building structural part 3

ConcreteACI31808 page

C t D iConcreteDesignPresentedby:SeanDang,P.E.

Date:April2011

Createdby:SeanDang,P.E.

ConcreteACI31808 page

ConcreteACI31808 page 1

h l dd d h f l fThisisnewlyaddedtotheSCOPEforclarificationpurposes.TheStrengthEvaluationofExistingStructureshasalreadybeenimplementedinChapter20ofthe2005ACICode.

ConcreteACI31808 pageFromACICommentaryFromACICode

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y

L NPiles,caissons,etciftheysupportastructureassignedtoSeismicDesignCategoriesD E andFaregovernby

LecturesNotes

CategoriesD,E,andFaregovernbyACI.AllothersareregulatedbytheBuildingCode(ie.Chapter18&19).

Example:Micropilesbeneathaforparkinglot

ConcreteACI31808 pageFromACICode

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Deformedsteelfibers(nextfewpages)Headedshearstuds(seebelow)

ConcreteACI31808 pageForRef.Only:nochangeinSec.11.11.4

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y g 4

ConcreteACI31808 pageConcreteACI31808FromACICode

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Sec.7.7.5specifiestheamountofconcretecoverforshearstudreinforcementcoverforshearstudreinforcement.

ConcreteACI31808 pageMainlyforslabsFromACICode

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yVerygoodtopreventshearcracks

TheCodedoesNOTmentionthisreinforcementanywhereelseagain.y gTherearenodesignparametersforthismaterial.Mixturecontent?Fibervs.ConcreteNoadditionalrebars required??

Deformedsteelfibers Deformedsteelfiberscastinconcrete

Noadditionalrebars required??Requiredthicknessoftheslab???

ConcreteACI31808 pageFromACICode

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ConcreteACI31808 pageConcreteACI31808C Becautious whenitis

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Cusedtoterminateverticalrebarforboundaryelementsofashearwall ashearwall.Theengineerneedstocheckthedevelopmentlengthincompression.

T


TherequirementsofStructuralIntegrityisnotnew,however,therequirementstogainstructuralintegrityhasbeenrevised.

ForSlabs,atleastonebottombartopassthruthecolumncore

ForPerimeter Beams,atleasttwobarstopassthruthecolumncore

InteriorBeamswillbediscussedlater

DenotesNeworChangesinACI31808

ConcreteACI31808 pageConcreteACI31808ForPerimeterBeams

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Theamountofbeamreinforcementtorequiredforstructuralintegritydidnotq g ychange.

Oldcodejustaskfortwocontinuousbarswithoutanyotherrequirements.

Newcoderequirescontinuousbarstopassthroughtheregionboundedbythel it di l i f t fth longitudinalreinforcementofthecolumnColumn

C lColumn

ConcreteACI31808 pageConcreteACI31808StructuraldetailshowingabeamthatForPerimeterBeams(continue)

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giswiderthanthesupportingcolumn.

Notetheamountofrebarpassingthruthecolumncoreforstructuralintegrity.

ConcreteACI31808 pageConcreteACI31808ForRef only:nochangeinthe

ForPerimeterBeams(continue)

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ForRef.only:nochangeinthedevelopmentlength

OldcodeallowedClassUstirrups

OldcodeallowedClassAOldcodeallowedClassAsplice.NewcoderequiresClassBsplice.Seeabove.??

ConcreteACI31808 pageConcreteACI31808ForPerimeterBeams(continue)

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Thisisnew!

OldcodeallowedClassUstirrups

ConcreteACI31808 pageConcreteACI31808ForPerimeterBeams(continue) FromACICommentary

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ThisconcernfortorquestressesisalsothereasonforrequiringaportionofthelongitudinalreinforcementswithinthePerimeterBeams(andnotforinteriorbeams),topassh h l f i l i

Transversereinforcementwithinaperimeterbeam.

thruthecolumncoreformoretorsional resistance.

ConcreteACI31808 pageConcreteACI31808ForRef.only:nochangeinpunchingForInteriorBeams

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y g p gshearrequirements

Column

Caution!OthersectionslikePunchingShearmaystillrequirethelongitudinalreinforcementtopass throughtheregionreinforcementtopass throughtheregionboundedbythelongitudinalreinforcementofthecolumn.

ConcreteACI31808 pageTheACIintroducesaLightweight

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TheACIintroducesaLightweight

Concretemultiplier thruouttheCodewhereeverisused.

Doyounoticeanythingdifferentabovethisdevelopmentlengthabovethisdevelopmentlengthequation?


Thisischanged!

Inthe2005Codelambda=1.3Inthe2008Code,lambda=0.75

ConcreteACI31808 pageConcreteACI31808Review

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Elastic:capableofreturningtoitsoriginallength,shape,etc.,afterbeingstretched deformed ie Elastic

NonlinearAnalysis??

stretched,deformed,ie.ElasticDisplacement,Deformation.

Inelastic:NOTreturningtoitsoriginalLinearAnalysis??

g gform.Duetocracks,rebarslippage,etc..InelasticDisplacement,Deformation.Ie.inelasticdisplacement,inelasticdeformation.

D ili i j ifi d i hYield:changefromelastictopermanentdeformationbuthasNOTnot collapse.

Ductilityisjustifiedwithtesting

Brittle:astiffelementthatfractureseasily

Ductile:aseriesofcyclicrotationinitsyieldedstateandstillabsorbingenergy.

Brittle:astiffelementthatfractureseasily

Collapse:Youshouldknowthis.

ConcreteACI31808 pageConcreteACI31808FromSection8.8.2: ThisisNew!

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Checkbuildingswayingunderwindl diloading:

Columns:1.4x0.70Ig =0.98IgBeams:1.4x0.35Ig =0.60Ig4 35 g gWalls:1.4x0.35Ig =0.60Ig

ThisismainlyfortallslenderOCCUPIEDBuildingsorhighrisestructures.


Thestrengthreductionfactorforspiralreinforcementhaschangedfrom0 90toreinforcementhaschangedfrom0.90to0.75

Inthe2008Code,thefactorwasincreasedto0.60from0.55.Notsurehowthisisused,butinLACityi f t i i db freinforceconcreteisrequiredbecauseof

SeismicityZone.

ConcreteACI31808 pageConcreteACI31808ThisisNew!

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Transversereinforcementshallnotexceedfy =80,000psiEXCEPT:

SpiralreinforcedcolumnsSpiralreinforcedcolumnsSpecialMomentFramesSpecialStructuralWalls(shearwalls)

Highstrengthtiescanhelpalleviaterebarcongestion(moreonthislater).

ConcreteACI31808 pageConcreteACI31808Eqn:(1010)willbefromacomputer

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q ( ) panalysis.Duetotheinelasticstorydrift.Forhandcalculationsitwouldbeeasiertoassumenotbracedagainstsideswaytoassume notbracedagainstsidesway ascheckforSlendernessEffect.

Thisprocedurehasnotchangedfromtheoldcode,exceptthatthecontenthasbeenreorganized.

ConcreteACI31808 pageConcreteACI318082008ACInowprovidesanalternativeway

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p ytodetermineswayornonswaycolumns.

Thisisnew!Butdifficulttousewithoutacomputer.Seepreviousslidesforhandcalc.alternative.

ConcreteACI31808 pageConcreteACI31808Thisisnew! FromACICommentary

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y

SecondordermeansPdeltaeffects

Pv m

hh

P m+

ConcreteACI31808 pageConcreteACI31808Nochangeintheprescriptivevaluesforh d d f

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thereducedmomentofinertia.

Thisisnew!The2008Codeprovidesalternativeequationstodeterminethereducedequationstodeterminethereducedmomentofinertia

ConcreteACI31808 pageSec.14.8.3Slenderwalldesign ACICommentary

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4 3 g y

ConcreteACI31808 pageThisisnew!

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Thisisnew!

Severalsectionshavebeenaddedtothischapter.

Wewillnotbediscussingtheseitems.

Itisashortchapterwith5pages.Itisashortchapterwith5pages.


21.1.1.3 StructuresassignedtoSeismicDesignCategoryAshallsatisfyrequirements LACityAmendment.DesignCategoryAshallsatisfyrequirementsofChapters1to19and22;Chapter21doesnotapply. StructuresassignedtoSeismicDesignCategoryB,C,D,EorFalsoshallsatisfy21.1.1.4through21.1.1.8,asapplicable.ExceptforstructuralelementsofplainconcretecomplyingwithSection1908.1.8oftheCaliforniaBuildingCode,structural Languageaddedtoprohibitplain(noni f d)theCaliforniaBuildingCode,structuralelementsofplainconcreteareprohibitedinstructuresassignedtoSeismicDesignCategoryC,D,EorF

reinforced)concrete.


21.1.1.7 StructuralsystemsdesignatedaspartoftheseismicforceresistingsystemshallberestrictedtothosepermittedbyASCE7.Except LACityAmendmentforSeismicDesignCategoryA,forwhichChapter21doesnotapply,thefollowingprovisionsshallbesatisfiedforeachstructuralsystemdesignatedaspartoftheseismicforce

LACityAmendment.

resistingsystem,regardlessoftheSeismicDesignCategory:(a)Ordinarymomentframesshallsatisfy21.2.(b)OrdinaryreinforcedconcretestructuralwallsandordinaryprecaststructuralwallsneednotsatisfyanyprovisionsinChapter21.(c)Intermediatemomentframesshallsatisfy21.3.

ThisisthefirsttimeACIprovidesdesignparametersfor:OrdinaryMomentFrames

(d)Intermediateprecaststructuralwallsshallsatisfy21.4.(e)Specialmomentframesshallsatisfy21.5through21.8. OrdinaryMomentFrames

OrdinaryShearwallsIntermediateMomentFrames

(f)Specialstructuralwallsshallsatisfy21.9.

(g)Specialstructuralwallsconstructedusingprecastconcreteshallsatisfy21.10.

ConcreteACI31808 pageN h f i d

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Nochangefrompreviouscode.NoideawhatASTM706isbuttherearenoqualifyingconditionsassociatedwiththismaterial.Buttheconditions(a)&(b)onlyappliestoASTMA615Grades40andGrades60reinforcement.

( h ll d hi l b Thishaschanged.Forinspectors:ThenewcodedoesNOTallowaretest.

(retestsshallnotexceedthisvaluebymorethananadditional3000psi)

Useoflongitudinalreinforcementwithstrengthsubstantiallyhigherthanthatassumedindesignwillleadtohighershearandbondstressesatthetimeofdevelopmentofyieldindesignwillleadtohighershearandbondstressesatthetimeofdevelopmentofyieldmoments.Theseconditionsmayleadtobrittlefailuresinshearorbondandshouldbeavoided.

So,isStrongeralwaysbetter?Theplanscallsoutforfy =40ksi andthecontractorinstallsfy =60ksi rebar.ThisisNOTacceptable.


Thisisnew!ThenewcodeallowsALL confinementreinforcementtonotexceed100,000psi.

InthepreviouscodelimitedAllconfinementreinforcementtonotconfinementreinforcementtonotexceed60,000psi(Sec.21.2.5)

Thisisnew!Thenewcodelimitsallshearreinforcementto60 000psi Thereinforcementto60,000psi.Thepreviouscodedidnothaveanyrestrictions.

ConcreteACI31808 pageConcreteACI31808Thisisnew!

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ThenewcodeprovidesdesignparametersforOrdinary momentframes.

21.3.3 isthecolumndesignforIntermediatemomentframes.( )

ThislimitationforuseinSDCBisfoundinthe

(nextslide)

Basically,ifthecolumnheightislessthan5xC1thenitis

CommentarySectionandnottheCode.

5consideredashortcolumnwhichistypicallycontrolledbyshearfailure.

ConcreteACI31808 pageConcreteACI31808ForReferenceonly:

d f

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NonewdesignparametersforIntermediatemomentframes.NOTpermittedinSDCD,E,&F.

ConcreteACI31808 pageConcreteACI31808 38Thisisnew!ThenewcodeprovidesdesignparametersThenewcodeprovidesdesignparametersforSpecialmomentframes.

Caution!!TheCodelanguagedoesnotmatchthediagram.ButasoftheThirdPrinting(October

C2and0.75C1ButasoftheThirdPrinting(October

2009)thiserrorhasbeenfixed.0.75 C

ConcreteACI31808 pageConcreteACI31808AfewChangesin:

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gTheSpecialMomentFrames

Thi i !Thisisnew!

10/4=2.5whichisthevaluefor.

ConcreteACI31808 pageConcreteACI31808 40Longbeamspanningbetweentwostiffwall.LikeamomentframeSec.21.5

Shortbeamspanningbetweentwostiffwall,therefore,shearwillcontrol

Thisisnew!Aclarification:ThebeamwillbehavelikeaMomentFrameBeam,therefore,useSec.21.5.2through21.5.4.

FromACICommentary:FromACICommentary:Experimentsshowthatdiagonallyorientedreinforcementiseffectiveonlyifthebarsareplacedwithalargeinclination.Therefore,di ll i f d li b diagonallyreinforcedcouplingbeamsarerestrictedtobeamshavingaspectratioln/h>4.The2008editionofthisCodewaschangedgtoclarifythatcouplingbeamsofintermediateaspectratiocanbereinforcedaccordingto21.5.2through21.5.4.

ConcreteACI31808 pageConcreteACI31808 41

Thisisnew!Thepreviouscodedidnothaveanyspecialrequirements

Thisisnew!Inotherwords,twoormorelayersof:

anyspecialrequirements.

, yaminimumfourbarcage.

Thepreviouscodeonlyrequiresaminimumof4barswithtiesminimumof4barswithties.

ConcreteACI31808 pageConcreteACI31808Thisisnew! FromACICommentary

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Section21.9.7.4(d)describesasecondoptionforconfinementofthediagonalsintroducedinthe2008Code(Fig.R21.9.7(b)).Thissecondoptionistoconfinetheentirebeampcrosssectioninsteadofconfiningtheindividualdiagonals.Thisoptioncanconsiderablysimplifyfieldplacementofhoops,whichcanotherwisebeespecially

Option#1likethepreviousCode,

p p ychallengingwherediagonalbarsintersecteachotherorenterthewallboundary.

requiresthediagonalbarstobeenclosed.


Again,designersmustprovideproperconfinementwhereeverplastichingearetooccur Thiswillcreateaductilesystemtoabsorbseismicenergy tooccur.Thiswillcreateaductilesystemtoabsorbseismicenergy.


LACityLACityAmendment

ConcreteACI31808 pageConcreteACI31808N t h iti

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Notsurewhyitisplainconcretewhenrebars arerequired.q

LACityAmendment


TheEnd

building structural part 3

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