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Chapter 6

Strength Design of Reinforced ConcreteStructures6.1 AnalysisandDesign- GeneralConsiderations

6.1.1 ConventionandNotationUnlessotherwiseexplicitlystated,thefollowingunitsshallbeimplicitforthecorresponding quantitiesin

thedesignandotherexpressionsprovidedinthischapter:

Lengths m m

Areas m m2

Secondmomentsofarea m m 4

Force(axial,shear) N

Moment,torsion N m m

Stress,strength MPa,N/mm2

6.1.1.1 Notation = Depthofequivalentrectangular stress blockasdefinedin6.3.2.7.1,mm, = Shearspan,equaltodistance from center ofconcentratedloadtoeither:(a)faceofsupportfor continuous or cantilevered members, or (b) center of support for simply supported

members,mm,Sec6.4,AppendixA = Area of an individual bar or wire, mm2,Sec6.3,Sec8.2

=Net

bearing

area

of

the

head

of

stud,

anchorbolt,

or

headed

deformed

bar,

mm

2

,

Sec8.2,

AppendixD = Crosssectionalarea of concrete section resisting sheartransfer,mm2,Sec6.4,Sec8.3 = Crosssectional area of a structural member measured to the outside edges of transversereinforcement,mm2,Sec6.3,Sec8.3 = Area enclosed by outside perimeter of concrete cross section, mm2, see 6.4.4.1, Sec 6.4,8.3.8.3 = Crosssectionalareaat one end of a strut inastrutandtiemodel,takenperpendiculartotheaxisofthestrut,mm2,AppendixA = Gross area of concrete section bounded by web thickness and length of section in thedirectionofshearforceconsidered,mm2,Sec8.3 = Area of concrete section of an individual pier, horizontal wall segment, or coupling beamresistingshear,mm2,Sec8.3

= Area of reinforcement in bracket or corbelresistingfactoredmoment,mm2,see6.4.7,Sec6.4 = Gross areaof concretesection,mm2 For ahollowsection, istheareaoftheconcreteonlyanddoesnotincludetheareaofthevoid(s), see 6.4.4.1, Secs6.2to6.4,6.6,6.7,6.10,8.3, = Total area of shear reinforcement parallel toprimary tension reinforcement ina corbelorbracket,mm2,see6.4.7,Sec6.4 = Effective crosssectional area within a oint in a plane parallel to plane of reinforcementgenerating shear in the joint, mm2, seeSec8.3 = Total area of longitudinal reinforcement toresisttorsion,mm2,Sec6.4,8.3, = Minimumareaoflongitudinalreinforcementtoresisttorsion,mm2,see6.4.4.5.3,Sec6.4

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= Area of reinforcement in bracket or corbelresisting tensile force, mm2, see 6.4.7,Sec6.4 = Areaofa faceofanodalzoneorasectionthroughanodalzone,mm2,AppendixA = Projected concrete failure area of a singleanchor or group of anchors, forcalculationofstrengthintension,mm2,seeD.5.2.1,AppendixD

= Projected concrete failure area of a singleanchor, for calculation of strength in tension if

not limited by edge distance or spacing,mm2,seeD.5.2.1,AppendixD = Gross area enclosed by shear flow path,mm2,Sec6.4 = Areaenclosedbycenterlineoftheoutermostclosedtransversetorsionalreinforcement,mm2,Sec6.4 = Areaofnonprestressed longitudinal tensionreinforcement,mm2,Sec6.3,6.4,6.6,6.8, = Areaof tensionreinforcementcorresponding tomomentofresistance,see6.3.15.1(b) = Areaofadditionaltensionsteel,see6.3.15.1(b) = Area of compression reinforcement, mm2,AppendixA = Areaofprimary tension reinforcement inacorbelorbracket,mm2,see6.4.7.3.5,Sec6.4, = Effective crosssectional area of anchor intension,mm2,AppendixD, = Effective crosssectional area of anchor inshear,mm2,AppendixD

= Area of reinforcement required to balance the longitudinal compressive force in the

overhangingportionoftheflangeofaTbeam,see6.3.15.2(b) = Totalcrosssectionalareaof transverse reinforcement(includingcrossties)withinspacingsandperpendicular to dimension,mm2,Sec8.3 = Total area of surface reinforcement atspacing si in the ith layer crossingastrut,withreinforcementatanangle totheaxisofthestrut,mm2,AppendixA, = Minimum area of flexural reinforcement,mm2,see6.3.5,Sec6.3 = Total area of nonprestressed longitudinal reinforcement (bars or steel shapes), mm2,Sec6.3,8.3 = Areaofstructuralsteelshape,pipe,ortubinginacompositesection,mm2,Sec6.3 = Areaofone legofaclosedstirrup resistingtorsionwithinspacings,mm2,Sec6.4 = Area of prestressing steel in a tie, mm2,AppendixA

=

Total

crosssectional

area

of

all transversereinforcement within spacing

sthat

crosses

the

potential plane of splitting through thereinforcement being developed,mm2,Sec8.2 = Area of nonprestressed reinforcement in atie,mm2,AppendixA = Areaofshearreinforcementspacings,mm2,Sec6.4,6.12 = Projected concrete failure area of a singleanchororgroupofanchors, forcalculationofstrengthinshear,mm2,seeD.6.2.1,AppendixD = Projected concrete failure area of a singleanchor, for calculation of strengthinshear,ifnotlimitedbycorner influences,spacing,ormemberthickness,mm2, seeD.6.2.1,AppendixD = Totalareaof reinforcement ineach group ofdiagonalbarsinadiagonallyreinforcedcouplingbeam,mm2,Sec8.3 = Area of shearfriction reinforcement, mm2,Sec6.4,8.3 = Area of shear reinforcement parallel to flexural tension reinforcement within spacing ,mm2,Sec6.4

, = Minimum area of shear reinforcement withinspacing s, mm2, see 6.4.3.5.1 and 6.4.3.5.3,Sec6.4 = Loadedarea,mm2,Sec6.3 = Areaof the lowerbaseof the largest frustumof a pyramid, cone, or tapered wedgecontainedwhollywithinthesupportandhavingforitsupperbasetheloadedarea,andhaving

sideslopesof1verticalto2horizontal,mm2,Sec6.3 = Widthof compression faceofmember, mm,Sec6.3 = Perimeterofcriticalsectionforshear in slabsand footings, mm, see 6.4.10.1.2,Sec6.4 = Widthofstrut,mm,AppendixA = Widthof thatpartof cross section containing theclosedstirrupsresisting torsion,mm,Sec

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BangladeshNationalBuildingCode2011 63

6.4 = Width of cross section at contact surfacebeinginvestigatedforhorizontalshear,mm,Sec6.12 = Web width, or diameter of circular section,mm,Sec6.3,6.4,8.2,8.3 = Dimensionof thecritical section measuredinthedirectionofthespanforwhichmomentsaredetermined,mm,Sec6.5 = Dimensionofthecritical section measuredin the direction perpendicularto,mm,Sec6.5

= Distance fromextreme compression fiber toneutralaxis,mm,Sec6.2,6.3,6.6,8.3

= Critical edge distance required to develop the basic concrete breakout strength of a postinstalled anchor in uncracked concrete without supplementary reinforcement to controlsplitting,mm,seeD.8.6,AppendixD, = Maximumdistancefrom center of an anchorshaft to the edge of concrete,mm,Appendix D, = Minimumdistancefrom center of an anchorshaft to the edge of concrete,mm,Appendix D = Distance from the centerofananchor shafttotheedgeofconcreteinonedirection,mm.Ifshear isapplied toanchor, is taken in the direction of the applied shear. If tension isappliedtotheanchor, istheminimumedgedistance,appendixd = Distance from center of an anchor shaft to theedgeofconcrete in thedirectionperpendicularto,mm,AppendixD = Smallerof: (a) thedistance from center of abarorwiretonearestconcretesurface,and(b)onehalfthecentertocenterspacingofbarsorwiresbeingdeveloped,mm,Sec8.2

= Clear cover of reinforcement, mm, see6.3.6.4,Sec6.3

= Distancefromtheinterior face of the columnto the slab edge measuredparalleltoc1,butnotexceeding,mm,Sec8.3 = Dimension of rectangular or equivalent rectangular column, capital, or bracketmeasured in the direction of the span forwhichmomentsarebeingdetermined,mm,Sec

6.4,6.5,8.3 = Dimension of rectangular or equivalent rectangular column, capital, or bracketmeasured in the direction perpendicular to,mm,Sec6.5 = Crosssectional constant to define torsionalpropertiesofslabandbeam,see6.5.6.4.2,Sec6.5 = Factorrelatingactualmoment diagram to anequivalentuniformmomentdiagram,Sec6.3 = Distance fromextreme compression fiber tocentroidoflongitudinal tensionreinforcement,mm,Sec6.26.4,6.6,6.12,8.18.3,

= Distance from extreme compression fiber to centroid of longitudinal compressionreinforcement,mm,Sec6.2 = Outsidediameterofanchor or shaft diameterof headed stud, headedbolt,orhooked bolt,mm,seeD.8.4,AppendixD = Valuesubstitutedforwhenanoversizedanchorisused,mm,seeD.8.4,AppendixD = Nominal diameter of bar, wire, or prestressing strand, mm, Sec 8.1-8.3 = Distance from extreme compression fiber to centroid of prestressing steel, mm, Sec6.4 = Diameter of pile at footing base, mm, Sec 6.8 = Distance fromextreme compression fiber tocentroidofextremelayeroflongitudinaltensionsteel,mm,Sec6.2,6.3 = Deadloads,orrelated internal moments andforces,Sec6.1,6.2,6.11,8.3

= Distancefromtheinner surface of the shaft of aJorLbolttotheoutertipoftheJ orLbolt,mm,

AppendixD = Distance between resultant tension load on a group of anchors loaded in tension andtheCentroid of the group of anchors loaded in tension, mm; is always positive,appendix d = Distance between resultant shear load on a group of anchors loaded in shear in thesameDirection, and the centroid of the group of anchors loaded in shear in the samedirection, mm; is always positive, appendix d = Loadeffectsofearthquake,orrelatedinternalmomentsandforces,Sec6.2,8.3 = Modulusofelasticityofconcrete,mpa,see6.1.7.1,Sec6.16.3,6.6,6.9

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= Modulusofelasticityofbeamconcrete,mpa,Sec6.5 = Modulusofelasticityofslabconcrete,mpa,Sec6.5 = Flexuralstiffnessofcompressionmember,Nmm2,see6.3.10.6,Sec6.3 = Modulusofelasticityofprestressingsteel,mpa,see6.1.7.3,Sec6.1 = Modulusofelasticityofreinforcement andstructuralsteel,mpa,see6.1.7.2,Sec6.1,6.3,6.6 = Specifiedcompressivestrengthofconcrete,mpa,Sec6.16.4,6.6,6.9,8.2,8.3,AppendixesA,

D = Squarerootofspecifiedcompressivestrengthofconcrete,mpa,Sec6.1,6.2,6.4,6.9,8.2,8.3,AppendixD = Effective compressive strength of the concrete in a strut or a nodal zone, mpa, Sec 6.8,AppendixA = Averagesplittingtensilestrengthoflightweightconcrete,mpa,See6.1.8.1Sec6.1,6.4,8.2.3.4(d),Sec8.2 = Stressduetounfactoreddeadload,atextremefiberofsectionwheretensilestressiscausedbyexternallyappliedloads,mpa,Sec6.4 = Compressive stress in concrete (afterallowance forallprestress losses)at centroidof crosssectionresistingexternallyapplied loadsoratjunctionofwebandflangewhenthecentroid

lieswithintheflange,mpa.(Inacompositemember, istheresultantcompressivestressatcentroidofcompositesection,oratjunctionofwebandflangewhenthecentroidlieswithin

theflange,duetobothprestressandmomentsresistedbyprecastmemberactingalone),Sec

6.4 = Compressivestress inconcretedue toeffectiveprestress forcesonly (afterallowance forallprestress losses) at extreme fiber of section where tensile stress is caused by externally

appliedloads,mpa,Sec6.4 = Stressinprestressingsteelatnominalflexuralstrength,mpa,Sec8.2 = Specifiedtensilestrengthofprestressingsteel,mpa,Sec6.4 = Modulusofruptureofconcrete,mpa,see6.2.5.2.3,Sec6.2,6.6 = Calculatedtensilestressinreinforcementatserviceloads,mpa,Sec6.3 = Stressincompressionreinforcementunderfactoredloads,mpa,AppendixA = Effective stress inprestressing steel (after allowance for allprestress losses),mpa, Sec8.2,AppendixA

=

Specifiedtensile

strength

ofanchor

steel,

mpa,

Appendix

D = Specifiedyieldstrengthofreinforcement, mpa,Sec6.26.4,6.6,6.9,6.12,8.18.3,AppendixA = Specifiedyieldstrengthofanchorsteel,mpa,AppendixD = Specifiedyieldstrengthoftransversereinforcement,mpa,Sec6.3,6.4,8.28.3 = Loads due to weight and pressures of fluids with welldefined densities and controllable

maximumheights,orrelatedinternalmomentsandforces,Sec6.2 = Nominalstrengthofastrut,tie,ornodalzone,N,AppendixA = Nominalstrengthatfaceofanodalzone,N,AppendixA = Nominalstrengthofastrut,N,AppendixA = Nominalstrengthofatie,N,AppendixA = Factored forceacting inastrut, tie,bearingarea,ornodalzone inastrutandtiemodel,N,AppendixA

= Overallthicknessorheightofmember,mm,Sec6.26.4,6.6,6.11,6.12,8.2,8.3,AppendixA

= Thicknessofmember inwhichananchor is located,measuredparallel toanchoraxis,mm,AppendixD = Crosssectional dimension of member core measured to the outside edges of the transversereinforcementcomposingarea,mm,Sec8.3 = Effectiveembedmentdepthofanchor,mm,seeD.8.5,AppendixD = ThicknessofoverhangingportionoftheflangeofaTbeam,see6.3.15.2(b) = Depthofshearheadcrosssection,mm,Sec6.4 = Heightofentirewallfrombasetotoporheightofthesegmentofwallconsidered,mm,Sec6.4,8.3 = Maximum centertocenter horizontal spacing of crossties or hoop legs on all faces of thecolumn,mm,Sec8.3

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= Loadsduetoweightandpressureofsoil,waterinsoil,orothermaterials,orrelatedinternalmomentsandforces,Sec6.2 = Momentofinertiaofsectionaboutcentroidalaxis,mm4,Sec6.3,6.4 = Momentofinertiaofgrosssectionofbeamaboutcentroidalaxis,mm4,see6.5.6.1.6,Sec6.5 = Momentofinertiaofcrackedsectiontransformedtoconcrete,mm4,Sec6.2 = Effectivemomentofinertiaforcomputationofdeflection,mm4,see6.2.5.2.3,Sec6.2 = Momentof inertiaofgrossconcretesectionaboutcentroidalaxis,neglectingreinforcement, mm

4

,Sec6.2,

6.3,

6.6

= Momentofinertiaofgrosssectionofslababoutcentroidalaxisdefinedforcalculatingand,mm4,Sec6.5 = Momentofinertiaofreinforcementaboutcentroidalaxisofmembercrosssection,mm4,Sec6.3 = Momentofinertiaofstructuralsteelshape,pipe,ortubingaboutcentroidalaxisofcompositemembercrosssection,mm

4,Sec6.3 = Effectivelengthfactorforcompressionmembers,Sec6.3,6.6 = Coefficientforbasicconcretebreakoutstrengthintension,AppendixD = Coefficientforpryoutstrength,AppendixD = Transversereinforcementindex,see8.2.3.3,Sec8.2

= Spanlengthofbeamoronewayslab;clearprojectionofcantilever,mm,Sec6.2

= Additionalembedmentlengthbeyondcenterlineofsupportorpointofinflection,mm,Sec8.2 = Length of compression member in a frame, measured centertocenter of thejoints in theframe,mm,Sec6.3,6.6 = Development length intensionofdeformedbar,deformedwire,plainanddeformedweldedwirereinforcement, orpretensionedstrand,mm,Sec6.9,8.18.3 = Developmentlengthincompressionofdeformedbarsanddeformedwire,mm,Sec8.2 = Development length in tension of deformed bar or deformed wire with a standard hook,measured fromcriticalsection tooutsideendofhook (straightembedment lengthbetween

criticalsectionand startofhook [pointof tangency]plus insideradiusofbendandonebar

diameter),mm,seeSec.8.2and8.3,Sec8.2,8.3 = Developmentlengthintensionofheadeddeformedbar,measuredfromthecriticalsectiontothebearingfaceofthehead,mm,Sec8.2

= Loadbearinglengthofanchorforshear,mm,seeD.6.2.2,AppendixD

= Lengthofclearspanmeasuredfacetofaceofsupports,mm,Sec6.16.5,6.10,8.2.9.3, Sec8.2,8.3 = Length, measured from joint face along axis of structural member, over which specialtransversereinforcementmustbeprovided,mm,Sec8.3 = Spanofmemberunder load test, takenas theshorterspan for twowayslab systems,mm.Span is the smaller of: (a) distance between centers of supports, and (b) clear distance

betweensupportsplusthicknessofmember.Span foracantilevershallbe takenas twicethedistancefromfaceofsupporttocantileverend,Sec6.11 = Unsupportedlengthofcompressionmember,mm,see6.3.10.1.1,Sec6.3 = Lengthofshearheadarmfromcentroidofconcentratedloadorreaction,mm,Sec6.4 = Lengthofentirewallorlengthofsegmentofwallconsideredindirectionofshearforce,mm,Sec6.4,6.6,8.3

= Lengthofspanindirectionthatmomentsarebeingdetermined,measuredcentertocenterofsupports,mm,Sec6.5 = Lengthofspan indirectionperpendicular to ,measuredcentertocenterofsupports,mm,see6.5.6.2.3and6.5.6.2.4,Sec6.5 = Liveloads,orrelatedinternalmomentsandforces,Sec6.1,6.2,6.11,8.3 = Roofliveload,orrelatedinternalmomentsandforces,Sec6.2 = Maximummoment inmemberdue to service loadsatstagedeflection is computed,Nmm,Sec6.2,6.6 = Factored moment amplified for the effects of member curvature used for design ofcompressionmember,Nmm,see6.3.10.6,Sec6.3 = Crackingmoment,Nmm,see6.2.5.2.3,Sec6.2,6.6

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= Momentcausingflexuralcrackingatsectiondue toexternallyappliedloads,Nmm,Sec6.4 = Factoredmomentmodified toaccount foreffectofaxialcompression,Nmm,see6.4.2.2.2,Sec6.4 = Maximumfactoredmomentatsectionduetoexternallyappliedloads,Nmm,Sec6.4 = Nominalflexuralstrengthatsection,Nmm,Sec6.4,6.6,8.2,8.3

= Nominalflexuralstrengthatsectionwithoutcompressionsteel,see6.3.15.1(b),andmoment

ofresistance developedbycompressionintheoverhangingportionoftheTflange,see6.3.15.2(b) = Additional nominal flexural strength at section due to added compression steel andadditionaltensionsteel,see6.3.15.1(b),andmomentofresistancedevelopedbythewebofaTbeam,see6.3.15.2(b) = Nominal flexural strength of column framing intojoint, calculated for factored axial force,consistentwiththedirectionoflateralforcesconsidered,resultinginlowestflexuralstrength,

Nmm,Sec8.3 = Totalfactoredstaticmoment,Nmm,Sec6.5 = Requiredplasticmomentstrengthofshearheadcrosssection,Nmm,Sec6.4 = Probable flexural strength of members, with or without axial load, determined using thepropertiesofthememberatthejointfacesassumingatensilestressinthelongitudinalbarsof

atleast

1.25andastrengthreductionfactor,

,of1.0,N

mm,Sec8.3

= Factoredmomentduetoloadscausingappreciablesway,Nmm,Sec6.3 = Portionofslabfactoredmomentbalancedbysupportmoment,Nmm,Sec8.3 = Factoredmomentatsection,Nmm,Sec6.36.6,8.3 = Momentatmidheightofwallduetofactoredlateralandeccentricverticalloads,notincludingeffects,Nmm,Sec6.6 = Momentresistancecontributedbyshearheadreinforcement,Nmm,Sec6.4 = Smallerfactoredendmomentonacompressionmember,tobetakenaspositiveifmemberisbentinsinglecurvature,andnegativeifbentindoublecurvature,Nmm,Sec6.3 = Factoredendmomentonacompressionmemberat theendatwhichM1acts,due to loadsthatcausenoappreciablesidesway,calculatedusingafirstorderelasticframeanalysis,Nmm,Sec6.3

, = Minimumvalueof

,N

mm,Sec6.3

=

Factoredend

moment

on

compression

member

atthe

end

atwhich

M2acts,

due

toloads

that

causenoappreciablesidesway,calculatedusingafirstorderelasticframeanalysis,Nmm,Sec6.3 = Factoredendmomentoncompressionmemberattheendatwhichacts,duetoloadsthatcauseappreciablesidesway,calculatedusingafirstorderelasticframeanalysis,Nmm,Sec6.3 = Numberofitems,suchasstrengthtests,bars,wires,monostrandanchoragedevices,anchors,orshearheadarms,Sec6.4,8.2,AppendixD = Basic concrete breakout strength in tension of a single anchor in cracked concrete, N, seeD.5.2.2,AppendixD = Nominalconcretebreakoutstrengthintensionofasingleanchor,N,seeD.5.2.1,AppendixD = Nominalconcretebreakoutstrengthintensionofagroupofanchors,N,seeD.5.2.1,AppendixD

= Nominalstrengthintension,N,AppendixD

= Pulloutstrength intensionofasingleanchorincrackedconcrete,N,seeD.5.3.4andD.5.3.5,AppendixD = Nominalpulloutstrengthintensionofasingleanchor,N,seeD.5.3.1,AppendixD = Nominalstrengthofasingleanchororgroupofanchors intensionasgovernedbythesteelstrength,N,seeD.5.1.1andD.5.1.2,AppendixD = Sidefaceblowoutstrengthofasingleanchor,N,AppendixD = Sidefaceblowoutstrengthofagroupofanchors,N,AppendixD = Factoredaxialforcenormaltocrosssectionoccurringsimultaneouslywith or ;tobetakenaspositiveforcompressionandnegativefortension,N,Sec6.4 = Factoredtensileforceappliedtoanchororgroupofanchors,N,AppendixD = Factoredhorizontaltensileforceappliedattopofbracketorcorbelactingsimultaneously with

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Vu,tobetakenaspositivefortension,N,Sec6.4 = Outsideperimeterofconcretecrosssection,mm,see6.4.4.1,Sec6.4 = Perimeterofcenterlineofoutermostclosedtransversetorsionalreinforcement, mm,Sec6.4 = Nominalaxialstrengthatbalancedstrainconditions,N,see6.3.3.2,Sec6.2,6.3 = Criticalbucklingload,N,see6.3.10.6,Sec6.3 = Nominalaxialstrengthofcrosssection,N,Sec6.2,6.3,6.6, = Maximumallowablevalueof,N,see6.3.3.6,Sec6.3

= Nominalaxialstrengthatzeroeccentricity,N,Sec6.3

= Unfactoredaxial loadatthedesign(midheight)section includingeffectsofselfweight,N,Sec6.6 = Factoredaxialforce;tobetakenaspositiveforcompressionandnegativefortension,N,Sec6.3,6.6,8.3 = Factoreddeadloadperunitarea,Sec6.5 = Factoredliveloadperunitarea,Sec6.5 = Factoredloadperunitarea,Sec6.5 = Stabilityindexforastory,see6.3.10.5.2,Sec6.3 = Radiusofgyrationofcrosssectionofacompressionmember,mm,Sec6.3 = Rainload,orrelatedinternalmomentsandforces,Sec6.2 = Centertocenter spacing of items, such as longitudinal reinforcement, transversereinforcement, prestressingtendons,wires,oranchors,mm,Sec6.3,6.4,6.9,6.11,6.12,8.2,

8.3,AppendixD

= Centertocenter spacing of reinforcement in the ith layer adjacent to the surface of themember,mm,AppendixA = Centertocenterspacingoftransversereinforcementwithinthelength,mm,Sec8.3 = Samplestandarddeviation,mpa,AppendixD = Centertocenterspacingoflongitudinalshearortorsionreinforcement, mm,Sec6.4 = Snowload,orrelatedinternalmomentsandforces,Sec6.2,8.3 = Moment, shear, or axial force at connection corresponding to development of probablestrengthat intended yield locations,based on the governingmechanism of inelastic lateral

deformation, consideringbothgravityandearthquakeloadeffects,Sec8.3 = Nominalflexural,shear,oraxialstrengthofconnection,Sec8.3 = Yieldstrengthofconnection,basedon,formoment,shear,oraxialforce,Sec8.3

= Wallthicknessofhollowsection,mm,Sec6.4

= Cumulative effect of temperature, creep, shrinkage, differential settlement, and shrinkagecompensatingconcrete,Sec6.2 = Nominaltorsionalmomentstrength,Nmm,Sec6.4 = Factoredtorsionalmomentatsection,Nmm,Sec6.4 = Requiredstrengthtoresistfactoredloadsorrelatedinternalmomentsandforces,Sec6.2 = Nominalshearstress,mpa,see6.4.10.6.2,Sec6.4,8.3 = Basicconcretebreakoutstrengthinshearofasingleanchorincrackedconcrete,N,seeD.6.2.2andD.6.2.3,AppendixD = Nominalshearstrengthprovidedbyconcrete,N,Sec6.1,6.4,6.5,8.3 = Nominalconcretebreakoutstrengthinshearofasingleanchor,N,seeD.6.2.1,AppendixD = Nominalconcretebreakoutstrengthinshearofagroupofanchors,N,seeD.6.2.1,AppendixD = Nominalshearstrengthprovidedbyconcretewhendiagonalcrackingresultsfromcombinedshearandmoment,N,Sec6.4

= Nominalconcretepryoutstrengthofasingleanchor,N,seeD.6.3.1,AppendixD = Nominalconcretepryoutstrengthofagroupofanchors,N,seeD.6.3.1,AppendixD = Nominal shear strength provided by concrete when diagonal cracking results from highprincipaltensilestressinweb,N,Sec6.4 = Shearforceatsectionduetounfactoreddeadload,N,Sec6.4 = Designshearforcecorrespondingtothedevelopmentoftheprobablemomentstrengthofthemember,N,Sec8.3 = Factoredshearforceatsectionduetoexternallyappliedloadsoccurringsimultaneously with,N,Sec8.3 = Nominalshearstrength,N,Sec6.1,6.3,6.4,8.3,AppendixD = Nominalhorizontalshearstrength,N,Sec6.12

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= Verticalcomponentofeffectiveprestressforceatsection,N,Sec6.4 = Nominalshearstrengthprovidedbyshearreinforcement,N,Sec6.4 = Nominal strength in shearofa singleanchoror groupofanchorsas governedby the steelstrength,N,seeD.6.1.1andD.6.1.2,AppendixD = Factoredshearforceatsection, N,Sec6.4,6.5,6.12,8.2,8.3

= Factoredshearforceappliedtoasingleanchororgroupofanchors,N,AppendixD

= Factoredshearforceontheslabcriticalsectionfortwowayactionduetogravityloads,N,seeSec.8.3 = Factoredhorizontalshearinastory,N,Sec6.3 = Density(unitweight)ofnormalweightconcreteorequilibriumdensityoflightweightconcrete,kg/m3,Sec6.1,6.2 = Factoredloadperunitlengthofbeamoronewayslab,Sec6.1 = Windload,orrelatedinternalmomentsandforces,Sec6.2 = Shorteroveralldimensionofrectangularpartofcrosssection,mm,Sec6.5 = Longeroveralldimensionofrectangularpartofcrosssection,mm,Sec6.5 = Distancefromcentroidalaxisofgrosssection,neglectingreinforcement, totensionface,mm,Sec6.2,6.4

= Angledefiningtheorientationofreinforcement, Sec6.4,8.3,AppendixA

= Coefficient defining the relative contribution of concrete strength to nominal wall shear

strength,Sec8.3 = Ratio of flexural stiffness of beam section to flexural stiffness of a width of slab boundedlaterallybycenterlinesofadjacentpanels(ifany)oneachsideofthebeam,see6.5.6.1.6,Sec

6.2,6.5 = Averagevalueofforallbeamsonedgesofapanel,Sec6.2 = indirectionofl1,Sec6.5 = indirectionof,Sec6.5 = Anglebetweentheaxisofastrutandthebarsintheithlayerofreinforcementcrossingthatstrut,AppendixA = Constantusedtocompute inslabsandfootings,Sec6.4 = Ratioofflexuralstiffnessofshearheadarmtothatofthesurroundingcompositeslabsection,see6.4.10.4.5,Sec6.4

= Ratiooflongtoshortdimensions:clearspansfortwowayslabs,see6.2.5.3.3;sidesofcolumn,concentratedloadorreactionarea,see6.4.10.2.1;orsidesofafooting,see6.8.4.4.2,Sec6.2,6.4,6.8 = Ratioofareaofreinforcementcutofftototalareaoftensionreinforcement atsection,Sec8.2 = Ratioused toaccount forreductionofstiffnessofcolumnsdue tosustainedaxial loads,see6.3.10.6.2,Sec6.3 = Ratiousedtoaccountforreductionofstiffnessofcolumnsduetosustainedlateralloads,see6.3.10.4.2,Sec6.3 = Factortoaccountfortheeffectoftheanchorageoftiesontheeffectivecompressivestrengthofanodalzone,AppendixA = Factorusedtocompute inprestressedslabs,Sec6.4 = Factor to account for the effect of cracking and confining reinforcement on the effectivecompressivestrengthoftheconcreteinastrut,AppendixA

= Ratiooftorsionalstiffnessofedgebeamsectiontoflexuralstiffnessofawidthofslabequaltospanlengthofbeam,centertocenterofsupports,see6.5.6.4.2,Sec6.5 = Factorrelatingdepthofequivalentrectangularcompressivestressblocktoneutralaxisdepth,see6.3.2.7.3,Sec6.3 = Factor used to determine the unbalanced moment transferred by flexure at slabcolumnconnections,see6.5.5.3.2,Sec6.4,6.5,8.3 = Factorusedtodeterminetheportionofreinforcement located incenterbandoffooting,see6.8.4.4.2,Sec6.8 = Factorusedtodeterminetheunbalancedmomenttransferredbyeccentricityofshearatslabcolumnconnections, see6.4.10.7.1,Sec6.4

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= Moment magnification factor to reflect effects of member curvature between ends ofcompressionmember,Sec6.3 = Momentmagnification factor for framesnotbracedagainstsidesway, to reflect lateraldriftresultingfromlateralandgravityloads,Sec6.3 = Designdisplacement,mm,Sec8.3 = Computed, outofplane deflection at midheight of wall corresponding to crackingmoment,,mm,Sec6.6

= Increaseinstressinprestressingsteelduetofactoredloads,mpa,AppendixA

= Computed, outofplane deflection at midheight of wall corresponding to nominal flexuralstrength,,mm,Sec6.6 = Relative lateral deflection between the top and bottom of a story due to lateral forcescomputedusinga firstorderelastic frameanalysisandstiffnessvalues satisfying6.3.10.5.2,

mm,Sec6.3 = Differencebetweeninitialandfinal(afterloadremoval)deflectionsforloadtestorrepeatloadtest,mm,Sec6.11 = Computed,outofplanedeflectionatmidheightofwallduetoserviceloads,mm,Sec6.6 = Computeddeflectionatmidheightofwallduetofactoredloads,mm,Sec6.6 = Measuredmaximumdeflectionduringfirstloadtest,mm,see6.11.5.2,Sec6.11 = Maximumdeflectionmeasuredduringsecondloadtestrelativetothepositionofthestructureatthebeginningofsecondloadtest,mm,see6.11.5.2,Sec6.11

= Nettensilestraininextremelayeroflongitudinaltensionsteelatnominalstrength,excluding

strainsduetoeffectiveprestress,creep,shrinkage,andtemperature,Sec6.16.3 = Anglebetweenaxisofstrut,compressiondiagonal,orcompressionfieldandthetensionchordofthemember,Sec6.4,AppendixA = Modification factor reflecting the reducedmechanicalpropertiesof lightweightconcrete,allrelative tonormalweight concrete of the same compressive strength, see6.1.8.1,6.4.5.4.3,

8.2.3.4(d),8.2.6.2,8.2.10.2(b),Sec6.2,6.4,6.9,8.2,8.3andAppendixesA,D = Multiplierforadditionaldeflectionduetolongtermeffects,see6.2.5.2.5,Sec6.2 = Coefficientoffriction,see6.4.5.4.3,Sec6.4,8.3 = Timedependentfactorforsustainedload,see6.2.5.2.5,Sec6.2 = Ratioof to,Sec6.4,6.5,8.3

= Ratioof

to

,see6.3.15.1(b), Sec6.2

= Ratioof toproducingbalancedstrainconditions,see6.3.3.2,Sec6.3,6.5,6.6 = Ratioofto,see6.3.15.2(b) = Ratioofareaofdistributedlongitudinal reinforcementtogrossconcreteareaperpendicular tothatreinforcement, Sec6.4,6.6,8.3 = Maximum reinforcement ratio allowed for beams corresponding to 0.004 , see6.3.15.1(a) = Ratio of volume of spiral reinforcement to total volume of core confined by the spiral(measuredouttooutofspirals),Sec6.3,8.3 = Ratio of area distributed transverse reinforcement to gross concrete area perpendicular tothatreinforcement, Sec6.4,6.6,8.3 = Ratiooftiereinforcementareatoareaofcontactsurface,see6.12.5.3.3,Sec6.12 = Ratioof to,see6.3.15.2(b),Sec6.4

= Strengthreductionfactor,see6.2.3,Sec6.16.6,6.9,6.11,6.12,8.3,AppendixesA&D

, = Factorusedtomodifytensilestrengthofanchorsbasedonpresenceorabsenceofcracks inconcrete,seeD.5.2.6,AppendixD, = Factorusedtomodifypulloutstrengthofanchorsbasedonpresenceorabsenceofcracksinconcrete,seeD.5.3.6,AppendixD, = Factorused tomodifyshearstrengthofanchorsbasedonpresenceorabsenceofcracks inconcreteandpresenceorabsenceofsupplementaryreinforcement, seeD.6.2.7foranchorsin

shear,AppendixD, = Factorusedtomodifytensilestrengthofpostinstalledanchors intendedforuse inuncrackedconcretewithoutsupplementaryreinforcement, seeD.5.2.7,AppendixD = Factorusedtomodifydevelopmentlengthbasedonreinforcementcoating,Sec8.2, = Factorusedtomodifytensilestrengthofanchorsbasedoneccentricity ofapplied loads,see

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D.5.2.4,AppendixD, = Factorused tomodifyshearstrengthofanchorsbasedoneccentricityofapplied loads,seeD.6.2.5,AppendixD, = Factorused tomodify tensile strengthofanchorsbasedon proximity toedgesof concretemember,seeD.5.2.5,AppendixD

, = Factor used to modify shear strength of anchors based on proximity to edges of concrete

member,seeD.6.2.6,AppendixD, = Factor used to modify shear strength of anchors located in concrete members with 1.5,seeD.6.2.8,AppendixD = Factorusedtomodifydevelopmentlengthbasedonreinforcementsize,Sec8.2 = Factorusedtomodifydevelopmentlengthbasedonreinforcementlocation,Sec8.2 = Factor used to modify development length for welded deformed wire reinforcement intension,Sec8.2 = Effectivetensionareaofconcretesurroundingtheflexuraltensionreinforcement andhavingthe same centroid as that of the reinforcement, divided by the number of bars. When the

flexural reinforcement consists ofdifferent bar sizes the numberof bars or wires shallbe

computedasthetotalareaofreinforcement dividedbytheareaofthelargestbarused = Areaofskinreinforcementperunitheightinasideface = Factorrelatingshearandtorsionalstressproperties= = Thicknessof concrete cover measured fromextreme tension fibre to centreof bar or wire

locatedclosestthereto = Momentofresistanceofasectionwithoutcompressionsteel = Additionalmomentof resistancedue toadded compressionsteel andadditional tensionsteelas2 = Spacingofshearortorsionreinforcementindirectionparalleltolongitudinal reinforcement = Torsionalmomentstrengthprovidedbyconcrete = Torsionalmomentstrengthprovidedbytorsionreinforcement = Shortercentretocentredimensionofclosedrectangularstirrup = Longercentretocentredimensionofclosedrectangularstirrup

= Quantitylimitingdistributionofflexuralreinforcement,seeEq(6.2.35)

= Coefficientequalto2 3 butnotmorethan1.51 = Factordefinedin6.2.3.7 = Timedependentfactorforsustainedload = Minimumratiooftensionreinforcement

6.1.2 General6.1.2.1 Membersshallbedesignedforadequatestrength inaccordancewiththeprovisions

ofthischapter,usingloadfactorsspecifiedin2.6.5.1andstrengthreductionfactors in6.2.3.1.

6.1.2.2 Design of reinforced concrete members using Working Stress Design method

(AppendixB)isalsopermitted.

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6.1.2.3 Structuresand structuralmembers shallbedesigned tohavedesignstrengthatall

sectionsatleastequaltotherequired strength(U)calculatedforthefactoredloads

and forces insuchcombinations asarestipulated inChapter2,Loads.Thenominal

strengthprovidedforthesectionmultipliedbythestrengthreductionfactorshallbeequaltoorgreaterthanthecalculatedrequiredstrengthU.

6.1.2.4 MembersshallalsomeetalltheotherrequirementsofthisCodetoensureadequate

performanceatserviceloads.

6.1.2.5 Design strength of reinforcement represented by the values of and used indesign calculationsshallnotexceed550MPa,except forprestressingsteeland for

transversereinforcement in6.3.9.3andSec.8.3. or mayexceed420MPa,onlyif theratiooftheactualtensilestrengthtotheactualyieldstrengthisnotlessthan

1.20,andtheelongationpercentageisnotlessthan16.

6.1.2.6 Forstructuralconcrete, shallnotbe less than17MPa.NomaximumvalueofshallapplyunlessrestrictedbyaspecificCodeprovision.

6.1.3 Loading

6.1.3.1 Loadsandtheircombinationsshallbeinaccordancewiththerequirementsspecified

inChapter2,Loads.

6.1.3.2 Structuresshallbedesignedtoresistallapplicableloads.

6.1.3.3 Effects of forces due to prestressing, crane loads, vibration, impact, shrinkage,

temperature changes, creep, expansion of shrinkagecompensating concrete, and

unequalsettlementofsupportsshallbedulyconsidered.

6.1.4 Methodsofanalysis6.1.4.1 Members of frames or continuous construction (beams or oneway slabs) shall be

designedforthemaximumeffectsoffactored loadsasdeterminedbythetheoryof

elastic analysis, except as modified for redistribution of moments in continuous

flexuralmembersaccordingto6.1.5.Designispermittedtobesimplifiedbyusingthe

assumptionsspecifiedin6.1.6&6.1.9through6.1.12.

6.1.4.2 Frame analysis by approximate methods shall be permitted for buildings of usual

typesofconstruction, spans,andstoryheights.

6.1.4.3 Provided (a)through (e)belowaresatisfied, theapproximatemomentsandshears

given here shall be permitted for design of continuous beams and oneway slabs

(slabs reinforced toresist flexuralstresses inonlyonedirection),asanalternate to

frameanalysis:

a) Therearetwoormorespans;

b) Spansareapproximately equal,withthelargeroftwoadjacentspansnotgreaterthan

theshorterbymorethan20percent;

c) Loadsareuniformlydistributed;

d) Unfactoredliveload,,doesnotexceedthreetimesunfactoreddeadload,;ande) Membersareprismatic.

Forcalculatingnegativemoments,istakenastheaverageoftheadjacentclearspanlengths.Positivemoment

Endspans

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Discontinuous endunrestrained 11 Discontinuousendintegralwithsupport 14 Interiorspans

16

Negativemomentsatexteriorfaceoffirstinteriorsupport

Twospans 9 Morethantwospans 10 Negativemomentatotherfacesofinterior

Supports 11

Negativemomentatfaceofallsupportsfor

Slabswithspansnotexceeding3.048m;

andbeamswhereratioofsumofcolumnstiffnessestobeamstiffnessexceeds8ateachendofthespan 12

Negativemomentatinteriorfaceofexteriorsupportformembersbuiltintegrallywith

supportsWheresupportisspandrelbeam 24 Wheresupportisacolumn

16

Shearinendmembersatfaceoffirst

interiorsupport1.152

Shearatfaceofallothersupports 2 6.1.4.4 Strutandtiemodels,providedinAppendixA,shallbepermittedtobeusedinthedesignof

structuralconcrete.

6.1.5 Redistributionofmomentsincontinuousflexuralmembers6.1.5.1 Itshallbepermittedtodecreasefactoredmomentscalculatedbyelastictheoryatsectionsof

maximumnegativeormaximumpositivemomentinanyspanofcontinuousflexuralmembers

foranyassumedloadingarrangementbynotmorethan1000percent,withamaximumof20percent,exceptwhereapproximatevaluesformomentsareused.

6.1.5.2 Redistribution ofmomentsshallbemadeonlywhenisequaltoorgreaterthan0.0075atthesectionatwhichmomentisreduced.

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6.1.5.3 Atallothersectionswithinthespans,thereducedmomentshallbeusedforcalculating

redistributedmoments.Staticequilibriumshallhavetobemaintainedafterredistribution of

momentsforeachloadingarrangement.

6.1.6 Spanlength6.1.6.1 Thespanlengthofasimplysupportedbeamshall betakenasthesmallerofthedistance

betweenthecentresofbearings,orthecleardistancebetweensupportsplustheeffective

depth.

6.1.6.2 Fordetermination ofmomentsinanalysisofframesorcontinuousconstruction, spanlength

shallbetakenasthedistancecentertocenterofsupports.

6.1.6.3 Designonthebasisofmomentsatfacesofsupportshallbepermittedforbeamsbuilt

integrallywithsupports.

6.1.6.4 Itshallbepermittedtoanalyzesolidorribbedslabsbuiltintegrallywithsupports,withclear

spansnotmorethan3m,ascontinuousslabsonknifeedgesupportswithspansequaltothe

clearspansoftheslabandwidthofbeamsotherwiseneglected.

6.1.7 Modulusof

elasticity

6.1.7.1 Modulusofelasticity,,forconcreteshallbepermittedtobetakenas .0.043 (inMPa)forvaluesofbetween1440and2560kg/m3.Fornormalweightconcrete,shallbepermittedtobetakenas4700.

6.1.7.2 Modulusofelasticity,,forreinforcement shallbepermittedtobetakenas200,000MPa.

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6.1.8 Lightweightconcrete6.1.8.1 Toaccountfortheuseoflightweightconcrete,unlessspecificallynotedotherwise,a

modificationfactorappearsasamultiplierofinallapplicableequationsandsectionsofthisCode,where 0.85forsandlightweightconcreteand0.75foralllightweightconcrete.Linearinterpolationbetween0.75and0.85shallbepermitted,onthebasisof

volumetricfractions,whenaportionofthelightweightfineaggregateisreplacedwith

normalweightfineaggregate.Linearinterpolation between0.85and1.0shallbepermitted,

onthebasisofvolumetricfractions,forconcretecontainingnormalweightfineaggregateand

ablendoflightweightandnormalweightcoarseaggregates.Fornormalweightconcrete, 1.0.Ifaveragesplittingtensilestrengthoflightweightconcrete,,isspecified, /0.56 1.0.6.1.9 Stiffness6.1.9.1 Forcomputingrelativeflexuralandtorsionalstiffnessesofcolumns,walls,floors,androof

systems,useofanysetofreasonableassumptionsshallbepermitted.Theassumptions

adoptedshallbeconsistentthroughoutanalysis.

6.1.9.2 Bothindeterminingmomentsandindesignofmembers,effectofhaunchesshallbe

considered.

6.1.10 Effectivestiffnessfordetermininglateraldeflections6.1.10.1 Lateraldeflectionsresultingfromservicelateralloadsforreinforcedconcretebuildingsystems

shallbecomputedbyeitheralinearanalysiswithmemberstiffnessdeterminedusing1.4

timestheflexuralstiffnessdefinedin6.1.10.2and6.1.10.3orbyamoredetailedanalysis.

Memberpropertiesshallnotbetakengreaterthanthegrosssectionproperties.

6.1.10.2 Lateraldeflectionsresultingfromfactoredlateralloadsforreinforcedconcretebuilding

systemsshallbecomputedeitherbylinearanalysiswithmemberstiffnessdefinedby(a)or

(b),orbyamoredetailedanalysisconsideringthereducedstiffnessofallmembersunderthe

loadingconditions:

a) Bysectionpropertiesdefinedin6.3.10.4.1(a)through(c);or

b) 50percentofstiffnessvaluesbasedongrosssectionproperties.

6.1.10.3 Lateraldeflectionsresultingfromfactoredlateralloadsshallbepermittedtobecomputedby

usinglinearanalysis,wheretwowayslabswithoutbeamsaredesignatedaspartofthe

seismicforceresistingsystem.Thestiffnessofslabmembersshallbedefinedbyamodelthat

isinsubstantialagreementwithresultsofcomprehensivetestsandanalysisandthestiffness

ofotherframemembersshallbeasdefinedin6.1.10.2.

6.1.11 ConsiderationsforColumns6.1.11.1 Columnsshallbedesignedtoresisttheaxialforcesfromfactoredloadsonallfloorsorroof

andthemaximummomentfromfactoredloadsonasingleadjacentspanofthefloororroof

underconsideration. Loadingconditionresultingthemaximumratioofmomenttoaxialload

shallalsobeconsidered.

6.1.11.2 Inframesorcontinuousconstruction,considerationshallbegiventotheeffectofunbalanced

floororroofloadsonbothexteriorandinteriorcolumnsandofeccentricloadingduetoother

causes.

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6.1.11.3 Itshallbepermittedtoassumefarendsofcolumnsbuiltintegrallywiththestructuretobe

fixed,whilecomputinggravityloadmomentsincolumns.

6.1.11.4 Resistancetomomentsatanyfloororrooflevelshallbeprovidedbydistributing themoment

betweencolumnsimmediatelyaboveandbelowthegivenfloorinproportiontotherelative

columnstiffnessesandconditionsofrestraint.

6.1.12 Liveloadarrangement

6.1.12.1 Thefollowingshallbepermittedtoassume:

a) Theliveloadisappliedonlytothefloororroofunderconsideration;and

b) Thefarendsofcolumnsbuiltintegrallywiththestructureareconsideredtobefixed.

6.1.12.2 Arrangementofliveloadshallbepermittedtobeassumedtobelimitedtocombinations of:

a) Factoreddeadloadonallspanswithfullfactoredliveloadontwoadjacentspans;and

b) Factoreddeadloadonallspanswithfullfactoredliveloadonalternatespans.

6.1.13 ConstructionofT-beam6.1.13.1 IntheconstructionofTbeam,theflangeandwebshallbebuiltintegrallyorotherwise

effectivelybondedtogether.

6.1.13.2 WidthofslabeffectiveasaTbeamflangeshallnotexceedonequarterofthespanlengthof

thebeam,andtheeffectiveoverhangingflangewidthoneachsideofthewebshallnot

exceed:

a) Eighttimestheslabthickness;and

b) Onehalfthecleardistancetothenextweb.

6.1.13.3 Theeffectiveoverhangingflangewidthforbeamswithaslabononesideonlyshallnot

exceed:

a) Onetwelfththespanlengthofthebeam;

b) Sixtimestheslabthickness;and

c) Onehalfthecleardistancetothenextweb.

6.1.13.4 Isolatedbeams,inwhichtheTshapeisusedtoprovideaflangeforadditionalcompression

area,shallhaveaflangethicknessnotlessthanonehalfthewidthofwebandaneffective

flangewidthnotmorethanfourtimesthewidthofweb.

6.1.13.5 WhenprimaryflexuralreinforcementinaslabthatisconsideredasaTbeamflange

(excludingjoistconstruction)isparalleltothebeam,reinforcementshallbeprovidedinthe

topoftheslabinthedirectionperpendicular tothebeamandinaccordancewiththe

following:

6.1.13.5.1 Transversereinforcementshallbedesignedtocarrythefactoredloadontheoverhanging

slabwidthassumedtoactasacantilever.Forisolatedbeams,thefullwidthofoverhangingflangeshallbeconsidered.ForotherTbeams,onlytheeffectiveoverhangingslabwidthneed

beconsidered.

6.1.13.5.2 Spacing of transverse reinforcement shall be not farther apart than five times the slab

thickness,norfartherapartthan450mm.

6.1.14 Constructionofjoist6.1.14.1 Constructionofjoistconsistsofamonolithiccombinationofregularlyspacedribsandatop

slabarrangedtospaninonedirectionortwoorthogonaldirections.

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6.1.14.2 Widthofribsshallnotbelessthan100mm,andtheribsshallhaveadepthofnotmorethan

31/2timestheminimumwidthofrib.

6.1.14.3 Clearspacingbetweenribsshallnotexceed750mm.

6.1.14.4 Joistconstruction notmeetingthelimitationsof6.1.14.1through6.1.14.3shallbedesignedas

slabsandbeams.

6.1.14.5 Whenpermanentburnedclayorconcretetilefillersofmaterialhavingaunitcompressive

strengthatleastequaltointhejoistsareused:6.1.14.5.1 Forshearandnegativemomentstrengthcomputations, theverticalshellsoffillersincontact

withtheribsshallbepermittedtoinclude.Otherportionsoffillersshallnotbeincludedin

strengthcomputations.

6.1.14.5.2 Slabthicknessoverpermanentfillersshallbenotlessthanonetwelfththecleardistance

betweenribs,norlessthan40mm.

6.1.14.5.3 Reinforcement normaltotheribsshallbeprovidedintheslabinonewayjoists,asrequiredby8.1.11

6.1.14.6 Whenremovableformsorfillersareused,whichdonotcomplywith6.1.14.5,then:

6.1.14.6.1 Slabthicknessshallbenotlessthanonetwelfththecleardistancebetweenribs,norlessthan

50mm.

6.1.14.6.2 Reinforcementnormaltotheribsshallbeprovidedintheslabasrequiredforflexure,

consideringloadconcentrations,ifany,butnotlessthanrequiredby8.1.11

6.1.14.7 Whereconduitsorpipesaspermittedbyrelevantprovisionsofembedmentsinconcreteare

embeddedwithintheslab,slabthicknessshallbeatleast25mmgreaterthanthetotaloverall

depthoftheconduitsorpipesatanypoint.Conduitsorpipesshallnotimpairsignificantlythe

strengthoftheconstruction.

6.1.14.8 Forjoistconstruction, shallbepermittedtobe10percentmorethanthatspecifiedinSec6.4.

6.1.15 Separatefloorfinish6.1.15.1 Unlessplacedmonolithicallywiththefloorslabordesignedinaccordancewithrequirements

ofSec.6.12,floorfinishshallnotbeincludedaspartofastructuralmember.

6.1.15.2 Allconcretefloorfinishesshallbepermittedtobeconsideredaspartofrequiredcoveror

totalthicknessfornonstructuralconsiderations.

6.2 STRENGTHANDSERVICEABILITYREQUIREMENTS

6.2.1 General6.2.1.1 Structuresandstructuralmembersshallbedesignedtohavedesignstrengthsatallsections

atleastequaltotherequiredstrengthscalculatedforthefactoredloadsandforcesinsuch

combinations asarestipulatedinthisCode.

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6.2.1.2 MembersalsoshallmeetallotherrequirementsofthisCodetoensureadequateperformance

atserviceloadlevels.

6.2.2 Requiredstrength6.2.2.1 Requiredstrengthshallbeatleastequaltotheeffectsoffactoredloadsinsuch

combinationsasarestipulatedinChapter2,Loads.

6.2.2.2 Ifresistancetoimpacteffectsistakenintoaccountindesign,sucheffectsshallbeincludedwith.

6.2.2.3 Estimationsofdifferentialsettlement,creep,shrinkage,expansionofshrinkagecompensating

concrete,ortemperaturechangeshallbebasedonarealisticassessmentofsucheffects

occurringinservice.

6.2.3 DesignStrength6.2.3.1 Designstrengthprovidedbyamember,anditsconnectionstoothermembers,intermsof

flexure,axialload,shear,andtorsion,shallbetakenasthenominalstrengthcalculatedin

accordancewiththerequirementsandassumptionsofthischapter,multipliedbyastrength

reductionfactorsasstipulatedin6.2.3.2,6.2.3.3,and6.2.3.4.6.2.3.2 Strengthreductionfactorshallbeasgivenin6.2.3.2.1through6.2.3.2.6:6.2.3.2.1 Tensioncontrolledsectionsasdefinedin6.3.3.4............................................... 0.90

6.2.3.2.2 Compressioncontrolledsections,asdefinedin6.3.3.3:

Memberswithspiralreinforcement conformingto6.3.9.3........................ 0.75

Otherreinforcedmembers.......................................................................... 0.65

Forsectionsinwhichthenettensilestrainintheextremetensionsteelatnominalstrength,,isbetweenthelimitsfor compressioncontrolledandtensioncontrolledsections,shallbepermittedtobelinearlyincreased from that for compressioncontrolled sections to0.90as

increases from the compression

controlledstrainlimitto0.005(AlsoseeFig. 6.2.3.1).While interpolating, it shallbepermittedtoroundtoseconddigitafterdecimal.

Fig.6.2.3.1Variationof withnettensilestrain inextremetensionsteel,and forGrade420reinforcementandforprestressingsteel(seesec.6.2.3.2.2)

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6.2.3.2.3 Itshallbepermittedforcompressioncontrolledsections,asdefinedin6.3.3.3,thefollowing

optional, more conservative alternative values of strength reduction factor, where lesscontrolled construction environment justifies such selection according to engineering

judgmentofthedesigner:

Memberswithspiralreinforcementconformingto6.3.9.3 0.70

Otherreinforcedmembers 0.60

Forsectionsinwhichthenettensilestrainintheextremetensionsteelatnominalstrength,,isbetweenthelimitsforcompressioncontrolledandtensioncontrolledsections,shallbepermittedtobelinearlyincreased from that for compressioncontrolled sections to 0.90 as increases from the compressioncontrolledstrainlimitto0.005(AlsoseeFig. 6.2.3.2).While interpolating, it shallbepermittedtoroundtoseconddigitafterdecimal.

Fig. 6.2.3.2Variation of with net tensile strain in extreme tension steel,

and

for Grade 420

reinforcementand

for

prestressing

steel

with

reduced

values

of

(0.6

and

0.7)

for

compression

controlled sections (see sec.6.2.3.2.3, Optional application in case of less controlled

environmentasperengineeringjudgment)

6.2.3.2.4 Shearandtorsion 0.75

6.2.3.2.5 Bearingonconcrete(exceptforposttensionedanchoragezonesandstrutandtiemodels:

0.65

6.2.3.2.6 Strutandtiemodels(AppendixA),andstruts,ties,nodalzones,andbearingareasinsuch

models:0.75

6.2.3.2.7CalculationofdevelopmentlengthspecifiedinSec8.2doesnotrequirea strengthreduction

factor.

6.2.3.3 ForstructuresrelyingonintermediateprecaststructuralwallsinSeismicDesignCategoryD,

specialmomentframes,orspecialstructuralwallstoresistearthquakeeffects,,shallbemodifiedasgivenin(a)through(c):

a) Foranystructuralmemberthatisdesignedtoresist,ifthenominalshearstrengthofthememberislessthantheshearcorrespondingtothedevelopmentofthenominal

flexuralstrengthofthemember,forshearshallbe0.60.Thenominalflexuralstrengthshallbedeterminedconsideringthemostcriticalfactoredaxialloadsandincluding;

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b) Fordiaphragms,forshearshallnotexceedtheminimumforshearusedfortheverticalcomponentsoftheprimaryseismicforceresistingsystem;

c) Forjointsanddiagonallyreinforcedcouplingbeams,forshearshallbe0.85.6.2.3.4 Strengthreductionfactor shallbe0.60forflexure,compression, shear,andbearingof

structuralplainconcrete.

6.2.4 Designstrengthforreinforcement

The values of and used in design calculations shall not exceed 550 MPa, except for transversereinforcement in6.3.9.3andSec.8.3.6.2.5 Controlofdeflections6.2.5.1 Reinforcedconcretememberssubjectedtoflexureshallbedesignedtohaveadequate

stiffnesstolimitdeflectionsoranydeformationsthatmayadverselyaffectstrengthor

serviceabilityofastructure.

6.2.5.2 Onewayconstruction(nonprestressed)

6.2.5.2.1 MinimumthicknessstipulatedinTable6.2.5.1shallapplyforonewayconstruction not

supportingorattachedtopartitionsorotherconstruction likelytobedamagedbylarge

deflections, unlesscomputationofdeflectionindicatesalesserthicknesscanbeusedwithout

adverseeffects.

6.2.5.2.2 Wheredeflectionsaretobecomputed,deflectionsthatoccur immediatelyonapplicationof

load shall be computed by usual methods or formulas for elastic deflections, considering

effectsofcrackingandreinforcement onmemberstiffness.

TABLE 6.2.5.1 MINIMUM THICKNESS OF NONPRESTRESSED BEAMS OR ONEWAY SLABS UNLESS

DEFLECTIONSARECALCULATED

Minimumthickness,Simplysupported Oneend

continuous

Bothendscontinuous

Cantilever

MemberMembersnotsupportingorattachedtopartitionsorotherconstructionlikelytobe

damagedbylargedeflections

Solidone way

slabs

/20 /24 /28 /10

Beamsorribbedone wayslabs /16 /18.5 /21 /8

Notes:

Values given shall be used directly for members with normalweight concrete and Grade 420

reinforcement.Forotherconditions,thevaluesshallbemodifiedasfollows:

a) For lightweight concrete having equilibrium density, , in the range of1440 to1840kg/m3

, thevaluesshallbemultipliedby1.65 0 .0003 butnot lessthan1.09.b)For otherthan420MPa,thevaluesshallbemultipliedby0.4/700.6.2.5.2.3 Ifnotstiffnessvaluesareobtainedbyamorecomprehensiveanalysis,immediatedeflection

shallbecomputedwiththemodulusofelasticityforconcrete,,asspecifiedin6.1.7.1(normalweightorlightweightconcrete)andwiththeeffectivemomentofinertia,,asfollows,butnotgreaterthan 1 6.2.1

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where

6.2.2and

0.62

6.2.36.2.5.2.4 shallbepermittedtobetakenforcontinuousmembersastheaverageofvaluesobtainedfromEq.(6.2.1)forthecriticalpositiveandnegativemomentsections.Forprismaticmembers,shallbepermittedtobetakenasthevalueobtainedfromEq.(6.2.1)atmidspanforsimpleandcontinuousspans,andatsupportforcantilevers.

6.2.5.2.5 Ifthevaluesarenotobtainedbyamorecomprehensiveanalysis,additionallongterm

deflectionresultingfromcreepandshrinkageofflexuralmembers(normalweightor

lightweightconcrete)shallbedeterminedbymultiplyingtheimmediatedeflectioncausedby

thesustainedloadconsidered,bythefactor 6.2.4 whereshallbethevalueatmidspanforsimpleandcontinuousspans,andatsupportforcantilevers. Itshallbepermittedtoassume,thetimedependentfactorforsustainedloads,tobeequalto:

5yearsormore 2.0

12months 1.4

6months 1.2

3months 1.0

6.2.5.2.6 Thevalueofdeflectioncomputedinaccordancewith6.2.5.2.2through6.2.5.2.5shallnot

exceedlimitsstipulatedinTable6.2.5.2.

6.2.5.3 Twowayconstruction(nonprestressed)

6.2.5.3.1 Theminimumthicknessofslabsorothertwowayconstruction designedinaccordancewith

theprovisionsofSec.6.5andconformingwiththerequirementsof6.5.6.1.2shallbegoverned

bySection6.2.5.3.Thethicknessofslabswithoutinteriorbeamsspanningbetweenthe

supportsonallsidesshallsatisfytherequirementsof6.2.5.3.2or6.2.5.3.4.Thethicknessof

slabswithbeamsspanningbetweenthesupportsonallsidesshallsatisfyrequirementsof

6.2.5.3.3or6.2.5.3.4.

6.2.5.3.2 Ifslabsarewithoutinteriorbeamsspanningbetweenthesupportsandhavearatiooflongto

shortspannotgreaterthan2,theminimumthicknessshallbeinaccordancewiththe

provisionsofTable6.2.5.3andshallnotbelessthanthefollowingvalues:

Slabswithoutdroppanelsasdefinedin6.5.2.5 125mm;

Slabswithdroppanelsasdefinedin6.5.2.5 100mm.

TABLE6.2.5.2MAXIMUMALLOWABLECOMPUTEDDEFLECTIONS

Typeofmember Deflectiontobeconsidered Deflection

Flatroofsnotsupportingorattachedto

nonstructuralelementslikelytobedamaged

bylargedeflections

Immediatedeflectionduetoliveload /180

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Floorsnotsupportingorattachedto

nonstructuralelementslikelytobedamaged

bylargedeflections

Immediatedeflectionduetoliveload /360

Rooforfloorconstructionsupportingor

attachedtononstructuralelementslikelyto

bedamagedbylargedeflections

Thatpartofthetotaldeflection

occurringafterattachmentof

nonstructuralelements(sumofthe

longtermdeflectionduetoallsustainedloadsandtheimmediate

deflectionduetoanyadditionallive

load)

/480

Rooforfloorconstructionsupportingor

attachedtononstructuralelementsnotlikely

tobedamagedbylargedeflections

l/240

*Limitnotintendedtosafeguardagainstponding.Pondingshouldbecheckedbysuitablecalculations

ofdeflection,includingaddeddeflectionsduetopondedwater,andconsideringlongtermeffectsofall

sustainedloads,camber,constructiontolerances,andreliabilityofprovisionsfordrainage.

Longtermdeflectionshallbedeterminedinaccordancewith6.2.5.2.5,butmaybereducedbyamount

ofdeflectioncalculatedtooccurbeforeattachmentofnonstructuralelements.Thisamountshallbe

determinedon

basis

ofaccepted

engineering

data

relating

totime

deflection

characteristics

of

memberssimilartothosebeingconsidered.

Limitmaybeexceededifadequatemeasuresaretakentopreventdamagetosupportedorattached

elements.

Limitshallnotbegreaterthantoleranceprovidedfornonstructuralelements.Limitmaybeexceeded

TABLE6.2.5.3MINIMUM THICKNESSOFSLABSWITHOUTINTERIORBEAMS*

, MPaWithout drop panels With drop panels

Exteriorpanels Interior Exteriorpanels Interior

Without

edgebeams

Withedge

beams

Without

edgebeams

Withedge

beams

280 /33 /36 /36 /36 /40 /40420 /30 /33 /33 /33 /36 /36520 /28 /31 /31 /31 /34 /34

*For twoway construction, is the length of clear span in the long direction,measuredfacetofaceofsupportsinslabswithoutbeamsandfacetofaceofbeamsor

othersupportsinothercases.

For between the values given in the table, minimum thickness shall bedeterminedbylinearinterpolation.

Droppanelsasdefinedin6.5.2.5.

Slabswithbeamsbetweencolumnsalongexterioredges.Thevalueof fortheedgebeamshallnotbelessthan0.8.6.2.5.3.3 Theminimumthickness,forslabswithbeamsspanningbetweenthesupportsonallsides,

shallbeasfollows:

a) Forequaltoorlessthan0.2,theprovisionsof6.2.5.3.2shallapply;b) Forgreaterthan0.2butnotgreaterthan2.0,shallnotbelessthan . . (6.2.5)

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andnotlessthan125mm;

c) For greaterthan2.0,shallnotbelessthan . 6.2.6andnotlessthan90mm;

d) An edge beam with a stiffness ratio not less than 0.80 shall be provided atdiscontinuousedges,ortheminimumthicknessrequiredbyEq.(6.2.5)or(6.2.6)shallbeincreasedbyatleast10percentinthepanelwithadiscontinuousedge.

Termin(b)and(c)islengthofclearspaninlongdirectionmeasuredfacetofaceofbeams.Term in(b)and(c)isratioofclearspansinlongtoshortdirectionofslab.

6.2.5.3.4 WhencomputeddeflectionsdonotexceedthelimitsofTable6.2.5.2,slabthicknesslessthan

the minimum required by6.2.5.3.1, 6.2.5.3.2, and 6.2.5.3.3 shall be permitted.Deflections

shallbecomputedtakingintoaccountsizeandshapeofthepanel,conditionsofsupport,and

natureofrestraintsatthepaneledges.Themodulusofelasticityofconcrete,,shallbeasspecified in6.1.7.1.Theeffectivemomentof inertia, , shallbe thatgivenbyEq. (6.2.1);othervaluesshallbepermittedtobeusediftheyresultincomputeddeflectionsinreasonable

agreement with results of comprehensive tests. Additional longterm deflection shall be

computedinaccordancewith6.2.5.2.5.

6.2.5.4 Compositeconstruction

6.2.5.4.1 Shoredconstruction

Where composite flexural members are supported during construction so that, after removal of

temporarysupports,deadloadisresistedbythefullcompositesection,itshallbepermittedtoconsider

the compositememberequivalent toa monolithically castmember for computationofdeflection. For

nonprestressedmembers,theportionofthemember incompressionshalldeterminewhethervalues in

Table6.2.5.1fornormalweightorlightweightconcreteshallapply.Ifdeflectioniscomputed,accountshall

betakenofcurvaturesresultingfromdifferentialshrinkageofprecastandcastinplacecomponents,and

ofaxialcreepeffectsinaprestressedconcretemember.

6.2.5.4.2 Unshoredconstruction

When the thickness of a nonprestressed precast flexural member meets the requirements of Table

6.2.5.1,deflectionneednotbecomputed.Ifthethicknessofanonprestressedcompositemembermeets

the requirementsofTable6.2.5.1, it isnotrequired tocomputedeflectionoccurringafter themember

becomes composite, but the longterm deflection of the precast member shall be investigated for

magnitudeanddurationofloadpriortobeginningofeffectivecompositeaction.

6.2.5.4.3 The computed deflection in accordance with 6.2.5.4.1 or 6.2.5.4.2 shall not exceed limits

stipulatedinTable6.2.5.2.

6.3 AXIALLOADSANDFLEXURE

6.3.1 ScopeTheprovisionsofSec.6.3shallbeapplicabletothedesignofmemberssubjecttoflexureoraxialloadsor

acombinationthereof.

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6.3.2 Designassumptions6.3.2.1 Theassumptionsgiven in6.3.2.2through6.3.2.7,andsatisfactionofapplicableconditionsof

equilibriumandcompatibilityofstrainsshallformthebasisofstrengthdesignofmembersfor

flexureandaxialloads.

6.3.2.2 Itshallbeassumed thatstrain inreinforcementandconcrete isdirectlyproportional tothe

distancefromtheneutralaxis,exceptthat,fordeepbeamsasdefinedin6.3.7.1,ananalysis

that considers a nonlinear distribution of strain shall be used. Alternatively, it shall be

permittedtouseastrutandtiemodel.See6.3.7,6.4.6,andAppendixA.

6.3.2.3 Itshallbeassumedthatthemaximumusablestrainatextremeconcretecompressionfiberis

equalto0.003.

6.3.2.4 For stress in reinforcementbelow, it shallbe takenas times steel strain.For strainsgreater than that corresponding to , stress in reinforcement shall be consideredindependentofstrainandequalto.

6.3.2.5 Inaxialandflexuralcalculations ofreinforcedconcrete,thetensilestrengthofconcreteshall

beneglected.

6.3.2.6 Therelationshipbetweenconcretecompressivestressdistributionandconcretestrainshall

be assumed to be rectangular, trapezoidal, parabolic, or any other shape that results in

predictionofstrengthinsubstantialagreementwithresultsofcomprehensive tests.

6.3.2.7 Anequivalentrectangularconcretestressdistributiondefinedby6.3.2.7.1through6.3.2.7.3

belowshallsatisfytherequirementsof6.3.2.6.

6.3.2.7.1 Concrete stress of 0.85shall be assumed uniformly distributed over an equivalentcompressionzoneboundedbyedgesofthecrosssectionandastraightlinelocatedparallelto

theneutralaxisatadistance fromthefiberofmaximumcompressivestrain.6.3.2.7.2 Distance from the fiber of maximum strain to the neutral axis, , shall be measured in adirectionperpendicular totheneutralaxis.6.3.2.7.3 Forbetween17and28MPa,shallbetakenas0.85.Forabove28MPa,shallbe

reducedlinearlyatarateof0.05foreach7MPaofstrengthinexcessof28MPa,butshallnotbetaken lessthan0.65.Forbetween28and56MPa,maybecalculatedfromEq.(6.3.1). 0.85 0.007143 28 0.65 0.85 6.3.1

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6.3.3 Generalprinciplesandrequirements6.3.3.1 Stressandstraincompatibilityusingassumptionsin6.3.2shallbethebasisfordesignofcross

sectionssubjecttoflexureoraxialloads,oracombinationthereof.

6.3.3.2 A cross section shall be considered to be in balanced strain conditions when the tension

reinforcement reachesthestraincorrespondingto justasconcreteincompressionreachesitsassumedultimatestrainof0.003.6.3.3.3 Sectionsarecompressioncontrolledifthenettensilestrainintheextremetensionsteel,,is

equal to or less than the compressioncontrolled strain limit when the concrete in

compression reaches its assumed strain limit of 0.003 (Fig.6.3.3.1). The compression

controlled strain limit is the net tensile strain in the reinforcement at balanced strain

conditions. For Grade 420 reinforcement, it shall be permitted to set the compression

controlled strain limit equal to 0.002. For other grades compressioncontrolled strain limit

maybedeterminedbydividingtheyieldstrengthbymodulusofelasticityEandthenrounding

the value obtained to four significantdigits after the decimal. For example, for Grade500

reinforcement,the

compression

controlled

strain

limit

shall

equal

to0.0025.

Fig.6.3.3.1Straindistributionandnettensilestrain

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6.3.3.4 Sections are tensioncontrolled if the net tensile strain in the extreme tension steel, , isequaltoorgreaterthan0.005whentheconcreteincompressionreachesitsassumedstrain

limit of 0.003. Sections with between the compressioncontrolled strain limit and 0.005constitute a transition region between compressioncontrolled and tensioncontrolled

sections.

6.3.3.5 Nettensilestrain intheextremetensionsteelatnominalstrength,

shallnotbe lessthan

0.004fornonprestressedflexuralmembersandnonprestressedmemberswithfactoredaxialcompressiveloadlessthan0.10

6.3.3.5.1 Useofcompressionreinforcement shallbepermitted inconjunctionwithadditionaltension

reinforcementtoincreasethestrengthofflexuralmembers.

6.3.3.6 Forcompressionmembers,designaxialstrengthshallnotbetakengreaterthan,,computedbyEq.(6.3.2)or(6.3.3).

6.3.3.6.1 FornonprestressedmemberswithspiralreinforcementconformingtoSec.8.1orcomposite

membersconformingto6.3.13:

, 0.850.85

(6.3.2)

6.3.3.6.2 Fornonprestressed memberswithtiereinforcementconformingtoSec.8.1:, 0.800.85 (6.3.3)6.3.3.7 Memberssubjecttocompressiveaxialloadshallbedesignedforthemaximummomentthat

canaccompanytheaxialload.Thefactoredaxialforceatgiveneccentricityshallnotexceedthatgiven in6.3.3.6.Themaximumfactoredmomentshallbemagnifiedforslendernesseffectsinaccordancewith6.3.10.

6.3.4 Spacingoflateralsupportsforflexuralmembers6.3.4.1 Distancebetweenlateralsupportsforabeamshallnotexceed50times

,theleastwidthof

compressionflangeorface.

6.3.4.2 Effects of lateral eccentricityof load shallbe taken intoaccount in determining spacing of

lateralsupports.

6.3.5 Minimumreinforcementformembersinflexure6.3.5.1 Atevery sectionofa flexuralmemberwhere tensile reinforcement is requiredbyanalysis,

except as provided in 6.3.5.2, 6.3.5.3, and 6.3.5.4, provided shall not be less than thatgivenby

,.

6.3.4andnotlessthan1.4/.

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6.3.5.2 Forstaticallydeterminatememberswithaflangeintension,,shallnotbelessthanthevaluegivenbyEq.(6.3.4),exceptthatisreplacedbyeither2orthewidthoftheflange,whicheverissmaller.

6.3.5.3 If,ateverysection,providedisatleastonethirdgreaterthanthatrequiredbyanalysis,therequirementsof6.3.5.1and6.3.5.2neednotbeapplied.

6.3.5.4 Forstructuralslabsandfootingsofuniformthickness,,inthedirectionofthespanshallbe the same as that required by 8.1.11. Maximum spacing of this reinforcement shall not

exceedthreetimesthethickness,nor450mm.

6.3.6 Distributionofflexuralreinforcementinone-wayslabsandbeams6.3.6.1 Rules fordistributionof flexural reinforcement to control flexural cracking inbeamsand in

onewayslabs(slabsreinforcedtoresistflexuralstressesinonlyonedirection)areprescribed

inthissection.

6.3.6.2 Distribution offlexuralreinforcementintwowayslabsshallbeasrequiredby6.5.3.

6.3.6.3 As prescribed in 6.3.6.4, flexural tension reinforcement shall be well distributed within

maximumflexuraltensionzonesofamembercrosssection.

6.3.6.4 Thespacingofreinforcementclosesttothetensionface,,shallbelessthanthatgivenby 380 2.5 (6.3.5)but shall not exceed 300280/, where is the least distance from surface ofreinforcement to the tension face. If there isonly onebar orwire nearest to the extreme

tensionface,usedinEq.(6.3.5)isthewidthoftheextremetensionface.Calculated stress in reinforcement closest to the tension face at service load shall becomputedbasedontheunfactoredmoment.Itshallbepermittedtotake

as

2/3.

6.3.6.5 Forstructuressubjecttoveryaggressiveexposureordesignedtobewatertight,provisionsof

6.3.6.4 are not sufficient. For such structures, special investigations and precautions are

required.

6.3.6.6 When flanges of Tbeam construction are in tension, part of the flexural tension

reinforcement shallbedistributedoveraneffective flangewidthasdefined in6.1.13,ora

widthequaltoonetenththespan,whicheverissmaller.Iftheeffectiveflangewidthexceeds

onetenththespan,some longitudinalreinforcement shallbeprovided intheouterportions

oftheflange.

6.3.6.7 Longitudinal skin reinforcement shall be uniformly distributed along both side faces of a

member(Fig.6.3.6.1),whereofabeamorjoistexceeds900mm.Skinreinforcementshallextendforadistance 2 fromthetensionface.Thespacingshallbeasprovidedin6.3.6.4,where isthe leastdistancefromthesurfaceoftheskinreinforcementtothesideface.Itshall be permitted to include such reinforcement in strength computations if a strain

compatibility analysisismadetodeterminestressintheindividualbarsorwires.

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Fig.6.3.6.1Skinreinforcementforbeamsandjoistswithh >900mm.

6.3.7 Deepbeams6.3.7.1 Deepbeamsaremembers loadedonone faceand supportedon theopposite face so that

compressionstrutscandevelopbetweentheloadsandthesupports,andhaveeither:

a) clearspans,,equaltoorlessthanfourtimestheoverallmemberdepth;orb) regions with concentrated loadswithin twice thememberdepth from the face of the

support.

Deepbeamsshallbedesignedeithertakingintoaccountnonlineardistributionofstrain,orby

AppendixA.(Seealso6.4.6.1and8.2.7.6)Lateralbucklingshallbeconsidered.

6.3.7.2 ofdeepbeamsshallbeinaccordancewith6.4.6.6.3.7.3 Minimumareaofflexuraltensionreinforcement,,,shallconformto6.3.5.6.3.7.4 Minimumhorizontalandverticalreinforcementinthesidefacesofdeepbeamsshallsatisfy

eitherA.3.3or6.4.6.4and6.4.6.5.

6.3.8 Designdimensionsforcompressionmembers6.3.8.1 Isolatedcompressionmemberwithmultiplespirals

Outerlimitsoftheeffectivecrosssectionofacompressionmemberwithtwoormoreinterlockingspirals

shallbetakenatadistanceoutsidetheextremelimitsofthespiralsequaltotheminimumconcretecover

requiredby8.1.7.

6.3.8.2 Monolithicallybuiltcompressionmemberwithwall

Outerlimitsoftheeffectivecrosssectionofaspirallyreinforcedortiedreinforcedcompressionmember

builtmonolithicallywithaconcretewallorpiershallbetakennotgreaterthan40mmoutsidethespiral

ortiereinforcement.

6.3.8.3 Equivalentcircularcompressionmemberreplacingothershapes

Inlieuofusingthefullgrossareafordesignofacompressionmemberwithasquare,octagonal,orother

shaped cross section, it shallbepermitted tousea circular sectionwithadiameterequal to the least

lateraldimensionoftheactualshape.Grossareaconsidered,requiredpercentageofreinforcement,and

designstrengthshallbebasedonthatcircularsection.

6.3.8.4 Limitsofsection

Foracompressionmemberwithacrosssectionlargerthanrequiredbyconsiderations ofloading,itshall

bepermittedtobasetheminimumreinforcementandstrengthonareducedeffectiveareanot less

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thanonehalfthetotalarea.Thisprovisionshallnotapplytospecialmomentframesorspecialstructural

wallsdesignedinaccordancewithSec.8.3.

6.3.9 Limitsofreinforcementforcompressionmembers6.3.9.1 Fornoncompositecompressionmembers,theareaoflongitudinalreinforcement,

,shallbe

not less than 0.01

or more than 0.06. To avoid practical difficulties in placing andcompactingofconcreteaswellastodeliverductilitytononcompositecompressionmembers,areaoflongitudinal reinforcement, ,ispreferrednottoexceed0.04 unlessabsolutelyessential.

6.3.9.2 Minimumnumber of longitudinal bars in compressionmembers shallbe4 for bars within

rectangularorcircularties,3forbarswithintriangularties,and6forbarsenclosedbyspirals

conformingto6.3.9.3.

6.3.9.3 Volumetricspiralreinforcementratio,,shallbenotlessthanthevaluegivenby

0.45

1

6.3.6wherethevalueofusedinEq.(6.3.6)shallnotexceed700MPa.Forgreaterthan420MPa,lapsplicesaccordingto8.1.9.3(e)shallnotbeused.6.3.10 Slendernesseffectsincompressionmembers

6.3.10.1 Slendernesseffectsshallbepermittedtobeneglectedinthefollowingcases:

a) forcompressionmembersnotbracedagainstsideswaywhen: 22 6.3.7b) forcompressionmembersbracedagainstsideswaywhen: 34 12 40 6.3.8

where

ispositiveifthecolumnisbentinsinglecurvature,andnegativeifthemember isbentin

doublecurvature.

Compressionmembersmaybeconsideredtobebracedagainstsideswaywhenbracingelementshavea

total stiffness, resisting lateral movement of that story, of at least 12 times the gross stiffness of the

columnswithinthestory.

TheJacksonandMorelandAlignmentCharts(Fig.6.3.10.1),whichallowagraphicaldeterminationofforacolumnofconstantcrosssectioninamultibayframemaybeusedastheprimarydesignaidtoestimate

theeffectivelengthfactor.

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6.3.10.1.1 Theunsupported lengthofa compressionmember, , shallbe takenas the cleardistancebetween floor slabs,beams, orother members capable of providing lateral support in the

direction being considered. Where column capitals or haunches are present, shall bemeasuredtothelowerextremityofthecapitalorhaunchintheplaneconsidered.

6.3.10.1.2 It shall be permitted to take the radius of gyration, , equal to 0.30 times the overalldimensioninthedirectionstabilityisbeingconsideredforrectangularcompressionmembers

and0.25timesthediameterforcircularcompressionmembers.Forothershapes, itshallbepermittedtocomputeforthegrossconcretesection.

Fig.6.3.10.1Effectivelengthfactorsk.

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6.3.10.2 When slenderness effects are not neglected as permitted by 6.3.10.1, the design of

compressionmembers,restrainingbeams,andothersupportingmembersshallbebasedon

thefactoredforcesandmomentsfromasecondorderanalysissatisfying6.3.10.3,6.3.10.4,or

6.3.10.5.Thesemembersshallalsosatisfy6.3.10.2.1and6.3.10.2.2.Thedimensionsofeach

membercrosssectionusedintheanalysisshallbewithin10percentofthedimensionsofthe

membersshown

on

the

design

drawings

orthe

analysis

shall

be

repeated.

6.3.10.2.1 Totalmomentincludingsecondordereffectsincompressionmembers,restrainingbeams,or

otherstructuralmembersshallnotexceed1.4timesthemomentduetofirstordereffects.

6.3.10.2.2 Secondordereffectsshallbeconsideredalongthe lengthofcompressionmembers.Itshall

bepermittedtoaccountfortheseeffectsusingthemomentmagnificationprocedureoutlined

in6.3.10.6.

6.3.10.3 Nonlinearsecondorderanalysis

Secondorderanalysisshallconsidermaterialnonlinearity,membercurvatureandlateraldrift,durationof

loads,shrinkageandcreep,and interactionwiththesupportingfoundation.Theanalysisprocedureshall

have

been

shown

to

result

in

prediction

of

strength

in

substantial

agreement

with

results

of

comprehensivetestsofcolumnsinstaticallyindeterminatereinforcedconcretestructures.

6.3.10.4 Elasticsecondorderanalysis

Elastic secondorder analysis shall consider section properties determined taking into account the

influenceofaxialloads,thepresenceofcrackedregionsalongthelengthofthemember,andtheeffects

ofloadduration.

6.3.10.4.1 Itshallbepermittedtousethefollowingpropertiesforthemembersinthestructure:

a) Modulusofelasticity...................... from6.1.7.1b) Momentsofinertia,Compressionmembers:

Columns 0.70Walls Uncracked 0.70Cracked 0.35

Flexuralmembers:

Beams 0.35Flatplatesandflatslabs 0.25c) Area 1.0Alternatively, the moments of inertia of compression and flexural members, , shall bepermittedtobecomputedasfollows:

Compressionmembers: 0.80 25 1 0.5 0.875 (6.3.9)where and shall be determined from the particular load combination underconsideration, orthecombinationofanddeterminedinthesmallestvalueof.neednotbetakenlessthan0.35.Flexuralmembers: 0.10 25 1.20.2 0.5 (6.3.10)

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Forcontinuous flexuralmembers,shallbepermitted tobetakenas theaverageofvaluesobtainedfromEq.(6.3.10)forthecriticalpositiveandnegativemomentsections.neednotbetakenlessthan0.25.Thecrosssectionaldimensionsandreinforcementratiousedintheaboveformulasshallbewithin10percentofthedimensionsandreinforcement ratioshown

onthedesigndrawingsorthestiffnessevaluationshallberepeated.

6.3.10.4.2 When sustained lateral loads are present, for compression members shall be divided by1

.The term

shallbe takenas the ratioofmaximum factoredsustainedshear

withina story to themaximum factored shear in that storyassociatedwith the same load

combination,butshallnotbetakengreaterthan1.0.

6.3.10.5 Procedureformomentmagnification

Columnsandstoriesinstructuresshallbedesignatedasnonswayorswaycolumnsorstories.Thedesign

ofcolumnsinnonswayframesorstoriesshallbebasedon6.3.10.6.Thedesignofcolumnsinswayframes

orstoriesshallbebasedon6.3.10.7.

6.3.10.5.1 A column in a structure shall be permitted to be assumed as nonsway if the increase in

column end moments due to secondordereffects does not exceed 5 percent of the first

orderendmoments.

6.3.10.5.2 Astorywithinastructureispermittedtobeassumedasnonswayif: 0.05 (6.3.11)whereandarethetotalfactoredverticalloadandthehorizontalstoryshear,respectively,inthestorybeingevaluated,andisthefirstorderrelativelateraldeflectionbetweenthetopandthebottomofthatstorydueto.6.3.10.6 ProcedureformomentmagnificationNonsway

Compressionmembersshallbedesignedforfactoredaxial forceandthefactoredmomentamplifiedfortheeffectsofmembercurvaturewhere (6.3.12)

where

. 1.0 (6.3.13)and

6.3.146.3.10.6.1 shallbetakenas

. (6.3.15)or

.

(6.3.16)

Asanalternative,shallbepermittedtobecomputedusingthevalueoffromEq.(6.3.9)dividedby1 .

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6.3.10.6.2 Thetermshallbetakenastheratioofmaximumfactoredaxialsustainedloadtomaximumfactoredaxialloadassociatedwiththesameloadcombination, butshallnotbe

takengreaterthan1.0.

6.3.10.6.3 Theeffectivelengthfactor,,shallbepermittedtobetakenas1.0.6.3.10.6.4 Formemberswithnotransverseloadbetweensupports,shallbetakenas 0.6 0.4 (6.3.17)where ispositiveifthecolumnisbentinsinglecurvature,andnegativeifthememberisbentindoublecurvature.Formemberswithtransverseloadsbetweensupports,shallbetakenas1.0.6.3.10.6.5 Factoredmoment,,inEq.(6.3.12)shallnotbetakenlessthan, 15 0.03 (6.3.18)abouteachaxisseparately,where0.6andare inmm.Formembers inwhich,exceeds,thevalue of in Eq. (6.3.17) shall either be taken equal to 1.0, or shall be based on the ratio of thecomputedendmoments, .6.3.10.7 Procedure

for

moment

magnification

Sway

Momentsandattheendsofanindividualcompressionmembershallbetakenas (6.3.19) (6.3.20)whereiscomputedaccordingto6.3.10.7.3or6.3.10.7.4.6.3.10.7.1 Flexuralmembersshallbedesignedforthetotalmagnifiedendmomentsofthecompression

membersatthejoint.

6.3.10.7.2 Thevaluesofand given in6.3.10.4shallbeused fordetermining theeffective lengthfactoranditshallnotbelessthan1.0.

6.3.10.7.3 Themomentmagnifiershallbecalculatedas 1 (6.3.21)IfcalculatedbyEq. (6.3.21)exceeds1.5,shallbecalculatedusingsecondorderelasticanalysisor6.3.10.7.4.

6.3.10.7.4 Alternatively,itshallbepermittedtocalculateas . 1 (6.3.22)whereisthesummationforallthefactoredverticalloadsinastoryandisthesummationforallswayresistingcolumnsinastory.iscalculatedusingEq.(6.3.14)with determinedfrom6.3.10.7.2andfrom6.3.10.6.1.

6.3.11 AxiallyloadedmemberssupportingslabsystemAxiallyloadedmemberssupportingaslabsystemincludedwithinthescopeof6.5.1shallbedesignedas

providedinSec.6.3andinaccordancewiththeadditionalrequirementsofSec.6.5.

6.3.12 ColumnloadtransmissionthroughfloorsystemIfofacolumnisgreaterthan1.4timesthatofthefloorsystem,transmissionofloadthroughthefloorsystemshallbeprovidedby6.3.12.1,6.3.12.2,or6.3.12.3.

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6.3.12.1 Concrete of strength specified for the column shall be placed in the floor at the column

location. Top surface of the column concrete shall extend 2 ft into the slab from face of

column.Columnconcreteshallbewell integratedwithfloorconcrete,andshallbeplaced in

accordancewithrelevantprovisionsforconstructionjointsofcolumns,wallsetc.withbeams,

slabsetc.Toavoidaccidentalplacingoflowerstrengthconcreteinthecolumns,thestructural

designershall indicateon thedrawingwherethehighand lowstrengthconcretesare tobe

placed.

6.3.12.2 Strengthofacolumn througha floorsystemshallbebasedon the lowervalueofconcrete

strengthwithverticaldowelsandspiralsasrequired.

6.3.12.3 Forcolumns laterallysupportedonfoursidesbybeamsofapproximatelyequaldepthorby

slabs,itshallbepermittedtobasestrengthofthecolumnonanassumedconcretestrengthin

the columnjointequal to75percentof column concrete strengthplus35percentof floor

concretestrength.Intheapplicationof6.3.12.3,theratioofcolumnconcretestrengthtoslab

concretestrengthshallnotbetakengreaterthan2.5fordesign.

6.3.13 Compositecompressionmembers6.3.13.1 All

members

reinforced

longitudinally

with

structural

steel

shapes,

pipe,

or

tubing

with

or

withoutlongitudinalbarsshallbeincludedincompositecompressionmembers.

6.3.13.2 Acompositememberstrengthshallbecomputedforthesamelimitingconditionsapplicable

toordinaryreinforcedconcretemembers.

6.3.13.3 Anyaxial loadstrengthassigned toconcreteofacompositemembershallbe transferredto

theconcretebymembersorbracketsindirectbearingonthecompositememberconcrete.

6.3.13.4 Allaxialloadstrengthnotassignedtoconcreteofacompositemembershallbedevelopedby

directconnectiontothestructuralsteelshape,pipe,ortube.

6.3.13.5 Forevaluationofslendernesseffects,radiusofgyration,

,ofacompositesectionshallbenot

greaterthanthevaluegivenby

/ (6.3.23)and,asanalternativetoamoreaccuratecalculation,inEq.(6.3.14)shallbetakeneitherasEq.(6.3.15)or

/ (6.3.24)6.3.13.6 Concretecoreencasedbystructuralsteel

6.3.13.6.1 Whenacompositemember isastructuralsteelencasedconcretecore,thethicknessof the

steelencasementshallbenotlessthan foreachfaceofwidthnor forcircularsectionsofdiameter6.3.13.6.2 Whencomputingand,longitudinalbarslocatedwithintheencasedconcretecoreshall

bepermittedtobeused.

6.3.13.7 Spiralreinforcementaroundstructuralsteelcore

A composite member with spirally reinforced concrete around a structural steel core shall conform to

6.3.13.7.1through6.3.13.7.4.

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6.3.13.7.1 Designyieldstrengthofstructuralsteelcoreshallbethespecifiedminimumyieldstrengthfor

thegradeofstructuralsteelusedbutnottoexceed350MPa.

6.3.13.7.2 Spiralreinforcementshallconformto6.3.9.3.

6.3.13.7.3 Longitudinalbarslocatedwithinthespiralshallbenotlessthan0.01normorethan0.06times

netareaofconcretesection.

6.3.13.7.4 Longitudinalbarslocatedwithinthespiralshallbepermittedtobeusedincomputingand.6.3.13.8 Tiereinforcementaroundstructuralsteelcore

Laterally tied concrete around a structural steel core forming a composite member shall conform to

6.3.13.8.1through6.3.13.8.7.

6.3.13.8.1 Designyieldstrengthofstructuralsteelcoreshallbethespecifiedminimumyieldstrengthfor

thegradeofstructuralsteelusedbutnottoexceed350MPa.

6.3.13.8.2 Lateralties

shall

extend

completely

around

the

structural

steel

core.

6.3.13.8.3 Lateral ties shall have a diameter not less than 0.02 times the greatest side dimension of

compositemember,exceptthattiesshallnotbesmallerthan10mmandarenotrequired

tobelargerthan16mm.Weldedwirereinforcementofequivalentareashallbepermitted.

6.3.13.8.4 Vertical spacing of lateral ties shall not exceed 16 longitudinal bar diameters, 48 tie bar

diameters,or0.5timestheleastsidedimensionofthecompositemember.

6.3.13.8.5 Longitudinalbarslocatedwithinthetiesshallbenotlessthan0.01normorethan0.06times

netareaofconcretesection.

6.3.13.8.6 A longitudinal barshallbe locatedateverycornerofarectangularcrosssection,withother

longitudinal bars spaced not farther apart than onehalf the least side dimension of the

compositemember.

6.3.13.8.7 Longitudinalbarslocatedwithinthetiesshallbepermittedtobeusedincomputingand.6.3.14 Bearingstrength6.3.14.1 Design bearing strength of concrete shall not exceed 0.85, except when the

supportingsurfaceiswideronallsidesthantheloadedarea,thenthedesignbearingstrength

of the loadedareashallbepermittedtobemultipliedby butbynotmore than2(Fig.6.3.14.1).

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Fig.6.3.14.1 DeterminationorareaA2insteppedorslopedsupportsusingfrustum(6.3.14.1).

6.3.15 DesignforFlexure6.3.15.1 DesignofRectangularBeams

a) Formula for singly reinforced beams : The following equations which are based on the

simplifiedstressblockof 6.3.2.7,are applicabletosinglyreinforcedrectangular beamsalongwithTbeamswheretheneutralaxislieswithintheflange.

/ (6.3.25)where

. (6.3.26)

Loaded area

Loaded area

A 1

A 1

A 2

45 deg

45 deg

Plan

Load

is measured on this plane

Elevation

2

1

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Byestimatinganinitialvalueofa,Eq(6.3.25)canbeusedtodetermineanapproximate

valueof.ThatvaluecanbesubstitutedinEq(6.3.26)togetabetterestimateofandhenceanew /2 canbedeterminedforsubstitutioninEq(6.3.25).InEq(6.3.25),nominalflexuralstrengthofsection,

maybetakenasfactoredmoment

atsection,dividedbystrengthreduction factor, 0.9asapreliminaryvalue.determined fromEq (6.3.25) shallhave togivea reinforcement ratio, notexceeding,where 0.85 1 0.004 (6.3.27)Above, 0.003 Additionally,determined fromEq (6.3.25) shallhave to satisfy the requirementsofminimumreinforcementformembersinflexureasper6.3.5.

Revisedshallbedeterminedfrom6.2.3.2basedoneither 1 or,whereisthenettensilestraininthereinforcementfurthestfromthecompressionfaceofthe

concrete at the depth. Strain, may be calculated from Eq. (6.3.27) by replacing0.004by andby.b) Design formulae fordoublyreinforcedbeams:Adoublyreinforcedbeamshallbedesigned

onlywhenthere isarestrictionondepthofbeamandmaximumtensilereinforcementallowed

cannotproducetherequiredmoment.Toestablishifdoublyreinforcedbeamisrequiredthefollowingapproachcanbefollowed:

Determine,

0.005 0.85 1

0.005 (6.3.28)

0.005 . (6.3.29)If is less thanrequiredmomentwith 0.9 ,adoubly reinforcedbeam isneededandthentakingvaluesofandfromabove,put and Then,thefollowingvaluesaretobeevaluated,

(6.3.30)

Assumingcompressionsteelyields(needstobecheckedlater), Check forcompressionsteelyielding,where

0.85 (6.3.31)If (i.e.compressionsteelyields),

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find . andfind,andconfirm 0.9 intheaboveequations.Valueof shallbe determined from 6.2.3.2 based on either or , as stated above forrectangularbeams.

If compression steel does not yield, is to be found from concrete section force equilibriumcondition,C=Twhichwillresultinaquadraticequationof.needstobecalculatedfromstraindiagramand revised.

shallbecalculatedfromforfinding.6.3.15.2 DesignofTBeams

a) General:

For effective widths and other parameters for T, L or isolated beams, 6.1.13.2 to

6.1.13.4shallapply.

b) FormulaeforTbeams:ATbeamshallbetreatedasarectangularbeamif

where

isobtainedfrom Eq(6.3.26).InusingEq(6.3.

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