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6/1/2015 751.24LFDRetainingWallsEngineeringPolicyGuide

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EPG751.24LFDRetainingWallspresentstheverylatestinformation,butthispdffilemaybehelpfulforthosewantingtoeasilyprinttheLFDseismicinformationasitwasinSeptember2011.

AdditionalInformationAASHTO5.1

AdditionalInformation

AASHTO5.2.1


AASHTO5.2.1.4&5.8

751.24LFDRetainingWallsFromEngineeringPolicyGuide

Contents1751.24.1General

1.1751.24.1.1WallTypeSelection1.2751.24.1.2Loads

2751.24.2MechanicallyStabilizedEarth(MSE)Walls2.1751.24.2.1Design2.2751.24.2.2Details

3751.24.3CastInPlaceConcreteRetainingWalls3.1751.24.3.1UnitStresses3.2751.24.3.2Design

3.2.1751.24.3.2.1SpreadFootings3.2.2751.24.3.2.2PileFootings3.2.3751.24.3.2.3CounterfortWalls

3.3751.24.3.3Example1:SpreadFootingCantileverWall3.4751.24.3.4Example2:LShapedCantileverWall3.5751.24.3.5Example3:PileFootingCantileverWall3.6751.24.3.6Dimensions3.7751.24.3.7Reinforcement3.8751.24.3.8Details

751.24.1General

Retainingwallshallbedesignedtowithstandlateralearthandwaterpressures,includinganyliveanddeadloadsurcharge,theselfweightofthewall,temperatureandshrinkageeffect,liveloadandcollisionforces,andearthquakeloadsinaccordancewiththegeneralprinciplesofAASHTOSection5andthegeneralprinciplesspecifiedinthisarticle.

751.24.1.1WallTypeSelection

Selectionofwalltypeshallbebasedonanassessmentofthemagnitudeanddirectionofloading,depthtosuitablefoundationsupport,potentialforearthquakeloading,presenceofdeleteriousenvironmentalfactors,wallsitecrosssectionalgeometry,proximityofphysicalconstraints,tolerableanddifferentialsettlement,facingappearanceandeaseandcostofconstruction.

ThefollowingwalltypesarethemostcommonlyusedinMoDOTprojects

MechanicallyStabilizedEarthRetainingWallsCastInPlaceConcreteCantileverRetainingWalls

CantileverWallsonSpreadFootingsCantileverWallonPileFootingsLShapedWallsonSpreadFootings

MechanicallyStabilizedEarth(MSE)RetainingWalls

MSEretainingwallsuseprecastblockorpanellikefacingelementscombinedwitheithermetallicorgeosynthetictensilereinforcementsinthesoilmass.MSEwallsarepreferredovercastinplacewallsbecausetheyareusuallymoreeconomical.Otheradvantagesincludeawidevarietyofdesignstyles,easeandspeedofinstallation,andtheirabilitytoaccommodatetotalanddifferentialsettlements.Walldesignheightsupwardsof80ft.aretechnicallyfeasible(FHFWSA96071).MSEwallsmaybeusedtoretainfillforendbentsofbridgestructures.

SituationsexistwheretheuseofMSEwallsiseitherlimitedornotrecommended.Someobstaclessuchasdropinlets,signtrusspedestalsorfootings,andfencepostsmaybeplacedwithinthereinforcingstriparea,however,theseobstaclesincreasethedifficultyandexpenseofprovidingsufficientreinforcingstripsforstability.BoxculvertsandhighwaydrainagepipesmayrunthroughMSEwalls,butitispreferablenottorunthepipesclosetoorparalleltothewalls.Utilitiesotherthanhighwaydrainageshouldnotbeconstructedwithinthereinforcingstriparea.




AASHTO3.20.1

BecautiouswhenusingMSEwallsinafloodplain.Afloodcouldcausescouringaroundthereinforcementandseepageofthebackfillmaterial.SoilreinforcementsshouldnotbeusedwhereexposuretogroundwatercontaminatedbyacidminedrainageorotherindustrialpollutantsasindicatedbyalowpHandhighchloridesandsulfatesexist.Galvanizedmetallicreinforcementsshallnotbeusedwherestrayelectricalgroundcurrentscouldoccuraswouldbepresentnearanelectricalsubstation.

Sufficientrightofwayisrequiredtoinstallthereinforcingstripswhichextendintothebackfillareaatleast8ft.,70%ofthewallheightorasperdesignrequirements,whicheverisgreater.Finally,barriercurbsconstructedoverorinlinewiththefrontfaceofthewallshallhaveadequateroomprovidedlaterallybetweenthebackofthewallfacingandthecurborslabsothatloadisnotdirectlytransmittedtothetopwallfacingunits.

ConcreteCantileverWallonSpreadFooting

Concretecantileverwallsderivetheircapacitythroughcombinationsofdeadweightandstructuralresistance.Thesewallsareconstructedofreinforcedconcrete.

ConcretecantileverwallsareusedwhenMSEwallsarenotaviableoption.Cantileverwallscanreducetherockcutrequiredandcanalsoprovidesolutionswhentherearerightofwayrestrictions.Concretewallsalsoprovidebetterstructuralcapacitywhenbarriercurbsontopofthewallsarerequired.

Counterfortsareusedonrareoccasions.Signboardtyperetainingwallsareaspecialcaseofcounterfortretainingwalls.Theyareusedwherethesoilconditionsaresuchthatthefootingsmustbeplacedwellbelowthefinishedgroundline.Forthesesituationsthewallisdiscontinued12in.belowthegroundlineorbelowthefrostline.Counterfortsmayalsobeacostsavingsoptionwhenthewallheightapproaches20ft.(FoundationAnalysisandDesignbyJosephE.Bowles,4thed.,1988).However,otherfactorssuchaspoorsoilconditions,slopeoftheretainedsoil,walllengthanduniformityinwallheightshouldalsobeconsideredbeforeusingcounterforts.

ConcreteCantileverWallonPileFooting

Concretecantileverwallsonpilefootingsareusedwhenthesoilconditionsdonotpermittheuseofspreadfootings.Thesewallsarealsousedwhenanendbentrequireswingslongerthan22feet.Inthesecasesastubwingisleftattachedtotheendbentandtherestofthewingisdetachedtobecomearetainingwall.

ConcreteLShapedRetainingWallonSpreadFootings

ConcreteLShapedwallsarecantileverwallswithoutheels.Thesewallsareusedwhentherearespacelimitationsforcantileverwalls.Sincethereisnoheeltheheightofthesewallsislimitedtoabout7ft.dependingonthesoilconditionsandtheslopeoftheretainedsoil.

LShapedWallsareoftenusednexttoroadwayswherethefootingsarefrequentlyusedasshouldersandwherethewallwillrequirestructuralcapacityforcollisionforces.

751.24.1.2Loads

DeadLoads

DeadloadsshallbedeterminedfromtheWeightofMaterialsTableoftheLoadsSectionintheBridgeManual.

EquivalentFluidPressure(EarthPressures)

FordeterminingequivalentearthpressuresforGroupLoadingsIthroughVItheRankineFormulaforActiveEarthPressureshallbeused.

RankineFormula: where:

Ca= =coefficientofactiveearthpressure

Pa=equivalentactiveearthpressure

H=heightofthesoilfaceattheverticalplaneofinterest

=unitweightofsoil

=slopeoffillindegrees

=angleofinternalfrictionofsoilindegrees



Example

Given:

=3:1(H:V)slope

=25

s=0.120kcf

H=10ft

=arctan =18.4

Ca= =0.515

Pa=(1/2)(0.515)(0.120kips/ft3)(10ft)2=3.090kipsperfootofwalllength

TheangleshallbedeterminedbytheMaterialsDivisionfromsoiltests.IftheanglecannotbeprovidedbytheConstructionandMaterialsDivision(http://wwwi/intranet/cm/default.htm)aangleof27degreesshallbeused.

Drainageshallbeprovidedtorelievewaterpressurefrombehindallcastinplaceconcreteretainingwalls.Ifadequatedrainagecannotbeprovidedthenwallsshallbedesignedtoresistthemaximumanticipatedwaterpressure.

SurchargeDuetoPoint,LineandStripLoads

Surchargeduetopointandlineloadsonthesoilbeingretainedshallbeincludedasdeadloadsurcharge.TheeffectoftheseloadsonthewallmaybecalculatedusingFigure5.5.2BfromAASHTO.

Surchargeduetostriploadsonthesoilbeingretainedshallbeincludedasadeadloadsurchargeload.ThefollowingprocedureasdescribedinPrinciplesofFoundationEngineeringbyBrajaM.Das(1995)shallbeappliedtocalculatetheseloadswhenstriploadsareapplicable.Anexampleofthisapplicationiswhenaretainingwallisusedinfrontofanabutmentsothatthewallisretainingthesoilfrombehindtheabutmentasastriploadonthesoilbeingretainedbythewall.

RetainingWallinfrontofanAbutment

Theportionofsoilthatisintheactivewedgemustbedeterminedbecausethesurchargepressureonlyaffectsthewallifitactsontheactive



wedge.TheactualfailuresurfaceinthebackfillfortheactivestatecanberepresentedbyABCshowninthefigurebelow.AnapproximationtothefailuresurfacebasedonRankine'sactivestateisshownbydashedlineAD.Thisapproximationisslightlyunconservativebecauseitneglectsfrictionatthepseudowalltosoilinterface.

Thefollowingvariablesareshowninthefigurebelow:

=slopeoftheactivefailureplaneindegrees=slopeoffillindegreesH=heightofthepseudowall(fomthebottomofthefooting).L1=distancefrombackofstemtobackoffootingheelL2=distancefromfootingheeltointersectionoffailureplanewithgroundsurface

DeterminationofActiveWedges

Inordertodetermine,thefollowingequationwhichhasbeenderivedfromRankine'sactiveearthpressuretheorymustbesolvedbyiteration:

=angleofinternalfrictionofsoilindegrees

Agoodestimateforthefirstiterationistolet=45+(/2).Inlieuofiteratingtheaboveequationaconservativeestimateforis45.Oncehasbeenestablished,anestimateofL1isneededtodetermineL2.Fromthegeometryofthevariablesshownintheabovefigure:

Theresultantpressureduetothestriploadsurchargeanditslocationarethendetermined.Thefollowingvariablesareshowninthefigurebelow:

q=loadperunitareaPs=resultantpressureonwalldueonlytosurchargeearthpressure=locationofPsmeasuredfromthebottomofthefooting

L3=distancefrombackofstemtowheresurchargepressurebegins




AASHTO3.20.3&5.5.2

SurchargePressureonRetainingWall

Fromthefigure:

Ps= where

where

Whenapplicable,Psisappliedtothewallinadditiontootherearthpressures.Thewallisthendesignedasusual.

LiveLoadSurcharge

Liveloadsurchargepressureofnotlessthantwofeetofearthshallbeappliedtothestructurewhenhighwaytrafficcancomewithinahorizontaldistanceequaltoonehalfofthewallheight,measuredfromtheplanewhereearthpressureisapplied.




AASHTO3.24.5.1.1&5.5.6.1


AASHTO3.24.2&3.30


AASHTOFigure2.7.4B

LiveLoadSurcharge

PLLS=(2ft.)sCaH=pressureduetoliveloadsurchargeonly

s=unitweightofsoil(Note:AASHTO5.5.2specifiesaminimumof125pcfforliveloadsurcharge,MoDOTpolicyallows120pcfasgivenfromtheWeightofMaterialsTableoftheLoadsSectionintheBridgeManual.)Ca=coefficientofactiveearthpressure

H=heightofthesoilfaceattheverticalplaneofinterest

Theverticalliveloadsurchargepressureshouldonlybeconsideredwhencheckingfootingbearingpressures,whendesigningfootingreinforcement,andwhencollisionloadsarepresent.

LiveLoadWheelLines

Liveloadwheellinesshallbeappliedtothefootingwhenthefootingisusedasaridingorparkingsurface.

DistributeaLLWLequalto16kipsasastriploadonthefootinginthefollowingmanner.

P=LLWL/E

whereE=0.8X+3.75

X=distanceinft.fromtheloadtothefrontfaceofthewall

Thewheellinesshallmove1ft.fromthebarriercurborwallto1ft.fromthetoeofthefooting.

CollisionForces

Collisionforcesshallbeappliedtoawallthatcanbehitbytraffic.Applyapointloadof10kipstothewallatapoint3ft.abovethefinishedgroundline.




1992AASHTODiv.IAEqns.C63and

C64

Section

Distributetheforcetothewallinthefollowingmanner:

Forceperftofwall=(10kips)/2L

Profile

Whenconsideringcollisionloads,a25%overstressisallowedforbearingpressuresandafactorofsafetyof1.2shallbeusedforslidingandoverturning.

WindandTemperatureForces

Theseforcesshallbedisregardedexceptforspecialcases,consulttheStructuralProjectManager.

Whenwallsarelongerthan84ft.,anexpansionjointshallbeprovided.

Contractionjointspacingshallnotexceed28feet.

SeismicLoads

RetainingwallsinSeismicPerformanceCategoryA(SPCA)andSPCBthatarelocatedadjacenttoroadwaysmaybedesignedinaccordancewithAASHTOspecificationsforSPCA.RetainingwallsinSPCBwhicharelocatedunderabridgeabutmentorinalocationwherefailureofthewallmayaffectthestructuralintegrityofabridgeshallbedesignedtoAASHTOspecificationsforSPCB.AllretainingwallslocatedinSPCCandSPCDshallbedesignedinaccordancetoAASHTOspecificationsforthecorrespondingSPC.

InseismiccategoryB,CandDdetermineequivalentfluidpressurefromMononobeOkabestaticmethod.

PAE=equivalentactiveearthpressureduringanearthquake

PAE=0.5sH2(1kv)KAEwhere

KAE=seismicactivepressurecoefficient




AASHTO5.2.2.3&Div.IA6.4.3


AASHTOTable3.22.1A


AASHTO5.14.2

s=unitweightofsoil

kv=verticalaccelerationcoefficient

kh=horizontalaccelerationcoefficientwhichisequalto0.5Aforallwalls,

but1.5AforwallswithbatteredpileswhereA=seismicaccelerationcoefficient

Thefollowingvariablesareshowninthefigurebelow:

=angleofinternalfrictionofsoil

=

=slopeofsoilface

=angleoffrictionbetweensoilandwallindegrees

i=backfillslopeangleindegrees

H=distancefromthebottomofthepartofthewalltowhichthepressureisappliedtothetopofthefillatthelocationwheretheearthpressureistobefound.

ActiveSoilWedge

GroupLoads

ForSPCAandB(ifwalldoesnotsupportanabutment),applyAASHTOGroupILoadsonly.Bearingcapacity,stabilityandslidingshallbecalculatedusingworkingstressloads.Reinforcedconcretedesignshallbecalculatedusingloadfactordesignloads.

AASHTOGroupILoadFactorsforLoadFactorDesignofconcrete:=1.3

D=1.0forconcreteweight

D=1.0forflexuralmember

E=1.3forlateralearthpressureforretainingwalls

E=1.0forverticalearthpressure

LL=1.67forliveloadwheellines

LL=1.67forcollisionforces

E=1.67forverticalearthpressureresultingfromliveloadsurcharge

E=1.3forhorizontalearthpressureresultingfromliveloadsurcharge

ForSPCB(ifwallsupportsanabutment),C,andDapplyAASHTOGroupILoadsandseismicloadsinaccordancewithAASHTODivisionIASeismicDesignSpecifications.




AASHTODiv.IA4.7.3

Whenseismicloadsareconsidered,loadfactorforallloads=1.0.

751.24.2MechanicallyStabilizedEarth(MSE)Walls

751.24.2.1Design

DesignsofMechanicallyStabilizedEarth(MSE)wallsarecompletedbyconsultantsorcontractorsinaccordancewithSection5oftheAASHTOSpecifications.MoDOTInternetsitecontainsalistingoffacingunitmanufacturers,soilreinforcementsuppliers,andwallsystemsupplierswhichhavebeenapprovedforuse.SeeSec720(http://www.modot.mo.gov/business/standards_and_specs/Sec0720.pdf)andSec1010(http://www.modot.mo.gov/business/standards_and_specs/Sec1010.pdf)foradditionalinformation.TheGeotechnicalSection(http://wwwi/intranet/cm/materials/Geotechnical.htm)isresponsibleforcheckingglobalstability,whichshouldbereportedontheFoundationInvestigationGeotechnicalReport.ForMSEwallpreliminaryinformation,seeEPG751.1.4.3MSEWalls(http://epg.modot.mo.gov/index.php?title=751.1_Preliminary_Design#751.1.4.3_MSE_Walls).

Generalpolicy

Smallblockwallsarelimitedtoa10ft.heightinonelift.

Forsmallblockwalls,topcapunitsshallbeusedandshallbepermanentlyattachedbymeansofaresinanchorsystem.

Forlargeblockwalls,capstonemaybesubstitutedforcopingandeithershallbepermanentlyattachedtowallbypaneldowels.

MSEwallsshallnotbeusedwhereexposuretoacidwatermayoccursuchasinareasofcoalmining.

MSEwallsshallnotbeusedwherescourisaproblem.

MSEwallswithmetallicsoilreinforcementshallnotbeusedwherestrayelectricalgroundcurrentsmayoccuraswouldbepresentnearelectricalsubstations.

Noutilitiesshallbeallowedinthereinforcedearthiffutureaccesstotheutilitieswouldrequirethatthereinforcementlayersbecut,orifthereisapotentialformaterial,whichcancausedegradationofthesoilreinforcement,toleakoutoftheutilitiesintothewallbackfill,withtheexceptionofstormwaterdrainage.

Theinterioranglebetweentwowallsmustbegreaterthan70.

Smallblockwallsmaybebatteredupto1.5in.perfoot.

Thefrictionangleusedforthecomputationofhorizontalforceswithinthereinforcedsoilshallbegreaterthanorequalto34.

Allreinforcementshallbeepoxycoatedintheconcretefaceforwallssubjecttosprayingfromadjacentroadways(approximately10ft.orlessfromthecurb.)

AllconcreteexceptfacingpanelsorunitsshallbeCLASSBorB1.

Thefrictionangleofthesoiltoberetainedbythereinforcedearthshallbelistedontheplansaswellasthefrictionangleforthefoundationmaterialthewallistoreston.

Seismicperformancecategoryandaccelerationcoefficientshallbelistedontheplans.

FactorsofSafetyforMSEwallsshallbe2.0foroverturning,1.5forsliding,2.0forultimatebearingcapacityand1.5forpulloutresistance.

FactorsofSafetyforseismicdesignshallbe1.5foroverturningand1.1forsliding.

Guttertypeshouldbeselectedatthecoreteammeeting.

Whengutterisrequiredwithoutfencing,useTypeAorTypeBgutter(fordetail,seeStd.Plan609.00(http://www.modot.mo.gov/business/standards_and_specs/documents/60900.pdf)).

Whengutterisrequiredwithfencing,useModifiedTypeAorModifiedTypeBgutter(fordetail,seeStd.Plan607.11(http://www.modot.mo.gov/business/standards_and_specs/documents/60711.pdf)).

Whenfencingisrequiredwithoutgutter,placeintubeandgroutbehindtheMSEwall(fordetail,seeFig.751.24.2.1.7,FencePostConnectionBehindMSEWall(withoutgutter).

Donotusesmallblockwallsinthefollowinglocations:

Withinthesplashzonefromsnowremovaloperations(assumedtobe15ft.fromtheedgeoftheshoulder).

Wheretheblockswillbecontinuouslywetted,suchasaroundsourcesofwater.



Whereblockswillbelocatedbehindbarriercurbsorotherobstaclesthatwilltrapsaltladensnowfromremovaloperations.

Forstructurallycriticalapplications,suchascontainingnecessaryfillaroundstructures.

Intieredwallsystems.

Forlocationswheresmallblockwallsarenotdesirable,considercoloringagentsand/orarchitecturalformsusinglargeblockwallsforaestheticinstallations.

Drainagepipesforalllargeandsmallblockwallsshallbeaminimumofa6in.diameterperforatedPVCorPEpipe(SeeSec1013(http://www.modot.mo.gov/business/standards_and_specs/Sec1013.pdf))unlesslargersizesarerequiredbydesignbythewallmanufacturer.Showdrainagepipesizeonplans.Screensshouldbeinstalledandmaintainedondrainpipeoutlets.Outletscreensandcleanoutsshouldbedetailed(shownonconstructiondrawing).

ForslabdrainlocationnearMSEWall,seeEPG751.10.3.1DrainType,AlignmentandSpacing.

RoadwayrunoffshouldbedirectedawayfromrunningalongfaceofMSEwallsusedaswingwallsonbridgestructures.

MSEWallConstruction:

CorrugatedMetalPipePileSpacersGuidance:

Corrugatedmetalpipepilespacers(CMPPS)shallbeusedatpilelocationsbehindmechanicallystabilizedearthwallstoprotectthewallreinforcementwhendrivingpileforthebridgesubstructureatendbents(s).CMPPSshallhaveaninsidediametergreaterthanthatofthepileandlargeenoughtoavoiddamagetothepipewhendrivingthepile.ThebottomoftheCMPPSshallbeplaced5ft.min.belowthebottomoftheMSEwalllevelingpad.Thepipeshallbefilledwithsandorotherapprovedmaterialafterthepileisplacedandbeforedriving.CMPPSshallbeaccuratelylocatedandcappedforfuturepileconstruction.

Alternatively,thecontractorshallbegiventheoptionofdrivingthepilesbeforeconstructionoftheretainingwallandplacingthewallreinforcingandbackfillmaterialaroundthepiling.Thecontractorshalladequatelysupportthepilingtoinsurethatproperpilealignmentismaintainedduringthewallconstruction.Thecontractorsplanforbracingthepileshallbesubmittedtotheengineerforreview.

Pilingshallbedesignedfordowndrag(DD)loadsduetoeithermethod.OversizedCMPPSwithsandplacedafterdrivingmaybeconsideredtomitigatesomeoftheeffectsofdowndrag(DD)loads.OversizedCMPPSshallaccountforpilesize,thermalmovementsofthebridge,pileplacementplan,andverticalandhorizontalplacementtolerances.

TheminimumclearancefromthebackfaceofMSEwallstothefrontfaceoftheendbentbeamshallbe3ft.9in.(typ.).The3ft.9in.dimensionisbasedontheuseof18in.CMPPS&FHWANHI1024,Figure517C,whichwillhelpensurethatsoilreinforcementisnotskewedmorethan15fornutandboltreinforcementconnections.Othertypesofconnectionsmayrequiredifferentmethodsforsplaying.Intheeventthatthe3ft.9in.dimensionorsetbackcannotbeused,thefollowingguidanceforCMPPSclearanceshallbeused:CMPPSshallbeplaced18in.clearmin.fromthebackfaceofMSEwallpanels12in.minimumclearanceisrequiredbetweenCMPPSandlevelingpadand18in.minimumclearanceisrequiredbetweenlevelingpadandpile.

MSEWallPlanandGeometrics

Aplanviewshallbedrawnshowingabaselineorcenterline,roadwaystationsandwalloffsets.Theplanshallcontainenoughinformationtoproperlylocatethewall.Theultimaterightofwayshallalsobeshown,unlessitisofasignificantdistancefromthewallandwillhavenobearingonthewalldesignorconstruction.

Stationsandoffsetsareestablishedbetweenoneconstructionbaselineorroadwaycenterlineandawallcontrolline(baseline).Somewalldesignscontainaslightbatter,whileothersarevertical.Awallcontrollineissetatthefrontfaceofthewall,eitheralongthetoporatthebaseofthewall,whicheveriscriticaltotheproposedimprovements.Forbatteredwalls,toallowforbatteradjustmentsofthesteppedlevelpadorvariationofthetopofthewall,thewallcontrolline(baseline)istobeshownatafixedelevation.Forbatteredwalls,theoffsetlocationandelevationofcontrollineshallbeindicated.Allhorizontalbreaksinthewallaregivenstationoffsetpoints,andwallswithcurvatureindicatestationoffsetstothePCandPTofthewall,andtheradius.

Anyobstacleswhichmaypossiblyinterferewithwallreinforcingstripsareshown.Drainagestructures,lighting,ortrusspedestalsandfootings,etc.aretobeshown,withstationoffsettocenterlineoftheobstacle,withobstaclesize.Skewanglesareshowntoindicatetheanglebetweenawallandapipeorboxwhichrunsthroughthewall.

Elevationsatthetopandbottomofthewallshallbeshownat25ft.intervalsandatanybreakpointsinthewall.

Curvedataand/oroffsetsshallbeshownatallchangesinhorizontalalignment.Ifbatteredwallsystemsareusedoncurvedstructures,showoffsetsat10ft.(max.)intervalsfromthebaseline.

Detailsofanyarchitecturalfinishes(formliners,concretecoloring,etc.).

Detailsofthreadedrodconnectingthetopcapblock.



Estimatedquantities,totalsq.ft.ofmechanicallystabilizedearthsystems.

Proposedgradeandtheoreticaltopoflevelingpadelevationshallbeshowninconstantslope.Slopelineshallbeadjustedperproject.Topofwallorcopingelevationandstationingshallbeshowninthedevelopedelevationperproject.Iflevelingpadisanticipatedtoencounterrock,thencontacttheGeotechnicalSectionforlevelingpadminimumembedmentrequirements.

MSEWallCrossSections

Atypicalwallsectionforgeneralinformationisshown.

Additionalsectionsaredrawnforanyspecialcriteria.Thefrontfaceofthewallisdrawnvertical,regardlessofthewalltype.

Anyfencingandbarriercurbareshown.

Barriersifneededareshownonthecrosssection.Concretebarriersareattachedtotheroadwayorshoulderpavement,nottotheMSEwall.StandardTypeBbarriercurbsareplacedalongwallfaceswhentraffichasaccesstothefrontfaceofthewallovershouldersofpavedareas.

751.24.2.2Details



Fig.751.24.2.2MSEWallDevelopedElevationandPlan



Fig.751.24.2.2TypicalSectionThroughGenericLargeBlockWall

Fig.751.24.2.2TypicalSectionThroughGenericSmallBlockWall



Fig.751.24.2.2CapstoneAnchorDetails

Notes: Holesare5/8"round,extend4"intothethirdlayerofblocks,recessed2"deepby11/2"round.RodsorreinforcingbarsaresecuredbyanapprovedresinanchorsysteminaccordancewithSec1039

(http://www.modot.mo.gov/business/standards_and_specs/Sec1039.pdf).Recessholetobebackfilledwithnonshrinkcementgrout.

BatteredSmallBlockWalls

Batteredmechanicallystabilizedearthwallsystemsmaybeusedunlessthedesignlayoutspecificallycallsforaverticalwall(largeblockwallsshallnotbebatteredandsmallblockwallsmaybebuiltvertical).IfabatteredMSEwallsystemisallowed,thenthefollowingnoteshallbeplacedonthedesignplans:

"Thetopandbottomofwallelevationsaregivenforaverticalwall.Ifabatteredsmallblockwallsystemisused,theheightofthewallshallbeadjustedasnecessarytofitthegroundslope.Iffenceisbuiltonanextendedgutter,thentheheightofthewallshallbeadjustedfurther."

Forbatteredwalls,noteontheplanswhetherthehorizontaloffsetfromthebaselineisfixedatthetoporbottomofthewall.Horizontaloffsetandcorrespondingverticalelevationshallbenotedonplans.

Fig.751.24.2.2TypicalSectionThroughGenericSmallBlockWall

Fencing

FencingmaybeinstalledontheModifiedTypeAorModifiedTypeBGutterorbehindtheMSEWall.

ForModifiedTypeAandModifiedTypeBGutterandFencePostConnectiondetails,seeStandardPlan607.11



(http://www.modot.mo.gov/business/standards_and_specs/documents/60711.pdf).

ForFencePostConnectionBehindMSEWall,seedetailbelow.

Fig.751.24.2.2FencePostConnectionBehindMSEWall(WithoutGutter)

751.24.3CastInPlaceConcreteRetainingWalls

751.24.3.1UnitStresses

ConcreteConcreteforretainingwallsshallbeClassBConcrete(f'c=3000psi)unlessthefootingisusedasaridingsurfaceinwhichcaseClassB1Concrete(f'c=4000psi)shallbeused.

ReinforcingSteel

ReinforcingSteelshallbeGrade60(fy=60,000psi).

PileFooting

Forpilingcapacities,seetheUnitStressesandPilingSectionsoftheBridgeManual.

SpreadFooting

Forfoundationmaterialcapacity,seetheUnitStressesSectionoftheBridgeManualandtheDesignLayoutSheet.

751.24.3.2Design

Iftheheightofthewallorfillisavariabledimension,thenbasethestructuraldesignofthewall,toe,andheelonthehighquarterpointbetweenexpansionjoints.




AASHTO5.5.5


AASHTO5.5.5


AASHTO5.5.5

Fig.751.24.3.2

751.24.3.2.1SpreadFootings

LocationofResultant

Theresultantofthefootingpressuremustbewithinthesectionofthefootingspecifiedinthefollowingtable.

WhenRetainingWallisBuilton: AASHTOGroupLoadsIVI ForSeismicLoads

Soila Middle1/3 Middle1/2b

Rockc Middle1/2 Middle2/3aSoilisdefinedasclay,clayandboulders,cementedgravel,softshale,etc.withallowablebearingvalueslessthan6tons/sq.ft.bMoDOTismoreconservativethanAASHTOinthisrequirement.cRockisdefinedasrockorhardshalewithallowablebearingvaluesof6tons/sq.ft.ormore.

Note:Thelocationoftheresultantisnotcriticalwhenconsideringcollisionloads.

FactorofSafetyAgainstOverturning

AASHTOGroupLoadsIVI:

F.S.foroverturning2.0forfootingsonsoil.F.S.foroverturning1.5forfootingsonrock.

Forseismicloading,F.S.foroverturningmaybereducedto75%ofthevalueforAASHTOGroupLoadsIVI.Forseismicloading:

F.S.foroverturning(0.75)(2.0)=1.5forfootingsonsoil.F.S.foroverturning(0.75)(1.5)=1.125forfootingsonrock.

Forcollisionforces:

F.S.foroverturning1.2.

FactorofSafetyAgainstSliding

Onlyspreadfootingsonsoilneedbecheckedforslidingbecausespreadfootingsonrockorshaleareembeddedintotherock.

F.S.forsliding1.5forAASHTOGroupLoadsIVI.F.S.forsliding(0.75)(1.5)=1.125forseismicloads.F.S.forsliding1.2forcollisionforces.




AASHTO5.5.5A


AASHTO5.5.2

AdditionalInformationMoDOTMaterials

Division(http://wwwi/intranet/cm/)

Theresistancetoslidingmaybeincreasedby:

addingashearkeythatprojectsintothesoilbelowthefooting.wideningthefootingtoincreasetheweightandthereforeincreasethefrictionalresistancetosliding.

PassiveResistanceofSoiltoLateralLoad

TheRankineformulaforpassivepressurecanbeusedtodeterminethepassiveresistanceofsoiltothelateralforceonthewall.Thispassivepressureisdevelopedatshearkeysinretainingwallsandatendabutments.

Thepassivepressureagainstthefrontfaceofthewallandthefootingofaretainingwallislooselycompactedandshouldbeneglectedwhenconsideringsliding.

RankineFormula: wherethefollowingvariablesaredefinedinthefigurebelow

Cp=

y1=

Pp=passiveforceatshearkeyinpoundsperfootofwalllength

Cp=coefficientofpassiveearthpressure

=unitweightofsoil

H=heightofthefrontfacefilllessthan1ft.min.forerosion

H1=Hminusdepthofshearkey

y1=locationofPpfrombottomoffooting


Theresistanceduetopassivepressureinfrontoftheshearkeyshallbeneglectedunlessthekeyextendsbelowthedepthoffrostpenetration.

Frostlineissetat36in.atthenorthborderofMissouriandat18in.atthesouthborder.

PassivePressureDuringSeismicLoading

Duringanearthquake,thepassiveresistanceofsoiltolateralloadsisslightlydecreased.TheMononobeOkabestaticmethodisusedtodeterminetheequivalentfluidpressure.

PPE=equivalentpassiveearthpressureduringanearthquake




1992AASHTODiv.IAEqns.C65and

C66


AASHTO5.5.2B

where:

KPE=seismicpassivepressurecoefficient

=unitweightofsoil

H=heightofsoilatthelocationwheretheearthpressureistobefound

kV=verticalaccelerationcoefficient


kH=horizontalaccelerationcoefficient

=slopeofsoilfaceindegrees

i=backfillslopeangleindegrees

=angleoffrictionbetweensoilandwall

SpecialSoilConditions

Duetocreep,somesoftclaysoilshavenopassiveresistanceunderacontinuingload.Removalofundesirablematerialandreplacementwithsuitablematerialsuchassandorcrushedstoneisnecessaryinsuchcases.Generally,thisconditionisindicatedbyavoidratioabove0.9,anangleofinternalfriction( )lessthan22,orasoilshearlessthan0.8ksf.Soilshearisdeterminedfromastandardpenetrationtest.

SoilShear

Friction

Intheabsenceoftests,thetotalshearingresistancetolateralloadsbetweenthefootingandasoilthatderivesmostofitsstrengthfrominternalfrictionmaybetakenasthenormalforcetimesacoefficientoffriction.Iftheplaneatwhichfrictionalresistanceisevaluatedisnotbelowthefrostlinethenthisresistancemustbeneglected.

WhenAShearKeyIsNotUsed

Slidingisresistedbythefrictionforcedevelopedattheinterfacebetweenthesoilandtheconcretefootingalongthefailureplane.Thecoefficientoffrictionforsoilagainstconcretecanbetakenfromthetablebelow.Ifsoildataisnotreadilyavailableorisinconsistent,thefrictionfactor(f)canbetakenas




AASHTO4.4.7.1.2&4.4.8.1.3


AASHTODiv.IA6.3.1(B)and

AASHTO5.5.6.2


f= where istheangleofinternalfrictionofthesoil(CivilEngineeringReferenceManualbyMichaelR.Lindeburg,6thed.,

1992).

CoefficientofFrictionValuesforSoilAgainstConcrete

SoilTypea CoefficientofFrictioncoarsegrainedsoilwithoutsilt 0.55coarsegrainedsoilwithsilt 0.45

silt(only) 0.35clay 0.30b

aItisnotnecessarytocheckrockorshaleforslidingduetoembedment.bCautionshouldbeusedwithsoilswith



AASHTO5.5.6.1criticalsectionforbendingmomentsshallbetakenatthefrontfaceofthestem.Thecriticalsectionforshearshallbetakenatadistanced(d=effectivedepth)fromthefrontfaceofthestem.

Heel

Therearprojection(heel)ofthebaseslabshallbedesignedtosupporttheentireweightofthesuperimposedmaterials,unlessamoreexactmethodisused.Theheelshallbedesignedasacantileversupportedbythewall.Thecriticalsectionforbendingmomentsandshearshallbetakenatthebackfaceofthestem.

ShearKeyDesign

Theshearkeyshallbedesignedasacantileversupportedatthebottomofthefooting.

751.24.3.2.2PileFootings

Footingsshallbecastonpileswhenspecifiedonthe"DesignLayoutSheet".Ifthehorizontalforceagainsttheretainingwallcannototherwiseberesisted,someofthepilesshallbedrivenonabatter.

PileArrangement

Forretainingwallssubjecttomoderatehorizontalloads(walls15to20ft.tall),thefollowinglayoutissuggested.

Section

Plan

Forhigherwallsandmoreextremeconditionsofloading,itmaybenecessaryto:

usethesamenumberofpilesalongallrows

usethreerowsofpiles

providebatterpilesinmorethanonerow

LoadingCombinationsforStabilityandBearing

Thefollowingtablegivestheloadingcombinationstobecheckedforstabilityandpileloads.Theseabbreviationsareusedinthetable:



DL=deadloadweightofthewallelements

SUR=twofeetofliveloadsurcharge

E=earthweight

EP=equivalentfluidearthpressure

COL=collisionforce

EQ=earthquakeinertialforceoffailurewedge

LoadingCase VerticalLoads HorizontalLoads OverturningFactorofSafetySlidingFactorofSafety

BatteredToePiles VerticalToePiles

Ia DL+SUR+E EP+SUR 1.5 1.5 2.0II DL+SUR+E EP+SUR+COL 1.2 1.2 1.2III DL+E EP 1.5 1.5 2.0

IVb DL+E None

Vc DL+E EP+EQ 1.125 1.125 1.5aLoadCaseIshouldbecheckedwithandwithouttheverticalsurcharge.bA25%overstressisallowedontheheelpileinLoadCaseIV.cThefactorsofsafetyforearthquakeloadingare75%ofthatusedinLoadCaseIII.BatteredpilesarenotrecommendedforuseinseismicperformancecategoriesB,C,andD.SeismicdesignofretainingwallsisnotrequiredinSPCAandB.RetainingwallsinSPCBlocatedunderabridgeabutmentshallbedesignedtoAASHTOSpecificationsforSPCB.

PilePropertiesandCapacities

ForLoadCasesIIVinthetableabove,theallowablecompressivepileforcemaybetakenfromthepilecapacitytableinthePilingSectionoftheBridgeManualwhichisbasedinpartonAASHTO4.5.7.3.Alternatively,theallowablecompressivepilecapacityofafrictionpilemaybedeterminedfromtheultimatefrictionalandbearingcapacitybetweenthesoilandpiledividedbyasafetyfactorof3.5(AASHTOTable4.5.6.2.A).Themaximumamountoftensionallowedonaheelpileis3tons.

ForLoadCaseVinthetableabove,theallowablecompressivepileforcemaybetakenfromthepilecapacitytableinthePilingSectionoftheBridgeManualmultipliedbytheappropriatefactor(2.0forsteelbearingpiles,1.5forfrictionpiles).Alternatively,theallowablecompressivepilecapacityofafrictionpilemaybedeterminedfromtheultimatefrictionalandbearingcapacitybetweenthesoilandpiledividedbyasafetyfactorof2.0.Theallowabletensionforceonabearingorfrictionpilewillbeequaltotheultimatefrictioncapacitybetweenthesoilandpiledividedbyasafetyfactorof2.0.

TocalculatetheultimatecompressiveortensilecapacitybetweenthesoilandpilerequirestheboringdatawhichincludestheSPTblowcounts,thefrictionangle,thewaterlevel,andthesoillayerdescriptions.

Assumetheverticalloadcarriedbybatteredpilesisthesameasitwouldbeifthepilewerevertical.ThepropertiesofpilesmaybefoundinthePilingSectionoftheBridgeManual.

NeutralAxisofPileGroup

Locatetheneutralaxisofthepilegroupintherepetitivestripfromthetoeofthefootingatthebottomofthefooting.

MomentofInertiaofPileGroup

Themomentofinertiaofthepilegroupintherepetitivestripabouttheneutralaxisofthesectionmaybedeterminedusingtheparallelaxistheorem:

I=(IA)+(Ad2)where:

IA=momentofinertiaofapileaboutitsneutralaxis

A=areaofapile

d=distancefromapile'sneutralaxistopilegroup'sneutralaxis

IAmaybeneglectedsotheequationreducesto:

I=(Ad2)



ResistanceToSliding

Anyfrictionalresistancetoslidingshallbeignored,suchaswouldoccurbetweenthebottomofthefootingandthesoilonaspreadfooting.

FrictionorBearingPilesWithBatter(Case1)

Retainingwallsusingfrictionorbearingpileswithbattershoulddeveloplateralstrength(resistancetosliding)firstfromthebattercomponentofthepileandsecondfromthepassivepressureagainsttheshearkeyandthepiles.

FrictionorBearingPilesWithoutBatter(Case2)

Retainingwallsusingfrictionorbearingpileswithoutbatterduetositeconstrictionsshoulddeveloplateralstrengthfirstfromthepassivepressureagainsttheshearkeyandsecondfromthepassivepressureagainstthepilebelowthebottomoffooting.Inthiscase,theshearkeyshallbeplacedatthefrontfaceofthefooting.

ConcretePedestalPilesorDrilledShafts(Case3)

Retainingwallsusingconcretepedestalpilesshoulddeveloplateralstrengthfirstfrompassivepressureagainsttheshearkeyandsecondfrompassivepressureagainstthepilebelowthebottomofthefooting.Inthiscase,theshearkeyshallbeplacedatthefrontofthefooting.Donotbatterconcretepedestalpiles.

ResistanceDuetoPassivePressureAgainstPile

Theprocedurebelowmaybeusedtodeterminethepassivepressureresistancedevelopedinthesoilagainstthepiles.Theprocedureassumesthatthepilesdevelopalocalfailureplane.

F=thelateralforceduetopassivepressureonpile

,where:

=unitweightofsoil

H=depthofpileconsideredforlateralresistance(Hmax=6B)

CP=coefficientofactiveearthpressure

B=widthofpile




ResistanceDuetoPileBatter

Usethehorizontalcomponent(duetopilebatter)oftheallowablepileloadasthelateralresistanceofthebatteredpile.(Thispresupposesthatsufficientlateralmovementofthewallcantakeplacebeforefailuretodeveloptheultimatestrengthofbothelements.)

b=theamountofbatterper12inches.

(#ofbatteredpiles)where:

PHBatter=thehorizontalforceduetothebatteredpiles

PT=theallowablepileload

Maximumbatteris4"per12".

ResistanceDuetoShearKeys

Ashearkeymaybeneededifthepassivepressureagainstthepilesandthehorizontalforceduetobatterisnotsufficienttoattainthefactorofsafetyagainstsliding.Thepassivepressureagainsttheshearkeyonapilefootingisfoundinthesamemannerasforspreadfootings.

ResistancetoOverturning

Theresistingandoverturningmomentsshallbecomputedatthecenterlineofthetoepileatadistanceof6B(whereBisthewidthofthepile)belowthebottomofthefooting.Amaximumof3tonsoftensiononeachheelpilemaybeassumedtoresistoverturning.Anyeffectsofpassivepressure,eitherontheshearkeyoronthepiles,whichresistoverturning,shallbeignored.




AASHTO5.5.6.2


AASHTO5.5.6.1

PileProperties

LocationofResultant

Thelocationoftheresultantshallbeevaluatedatthebottomofthefootingandcanbedeterminedbytheequationbelow:

where:

e=thedistancebetweentheresultantandtheneutralaxisofthepilegroup

M=thesumofthemomentstakenabouttheneutralaxisofthepilegroupatthebottomofthefooting

V=thesumoftheverticalloadsusedincalculatingthemoment

PileLoads

Theloadsonthepilecanbedeterminedasfollows:

where:

P=theforceonthepile

A=theareasofallthepilesbeingconsidered

M=themomentoftheresultantabouttheneutralaxis

c=distancefromtheneutralaxistothecenterlineofthepilebeinginvestigated

I=themomentofinertiaofthepilegroup

StemDesign

Theverticalstem(thewallportion)ofacantileverretainingwallshallbedesignedasacantileversupportedatthebase.

FootingDesign

Toe

Thetoeofthebaseslabofacantileverwallshallbedesignedasacantileversupportedbythewall.Thecriticalsectionforbendingmomentsshallbetakenatthefrontfaceofthestem.Thecriticalsectionforshearshallbetakenatadistanced(d=effectivedepth)fromthefrontfaceofthestem.

HeelThetopreinforcementintherearprojection(heel)ofthebaseslabshallbedesignedtosupporttheentireweightofthesuperimposedmaterialsplusanytensionloadintheheelpiles(neglectcompressionloadsinthepile),unlessamoreexactmethodisused.Thebottomreinforcementintheheelofthebaseslabshallbedesignedtosupportthemaximum



compressionloadinthepileneglectingtheweightofthesuperimposedmaterials.Theheelshallbedesignedasacantileversupportedbythewall.Thecriticalsectionsforbendingmomentsandshearshallbetakenatthebackfaceofthestem.

ShearKeyDesignTheshearkeyshallbedesignedasacantileversupportedatthebottomofthefooting.

751.24.3.2.3CounterfortWalls

Assumptions:

(1)StabilityTheexternalstabilityofacounterfortretainingwallshallbedeterminedinthesamemannerasdescribedforcantileverretainingwalls.Thereforerefertopreviouspagesforthecriteriaforlocationofresultant,factorofsafetyforslidingandbearingpressures.

(2)Stem

where:

Ca=coefficientofactiveearthpressure

=unitweigtofsoil

Designthewalltosupporthorizontalloadfromtheearthpressureandtheliveloadsurcharge(ifapplicable)asoutlinedonthepreviouspagesandasdesignatedinAASHTDSection3.20,exceptthatmaximumhorizontalloadsshallbethecalculatedequivalentfluidpressureat3/4heightofwall[(0.75H)P]whichshallbeconsideredapplieduniformlyfromthelowerquarterpointtothebottomofwall.

Inaddition,verticalsteelInthefillfaceofthebottomquarterofthewallshallbethatrequiredbytheverticalcantileverwallwiththeequivalentfluidpressureofthat(0.25H)height.

Maximumconcretestressshallbeassumedasthegreaterofthetwothusobtained.

Theapplicationofthesehorizontalpressuresshallbeasfollows:



CounterfortWallSectionMomentsaretobedeterminedbyanalysisasacontinuousbeam.Thecounterfortsaretobespacedsoastoproduce

approximatelyequalpositiveandnegativemoments.

(3)CounterfortCounterfortsshallbedesignedasTbeams,ofwhichthewallistheflangeandthecounterfortisthestem.Forthisreasontheconcretestressesanenormallylowandwillnotcontrol.

Forthedesignofreinforcingsteelinthebackofthecounterfort,theeffectivedshallbetheperpendiculardistancefromthefrontfaceofthewall(atpointthatmomentisconsidered),tocenterofreinforcingsteel.

(4)Footing

Thefootingofthecounterfortwallsshallbedesignedasacontinuousbeamofspansequaltothedistancebetweenthecounterforts.

Therearprojectionorheelshallbedesignedtosupporttheentireweightofthesuperimposedmaterials,unlessamoreexactmethodisused.RefertoAASHTDSection5.5.6.

Dividefooting(transversely)intofour(4)equalsectionsfordesignfootingpressures.

Counterfortwallsonpileareveryrareandaretobetreatedasspecialcases.SeeStructuralProjectManager.

(5)SignBoardtypewalls

TheSignBoardtypeofretainingwallsareaspecialcaseofthecounterfortretainingwalls.ThistypeofwallisusedwherethesoiIconditionsaresuchthatthefootingsmustbeplacedagreatdistancebelowthefinishedgroundline.Forthissituation,thewallisdiscontinuedapproximately12in.belowthefinishedgroundlineorbelowthefrostline.

Duetothelargedepthofthecounterforts,itmaybemoreeconomicaltouseasmallernumberofcounterfortsthanwouldotherwisebeused.

Alldesignassumptionsthatapplytocounterfortwallswillapplytosignboardwallswiththeexceptionoftheapplicationofhorizontalforcesforthestem(orwalldesign),andthefootingdesignwhichshallbeasfollows:

Wall



Footing

Theindividualfootingsshallbedesignedtransverselyascantileverssupportedbythewall.RefertoAASHTOSection5.

751.24.3.3Example1:SpreadFootingCantileverWall

TypicalSectionthruWall(SpreadFooting)

f'c=3,000psify=60,000psi=24in.s=120pcf(unitwgtofsoil)Allowablesoilpressure=2tsfc=150pcf(unitwgtofconcr.)RetainingwallislocatedinSeismicPerformanceCategory(SPC)B.A=0.1(A=seismicaccelerationcoefficient)



Assumptions

Retainingwallisunderanabutmentorinalocationwherefailureofthewallmayaffectthestructuralintegrityofabridge.Therefore,itmustbedesignedforSPCB.

Designisforaunitlength(1ft.)ofwall.

Summomentsaboutthetoeatthebottomofthefootingforoverturning.

ForGroupLoadsIVIloading:

F.S.foroverturning2.0forfootingsonsoil.F.S.forsliding1.5.

Resultanttobewithinmiddle1/3offooting.

Forearthquakeloading:

F.S.foroverturning0.75(2.0)=1.5.F.S.forsliding0.75(1.5)=1.125.Resultanttobewithinmiddle1/2offooting.

Baseoffootingisbelowthefrostline.

Neglecttoponefootoffillovertoewhendeterminingpassivepressureandsoilweight.

Useofashearkeyshiftsthefailureplaneto"B"whereresistancetoslidingisprovidedbypassivepressureagainsttheshearkey,frictionofsoilalongfailureplane"B"infrontofthekey,andfrictionbetweensoilandconcretealongthefootingbehindthekey.

Soilcohesionalongfailureplaneisneglected.

Footingsaredesignedascantileverssupportedbythewall.

Criticalsectionsforbendingareatthefrontandbackfacesofthewall.Criticalsectionsforshearareatthebackfaceofthewallfortheheelandatadistanced(effectivedepth)fromthefrontfaceforthetoe.

Neglectsoilweightabovetoeoffootingindesignofthetoe.

Thewallisdesignedasacantileversupportedbythefooting.

LoadfactorsforAASHTOGroupsIVIfordesignofconcrete:

=1.3.E=1.3forhorizontalearthpressureonretainingwalls.E=1.0forverticalearthpressure.

Loadfactorforearthquakeloads=1.0.

LateralPressuresWithoutEarthquake

Ca=

Ca= =0.546



Load Area(ft2) Force(k)=(UnitWgt.)(Area) Arm(ft.) Moment(ftk)(1) (0.5)(6.667ft)(2.222ft)=7.407 0.889 7.278 6.469(2) (6.667ft)(6.944ft)=46.296 5.556 6.167 34.259(3) (0.833ft)(8.000ft)+(0.5)(0.083ft)(8.000ft)=7.000 1.050 2.396 2.515(4) (1.500ft)(9.500ft)=14.250 2.138 4.750 10.153(5) (2.500ft)(1.000ft)=2.500 0.375 2.500 0.938(6) (1.000ft)(1.917ft)+(0.5)(0.010ft)(1.000ft)=1.922 0.231 0.961 0.222 V=10.239 MR=54.556

PAV 1.178 9.500 11.192

resisting V=11.417 MR=65.748

PAH 3.534 3.556 12.567PP 2.668 1.3891

1Thepassivecapacityattheshearkeyisignoredinoverturningchecks,sincethiscapacityisconsideredinthefactorofsafetyagainstsliding.Itisassumedthataslidingandoverturningfailurewillnotoccursimultaneously.Thepassivecapacityattheshearkeyisdevelopedonlyifthewalldoesslide.

Overturning

F.S.= o.k.

where:MOT=overturningmomentMR=resistingmoment

ResultantEccentricity

=4.658ft.

o.k.

Sliding

CheckifshearkeyisrequiredforGroupLoadsIVI:

F.S.= =0.896nogoodshearkeyreq'd

where:sc=angleoffrictionbetweensoilandconcrete=(2/3)ss

F.S.=

where:ss=angleofinternalfrictionofsoil

F.S.= =1.7891.5o.k.

FootingPressure



PH=pressureatheel =1.132k/ft2

PT=pressureattoe =1.272k/ft2

Allowablepressure=2tons/ft2=4k/ft21.272k/ft2o.k.

LateralPressuresWithEarthquake

kh=0.5A=0.5(0.1)=0.05

kv=0

ActivePressureonPsuedoWall

==24(istheangleoffrictionbetweenthesoilandthewall.Inthiscase,==becausethesoilwedgeconsideredisnexttothesoilabovethefooting.)

i=18.435

=0

KAE=0.674

PAE=sH2(1kv)KAE

PAE=[0.120k/ft3](10.667ft)2(1ft.)(10)(0.674)=4.602k

PAEV=PAE(sin)=4.602k(sin24)=1.872k

PAEH=PAE(cos)=4.602k(cos24)=4.204k

P'AH=PAEHPAH=4.204k3.534k=0.670k

P'AV=PAEVPAV=1.872k1.178k=0.694k

where:P'AHandP'AVaretheseismiccomponentsoftheactiveforce.

PassivePressureonShearKey

==24(=becausethesoilwedgeconsideredisassumedtoforminfrontofthefooting.)

i=0

=0



KPE=0.976

PPE=sH2(1kv)KPE

PPE=[0.120k/ft3][(5.0ft)2(2.5ft2)](1ft.)(10)(0.976)=1.098k

Load Force(k) Arm(ft) Moment(ftk)(1)thru(6) 10.239 54.556

PAV 1.178 9.500 11.192P'AV 0.694 9.500 6.593

resisting V=12.111 MR=72.341

PAH 3.534 3.556 12.567P'AH 0.670 6.400a 4.288PPEV 0.447b 0.000 0.000PPEH 1.003b 1.389c 0.000

MOT=16.855aP'AHactsat0.6Hofthewedgeface(1992AASHTODiv.IACommentary).bPPEHandPPEHarethecomponentsofPPEwithrespectto(thefrictionangle).PPEdoesnotcontributetooverturning.cThelineofactionofPPEHcanbelocatedaswasdoneforPP.

Overturning

o.k.


o.k.

Sliding

o.k.

FootingPressure

foreL/6:




1992AASHTODiv.IACommentary

=1.139k/ft2

=1.411k/ft2

Allowablesoilpressureforearthquake=2(allowablesoilpressure)

(2)[4k/ft2]=8k/ft2>1.411k/ft2o.k.

ReinforcementStem

d=11"2"(1/2)(0.5")=8.75"

b=12"

f'c=3,000psi

WithoutEarthquake

PAH=[0.120k/ft3](0.546)(6.944ft.)2(1ft.)(cos18.435)=1.499k

=1.3

E=1.3(activelateralearthpressure)

Mu=(1.3)(1.3)(1.499k)(2.315ft)=5.865(ftk)

WithEarthquake

kh=0.05

kv=0

=2.862

=/2=24/2=12forangleoffrictionbetweensoilandwall.Thiscriteriaisusedonlyforseismicloadingiftheangleoffrictionisnotknown.

=24

i=18.435

=0

KAE=0.654

PAEH=1/2sKAEH2cos

PAEH=1/2[0.120k/ft](0.654)(6.944ft.)2(1ft.)cos(12)=1.851k

Mu=(1.499k)(2.315ft.)+(1.851k1.499k)(0.6(6.944ft.))=4.936(ftk)

Themomentwithoutearthquakecontrols:




AASHTO8.17.1.1&8.15.2.1.1

=85.116psi

=

= =0.00144

min= =0.00245

Use=4/3=4/3(0.00144)=0.00192

ASReq=bd=0.00192(12in.)(8.75in.)=0.202in.2/ft

One#4barhasAS=0.196in2

s=11.64in.

Use#4's@10"cts.

CheckShear

VuVn

WithoutEarthquake

Vu,=(1.3)(1.3)(1.499k)=2.533k

WithEarthquake

Vu=1.851k

Theshearforcewithoutearthquakecontrols.

=28.4psi

=109.5psi>28.4psio.k.

ReinforcementFootingHeel

Note:Earthquakewillnotcontrolandwillnotbechecked.

E=1.0(verticalearthpressure)



d=18"3"(1/2)(0.750")=14.625"

b=12"

f'c=3,000psi

Mu=1.3[(5.556k+1.500k)(3.333ft)+0.889k(4.444ft)+1.178k(6.667ft)]

Mu=45.919(ftk)

=238.5psi

= =0.00418

min= =0.00235

ASReq=0.00418(12in.)(14.625in.)=0.734in2/ft.

Use#6's@7"cts.

CheckShear

Shearshallbecheckedatbackfaceofstem.

Vu=1.3(5.556k+1.500k+0.889k+1.178k)=11.860k

=109.5psio.k.

ReinforcementFootingToe

d=18"4"=14"

b=12"

WithoutEarthquake

ApplyLoadFactors

load4(weight)=0.431k(1.3)(1.0)=0.560k

E=1.3forlateralearthpressureforretainingwalls.

E=1.0forverticalearthpressure.

MOT=12.567(ftk)(1.3)(1.3)=21.238(ftk)



MR=[54.556(ftk)+11.192(ftk)](1.3)(1.0)=85.472(ftk)

V=11.417k(1.3)(1.0)=14.842k

=4.328ft.

e=(9.5ft./2)4.328ft.=0.422ft.

=1.146k/ft2

=1.979k/ft2

=1.811k/ft.

Mu=2.997(ftk)

WithEarthquake

PH=1.139k/ft

PT=1.411k/ft

=1.356k/ft

Mu=2.146(ftk)

Themomentwithoutearthquakecontrols.

=16.990psi

= =0.000284

min= =0.00257

Use=4/3= =0.000379

ASReq=0.000379(12in.)(14.0in.)=0.064in.2/ft.

s=36.8in.

Minimumis#4barsat12inches.Thesewillbethesamebarsthatareinthebackofthestem.Usethesmallerofthetwospacings.



Use#4's@10"cts.

CheckShear

Shearshallbecheckedatadistance"d"fromthefaceofthestem.

WithoutEarthquake

=1.913k/ft.

=1.240k

WithEarthquake

=1390k/ft.

=0.788k

Shearwithoutearthquakecontrols.

=109.5psio.k.

ReinforcementShearKey

Thepassivepressureishigherwithoutearthquakeloads.

=1.3

E=1.3(lateralearthpressure)

d=12"3"(1/2)(0.5")=8.75"

b=12"

Mu=(3.379k)(1.360ft.)(1.3)(1.3)=7.764(ftk)

=112.677psi

= =0.00192

min= =0.00292



Use=4/3=4/3(0.00192)=0.00256

ASReq=0.00256(12in.)(8.75in.)=0.269in.2/ft.

Use#[email protected].

CheckShear

=109.5psio.k.

ReinforcementSummary

751.24.3.4Example2:LShapedCantileverWall

TypicalSectionthruWall(SpreadFooting)

f'c=4000psi



fy=60,000psi

=29

s=120pcf

Allowablesoilpressure=1.5tsf=3.0ksf

RetainingwallislocatedinSeismicPerformanceCategory(SPC)A.

=21.801

=0.462

=2.882

PA=1/2sCaH2=1/2(0.120k/ft3)(0.462)(4.958ft.)2=0.681k

Forsliding,PPisassumedtoactonlyontheportionofkeybelowthefrostlinethatissetatan18in.depthonthesouthernborder.

PP=1/2(0.120k/ft3)(2.882)[(2.458ft.)2(1.500ft.)2]=0.656k

Assumptions

Designisforaunitlength(1ft.)ofwall.

Summomentsaboutthetoeatthebottomofthefootingforoverturning.

F.S.foroverturning2.0forfootingsonsoil.

F.S.forsliding1.5forfootingsonsoil.

Resultantofdeadloadandearthpressuretobeinbackhalfofthemiddlethirdofthefootingifsubjectedtofrostheave.

Forallloadingcombinationstheresultantmustbeinthemiddlethirdofthefootingexceptforcollisionloads.

Thetop12in.ofthesoilisnotneglectedindeterminingthepassivepressurebecausethesoiltherewillbemaintained.

Frostlineissetat18in.atthesouthborderforMissouri.

Portionsofshearkeywhichareabovethefrostlineareassumednottoresistslidingbypassivepressure.

Useofashearkeyshiftsthefailureplaneto"B"whereresistancetoslidingisalsoprovidedbyfrictionofsoilalongthefailureplaneinfrontoftheshearkey.Frictionbetweenthesoilandconcretebehindtheshearkeywillbeneglected.

Soilcohesionalongthefailureplaneisneglected.

Liveloadscanmovetowithin1ft.ofthestemfaceand1ft.fromthetoe.


Footingisdesignedasacantileversupportedbythewall.Criticalsectionsforbendingandshearwillbetakenatthefaceofthewall.

LoadfactorsforAASHTOGroupsIVIfordesignofconcreteare:

=1.3.

E=1.3forhorizontalearthpressureonretainingwalls.

E=1.0forverticalearthpressure.

LL=1.67forliveloadsandcollisionloads.

DeadLoadandEarthPressureStabiltyandPressureChecks



DeadLoadandEarthPressureStabiltyandPressureChecksLoad Force(k) Arm(in.) Moment(ftk)(1) (0.833ft.)(5.167ft.)(0.150k/ft3)=0.646 5.333 3.444(2) (0.958ft)(5.750ft)(0.150k/ft3)=0.827 2.875 2.376(3) (1.000ft)(1.500ft)(0.150k/ft3)=0.22534.259 4.250 0.956

V=1.698 MR=6.776

PAV 0.253 5.750 1.455

V=1.951 MR=8.231

PAH 0.633 1.653 1.045PP 0.656 1.061

MOT=1.0451Thepassivepressureattheshearkeyisignoredinoverturningchecks.

Overturning

=7.8772.0o.k.

LocationofResultant

MoDOTpolicyisthattheresultantmustbeinthebackhalfofthemiddlethirdofthefootingwhenconsideringdeadandearthloads:

=3.683ft.o.k.

Sliding

where:

ss=angleofinternalfrictionofsoil

sc=angleoffrictionbetweensoilandconcrete=(2/3)ss

=2.3391.5o.k.

FootingPressure

=0.808ft.

Heel: =0.625ksf



Stabilityisnotanissuebecausetheliveloadresistsoverturningandincreasestheslidingfrictionforce.

Theliveloadwillbedistributedas:

whereE=0.8X+3.75

X=distanceinfeetfromtheloadtothefrontfaceofwall

Theliveloadwillbepositionedasshownbythedashedlinesabove.Thebearingpressureandresultantlocationwillbedeterminedforthesetwopositions.

LiveLoad1ftFromStemFace


X=1ft.

E=0.8(1ft.)+3.75=4.55ft.

=3.516k

=3.834ft.

=5.75ft.o.k.

FootingPressure

AllowablePressure=3.0ksf

Heel: =1.902ksf

Toe: =0.000ksf

LiveLoad1ftFromToe


X=3.917ft.

E=0.8(3.917ft.)+3.75=6.883ft.



=2.324k

=2.225ft.

=0.958ft.o.k.

FootingPressure

AllowablePressure=3.0ksf

Heel: =0.239ksfo.k.

Toe: =1.248ksfo.k.

DeadLoad,EarthPressure,CollisionLoad,andLiveLoadStabilityandPressureChecks

Duringacollision,theliveloadwillbeclosetothewallsocheckthiscombinationwhentheliveloadisonefootfromthefaceofthestem.Sliding(ineitherdirection)willnotbeanissue.Stabilityabouttheheelshouldbecheckedalthoughitisunlikelytobeaproblem.Therearenocriteriaforthelocationoftheresultant,solongasthefootingpressuredoesnotexceed125%oftheallowable.Itisassumedthatthedistributedcollisionforcewilldevelopanequalandoppositeforceonthefillfaceofthebackwallunlessitexceedsthepassivepressurethatcanbedevelopedbysoilbehindthewall.

FLL=3.516k

FCOLL= =1.667k

=1.867

PPH=2.556k>FCOLLThusthesoilwilldevelopanequalbutopp.force.

OverturningAbouttheHeel

F.S.=

F.S.= =1.8471.2o.k.



FootingPressure

=1.022ft.fromheel

e= =1.853ft.

AllowablePressure=(1.25)(3.0ksf)=3.75ksf

Heel: =3.566ksfo.k.

StemDesignSteelinRearFace

=1.3

E=1.3(activelateralearthpressure)

d=10in.2in.(0.5in./2)=7.75in.

PAH=0.412k

Mu=(1.333ft.)(0.412k)(1.3)(1.3)=0.928(ftk)

=17.160psi

=0.000287

=0.00298

Use=(4/3)=(4/3)(0.000287)=0.000382



One#4barhasAS=0.196in2,sotherequiredminimumofone#4barevery12in.controls.

Use#4's@12in.(min)

(Thesebarsarealsothebarsinthebottomofthefootingsothesmallerofthetworequiredspacingswillbeused.)

CheckShear

=8.8psi

=126.5psi>8.8psio.k.

StemDesignSteelinFrontFace(CollisionLoads)

Thesoilpressureonthebackofthestembecomespassivesoilpressureduringacollision,howeverthispressureisignoredforreinforcementdesign.

=1.3

LL=1.67

=7.75in.

=1.667k/ft.

Mu=1.667k/ft.(1ft.)(3ft.)(1.3)(1.67)=10.855(ftk)

=200.809psi

=0.00345

=0.00298



One#4barhasAS=0.196in2.

s=7.3in.

Use#4's@7in.

CheckShear

=45.8psi



=0.653ksf

MomentatWallFace:

=1.524(ftk)

DeadLoad,EarthPressure,andLiveLoad

LiveLoad1ft.FromStemFace

E=1.3(lateralearthpressure)

LL=1.67

=1.3

ApplyLoadFactors:

FLL=3.516k(1.3)(1.67)=7.633k

V=7.633k+1.951k(1.3)=10.169k

MOT=1.045(ftk)(1.3)(1.3)=1.766(ftk)

MR=8.231(ftk)(1.3)+3.917ft.(7.633k)=40.599(ftk)

=3.819ft.

e=3.819ft.(5.75ft./2)=0.944ft.

=0.026ksf

=3.511ksf

=3.006ksf

=2.400ksf

Footingwt.fromfaceofwalltotoe:



Footingwt.= =0.919k

Footingwt.fromLLWLtotoe:

Footingwt.= =0.732k

MomentatWallFace:

MW=

MW=2.430(ftk)

MomentatLLWL:

MLL= =4.837(ftk)

LiveLoad1ft.FromToe

ApplyLoadFactors:

FLL=2.324k(1.3)(1.67)=5.045k

V=5.045k+1.951k(1.3)=7.581k

MOT=1.045(ftk)(1.3)(1.3)=1.766(ftk)

MR=8.231(ftk)(1.3)+5.045k(1ft.)=15.745(ftk)

=1.844ft.

=1.031ft.

PH=0ksf

=2.741ksf

L1=3[(L/2)e]

L1=3[(5.75ft./2)1.031ft.]=5.532ft.



=0.305ksf

=2.196ksf

MomentatWallFace:

MW=

=1.298(ftk)

MomentatLLWL:

MLL= =1.186(ftk)

DesignFlexuralSteelinBottomofFooting

d=11.5in.4in.=7.500in.

Mu=4.837(ftk)(controllingmoment)

=0.096ksi

=0.00162

=0.00421

Use=(4/3)=(4/3)(0.00162)=0.00216

ASReq=0.00216(12in.)(7.5in.)=0.194in2/ft.

s=12.1in.

Use#4'[email protected].(Alsousethisspacinginthebackofthestem.)

CheckShear

DeadLoadandEarthPressureOnly

VW=1.038k

LiveLoad1ft.FromStemFace

Shearatthewallcanbeneglectedforthisloadingcase.



VLL=4.019k

LiveLoad1ft.FromToe

VW=1.525k

VLL=2.282k

UseVU=4.019k

=126.5psi

ShearKeyDesign

Forconcretecastagainstandpermanentlyexposedtoearth,minimumcoverforreinforcementis3inches.

=8.75in.

=0.331k/ft.

=0.850k/ft.

Mu=1.287(ftk)

=0.0187ksi

=0.000312

=0.00337

Use=(4/3)=(4/3)(0.000312)=0.000416

ASReq=0.000416(12in.)(8.75in.)=0.0437in2/ft.



s=53.8in.

Use#4'[email protected].(min)

CheckShear

V=0.886k

=16.8psi



fc=3,000psi

fy=60,000psi

=27

s=120pcf

Piletype:HP10x42

Allowablepilebearing=56tons

Pilewidth=10inches

Toepilebatter=1:3

Barriercurbweight=340lbs/ft.oflength



Barriercurbresultant=0.375ft.fromitsflatback

Assumptions

Retainingwallislocatedsuchthattrafficcancomewithinhalfofthewallheighttotheplanewhereearthpressureisapplied.

Reinforcementdesignisforonefootofwalllength.

Summomentsaboutthecenterlineofthetoepileatadistanceof6B(whereBisthepilewidth)belowthebottomofthefootingforoverturning.

Neglecttoponefootoffillovertoeindeterminingsoilweightandpassivepressureonshearkey.

Neglectallfillovertoeindesigningstemreinforcement.


Footingisdesignedasacantileversupportedbythewall.

Criticalsectionsforbendingareatthefrontandbackfacesofthewall.

Criticalsectionsforshearareatthebackfaceofthewallfortheheelandatadistanced(effectivedepth)fromthefrontfaceforthetoe.

Forloadfactorsfordesignofconcrete,seeEPG751.24.1.2GroupLoads.

=0,=27soCAreducesto:

=0.376

=2.663

Table751.24.3.5.1isforstabilitycheck(momentstakenaboutC.L.oftoepileatadepthof6Bbelowthebottomofthefooting).

Table751.24.3.5.1

Load Force(kips/ft) ArmaboutC.L.oftoepileat6Bbelowfooting(ft.)Moment(ftkips)perfootof

walllength

DeadLoad

(1) 0.340 2.542 0.864

(2) (1.333ft.)(7.000ft.)(0.150k/ft3)=

1.4002.833 3.966

(3) (3.000ft.)(8.500ft.)(0.150k/ft3)=

3.8254.417 16.895

(4) (1.000ft.)(1.750ft.)(0.150k/ft3)=

0.2634.417 1.162

V=5.828 MR=22.887

EarthLoad

(5) (7.000ft.)(5.167ft.)(0.120k/ft3)=

4.3406.083 26.400

(6) (2.000ft.)(2.000ft.)(0.120k/ft3)=

0.4801.167 0.560

V=4.820 MR=26.960

LiveLoadSurcharge

PSV(2.000ft.)(5.167ft.)(0.120k/ft3)=

1.2406.083 MR=7.543

PSH(2.000ft.)(0.376)(10.000ft.)

(0.120k/ft3)=0.90210.000 MOT=9.020

EarthPressurePA 2.2561 8.333 MOT=18.799

PP 3.2852



CollisionForce(FCOL)

(10.000k)/[2(7.000ft.)]=0.714 18.000 MOT=12.852

HeelPileTension(PHV)

(3.000tons)(2k/ton)(1pile)/(12.000ft.)=0.500 7.167

MR=3.584

ToePileBatter(PBH) 5.9033 PassivePilePressure

(Ppp) 0.8324

1

2

3

4

Table751.24.3.5.2isforbearingpressurechecks(momentstakenaboutC.Loftoepileatthebottomofthefooting).

Table751.24.3.5.2

Load Force(kips/ft) ArmaboutC.L.oftoepileat6Bbelowfooting(ft.)Moment(ftkips)perfootof

walllength

DeadLoad

(1) 0.340 0.875 0.298

(2) (1.333ft.)(7.000ft.)(0.150k/ft3)=

1.4001.167 1.634

(3) (3.000ft.)(8.500ft.)(0.150k/ft3)=

3.8252.750 10.519

(4) (1.000ft.)(1.750ft.)(0.150k/ft3)=

0.2632.750 0.723

V=5.828 MR=13.174

EarthLoad

(5) (7.000ft.)(5.167ft.)(0.120k/ft3)=

4.3404.417 19.170

(6) (2.000ft.)(2.000ft.)(0.120k/ft3)=

0.4800.500 0.240

V=4.820 MR=18.930

LiveLoadSurcharge

PSV(2.000ft.)(5.167ft.)(0.120k/ft3)=

1.2404.417 MR=5.477

PSH(2.000ft.)(0.376)(10.000ft.)

(0.120k/ft3)=0.9025.000 MOT=4.510

EarthPressurePA 2.256 3.333 MOT=7.519

PP 3.285 CollisionForce

(FCOL)(10.000k)/[2(7.000ft.)]=0.714 13.000 MOT=9.282

HeelPileTension(PHV)

(3.000tons)(2k/ton)(1pile)/(12.000ft.)=0.500 5.500

MR=2.750

ToePileBatter(PBH) 5.903 PassivePilePressure

(Ppp)0.832

Investigatearepresentative12ft.strip.Thiswillincludeoneheelpileandtwotoepiles.Theassumptionismadethatthestiffnessofabatterpileintheverticaldirectionisthesameasthatofaverticalpile.



NeutralAxisLocation=[2piles(1.5ft.)+1pile(7ft.)]/(3piles)=3.333ft.fromthetoe.

I=Ad2

Forrepetitive12ft.strip:

Totalpilearea=3A

I=2A(1.833ft.)2+A(3.667ft.)2=20.167(A)ft.2

Fora1ft.unitstrip:

Totalpilearea=(3A/12ft.)=0.250A

CaseI

F.S.foroverturning1.5

F.S.forsliding1.5

CheckOverturning

NeglectresistingmomentduetoPSVforthischeck.

MR=22.887(ftk)+26.960(ftk)+3.584(ftk)

MR=53.431(ftk)

MOT=9.020(ftk)+18.799(ftk)=27.819(ftk)

F.S.OT= =1.921>1.5o.k.

CheckPileBearing

WithoutPSV:

V=5.828k+4.820k=10.648k

e= =1.885ft.



Momentarm=1.885ft.1.833ft.=0.052ft.

Allowablepileload=56tons/pile.EachpilehasareaA,so:

o.k.

o.k.

WithPSV:

V=5.828k+4.820k+1.240k=11.888k

=2.149ft.


o.k.

o.k.

CheckSliding

=3.1731.5o.k.

CaseII


F.S.forsliding1.2

CheckOverturning

MR=(22.887+26.960+7.543+3.584)(ftk)=60.974(ftk)

MOT=(9.020+18.799+12.852)(ftk)=40.671(ftk)

=1.4991.2o.k.

CheckPileBearing

=1.369ft.




o.k.

=35.519k

o.k.

CheckSliding

=2.5881.2o.k.

CaseIII


F.S.forsliding1.5

CheckOverturning

MR=(22.887+26.960+3.584)(ftk)=53.431(ftk)

MOT=18.799(ftk)

=2.8421.5o.k.

CheckPileBearing

=2.309ft.


=37.065k

o.k.

=53.649k

o.k.

CheckSliding

=4.4411.5o.k.

CaseIV

CheckPileBearing

=3.015ft.




25%overstressisallowedontheheelpile:

o.k.

=28.868k

o.k.

ReinforcementStem

b=12in.

cover=2in.

h=16in.

d=16in.2in.0.5(0.625in.)=13.688in.

FCollision=0.714k/ft

ApplyLoadFactors

FCol.=LL(0.714k)=(1.3)(1.67)(0.714k)=1.550k

PLL=E(0.632k)=(1.3)(1.67)(0.632k)=1.372k

PAStem=E(1.105k)=(1.3)(1.3)(1.105k)=1.867k

Mu=(10.00ft.)(1.550k)+(3.500ft.)(1.372k)+(2.333ft.)(1.867k)

Mu=24.658(ftk)



=0.146ksi

=0.00251

=0.00212

=0.00251

One#5barhasAS=0.307in2

s=8.9in.


CheckShear

VuVn

Vu=FCollision+PLL+PAStem=1.550k+1.372k+1.867k=4.789k

=34.301psi

=109.5psi>34.3psio.k.

ReinforcementFootingTopSteel

b=12in.

cover=3in.

h=36in.

d=36in.3in.0.5(0.5in.)=32.750in.

Designtheheeltosupporttheentireweightofthesuperimposedmaterials.

Soil(1)=4.340k/ft.



LLs=1.240k/ft.

=2.325k/ft.

ApplyLoadFactors

Soil(1)=E(4.340k)=(1.3)(1.0)(4.340k)=5.642k

LLs=E(1.240k)=(1.3)(1.67)(1.240k)=2.692k

Slabwt.=D(2.325k)=(1.3)(1.0)(2.325k)=3.023k

Mu=(2.583ft.)(5.642k+2.692k+3.023k)=29.335(ftk)

=0.0304ksi

=0.000510

=0.00188

Use=4/3=4/3(0.000510)=0.000680

One#4barhasAs=0.196in.2

s=8.8in.


CheckShear

=33.998psi109.5psi=co.k.

ReinforcementFootingBottomSteel

Designtheflexuralsteelinthebottomofthefootingtoresistthelargestmomentthattheheelpilecouldexertonthefooting.ThelargestheelpilebearingforcewasinCaseIV.Theheelpilewillcausealargermomentaboutthestemfacethanthetoepile(eventhoughtherearetwotoepilesforeveryoneheelpile)becauseithasamuchlongermomentarmaboutthestemface.



Pileisembeddedintofooting12inches.

b=12in.

h=36in.

d=36in.4in.=32in.

ApplyLoadFactorstoCaseIVLoads

V=13.842k/ft.

M=41.735(ftk)/ft.

e= =3.015ft.


=7.588k/ft.

=27.825(ftk)/ft.

=0.0301ksi

=0.000505



=0.00196

Use=4/3=4/3(0.000505)=0.000673

ASReq=bd=(0.000673)(12in.)(32in.)=0.258in2/ft.

One#4barhasAs=0.196in2.

s=9.1in.


CheckShear

Thecriticalsectionforshearforthetoeisatadistanced=21.75inchesfromthefaceofthestem.Thetoepileis6inchesfromthestemfacesothetoepilesheardoesnotaffecttheshearatthecriticalsection.Thecriticalsectionforshearisatthestemfacefortheheelsoalloftheforceoftheheelpileaffectstheshearatthecriticalsection.TheworstcaseforshearisCaseIV.

Vu=7.588k

=23.248psi109.5psi=co.k.

ReinforcementShearKey

b=12in.

h=12in.

cover=3in.

d=12in.3in.0.5(0.5in.)=8.75in.

ApplyLoadFactors

PP=E(3.845k)=(1.3)(1.3)(3.845k)=6.498k

Mu=(0.912ft.)(6.498k)=5.926(ftk)

=0.0860ksi

=0.00146

=0.00292

Use=4/3=4/3(0.00146)=0.00195

ASReq=bd=(0.00195)(12in.)(8.75in.)=0.205in.2/ft.

One#4barhasAs=0.196in2



s=11.5in.


CheckShear

=72.807psi



Eachsectionofwallshallbeinincrementsof4ft.withamaximumlengthof28'0".



CantileverWallsLShaped




CounterfortWalls

Notes:Dimension"A"



*Maximumlength=28'0".*Eachsectiontobein4'0"increments.

*(Seerusticationrecessdetails.)Dimensions"B"&"C"

*Asrequiredbythedesigntobalancethenegativeandpositivemoments.(Seethedesignassumptions).

Notes:Batter"D":

*Asrequiredtomaintain9"minimumatthetopofthecounterfortand12"minimumedgedistanceatthetopofthefooting,betweencounterfortandfootingedge.

*Battertobegivenaneighthofaninchperfootofcounterfortheight.Dimension"L":

*Asrequiredforstability.*Asanestimate,use"L"equalto1/2theheightof"H".

SignBoardTypeCounterfortWalls



Notes:Dimension"A"

*Maximumlength=28'0".*Eachsectiontobein4'0"increments.

*(Seerusticationrecessdetails.)Dimensions"B"&"C"

*Asrequiredbythedesigntobalancethenegativeandpositivemoments.(Seethedesignassumptions).

Dimension"E"*(Signboardtypeonly)

*Asrequiredtomaintainfootingpressurewithintheallowableforexistingfoundationmaterial.12"minimum.



Notes:Batter"D":

*Asrequiredtomaintain9"minimumatthetopofthecounterfortand12"minimumedgedistanceatthetopofthefooting,betweencounterfortandfootingedge.

*Battertobegivenaneighthofaninchperfootofcounterfortheight.Dimension"L":

*Asrequiredforstability.*Asanestimate,use"L"equalto1/2theheightof"H".

751.24.3.7Reinforcement

CantileverWalls



(*)Alternatelongandshortbarsatequalspaces.(**)Ifcollisionfrocesareassumed,use#4@12"cts.min.andextendatleastdevelopmentlengthintofooting.(SeeSection

2.4)(***)Theo.cutoffforbending+developmentlength.(Wallheightover10'only.)



(*)Alternatelongandshortbarsatequalspaces.(**)Ifcollisionfrocesareassumed,use#4@12"cts.min.andextendatleastdevelopmentlengthintofooting.(SeeSection

2.4)(***)Theo.cutoffforbending+developmentlength.(Wallheightover10'only.)

(****)Duetositeconstriction.

CantileverWallsLShaped



(*)Donotsplicestressbarsinthefillfaceattopoffooting.(**)Ifcollisionfrocesareassumed,use#4@12"cts.min.andextendatleastdevelopmentlengthintofooting.(SeeSection2.4)

CounterfortWalls

WallandStem



(Forfootingreinforcement,seethe"Footing"diagram,below)(*)Usedevelopmentlength(otherthantopbar)orstandardhookwith(Min.)tensionembedment"E"(SeeManualSection2.4).

(**)SeelapsplicesClassB(otherthantopbars).(SeeManualSection2.4.)

Footing



(*)Bydesignforloadsandfootingpressuresonsectionunderconsideration.(#5@12"cts.istheminimum.)

CounterfortWallsSignBoardType

WallandStemReferto"CounterfortWalls,WallandStem",above.

SpreadFooting

Iftheshearlineiswithinthecounterfortprojected(longitudinallyortransversely),thefootingmaybeconsideredsatisfactoryforallconditions.Ifoutsideofthecounterfortprojected,thefootingmustbeanalyzedandreinforcedforbendingandcheckedforbondstressandfordiagonaltensionstress.



751.24.3.8Details

NonKeyedJoints




SeeManualSection4.0forappropriatenotes.

KeyedJoints



SeeManualSection4.0forappropriatenotes.

RusticationRecess



Drains



Note:Frenchdrainsshallbeusedonallretainingwalls,unlessotherwisespecifiedontheDesignLayout.



ConstructionJointKeys:

CantileverWalls



CounterfortWalls

Keylength:Dividethelength"A"intoanoddnumberofspacesofequallengths.Eachspaceshallnotexceedalengthof24inches.Useasfewspacesaspossiblewiththeminimumnumberofspacesequaltothree(oronekey).

Keywidth=Counterfortwidth/3(tothenearestinch)

Keydepth=2"(nominal)

SignBoardWalls



Keylength=dividelength"A"or"B"intoanoddnumberofspacesofequallengths.Eachspacelengthshallnotexceed24inches.Useasfewspacesaspossiblewiththeminimumnumberofspacesequaltothree(oronekey).

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