cm2 ascompresiivestrength correspond-ing to 40 kg~cm2fi~xural strength, sych general assumpuonsshould be avoided as far as possible in view of the variety offactorswhich influencethe correlation betweenthe two strengths.
For general guidance, the value of t and~ for concretecompressivestrengthvalueof 280 kg/cm2 aregiven in TableS fordifferent degrees of quality control. For design of cementconcrete mix, IRC: 44-1972 Tentative Guidelines for CementConcreteMix Designfor RoadPavements(for non-airentrainedand continuouslygradedconcrete)may be followed.
8
IRC 58-1988
TABLE 5. CoNcRETE Mix Drsicn STnNOTH FOR DTFIERnJT DroRusOF QUAI FrY Cot~i~ot,FOR STRUCTURAL DF5IGN VAUm OF280 kg/sq.cm FOR CONCRETE CoMPREss~vrSi Rrr’JOIH
Degree of Toqualitycontrol
lerancelevel
Tolerancefactor,
t
Coefficientof wad-ation
Mix designstrength
kg./sq.cm.
Standarddeviationkg/sq.cm.
Very goodGood
1I
in 15in 15
1.50t.50
7%10%
315330
2233
Fair I in 10 1.20 15% 350 52
Notes.’ Very good qua/flycontrol : Control with weigh hatching, use ofgraded aggregates, moisture determination of aggregates, etc.Rigid andconstantsupervisionby thequality control team.Goodquality control: Control with weigh-batching, use of gradedaggregates, moisture determination of aggregates,etc. Constantsupervisionby the quality control team.Fair qualitycontrol: Control with volume-batchingfor aggregates.Occasionalchecking of aggregatemoisture. Occasionalsupervisionby the qualitycontrol team,
3.4.2. Modulus of elasticity and Poisson’sratio: The modulusof elasticity,E, and Poisson’s ratio, ~ of concreteareknownto vary with concrete materials and strength. The elasticmodulusincreaseswith increasein strength,and Poisson’s ratiodecreaseswith increase in the modulusof elasticity. While itis desirable that the valuesof theseparametersareascertainedexperimentallyfor the concretemix and materialsactually to beusedat the construction, this information may not always beavailable atthe design stage. In such cases,it is suggestedthatfor designpurposes,the following values may be adoptedforconcretein the 38-42kg/cm2 fiexural strengthrange
Modulusof elasticityof concrete, Er, 3 x lO~kg/cmiPoisson’sratio, p. 0.15
3.4.3, Coefficientofthermal expansion: The coefficient ofthermalexpansion,a, of concretesof the same mix proportionsvarieswith the fl’pe of aggregate,being in general high for sili-ceous aggregates, medium for igneous rocks and low forcalcareousones. However,for designpurposes,a value ~= 10 xlO”/°Cmay be adoptedin all cases.
4. DESiGN OF SLAB THICKNESS
4.1. Critical StressCoaditionConcretepavements in service are subjected tostressesdue
9
IRC : 58-1988
to a variety of factors,actingsimultaneously,the severestcom-bination of which inducing the higheststressin the pavementwill give the critical stresscondition. The factorscommonlyconsideredfor design of pavementthicknessaretraffic loadsandtemperaturevariations, as the two areadditive. The effectsofmoisture changesand shrinkage, being generally opposedtothoseof temperatureandof smallermagnitude,would ordinarityrelievethe temperatureeffects to some extent,andare not nor-mally consideredcritical to thicknessdesign.
For purposesof analysis,threedifferent regionsare recog-nised in a pavement slab—corner, edge and interior—whichreactdifferently from one another to the effect of temperaturedifferentials,as well as loadapplication.
Thc concretepavementsundergoa daily cyclic change oftemperaturedifferentials, the top being hotter than the bottomduring day,and cooler during night. The consequenttendencyof the pavementslabs to warpupwards(top convex) during theday and downwards (top concave) during the night, andre-straint offered to this warping tendencyby self-weightof thepavement induces stresssesin the pavement,referredto coni-monly as temperaturestresses. Thesestressesare flexural innature,beingtensileat bottom duringthe dayandat tap duringnight. As the restraintoffered to warpingat any section of theslabwould be a function of weight of the slabupto that Section,it is obvious that corners havevery little such restraint. Therestraint is maximumin the slab interior, andsomewhat less atthe edge. Consequentlythe temperaturestressesinduced in thepavementarenegligible in the cornerregion, and maximum atthe interior.
Under the action of load application, maximum stressisinducedin the corner region, as the corner is discontinuous intwo directions. The edgebeing discontinuousin one directiononly, has lower stress, while the least stressis induced in theinterior where the slab is continuousin all directions. Further-more, the corner tendsto bend like a cantilever, giving tensionat the top, interior like a beamgiving tensionat bottom. Atedge, main bending is alongthe edgelike a beamgiving maxi-mum tensionat bottom.
The maximum combinedtensilestressesin the threeregionsof the slabwill thusbe causedwheneffects of temperature diffe-rentialsaresuch as to be additiveto the loadeffetts. This wouldoccurduring the dayin caseof interior andedgeregions, at the
10
1 RC:5$-t98$
time of maximum temperaturedifferential in the slab. In thecornerregion, the temperaturestressis negligible, but the loadstressis maximum at night when the slab cornershavea tendencyto lift up due to warping and lose partly the foundation support.Consideringthe total combinedstressfor the threeregions, viz.,corner:edgeand interior, for which th~load stressdecreases inthat order while the temperaturestress increases,the criticalstresscondition is reachedin the edgeregion where neitherofthe load and temperaturestressesare the minimum, It is, there-lore, felt that both the corner and the edgeregionsshould becheckedfor total stressesand designof slab thickness based onthe more critical conditionof the two,
4.2. (:alculationof Stresses
4.2.1. Edge stresses(a) Due to load : The load stressin the critical edgeregion
may be obtained as per Westergaardanalysis and modified byTeller and Sutherland from the following correlation(metricunits)
a!,=:::O.529 (1+0.54p) [41o~w ~—log1,,h-0.4O48~‘~ 4
with oh:ii load stressin the edgeregion,kg/cm2,
designwheel load, kg,
h:::r pavementslab thickness,em,/.L::= Poisson’sratio for concrete,
modulusof elasticityfor concrete,kg/cm2,K::::~reaction modulusof the pavementfoundation,kg/em3,1=: radiusof relativestiffness, cm
~ [FM 5
-radiusof equiv. distribution of pressure
a for{> 1,724
:: .if~~z—O,675h for ~< 1.724 ...(6)
and a radius of load contact,cm, assumedcircular,
The valuesof! and6 canbe ascertaineddirectly from Tables 6and7. For ready reference,4-figure log tablesareincludedinAppendix2
11
IRC: 51-198*
TAiLS 6. RAWUS Op R,PLA’TIvs Snnsns,I, mi n~su?11’VAt,u~o~PAvEMENT Su~.THICENUS, h, AND FOUNDA’t’IoN RFACI1OP4
MooUius, K, ~oscowckEn £ 3.Ox10’ kg/cm~
15 61.44 57,18 54.08 48,86 41.0916 64.49 60.02 56.76 51,29 43,31
17 67.49 62.81 5~).40 53.67 45.14
18 70.44 65,56 62.01 56.03 4707
19 73,36 68,28 64.57 58.35 49.0620 76.24 70,95 67.10 60,63 50.99
21 79,08 73.59 69.60 63.89 52.89
22 81.89 76.20 72.08 65.13 54.77
23 84,66 78.80 74.52 67,33 56.62
24 87,41 81,35 76.94 69.31 58,45
25 90.13 83.88 79,32 71.68 60.28
‘rASLE 7. RADtL~so~E~tnv.DISTRIBUTIONOP PRESSURE SEcrION, b, iuTEgMS op R4tnu5 o~CoN TACT, a, ANO SLAB TH!cK~sss,h
b/h a/h b/ha/h
0.0 0,325 1.0 0.937
0.1 0,333 1.1 1,039
0.2 0.357 1.2 1,143
0.3 0.387 1,3 1.2500.4 0,44k 1.4 1.358
0.5 0,508 1:5 1.470
0.6 0.580 1,6 1.582
0.7 0,661 1,7 1695
0.8 0,747 1,724 1.724
0.9 0.840 >1,724 a/h
h (cm)
Radiusof relativestiffness1 (cm) for differentvaluesof K (kg/cm)’
Kr 8 KrlS Kr 30
12
58-1988
(b) Due to temperature : The temperature stressat the criti-cal edge region may be obtained as per Westergaardanalysis.using Bradbury’s coefficient, from the following correlation
-Yc . (7)
with ~i ‘-~ temperature stress in the edge region~
= maximum temperaturedifferential during daybetweentop and bottom of the slab,
coefficient of thermalexpansionof concrete,
C :‘r Bradbury’scoefficient, which can be ascertaineddirectly from Biadbury’s chart againstvalues ofL/! and WI!,
L ~ slab length. or spacing between consecutivecon-traction joints,
13’ stab width, and
/ ~ radius of relative stiffness.
Values of the coefficient, C. basedon the curvesgiven inBradbury’s chart, are given in Table 8.
TASLI 8. VALUISOI Co-i.IFICIENT ‘C’ BAS!~DOP’~ BR..~DBUk’~’SCHART
L/lor W/t C
I 0.000
2 0.0403 ‘ 0.1754 0.440
S 0.7206 0.9207 1.0308 1.0759 1.080
10 1.07511 lOSt)
12 andabo~ .t~J0
13
ftC: 58-1988
4.2.2. Corner stresses:The loadstress in the corner regionmay be obtained as per Westergaard’s analysis, as modified byKelley, from the following correlation
a/c = ~ -
with ale = load stress in the corner region, other notationsremaining the sameas in the caseof the edgetoad stressformula.
The temperaturestressin the corner region is negligible asthe corners are relatively free to warp, and may be ignored.
4.3. DeslgoCharts
Figs. 1 and 2 give ready-to-usedesign charts for calculationof toad stressesin the edgeand corner regions of rigid pavement
Edge iad stressdesignparametersP=5100kg, a=15cmEr4xiO’ kgjcm%~”0.l5
ka3OkelS
-k—tOEU0b.4
b
50
45
40
35
30
25
20
15
10
5
014 16 là 70
Slab thickness,k (cm)Fig. 1, Design chart for calculation of
edge load stress
14
IRC: 58-1988
UCo
(I
4~
‘0CC0
C
Slabthickness,h (cm)
Fig. 2. Designchart for calculation of corner loadstress
stabs for the design wheel load of 5100 kg.’ Fig. 3 gives a design
chart for calculation of temperature stressesin the edge region.
4.4. RecommendedDesignProcedureStep 1 Stipulate design vaiues for the various parameters.Step 2 ‘Decide joint spacing and land-widths (vide
para 5.1).Step3 Select tentative design thicknessof pavementslab.Step 4 : Ascertain maximum temperature stress for the
critical edge region from Equation (7) or Fig. 3.
Step 5 Calculate the residual available strength ofconcrete for suppor.ting traffic loads.
Step 6 Ascertain edge• load stress from Equation (4) orFig. l~and calculate factor of safety thereon.
Co’rner load stresadesignparametersP~5100kg. a~=15cmE..’3x 10’ kg~cm*i&~-0.15
ic ..3OIrVclfl3
‘kwlOB6
14 16 18 20 22 24
15
EU
U
U
U
U
UCo
‘0
~RC 58~I988
40
30
25
20
‘S
10
5
00 5 10 .15
TemperaturedifferentialChart for determination of coetlicient~
LfI Ior C or CWI! WI!
I 0.000 7 1.0)02 0.040 8 1.0773 tJ.lli 9 1.0804 0.440 10 1.0755 0.720 II 1.0506 0.920 2 .000
I 1g. 3. Designchartfor calcula)ion of edge)emperaturcS(ress
1RC : 58-1988
Step 7 In casethe available factor of safety is less thanor far in excess of 1, adjust the tentative slabthicknessand repeat steps3 to 6 till the factor ofsafety is I or slightly more. Denote the corres-poding slab thicknessas h1.
Step 8 Check for adequacy of thickness in the cornerregion by ascertaining corner load stress fromEquation (8) of Fig. I and readjust the thicknessIts, if inadequate;
Step 9 : Adjust h~for traffic intensity. The adjusted designthickness,Ii, may be obtined from
h h~f/~~The valuesof Ii~may be taken from Table 9.
TABLE 9. Ricto PAvEMEt’~TTHICKNESS AoJUs’IMlNT FACTOR, he,loP T~pric INTENSiTY
Traffic classification A B C D E F G
h~(cm) —5 —5 —2 —2 +0 -tO +2
Note: SeeTable I for Traffic Classification.
An illustrative exampleof designof slab thicknessis given
ii) Appendix 3.
5. DESIGN OF JOINTS
5. 1. Spacingand Layout
The recQrnmendations of the IRC 15-1981, para 8 andSupplementary Notes para N. 2 “Arrangement of Joints”, maybe followed with regard to joint layout and contraction jointspacings
As rrgardsexpansionjoints, it is possible to adopt muchgreater spacings than recommended in the Code. Basedon arecent study by the Central Road Research Institute which givesthe maximum spacing of expansionjoints that can be adoptedfor concrete pavements in India, from a consideration of dailyand annual temperature variations in the pavementsin differentparts of the country, degree of foundation roughness as well asthe seasonof construction, the maximum recommendedspacingsof expansionjoints are given in Table 10.
17
IRC 58-1988
TABLE 10. REcOMMENDED S~ctsnOF JOINTS IN R1GrnPAVEMEMrs FOR HIOHw&vs
(a) ExpaisionJoint Spacings(basedon CRRI Study)(for 25 mm wide expansionjoints)
Period ofconstruction
Degreeof foun-dation roughnes
Maximum expansionjoint spacing (in)
Slab thickness (cm)iS 20 25
Winier Smooth 50 50 60(Oct-March) Rough 140 140 140
Summer Smooth 90 90 120(April-Sept) Rough 140 140 140
No/es : 1. SeeTable 4 for classificationof different types of foundationlayersaccordingto degreeof roughness.
(b) Contraction Joints Spacings(basedon IRC 1519$1)
Slab thickness(cm)
Maximum contractionjoint spacing(rn)
Weight of reinforcementin welded fabric (for
reinforced pavementsonly)(kg mt)
Unreinforred Slabs
Reinforced Slabs
5.2. Load Transfer at Transverse Joints
5.2.1. Load transfer to relieve part of the load stressesinedge and corner regions of pavement slab at transversejoints isprovided by meansof mild steel dowel bars. For general provi -
tO 4.515 4.520 4.5
tO1520
7.513.014.0
2.22.73.8
18
IR.C : 58-1988
sions in respect of dowel bars, stipulations laid down in IRC:15-1981,Supplimentary Notespara N. 4,2 “Dowel Bars”, may befollowed. The method of design of dowel bars asper Bradbury’s~inalysisis recommended.
5.2.2. Designofdowel bars: The dowel bar systemmay bedesigned on the basis of Bradbury’s analysis which gives thefollowing formulae for load transfer capacity of a single dowelbar in shear, in bending and inbearing on concrete
0.785d2fe’ (shear) ... (10)2~f~
— r±8.8~ (bending in the bar) ... (11)
-— _________
P f~(r-i-1.5z) (bearingon the concrete) .,. (12)with T = load transfer capacity of a single dowel bar,
d = diameter of dowel bar,r = length of embedmentof dowel bar,z = joint width,
fa’ permissible shear stressin dowel bar,= permissible flexural stress in dowel bar, and
f~= permissibie.bearingstress in concrete.
For balanced design, for equal capacity in bending andbearing, the length of embedmentof dowel is first obtained byequating 7 values from equations (II) and (12) as follows, forthe assumedjoint width z and dowel diameter d:
J ft r+1.5z ~r 5”L’7~” r-t-8.SzJ ... (13)
Knowing z, d and r, the load transfer capacity of a singledowel is determined from the equationS (11) and (12) givenabove.
To calculate the spacingof dowel bars, the required capa-city frctor, ii, is first determined from
ioad transfer capacity required from thedowel systemload transfer capacityof a singledowel bar
(14)
19
IRC : 58-1988
The distance on either side of the load position upto whichthe dowel bars are effective in load transfer is taken as 1.8 1,where / is the radius of relative stiffness(Equation 6).
Assuming linear variation of the capacity factor for asingle dowel bar from 1.0 under the load to 0 at a distance of1.8 / therefrom, the capacity factors for the dowet systemarecalculated for different spacings. The spacing which conformsto the required capacity factor, n, is selectedfor adoption. Ancxampte of the designof dowel bars is given in Appendi.v4.
5.2.3. Dowel bars are not satisfactory for slabs of smallthickness, and shall not be provided for slabs less than 15 cmthick.
TARL! 11. DEsIGN DETAILS op Dowit. BARS FOR RicinHiGHwAY PAVEMENTS
Designloading
Slabthickness (cm)
bowel ba r details
Diameter (mm) Length (mm)Spacing(mm)
5~O0kg 15 25 500 200
20 25 500 2.50
25 25 500 300
Therecommendeddetails are based on the following valuesof differ-ent designparameters; Is = 1400 kg/cmt; 1. 100kg/cm’;E~ 3.0 X
tV kgfcm’ ~s 0.15; K1 8.3 kg/cmt max, joint width = 20 mm;
designload transfer= 40 per cent.
5.2.4. Typical dowel bar designsfor usc in 20 mm widecxpansionjoints for highway pavements, for 40 per cent loadtransfer are given in Table 11. In case of dummy contractionjoints, aggregateinterlock is relied upon to provide load transferto someextent, and dowel bars are not provided, ordinarily.Dowel bars shall, however, be provided in case of full depthconstruction joints.
5.3. Tie Barsfor. LongitadbiaLJolnts
5,3.1. In caseopening of longitudinal joints is antIcipatedin service, for example, in caseof heavy traffic, sidelong ground,
20
IRC : 58-l98~
expansive subgrades, etc., tic bars maybe designed inaccord-ancewith the recommendationsof IR.C: 15-198?,SupplimentaryNote, paraN. 5 Tie Bars For the sake of convenienceof thedesigners the design procedurerecommendedin IRC: 15-1981is given herein.
5.3.2. Designof the bars : The areaof steel required perm length of joint may be computed by using the followingformula
A, b/H’ ... (15)
in whicharea of steel in cm2 requiredper rn length of joint.
h distancebetweenthe joint in questionandthe nearestfree joint or edge inm,coefficientof friction betweenpavementandthe sub-grade(usuallytakenas 1.5),
W weight of slab in kg/rn2,andS = allowableworking stress ofsteel in kg/cm2.
The length ofany tie bar should be at least twice that requ-ired to develop a bond strength equal to the working stressofthe steel. Expressedas a formula, this becomes:
2S4.,.(16)
in which1. length of tic bar (cm)S = allowable working stress in steel(kg/cm2)A = cross-sectionalarea of one tie bar (cm2)P = perimeterof tie bar (cm), and
B permissibJ~bond stressin (i) deformed tie bars—24.6kg/cm2,(ii) Plain tie bars—17.5kg/cm2
5.3.3. To permit warping at the joint the maximumdiameter in case of tie bars maybe limited to 20 mm,and toavoid concentration of tensile forcesthey should not be spacedmore than75 cm apart. The calculatedlength, L, may be mere-sed by 5-8 cm to account for any inaccuracyin placementduringconstruction. An exampleof designof tic bar is givenin Appendix4.
5.3.4. Typical tie bar details for use at. central Longjtu-dinal joint in double-lanerigid pavementswith a lane width of3.50m are given in Table 12.
21
1RC :58-1988
lAst.! 12. DErAILS OP Ite B~*s,oR CEMTIUU. LONGIrUDINALJOINT OP TwO-L’~wE RIGID Hio*tw~yPAvEMENTS
. Tiebardeiails
Slab thickness(cm)
:,~
Diamçter(mm)
Maximumspacing(cm)
Minimum length (cm)
~Plain Deformedbars bars
IS 810
3860
40 3045 35
20 tO12
4564
45 -3555 40
25 101214
304562
45 3555 4065 46
Wot. : The recommendeddetailsare basedon thefollowing values of differ-ent designparameters:ft = 1400 kg/cm’, R~= 17.5 kg/cm’ for plain barsand24.6 kg/cm’ fordeformedbars,!=1.5, W — 24 kgjm’Icm of slabthickness.
6. DESIGN OF REINFORCEMENT
6.1. Reinforcement, when provided in concrete pave-ments, is intended for holdingthe fracturedfacesat the crackstightly closed together, so as to prevent deterioration of thecracksand to maintain aggregateinterlock thereat for loadtransfer. It doesnot increasethe flexuratstrengthof unbrokenslabwhen used inquantitieswhichare consideredeconomical.Where the slabs are providedadequatelywith joints to contrOlcracking,such reinforcementhas nofunction.
6.2. Reinforcementin concreteslabs is designed to coun-teract the tensile stressescausedby shrinkageandcontractionclue to tenrperatureor moisturechanges.The maximum tensionin the steel across the crackequals the forcerequiredto over-comefriction between thepavement and its foundation, fromthe crackto the nearestJoint or free edge. This force is thegreatest when the crack occurs at the middle of the slab.Reinforcementis designedfor this critical location, However,
22
IRC : 58-1988
for practical reasons,reinforcementis kept uniform throughoutthe length, for short slabs.
The amountof longitudinal and transverse steel requiredper m width or length of slab is computed by the followingformula:
A = ... (17)
in whichA --= areaof steel in cm2 requiredper m width or length
of slab,£ = distance in m between free transversejoints (for
longitudinal steel) or free longitudinal joints (fortransversesteel).
j coefficient of friction betweenpavementand subgrade(usuallytakenas 1.5),
W = weightof slabin kg/rn2,andS = allowableworking stressin steel in kg/cm2 (usually
takenas 50 to 60 per cent of the minimum yieldstressof steefl.
6.3. Sincereinforcementin the concreteslabs is not inten-ded to contribute towards its flexural strength, its positionwithin theslab is not importantexcept that it should be adequ-ately protectedfrom corrosion.Sincecracksstartingwith highertensile stress at the top surfacearemorecritical when they tendto open,the general preferenceis for theplacingofreinforcementabout 50 mm below the surface. Reinforcementis often conti-nued acrossdummygroove joints to servethe same purpose astie bars, but at all full depthjoints it is keptat least 50 mmaway from the faceof the joint or edge.
I-
21
IRC: 58-1988
AppendIx 1
EXTRACtS FROM IEC: 15-1951“STANDARD SPECIFICATIONSANt) CODE OF PRACTICE FOR CONSTRUCTION OF
coNcRETE ROADS,, .(SecondResislon)
6. PREPARATION OF SUEGRADE AND SUB-BASE
6.1. GeneralThe subgradeor sub-basefor layfng of paving concrete slabsshall comply
with the following requirements:
(1) that no soft sportsarepresentin the subgradeor sub-base;
(2) that the uniformly compacted subgrade or sub-base extends at least300mm on eitherside of thewidth to beconcreted;~
(3) thatthe subgradeis properlydrained;
(4) that theminimum modulus of subgrade reaction obtainedwith a plate
bearingtest shall be5.5 kg/cm’Themannerof achieving theserequirements shall,bedetermineddepending
upon thetypeof subgradeor sub-base on whichconcreteis to belaid, andthefollowing requirementsin respectof the varioustypesshall be satisfactorily met.Theconstruction proceduresfor subgradeand sub-basesshould follow relevantIRC specifications, and quality control should be exercised as laiddowninIRC: SP-1l.
6.2. Subgrade6.2.1. Wherethetype of soil in the formation of the road is of a quality
to ensurethe requirementsin the aforementioned para, no intermediatesub-baseneedbe used. The top 150 mm layer of the formation shall be compactedat or slightly abov~theoptimum moisturecontent t~e.theexactprofileshowninthedrawing. Itshall be checked for trueness by meansof a scratch template(seelR.C : 43-1912for delail~)resting on theside formsandset to theexactprofile of the base course.The template shalt be drawn alongtheforms atright anglesto the centreline of the road, Unevennessof the surfaceas mdi-~aieUby the scratchpoints shallnot exceed12 mm in 3 in. The surfaceirregul-aritiesin excessof this shall be properly rectified and thesurfacerolled ortampeduntil it is smoothand,firm. Thesubgrade shall be prepared and chec-ked at least two daysin advanceof concreting.
6.2.2. Whereno sub-baseis considered necessaryandconcrete is laiddirectly on the prepared subgrade,the subgrade. shall be itt moist conditionat the tim’e the concrete is placed. If necessary, it should be saturated
with waternot less than6 hoursnor more than 20 hoursin advanceof placingconcrete. 11 it becomes dry prior to the actualplacing of theconcrete,it shallbe sprinkledwith watertakingcareto see thatno poolsof water or soft patchesareformedon thesurface. It is desirable to layalayerof water-proofpaperwheneverconcreteis laid directly over soil subgrade. Where such alayerofwaterpoorfpaperis proposedto be placed betweenconcreteandthesub~rade,the moisteningof the subgradeprior to placing of the concrc~eshall beomitted.
25
IRC: 58-1988
63. Sub-base63,1 Wherethe subgrade is of a type not satisfytngthe requirementsof
para61., a Sub-baselayer should be provided before laying theconcl’tte. Thesub-basemay be of granular material, stahilised soil or semi-rigid material aslisted below
(a) Granular material(I) one layer flat brick solinghavingjoints filled with sandunderone
layerof water bound macadamconforming to JRC : 19-1977.
(ii) Two layersof waterboundmacadam.(iii) Well-graded granular materials like natural gravel,crushedslag,
crushed concrete,brick metal, laterite, kankar, etc. conformingtoIRC : 63-1975.
(iv) Well-gradedsoil aggregatemixturesconformingtoIRC 63-1976.
(h) Siabilised roilLocal soil or moos-urn stabilised with lime or lime-fly ashorcement,as appropriate to give a minimum soakedCBR of 50after 7 days curing. For guidance as regards designof mixeswith lime or cement, reference may be made to IRC 51 and 50respectively
(c) Semi-rigid material(i) Lime-burnt clay puazolana concrete. The lime-pazzolana mixture
should conform to L.P. 40or L.P. 20 of IS : 4098-1967. The 28 daycompressivestrength of the concrete should be in the range of40-60km/cm’.
(ii) Lime-fly ashconcreteconformingto 1RC : 60-1976.(iii) Leancementconcreteor lean cement-fly ash concrete conforming
to IRC: 74-1979.6.3.2. Thicknessof sub-baseshouldbe 15 cm when the material used is
of any of the types listed in paras6.3.!. (a) and(b!. This may, however,bereducedto 10 cm for semi-rigid materials in para 6.3.1, (c). The sub-baseshould be constructedin accordancewith the respective specification andthe surfacefinishedto therequiredlines, ievelsandcross-section,
6.3.3. Wherethe subgradeconsists of heavy clay (L.L. >50) such asblac~cottonsoil, the sub-baseshould belaid overa 15 cm thick blanket courseconsisting of non-plastic granularmaterial like local sand,gravel,kankar,etc.or local soil stabilisedwith lime.
6.3.4. In water-loggedareasand wherethesubgradesoil is impregnatedwith deleterious salts such as sodium sulphate etc. in injurious amounts”~acapillarycut-off should be provided before constructing the sub-base, videdetails given in para 64.
6.3.5. Thesub-baseor blanket course, as thecasemay be, shall he laidover a properly compactedsubgradeto give uniform support.
**Sulphate concentration(assulphurtrioxide) more than0.2% in subgrade soiland more than0.3% in groundwater,
26
IRC: 58-1988
6.3.6. rhe sub-bdsc shallhe in moist condition at the time the concreteis placed. There shalt, however, be no pools ofwateror softpatches formedor the sub-base surface. In casewhere a sand layer is placed betweenthesub-base andpavement concrete,a layer of water-proof paper shall be laidover shesand layer. No moisteningof thesub-base shall bedonein this case.
6.4. Cnplllar~Cut-off6.4.1. A~a result of migration of water by capillarity from the high
v~atertable,the soil immediatelybelow thepavementgetsmoreand more wetandthis leadsto gradual loss in its bearing value besidesunequal support.Several measuressuch as depressingthe sub-soil water table by drainagemeasures, raising ofthe embankmentand provisionof acapillarycut-offareavailable for mitigatingthis deficiencyandshould beinvestigatedfor arrivingat theoptimum solution, However, wheredeleterioussalts in excess of thesafe limits arepresentin the subgradesoil, a capillary cut-off shouldbe’providedin addition to other measures.
6.4.2. The capillar’~cut-off may be a layerof coarseor fine sand, gradedgravel, bituminisedmaterial, or an impermeablemembrane. Layer thicknessesrecommendedfor different situationsaregiven inTable 4.
TAIILE 4. RECOMMENDED THscxNL~sOPSAND/GRADED GRAVEL L*Y!R P0kC’~P1LLARv CuT-on
Thicknessor layercm
SI. SituationNu, Coarsesand Finesand GradedgraveI
(meandia (mean dia (40 mmand’0.64mm) 0.18mm) downwithout
fines)I
Watertable atthesamelevel 15 45 15as thesuhgradesurface
2. lEmbankmentabout0.6—1.0 in 12 35 Iihigh
3. Embaokmentabou~0,6—1.0 m 10 30 8high hut with thetop 15 cmsubgradelayerbeingof sandysoil having’P1 of S or lessandsandcontentnot less thanSO percent
6.4,3, Cut-off,with bituminised orother materialsmay beprovided in anyof the following ways
(i~ Bituminous Impregnation using prImer treatment50 percentstraighl run bitumen(80-100)with 50 percenthigh speeddiesel oil or itsequivalentin two applicationsof I kg sq. m. each,allowing the firstapplicationto penetrate beforeapplying the secondpne. Theseapplications shouldbegivenunderthe roadbedas wellasonto thesides.
27
IRC: 58-1988
(ii) Heavy-duty tar feltEnveloping sidesand bottom of the roadbed with heavy-duty tarfelt.
(iii) PolyethyleneenvelopeEnvelopingsidesandbottom of the roadbedwith polyeth~,ienesheetsof at least400gauge.
(iv) SitumiaousestabilisesoilProvidingbituminousstabilisedsoil in a thicknessof at least4cm.
Note Experienceon the successful use of the abovecapillary cut-otisis, however,limited.
6.4.4. For moredetailsaboutmitigating the adverseeffectsof high watertable,reference may be madeto IRC : 34-1970“Recommendationsfor RoadConstructionin WaterloggedAreas”.
‘6.5. FrostAffected Areas6.5.1. In frost affected areas, the sub-base may consist of any of the
specificationsgivenin 6. 3.1. (a), (b)or (c) exceptingthat in the caseof the items63 1. (b) and6.3.1. (c), thecompressivestrength of thestabilised or semi-rigidmaterialcuredinwet condition shall be at, least 35kg/cm’ at 7 days. Formoderateconditions,suchasthoseprevailing in areas at an altitudeof 3,000 mand below, the thicknessof frost affected depth will be about 45 cot. For pro-tectionagainstfrost, thebalance between the frost depth (45)cm and totalpavementthicknessshould be madeup with non-frostsusceptiblematerial.
6.5.2. For extreme conditions,such as thoseprevailing in areas aboveanaltitude of 3,000 m, the foundation may be designed individually for everylocationafter determining the depth of frost.
6.5.3. The suggestedcriteria for she selection of non-frost susceptiblematerialsareas follows
(i~Graded gravel:Not more than 8 per cent passing75 micron sievePlasticity index notmore than6. Liquid limit not more than 25.
(ii) Poorly graded sands, generally 100 per cent passing 475 mmsieveMax. 10 per centpassing75 micron sieveMax. 5 per cent passing 50 micronsive
(iii) Fine uniform sand, generally 100 per cent passing 425 micronsieve:’Max. 18 percentpassing75 micron sieveMax. 8 percentpassing50 micron sieve
28
IRC
:58-1988
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d1pperdix3
AN ILLUSTRATIVE EXAMPLE OF DESIGN OF SLAB THICKNESS
1. DesignParametersLocationof pavementDelhiDesignssheelloadp~-”5100kgPresenttraffic intensity~300veh)dayDesign tyre pressurep’=7.2 kg/cm’FoundationStrengthk=6 kg’cm’Concreteflexural strengthlB =40 kg/cm’OtherconcreteparametersE=3,0x10’ kg/cm’0=0,15=lOxlO”
tmC
2. Design Procedure
StepI, As in paraI above,
Step 2. Joint spacingandlane-widthsContractionJointspacingL.=4,5 mLanewidth, W—3,5m
Step3. Tentativedesignvalueof slabthickness,h=22 cm
Step 4,Temperaturestress foredgeregion,
(i) From Table2 for 22 cm thick pavementslabs in Delhi max,valueof temperaturedifferential-S—about13.~C
(it1 for h—fl cm E—3~0~<10’ kg/cm
0From Table 6, 1=81,89 cm
L/L-.53, W/I-’4,3From TableS, CL-’O.82, C~=0,52
(iii) From Fig~3, for C=O.82 and1—13.5 ‘CoSe—16,Okg/cm’.
Step5. Residualconcrete strengthfor supportingloadsIL”fR” at~—4O.0—16.~l—24,Okg/cm’
Step 6.LoadStressfor edgeregionFrom Fig. 1, for Is—flcm,k=6 kg/cm’aIi~o.23,4kg/cm’
38
IRC 58-1988
Step 7. Available factor of safetyon load stress
= ‘‘~“1,03>l ,‘, O.K
Step8, Cornerload StressFrom Fig, 2, eI~=26:8kg/cm’<114 ,‘, O,K.
Step 9. Adjustment for traffic intensityDesign traffic intensityT=300’ (1+0.075)20
-a300x4.2~=1275,which falls undertraffic classificationE (Table 1)
From Table9Requiredthicknessadjustmen=0Designthicknessof paymentslab—22cn’.
39
IRC:
App.sdlx 4
AN ILLUSTRATIVE EXAMPLE OF DESIGN OF DOWELBARS AND TIE BARS
1. DOWEL BARS
1,1, DesignParametres
Designwheel load=5100 kgDesignload transfer-a40%Slabthickness,h’=22 cmJoint width, z=20cmPermissibleflexural stressin dowel bar—1400kg/cm0Permissibleshear stressin dowel bar— 1000 kg/cm’Permissiblebearingstressoil concrete—100kg/cm’K —valueon sub-base—SkgJcm’/cmOther concrete parametersL—3x100 kg/cm’o—0.15
1,2. DesignProcedure
Steps 1: Dowel lengthAssumeDoweldiameter, 1=2,5cm
Then, for equal capacity in bending and bearing, from Eqn(13)
~(t4O0 r+3) 1’~Sx25x~~~j~rn ~<__-‘~_j
which giveson solution, r=40,5 cmSo that dowel length,L=r+2—40.5+2—42jcm
say 45 cm
Step2 Loid transfercapacityof single dowel
From equations(10), (11) and (12), load transfer capacttyof asingle dowelis obtained
P (in shear)~0.705l’f’S=0,7*5x2.5x2,5x1000—4900kg
Y (in bending) ~TgI~
2x2.5x2,3x2.5x1400
40
1RC : 58~1988
Ffln bearing)— l2~(r+15z)
l00:~~40,5 x405 ~‘ 2 5125(40.5 i-3)
754 kgTaking the leastof these values for designpurposes,P753 kg
Step 3: Capacityfactor requiredof dowel systemLoad transfercapacity of
the dowelsystem--~5l00:<40%=2040kg
- - 2040 -
requiredcapacityfactor— =2.70
Step 4 Spacing,of dowel barsFork=8 kg(cn’fcm, 1 =76.20 tfroin Table6)Considering thejoint corner, thedistance overwhich dowel barsareeffectivein load transfcr=l,8“~1=1,8x 76,2=137.0cm about,Assuming adowelspacingof 25 cmAvailable capacityfactor
137—25 137—50 137—75~r37
=4_4~-_4_l.09
=2,91which is slightly greaterthan therequiredcapacity -factor of 2.70, Henceadopt25 cm asdowelspacing.
2. TIE BARS
21. Dcslg.Parameters
S1~thickness,h—22 cmSlabwidth, b=3,35 mNo. of lanesto be tied=2Coefficient of friction between paymentand subgrade=f= 1,5Weight per m’ ofconcretestab, w=528kgAllowable working tensile stressin steel S—1400kg/cm’Maximum Permissiblebondstress,8 in:(1) Plain tie bars—u.Skg/cm’
(ii) Deformedbars=24kg/cm’
2,2, DesIgn Precedure
Step 1: Diameterandspacingof tie barsWeight perm’ of concreteslab, W=528 kg
4L
IRC Sf-1988
Area of steelrequiredper in width of joint4 bfW3.35x1.5x
528i 89 cm(m
Assumingdiaof tie bars;d’.: 10 mmA.:. crosssectionof onetie bar=78,54mm’P—Perimeterof tie bar—31,42mm
- . A~ 1.89No, of tie barsrequiredperm, N=—A~=--o_~.3
4and- , 100 100x03854
Spacing of tie bars~’-~ 1 89 —41.5cm Say42 cm
Step 2 : Lengthof the tie bars2s4 2x1400x78,54x10Length of tie bar—~8?‘ ~
L=40 cm for plain tie bars,and29,2cm for deformedtie barsIncreasingabout5 cm for tolerancein placementL=45 cm for plain tie barsand L=35 cmfor deformedtie bars
42
LIST OP OTHER CEMENT CONCRET�ROAD STANDARDS
Ri. P.
I. IRC: 154981 StandardSpecifications& Code of Practicefor Constructionof Concrete Roads (SecondRevision) 16-00
2. 1RC: 43-1972 RecommendedPractice forTools, Equipmentand Appliances for Concrete PavementConstruction 12-00
3. IRC:: 44-1972 Tentative Guidelines for CementConcreteMix Design (for Road Pavementsfor non-airentrainedand continuously graded concrete(First Revision) 8-00
4, IRC: 57-1974 RecommendedPracticefor Sealingof JointsinConcretePavements 3-00
S. IRC 59-1976 Tentative Guidelines for the Design of GapGraded CementConcrete Mixes for RoadPavements 5-00
6. IRC: 60-1976 Tentative Guidelines for the Use of Lime-flyash Concrete as Pavement Base orSub-Base 5-00
7, JRC: 61-1976 Tentative Guidelines for theConstructionofCementConcretePavementsin Hot-Weather 5-00
8, IRC: 68-1976 Tentative Guidelines on Cement-FlyashConcre*efor Rigid PavementConstruction 6-00
9. IRC: 74-1979 Tentative Guidelines for Lean-CementCon-crete and LeanCementFlyashConcreteas aPavementBase or Sub-Base 8-00
10. IRC: 76-1979 Tentative Guidelinesfor Structural StrengthEvaluationof Rigid Airfield Pavements . 10-00
11, IR.C: 77-1979 TentativeGuidelines for Repair of ConcretePavementsusing SyntheticResin 15-00
12. IRC 84-1983 Codeof Practice for Curing ofCementCon-cretePavements 8-00
13. 1RC: ‘~5-t983 Recommended Practice for AcceleratedStrength Testing and Evaluationof Concretefor RoadaMd Airfield Constructions 8-00
14, IRC:: 91-1985 Tentative Guidelines for Construction ofCementConcretePavementsin Cold Weather 8-00
is, 1RC: 101-1988 Guidelines for Design of ContinuouslyRein-forcedConcrete Pavementwith Elastic Joints 2-00
Handbook of Quality Control for Construc-tion of RoadsandRunways (Second Revision)
16. IRC: SP: 11-197732-00
17, IRC: SP: 16-1977 SurfaceEvennessof H ighway Pavement 7-00
IS. IRC: SP: 17-1977 RecommendationsAbout Overlayson CementConcretePavements 15-00
19. MOST Ministry ofShippingSTransport(RoadsWing)Handbook on RoadConstruction,Machinery(1985) . 32-00
20. MOST Ministry of Surface Transport (RoadsWing), Specificationsfor Road and BridgeWorks(SecondRevision)
21. MOST Ministry of Shipping & Transport (RoadsWing) Manual for Maintenanceof Roads 24-00
