Tanks CHG Oct 2012 v12.ppt - SPATA

1 08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks1 Charles GoodchildCEng., MCIOB, MIStructEPrincipal Structural EngineerThe concrete CentreConcrete (swimming pool) TanksGuidance on the design of in-situ concrete water retaining structuresSPATA Training 4 Oct 2012 OutlineScopeStructural Design Eurocodes ULS design SLS designMaterialsSpecificationAOBO utlineScopeStructural Design Eurocodes ULS design SLS designMaterialsSpecificationAOBS copeConcrete swimming pool tanksThese would normally be constructed from shuttered in-situ reinforced concrete to BS 8007. They can be formed with or without a screed / render and normally have a ceramic tile additives can be used to reduce the risk of leakage. The tank structure should be thoroughly tested for water tightness, through a full depth tank test before finishes are applied. Any faults should be remedied after allowing the pool tank to dry out thoroughly, and before tiling or lining work is undertaken.

2 Any repair is more effective from the wet .. hx?.. tr ochur mmi tfoli ml# mmi tfoli ml#id_37 /pools/c ommer cial-poolsScope08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 .. hx?.. mmi :LocationTypeShapeDimensionsDiving? Sub Aqua? FeaturesRoof structurePlantServicesChanging facilitiesSpectator facilitiesOther amenitiesArchitectStructural engineer, M & E consultant Interior designerSwimming pool specialistDesign:Hydraulic design criteria, AHU spec., ducts, pipes filters/pumps and water treatment, plantroom, penetrations, lighting, moving floorsStructural engineer, ScopeOutlineScopeStructural Design Eurocodes ULS design SLS designMaterialsSpecificationAOB Withdrawal of BS 8110, BS 8007 etc Eurocodes New information: CIRIA C660 Revision to BS 8102 Debate S Alexander, TSE Dec 06 B Hughes, TSE Aug 08? ICE project 0706 on reinforcement to control cracking (report Feb 2010)What s new in water retaining structures)?

3 EurocodesBS 8007 Eurocodes08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks313BS EN 1990 BASIS OF STRUCTURAL DESIGNBS EN 1991 ACTIONS ON STRUCTURESBS EN 1992 DESIGN OF concrete STRUCTURESPart 1-1: General Rules for StructuresPart 1-2: Structural Fire DesignBS EN 1992 Part 2: BridgesBS EN 1992 Part 3: Liquid Ret. StructuresBS EN 1994 Design of Comp. EN 13369 Pre-cast ConcreteBS EN 1997 GEOTECHNICAL DESIGNBS EN 1998 SEISMIC DESIGNBS EN 13670 Execution of StructuresBS 8500 Spe cifying ConcreteBS 4449 Reinforcing SteelsBS EN 10080 Reinforcing SteelsBS EN 206 ConcreteNSCSDMRB?NBS?Rail?CESWI?BS EN 10138 Prestressing SteelsEurocodesEurocode 2: relationships Pic of eurocodes incl pt 3BS EN 1992-3 EurocodesBS EN 1992-3 (cont)EurocodesTypical water-retaining structureBS EN 1992-3 (cont)Utility structures -all about minimising material and maintenance cost A degree of leakage may be acceptable -discuss tightness class with clients.

4 Crack width? to or mmi tfoli ml# .. hx?..Edge detailsEurocodes08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks4 StructuralOption 1: Monolithic design for whole of tank and pool surrounds when constructed from in-situ water retaining concrete to BS 8007/ BS EN 1992 Part 3 gives a highly stable structureOption 2: Gunitesprayed reinforced concrete Reinforced concrete block work with waterproof renders /coatingsAn Integral transfer channel is the most common optionFixtures and fittings need to be integrated into the tank designWaterproofing Inherent within well constructed in-situ reinforced concrete pools meeting BS 8007/ BS EN 1992 Part 3 Can be augmented by waterproof liner and/or renderFinishesOption 1 Fully ceramic tiles on render backing is the preferred finishOption 2 Specialist finish renders and paint finishes have been used where long term durability is not so importantConcrete pool.

5 Hx?..EurocodesOutlineScopeStructural Design Eurocodes ULS design SLS designMaterialsSpecificationAOBTank empty(Tank in ground)Tank full(Tank in or above ground)Actions for ULSSoil loadsGroundwater loadsCompaction loadsWater loads Normal level Accidental levelAnalysisSlabEquilibriumFlexureWalls FlexureSlabFlexureTensionSoil structure interactionWallsFlexureTensionShearActio ns for SLSAs above plus: Early age thermal AutogenousAs above plus: Drying Differential temperatureStructural design: loads casesDesign for Ultimate Limit StateEQU Equilibrium Limit StateSTR & GEO Structural and GeotechnicalLimit States Partial factor for water actions: gQfor silos and Tanks BS EN 1991-4 Maximum design liquid level during operationsgQ= gFfor Normal level ?gF= Structural design As per normal elements 3D nature of designStructural design -ULSA nalysisWas plate theoryManifested by graphs or tablesStructural design -ULSnow often FEA (via grillage).

6 Horizontal moments in a 8 x 6 x 4 m deep tank Courtesy HACS tructural design -ULS08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks5 Design for tension:Not only tensile forces from restraint but also tension from loadingSection/ElevationgFrwhAxial tension due to water pressure on Wall BAxial tension due to water pressure on Wall APlan Section at cornerNot forgetting tension in base slabs!!Structural design -ULSW ater Retaining : N-M where tension exists Shear:VRdcis affected by tensionStructural design -ULSD esign for Ultimate Limit StateGEO in the ground Combinations 1 and 2 gFfor ground water oNormal gF= (BS EN 1997)oMost unfavourable gF= (NA to BS EN 1991-4)Structural design -ULST anks in the ground:BS EN 1997, Combination 1 and 2 Characteristic actions on basement wall and adjacent slabs: LC1 water at ground levelCombination 1 Combination 2 Structural design -ExampleThis guide covers the design and construction of reinforced concrete basements and is in accordance with the aim of the guide is to assist designers of concrete basements of modest depth, not exceeding 10 metres.

7 It will also prove relevant to designers of other underground structures. It brings together in one publication the salient features for the design and construction of such water-resisting guide has been written for generalist structural engineers who have a basic understanding of soil mechanics. Structural design below groundFor empty Tanks in the ground see concrete Basements08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks6 OutlineScopeStructural Design Eurocodes ULS design SLS designMaterialsSpecificationAOBD esign for Serviceability Limit State Control of crackingStructural design -SLS1. Test for restraint crackingA section will crack if:er = Raxefree= K[([acT1+eca)]R1+ ([acT2R2)]+ ecdR3] >ectuwhereK=allowanceforcreep= (SeeCIRIAC660forvalues).SeeTableA6fortyp icalvaluesT1=differencebetweenthepeaktem peratureofconcreteduringhydr ationandambienttemperature C(SeeCIRIAC660).

8 TypicalvaluesarenotedinTableA7eca=Autoge nousshrinkagestrain valueforearlyage(3days:seeTableA9)R1,R2, R3= (SeeFigureA2andnote).Forendrestraint, ,forinst , Cforconcretecastinthesummerand10 [60] ,dependentonambientRH,cementcontentandme m bersize(seeBSEN1992-1-1 Exp.( )orCIRIAC660orTableA10).CIRIAC660alludes to45%RHforinternalconditionsand85% design -SLSCIRIA C660 Cl 1 Values of restraint factor Rfor a particular pour configuration0,8 to 1,0 Infill bays, rigid restraint0,2 to 0,4 Suspended slabs0,3 to 0,4 at base 0,1 to 0,2 at topMassive pour cast onto existing concrete0,1 to 0,2 Massive pour cast onto blinding0,6 to 0,8 at base 0,1 to 0,2 at top Thin wall cast on to massive concrete baseRPour configurationBS EN 1992-3 Annex LBeware: effects of creep includedusually design -SLSR estraint factorsCS TR 67 Short term load strengthLong term load strengthStressdue to early thermal allowing for creepStress due to early thermal & drying shrinkageStress due to early thermal & shrinkage & seasonalSLS Design vs timeStructural design -SLS2.

9 Minimum reinforcementAs,min= kck Act(fct,eff/fyk)wherekc== < >800mm(interpolationallowedforthicknesses between300mmand800mm).Act=area of concrete in the tension zone just prior to onset of cracking. Actis determined from section properties but generally for basement slabs and walls is most often based on full thickness of the section. fct,e ff==fctmmeantensilestrengthwhencrackingm aybefirstexpectedtooccur: for early thermal effects 3 days for long-term effects, 28 days (which considered to be a reasonable approximation) [1]CIRIA C660 Recent research[61]would suggest that a factor of should be applied to fct,effin the formula for crack inducing strain due to end restraint. This factor accounts for long-term loading, in-situ strengths compared with laboratory strengths and the fact that the concrete will crack at its weakest point. TR 59[62]concludes that the tensile strength of concrete subjected to sustained tensile stress reduces with time to 60 70% of its instantaneous of minimum reinforcement does not guarantee any specific crack width.

10 It is simply a necessary amount presumed by models to control cracking; but not necessarily a sufficient amount to limit actual crack widths. Structural design -SLSBS EN 1992-1-1 Exp ( )08/10/2012 SPATA Training 4 Oct 2012 - eurocode 2 Part 3 Tanks7 Tightness Classes3. Crack widths and watertightnessStructural design -SLSBS EN 1992-3 Cl pools?Tiled pools (most?)Above ground?Special?Tightness Classes -notes3. Crack widths and watertightnessStructural design -SLSBS EN 1992-3 Cl Crack width calculationsCrack width, wk= sr, ,max= Maximum crack spacing = + (k1k2f/rp,eff)ecr= Crack-inducing strain = Mean strain in steel mean strain in concrete , over the debondinglength either side of the crack= (ecs-ecm ) .. wherec=nominalcover,cnomk1= ( )k2=== ( ) (e1+e2)/2e1forcombinationsofbendingandte nsionf= ,eff=As/Ac,effAc,effforeachfaceisbasedon { ; (c+ );(h x)/3}whereh=thicknessofsectionandx= design -SLSBS EN 1992-1-1 Exp ( ) ecr =(ecs -ecm )esm-ecm sm cm = 0 sm cm = 0ectuStrainPlan (or section)Strain in reinforcementStrain in concrete c s c s Sr,maxStructural design -SLSecm ectu /2wk= sr,maxecr= sr,max(esm-ecm)Consider a crack in a section: Debonding lengthecr = Crack-inducing strain =.