ACI 313R-97 Commentary on Standard Practice for De

313R-1ThisCommentarypresentssomeoftheconsiderationsandassumptionsofACICommittee313indevelopingtheprovisionsoftheStandardPracticeforDesignandConstructionofConcreteSilosandStackingTubesforStoringGranularMaterials.Italsoprovidessuggestedmethodsforcalcu-latingcrackwidthandthrough-the-walltemperaturegradientduetohotstoredmaterials.CommentsonspecificprovisionsoftheStandardpracticearemadeusingthecorrespondingchapterandsectionnumbersoftheStandardpractice.AlistofselectedreferencesisgivenattheendoftheCommentary.Notations,notdefinedherein,aredefinedinAppendixAoftheStandard.Keywords:asymmetricflow;bins;circumferentialbending;concrete;concreteconstruction;deadloads;dynamicloads;earthquakeresistantstructures;formwork(construction);funnelflow;granularmaterials;hop-pers;jumpforms;lateralloads;loads(forces);loweringtubes;massflow;overpressure;qualitycontrol;reinforcedconcrete;reinforcingsteels;silos;slipformconstruction;stackingtubes;stavesilo;stresses;structuralanaly-sis;structuraldesign;thermalstresses;thickness;walls.CONTENTSChapter1—General,p.313R-2R1.1—IntroductionR1.2—DefinitionsR1.4—Drawings,specificationsandcalculationsChapter2—Materials,p.313R-2R2.2—CementsR2.3—AggregatesR2.5—AdmixturesChapter3—Constructionrequirements,p.313R-3R3.1—NotationR3.2—ConcretequalityR3.3—SamplingandtestingconcreteR3.4—DetailsandplacementofreinforcementR3.5—FormsR3.6—ConcreteplacingandfinishingR3.7—ConcreteprotectionandcuringChapter4—Design,p.313R-4R4.1—NotationR4.2—GeneralCommentaryonStandardPracticeforDesignandConstructionofConcreteSilosandStackingTubesforStoringGranularMaterials(ACI313-97)ACI313R-97MostafaH.MahmoudChairmanVaheA.AprahamianDonaldMidgleyWilliamD.ArockiasamyGermanR.GurfinkelJackMollLeonBialkowskiErnestC.HarrisLeeA.NashAlfredG.BisharaDonaldS.JackRodneyM.NohrWilliamH.BokhovenRichardT.JenkynJ.MichaelRotterWilliamL.ClarkMichaelE.JohnsonJohnE.SadlerJamesM.EbmeierRobertD.JohnsonSargisS.SafarianStephenG.FrankoskyF.ThomasJohnstonJosephR.TuckerReportedbyACICommittee313ACI313R-97becameeffectiveJanuary7,1997.Copyright1998,AmericanConcreteInstitute.Allrightsreservedincludingrightsofreproductionanduseinanyformorbyanymeans,includingthemakingofcopiesbyanyphotoprocess,orbyelectronicormechanicaldevice,printed,written,ororal,orrecordingforsoundorvisualreproduc-tionorforuseinanyknowledgeorretrievalsystemordevice,unlesspermissioninwritingisobtainedfromthecopyrightproprietors.ACICommitteeReports,Guides,StandardPractices,andCommen-tariesareintendedforguidanceinplanning,designing,executing,andinspectingconstruction.Thisdocumentisintendedfortheuseofindividualswhoarecompetenttoevaluatethesignifi-canceandlimitationsofitscontentandrecommendationsandwhowillacceptresponsibilityfortheapplicationofthematerialitcontains.TheAmericanConcreteInstitutedisclaimsanyandallresponsibilityforthestatedprinciples.TheInstituteshallnotbelia-bleforanylossordamagearisingtherefrom.Referencetothisdocumentshallnotbemadeincontractdocu-ments.IfitemsfoundinthisdocumentaredesiredbytheArchi-tect/Engineertobeapartofthecontractdocuments,theyshallberestatedinmandatorylanguageforincorporationbytheArchitect/Engineer.313R-2ACICOMMITTEEREPORTR4.3—DetailsandplacementofreinforcementR4.4—LoadsR4.5—WalldesignR4.6—HopperdesignR4.7—ColumndesignR4.8—FoundationdesignChapter5—Stavesilos,p.313R-13R5.1—NotationR5.4—ErectiontolerancesR5.5—WalldesignR5.6—HoopsforstavesilosR5.7—ConcretestavetestingChapter6—Post-tensionedsilos,p.313R-16R6.1—NotationR6.2—ScopeR6.4—TendonsystemsR6.5—BondedtendonsR6.6—UnbondedtendonsR6.7—Post-tensioningductsR6.8—WrappedsystemsR6.12—DesignR6.13—Verticalbendingmomentandshearduetopost-tensioningR6.14—TolerancesChapter7—Stackingtubes,p.313R-18R7.2—GenerallayoutR7.3—LoadsR7.6—FoundationorreclaimtunnelCHAPTER1—GENERALR1.1—IntroductionSilofailureshavealerteddesignengineerstothedangerofdesigningsilosforonlystaticpressuresduetostoredmaterialatrest.Thosefailureshaveinspiredwide-spreadresearchintothevariationsofpressuresandflowofmaterials.Theresearchthusfarhasestablishedbeyonddoubtthatpressuresduringwithdrawalmaybesignificantlyhigher1-4orsignificantlylowerthanthosepresentwhenthematerialisatrest.Theex-cess(abovestaticpressure)iscalled“overpressure”andtheshortfalliscalled“underpressure.”Oneofthecausesofover-pressureistheswitchfromactivetopassiveconditionswhichoccursduringmaterialwithdrawal.5Underpressuresmayoc-curataflowchannelincontactwiththewallandoverpres-suresmayoccurawayfromtheflowchannelatthesamelevel.6-8Underpressuresconcurrentwithoverpressurescausecircumferentialbendinginthewall.Impactduringfillingmaycausetotalpressuretoexceedthestatic.Whileoverpressuresandunderpressuresaregenerallyimportantindeepersilos,impactisusuallycriticalonlyforshallowones(bunkers)inwhichlargevolumesaredumpedsuddenly.Obviously,todesignwithdisregardforeitheroverpres-sure,underpressureorimpactcouldbedangerous.R1.2—DefinitionsTheterm“silo”usedhereincludesbothdeepbinsandshal-lowbins,thelattersometimesreferredtoas“bunkers.”Wher-evertheterm“silo”isused,itshouldbeinterpretedasmeaningasilo,binorbunkerofanypro