Draft

11.4ACICode 195

whereloadcombinationsshallincludebothfullvalueandzerovalueof L to determinethemore

severecondition,and

U= 0: 9 D+ 1: 3 W

butforany combinationof D,L, andW,requiredstrengthU shallnotbe lessthanEq.(9-1).

9.3.1- Designstrengthprovidedby a member,itsconnectionsto othermembers,andits

crosssections,in termsof
exure,axialload,shear,andtorsion,shallbe taken as thenominal

strengthcalculatedin accordancewithrequirements andassumptionsof thiscode,multiplied

by a strengthreductionfactor.

9.3.2- Strengthreductionfactor shallbe as follows:

9.3.2.1- Flexure,withoutaxialload0.90

9.4- Designstrengthforreinforcement Designsshallnotbe basedona yieldstrengthof

reinforcementfyin excessof 80,000psi,exceptforprestressingtendons.

10.2.2- Strainin reinforcement andconcreteshallbe assumeddirectlyproportionalto

thedistancefromtheneutralaxis,except,fordeep
exuralmemberswithoveralldepthto

clearspanratiosgreaterthan2/5forcontinuousspansand4/5forsimplespans,a non-linear

distributionof strainshallbe considered.SeeSection10.7.

10.2.3- Maximumusablestrainat extremeconcretecompressionber shallbe assumed

equalto 0.003.

10.2.4- Stressin reinforcement below speciedyieldstrengthfyforgradeof reinforcement

usedshallbe taken asEstimessteelstrain.For strainsgreaterthanthatcorrespondingtofy,

stressin reinforcement shallbe consideredindependent of strainandequaltofy.

10.2.5- Tensilestrengthof concreteshallbe neglectedin
exuralcalculationsof reinforced

concrete,exceptwhenmeetingrequirements of Section18.4.

10.2.6- Relationshipbetweenconcretecompressive stressdistributionandconcretestrain

may be assumedto be rectangular,trapezoidal,parabolic,or any othershape thatresultsin

predictionof strengthin substantialagreement withresultsof comprehensive tests.

10.2.7- Requirements of Section10.2.5may be consideredsatisedby anequivalent rect-

angularconcretestressdistributiondenedby thefollowing:

10.2.7.1- Concretestressof 0: 85 f

0

cshallbe assumeduniformlydistributedover anequiva-

lent compressionzoneboundedby edgesof thecrosssectionanda straight linelocatedparallel

to theneutralaxisat a distance(a= 1 c) fromtheber of maximumcompressive strain.

10.2.7.2- Distancecfromber of maximumstrainto theneutralaxisshallbe measured

in a directionperpendicularto thataxis.

10.2.7.3- Factor 1 shallbe takenas 0.85forconcretestrengthsf

0

cupto andincluding

4,000psi.For strengthsabove 4,000psi, 1 shallbe reducedcontinuouslyat a rateof 0.05for

each 1000psiof strengthin excessof 4,000psi,but 1 shallnotbe takenlessthan0.65.

10.3.2- Balancedstrain conditionsexist ata crosssectionwhentensionreinforcement

reachesthestraincorrespondingto its speciedyieldstrengthfyjustas concretein compression

reachesitsassumedultimatestrainof 0.003.

10.3.3- For
exuralmembers,andformemberssubjectto combined
exureandcompres-

sive axialloadwhenthedesignaxialloadstrength(Pn) is lessthanthesmallerof (0: 10 f

0

c

Ag)

or (Pb), theratioof reinforcement p providedshallnotexceed0.75of theratiobthatwould

producebalancedstrainconditionsforthesectionunder
exurewithoutaxialload.For mem-

berswithcompressionreinforcement, theportionofbequalizedby compressionreinforcement

neednotbe reducedby the0.75factor.

10.3.4- Compressionreinforcement in conjunctionwithadditionaltensionreinforcement

may be usedto increasethestrengthof
exuralmembers.