2017 VERSION 1

AUSTRAL DECKtechnical guide

AUSTRAL PRECAST

/ 2 / / 3 /

Austral Deck TECHNICAL GUIDE

CONTENTSbuild faster, build smarter, build better

1. Introduction

1.1 Austral Deck – Overview 6

1.2FeaturesandBenefits 8

1.3 Applications 9

2. Properties of Austral Deck

2.1 Standard Austral Deck Design Thicknesses, 10

Span Table and Graph

2.2 Calculation of Austral Deck Weight Reduction 12

2.2.1 Basic Self-Weight Calculations 12

2.2.2RefinementstotheSelf-Weight 12

2.2.3Multi-SpanWeightCalculationExample 13

2.2.4 Calculations Using Software 13

2.3 Calculation of Austral Deck Stiffness 15

2.3.1 Calculation of the Neutral Axis – 15

Elastic Section

2.3.2CalculationoftheMomentofInertia 15

2.3.3 Calculation of Elastic Stiffness Allowing for 16

Joints

3. Modelling Austral Deck

3.1 Design Principles 17

3.2 General Modelling 17

3.2.1OutputsfromModelling 17

3.2.2CodeCompliance 17

3.3UsingRamConcept 17

3.3.1AdjustmentforStructuralWeight 18

3.3.2 Average Slab Thickness 19

3.3.3 Reduced Concrete Stiffness 19

3.3.4IsotropicvsOrthotropicStiffness 20

3.3.5 Austral Deck and Orthotropic Stiffness 20

3.3.6 Orthotropic Stiffness and Australia Code

Compliance 20

3.3.7 Austral Deck and RAM Concept Design Strips 21

3.3.8RAMConceptandAS3600-2009 21

Implementation

3.3.9AustralDeckandRAMConceptDeflection 21

Analysis

3.3.10ExampleAustralDeckLoadHistorySettings 22

3.4AustralDeckDesignStripLayoutinRAMConcept 23

3.4.1ExampleDesign 23

3.4.2 Flat Plate 24

3.4.3BandedSlab 28

4. Austral Deck and AS3600 Detailing Requirements

4.1 Concrete Cover 30

4.1.1CodeRequirements 30

4.2DuctilityRequirementsinFlexuralReinforcement 31

4.3ReinforcementLayingSequence 31

4.4DetailingofSpanDirectionReinforcement 32

4.4.1 End Supports 32

4.4.2InternalSupports 32

4.4.3NegativeReinforcement 32

4.5DetailingofCrossDirectionReinforcement 32

4.6 Calculation of Splice Bars 33

4.7 Punching Shear 33

4.7.1GeneralDesignIssues 33

4.7.2PunchingShearReinforcementand 33

Austral Deck

4.7.3 Basic Punching Shear Checks 33

4.7.4 Punching Shear Using Rebar Trusses 34

4.7.5 Alternatives for Punching Shear 34

4.8LongitudinalShear 35

5. Austral Deck Design as Formwork

5.1Stageone:Designasformwork 36

5.2DesignCriteriaandSpecifications 37

5.2.1 Strength 37

5.2.2 Stiffness 37

5.2.3 Surface Finish 37

5.2.4 Panel Capacity 37

5.2.5MaximumSpan 37

5.2.6StackedMaterials 38

5.2.7Assumptions 38

5.3 Panel Properties 39

5.3.1ConstructionLoads 39

5.3.2LoadCombinations 39

5.3.3DesignLoad 39

5.3.4 Truss Properties 39

5.3.5 Top Chord 39

5.3.6BottomChord 39

5.3.7DiagonalLacing 39

5.3.8Mesh 39

5.3.9 Capacity Calculations 40

5.3.10TopChordCompression 40

5.3.11 Top Chord Tension 40

5.3.12BottomChordCompression 40

5.3.13BottomChordTension 40

5.4 Panel Properties 39

5.4.1BottomChordTension 40

5.4.2DiagonbalLacingCompression 41

5.4.3ConcretePanelCompression 41

5.3.4 Control for Concrete Tensile Strength 41

5.3.5 Crack Control for Flexure 41

5.3.6Deflection 42

5.3.7MaximumScansSummary 42

5.3.8SingleSpan 43

5.3.9 Two Span 43

6. Example Models and Calculations

6.1SensitivityAnalysisofTwo-WaySlabs–Example1 44

6.2 Worked Calculations 46

6.1.1 Strip 1 – Vertical Span 47

6.1.1Strip2–HorizontalSpan 48

6.1.3CheckonColumnStripWidth 48

6.1.4CheckonSecondaryMomentDirection 48

6.1.5 Check on Punching Shear 49

7. Fire and Thermal Resistance

7.1 Fire Resistance Period 51

7.1.1AustralDeckProfile 51

7.1.2ThermalResistance 51

7.1.3DefinitionsandReferences 51

8. Typical Installation Details

8.1TypicalWallConnection–EndSupport 52

8.1.1EndSupporttoExternalPrecastWall-Option1 52

8.1.2EndSupporttoExternalPrecastWall-Option253

8.1.3EndSupporttoInternalPrecastWall 53

8.2TypicalWallConnection–LongitudinalSide 54

8.2.1LongitudeSidetoExternalPrecastWall 54

8.2.2SideJointDetails 54

8.3TypicalWallConnection–InternalPrecastWalland 54

Double Wall

8.3.1EndSupport–InternalPrecastWallUnder 54

8.3.2MidSpan–InternalPrecastWallAbove 55

8.3.3EndSupport–DoubleWallConnection 55

8.4TypicalBeamConfiguration 55

8.4.1BeamReinforcementwithinSlabThickness 55

8.4.2PrecastBeam 56

8.4.3BandBeamformedbyAustralDeck 56

8.5BalconyandCantileverArrangement 57

8.5.1BalconyandCantileverArrangement 57

8.5.2ExternalPrecastWallwithBalcony 57

8.6ProposedProppingArrangement 58

LIST OF FIGURES

Figure 1 – Typical Austral Deck Cross Section 7

Figure2–Integrationwithsteelframedsructure 8

Figure 3 – Austral Deck Cross Sections 12

Figure4–PlanofAustralDeckAroundColumn 13

Figure5–TypicalMultipleSpanAustralDeckLayout 14

Figure 6 – Elastic Analysis of Panel Joints 16

Figure7–RAMConceptMenu 18

Figure8–SlabpropertiesshowingAustralDeck 19

concretemixandcustomreducedstiffness

Figure9–Designstripdistributionfrom 20

AS3600-2009 Table 6.9.5.3

Figure 10 – RAM Concept load history options 21

Figure11–RAMConceptstriplayoutexample 23

Figure 12 – RAM Concept strip layout - 3D render 23

Figure13–Examplemodelshowingmesharealayouts 24

Figure14–Exampleplanklayout#1 25

Figure15–Exampleplanklayout#2 25

Figure16–Latitudeandlongitudedesignstrips 26

Figure17–Longitudinalsectionsgeneratedfrom 27

design strips

Figure18–Bandedslablayout 28

Figure19–Bandedslab3Drender(viewedfrombelow) 28

Figure20–Longitudestriplayoutforbandedslab 29

Figure21–Bandedslabdeflectionprofile 29

Figure22–CoverrequirementsforAustralDeckplanks 30

Figure23–Reinforcementbarlayingsequence 31

Figure 24 – Typical internal support splice bar locations 32

Figure 25 – Splice bar calculation of forces 33

Figure 26 – Punching Shear Setback 34

Figure27–InteriorSupportDuringConstruction 36

Figure28–Longterm(30year)deflectionfor100%, 44

75%and50%secondarystiffness

Figure29–Primarypositivemoment(aboutRaxis) 45

Figure30–Primarynegativemoment(aboutRaxis) 45

Figure31–Secondarypositivemoment(aboutSaxis) 45

Figure32–Secondarynegativemoment(aboutSaxis) 45

Figure33–ExampleSlab 46

Figure34–ExampleSlab 47

Figure35–AustralDecksideprofile 51

Figure 36 – Effective thickness for FRP ccalculation Austral 51

AustralDeckprofile

Figure 37 – End Support to External Precast Wall - Option 1 52

Figure38–EndSupporttoExternalPrecastWall-Option253

Figure39–EndSupporttoInternalPrecastWall 53

Figure40–LongitudeSidetoExternalPrecastWall 54

Figure41–EndSupport–InternalPrecastWallUnder 54

Figure42–MidSpan–InternalPrecastWallAbove 55

Figure 43 – End Support – Double Wall Connection 55

Figure44–BeamReinforcementwithinSlabThickness 55

Figure45–PrecastBeam 56

Figure46–BandBeamformedbyAustralDeck 56

Figure47–BalconyandCantileverArrangement 57

Figure48–ExternalPrecastWallwithBalcony 57

Figure49–ProposedProppingArrangement 58

LIST OF TABLES

Table 1 – Standard Austral Deck Slab Thicknesses 10

and Design Properties

Table 2 – Span to Deck ratios for residential application 11

Table3–RAMConceptConcreteMixProperties 18

Table 4 – Reduced Austral Deck densities for regular 19

andbathroomslabareas

Table5–Designcolumnandinteriorstripsas 20

definedbyAS3600-2009Section6.1

Table 6 – Typical load history settings for a 22

residential Austral Deck slab

Table 7 – AS3600-2009, Table 4.3 - Concrete 30

ExposureClassification

Table8–AS3600-2009Table4.10.3.3-ConcreteCover 30

LIST OF CHARTS

Chart 1 – Span Chart Guide 11

Chart2–Maximumdistancebetweensupportsfor 43

single span

Chart3–Maximumdistancebetweensupportsfor 43

multispan

Chart 4 –Fire Resistance Period 11

/ 4 / / 5 /

Austral Deck TECHNICAL GUIDE

Theinformationcontainedinthisdocumentisprovided

asageneralguideonlyanddoesnotreplacetheneedforthespecificationto

bereviewedandcheckedbyaqualifiedpersoninthefieldofconcrete,

energy,buildingconstruction,sound,design,servicesand/orfire.

Thismaterialhasbeenpreparedinthecontextofrelevant

AustralianStandards,theNationalConstructionCode(NCC)andthe

BuildingCodeofAustralia(BCA).Usersshouldmakethemselvesawareof

anyrecentchangestothesedocumentsreferredtotherein

andtolocalvariationsorrequirements.

Austral Precast has dedicated engineering services available for project

assistance.Weareabletoprovidedesignsupportforengineerstodetermine

thebestwaytospecifyanddocumentAustralDeck.

Ourtechnicalexpertscanidentifythemostefficientpanelgeometrymeeting

projectrequirements,specificationsandinstallationprocess.

Austral Precast offers fully detailed shop drawings as part of the

Austral Deck supply.

Itistheclient’sdesignerwhoisresponsibletodesignandcertifythe

concreteslab,theentirestructureandcertifythepaneldesignfortemporary

propping and construction loads.

AUSTRAL DECKdesign for construction, loading,

permanent formwork, span capacity and final in service slab

AUSTRAL PRECAST

AUSTRAL PRECAST

/ 6 /

WelcometoAustralDeck,aninnovative,costeffectiveand

timesavingprecastconcreteflooringsolution,designedto

provideaonewayandtwo-wayspanningconcretefloorslab

andformworksolutioninone.

AustralDeckcombinesfeaturesdevelopedfrommanyyearsof

research,developmentandconstructionprojectstoprovidea

flexiblesolutionthatenablesengineers,architectsand

builderstounderstandandusethesolutionasseamlesslyasif

theyweredesigningatraditionalconcreteframedbuilding.

TheGuideaimstoenableusersto:

•AchieveapreliminaryunderstandingoftheAustralDeck

solution,spans,costsandlimitations

• Undertake designs and understand the theory behind their

implementation

• Understand the way that Austral Deck is constructed, and

plan accordingly.

1.1 Austral Deck – OverviewAustralDeckisbasedaroundasmallnumberofkey

components,thatcombinetoformafullybonded,concrete

slab.

Thecomponentscombinethestrengths,savingsandbenefits

ofprecastconcretewiththeflexibilityandsimplicityof

traditionalin-situformed,pouredandfinishedfloorslabs.

The solution can be broken down into the following key

components(Figure1):

1. A thin precast concrete “Austral Deck panel” providing a

Class2bottomsoffitfinishwhilstservingasformwork.

2.Reinforcementbar(rebar)andmeshcastintotheAustral

Deck panel, providing concrete spanning capability and

contributestoslabreinforcement.

3.Triangularsteellatticegirder“trusses”madefromwelded

rebar,providingtemporarystiffnessfortransportand

installation.Theyprovidepermanentshearflowtransfer

capability.

4.Voidformers,reducingtheweightoftheoverallslaband

increasingtheefficiencyoftheconcretesection.

5.On-siteinstallationoftopreinforcementandsplicebars,

providing easy access to cast in services whilst achieving

rapidsteelfixingtimeframesonsite.

6.In-situpouredconcretetopping.

1. INTRODUCTION

01 Austral Deck

02 Steelreinforcementifspecified03 Steel lattice girder

04SteelmeshcastedintheAustralDeck05Voidformers06In-situconcretetopping07 Slab thickness

Figure 1 – Typical Austral Deck Cross Section

07

06

01

0304

02

05

Austral Deck TECHNICAL GUIDE

/ 7 /

AUSTRAL PRECAST

/ 8 / / 9 /

Austral Deck TECHNICAL GUIDE

1.2 Features and BenefitsAustral Deck is easy to design with and fast to install, saving

timeandmoneyacrosstheconstructionlifecycle.

Aflexibleandadaptableformwork,AustralDeckintegrates

well with Austral Precast walling solutions, covering the

entire structure including cantilevers and balconies.

A unique flooring solution

•AnAustralDeckpanelispartofacompositefloorsolution

thatprovidesrigidformworkthatbecomespartofthefinal

structure. During construction the panel can stand

constructionloadsandbeusedasaplatformforworkersand

materials.

•Aneffectivewaytomaintainthestructuralintegrityofa

monolithicslab.

•Compositeplatformsandshearconnectionpanelscanbe

constructed easily with partial or full-length gaps or pockets

ofconcretevoids.Thegapswillbelocatedtoaccommodate

structuralbeamconfigurations.Thisallowsforthe

placementoftheAustralDeckdirectlyoverprecast,cast

in-situconcreteorsteelbeams.Trussesandsteel

reinforcementcanremainuninterruptedthroughthesegaps

for structural continuity. – Figure 2.

•Thispermanentformworksolutionhasbeenapprovedby

manystateroadauthorities,providingsaferandmore

efficientconstructionofbridgesuperstructures.

•ThequalityoftheformClass2finishontheundersideofthe

AustralDeckfloorcaneliminatetheneedforafalseceiling,

maximisingfloortofloorheight.

A flexible and adaptable formwork replacement

•AustralDeckimposesminimumrestrictionsondesigners

andbuilders.Custommadesizesandshapescanbe

manufacturedtosuitconstructionlayoutanddesign

specifications.

• Austral Deck panels can cover the entire width of a

structure, including the cantilever beyond the external

support.RefertoSection8,TypicalInstallationDetails.

•Thesolutionintegrateswellwithconcreteorsteelframed

structures. – Figure 2.

•Cast-initemssuchasferrules,conduitsandotherservice

fixingsandpenetrationscanbeaccommodatedduringthe

manufactureofAustralDeck.

•BalconiesandedgeformscanbecastwithintheAustral

Deckpanel.Thesecaneliminateedgeformworkandscaffold

costs.Integratededgeformsallowsforearlyinstallationof

temporaryorpermanentbalustrades.

•Safetyrailpostholescanbeprefittedtothepanelspriorto

installation,improvingsitesafety.

Economic and fast to install

Austral Deck offers all the advantages of a precast concrete

system;

•Reductioninformworkandproppingcomparedto

conventionalformwork.

•Tofurtherincreaseefficiencyonsite,AustralDeckpanels

maybeproducedwithvoidformerblocksattachedtothetop

oftheprecast.Theseformersreducethevolumeofin-situ

concretetoppingvolumesandreducetheoverallmassofthe

floorstructurebyupto30%.

•Constructiontradescancommenceworkingonthestructure

immediatelyafterinstallation.Serviceductsandconduits

canbeinstalledandaccommodatedintothecastin-situ

portion of the slab.

• Austral Deck can be lifted straight into position, reducing

conventionalinstallationtime.Anaverageof10AustralDeck

panels(coveringanareaof150m2)cantypicallybeinstalled

per hour.

• The panels have a relatively thin layer of concrete, which

makesitlightertotransportandinstall.

•AustralDeckhasthepropertiestoachievefireresistanceand

energyefficiencyprovisionsasspecifiedinrelvantstandards

and building code of practice. Refer to Section 7 in this guide

"FireandThermalResistance".

1.3 ApplicationsAustralDeckhasbeendesignedtobeasflexibleaspossible,

and therefore ideally suited for a broad range of construction

applications.

SomeoftheapplicationsthatAustralDeckissuitedforareas

follows:

•Multi-LevelResidentialDevelopments,including:

>Exposedflatsoffitswithqualityconcretefinish

>Upstandsandbalconiespreformedand/orprecast

>Irregularcolumngrids

> Flexibility of loads, penetrations, ducts and set-downs

•CommercialDevelopments,including:

>Longspanfloorplates

> Flat slabs, reduce losses in ceiling space for tenant

servicesandmechanicalservicesreticulation

>Highloadedareassuchascompactusandstorage

zones

> Good interaction and connection with precast concrete

lift and stair cores, shear walls and other features

>Cast-infittingsforcurtainwallingsystems

• Parking and open-deck applications

>Fastconstructiontimesallowopeningofcarparks

sooner,minimisinglossofcarbaysandmaximising

economicbenefits

>Lightweightconcretespansallowformoreefficient

structures

>Ramps,aislesandtrafficmovementareascaneasilybe

accommodatedwithintheAustralDeckdesign

•Decksandplatforms

>Trafficandpedestrianbridges

>Curvedonandofframpstructures

>Railplatforms

>Marinejettiesandplatforms

• Roofs and lids

> Tunnel and shaft roof panels

> Culverts

> Tank lids

Figure 2 – Integration with steel framed structure.

AUSTRAL PRECAST

/ 10 / / 11 /

Austral Deck TECHNICAL GUIDE

ThischapterwilldetailthestructuralandgeometricpropertiesofAustralDeck.

AustralDeckhasbeendesignedtobecompletelyflexiblewithregardstodepths,sizesandlayouts.Thestandarddesignsbelow

allowforastreamlineddetailingprocess,asmanyoftheforms,trusses,chairsandjigsarealreadyavailableinmanyofAustral

Precast’sfactoriesaroundAustralia.

2.1 Standard Austral Deck Design Thicknesses, Span Table and Graph

Table 1 shows various standard thicknesses of Austral Deck.

Thereareseveralkeyassumptionsinherentinthestandard

design table, which are detailed as follows.

•Generally,thepanelsareoptimisedtoallowfor60mmor

90mmprecastbiscuitatthebaseandminimum60mmcover

tothetopofthepolystyrenevoidformer.

• Weight reduction and equivalent stiffness factors are based

onatypicalplank,2500x7800mm,with18voidformersof

size550x1000each.

• * Theoretical weight reduction ignores any additional void

formersremovedaroundcolumnsandwalls,penetrations,

cast-inanchors,transferbeamsorotherfeaturesthat

require full thickness concrete.

• Stiffness equivalents are based on elastic section analysis of

theconcretecrosssectiononly.Crackedortransformed

section analysis should be carefully undertaken by the

design engineer.

2. PROPERTIES OF AUSTRAL DECK

mm mm mm mm mm % mm % mm %

AD150 150 60 90 N/A 150 0.0% 150 100% 150 100%

AD175 175 60 115 N/A 175 0.0% 175 100% 175 100%

AD200 200 60 140 50 175 12.7% 199 98% 198 98%

AD225 225 60 165 100 174 22.6% 221 94% 220 93%

AD250 250 60 190 120 189 24.4% 244 93% 243 91%

AD275 275 60 215 145 201 26.8% 266 90% 264 89%

AD300 300 90 210 130 234 22.0% 294 95% 293 94%

AD350 350 90 260 160 269 23.2% 342 94% 341 93%

AD400 400 90 310 210 293 26.7% 387 90% 384 89%

Total Precast Topping Void Theoretical Equivalent Stiffness Equivalent Stiffness Code Depth Panel WeightReduction*(StrongAxis)(WeakAxis)

Table 1 – Standard Austral Deck Design Thicknesses

Table 2 – Span to Depth ratios for residential application

Chart 1 – Span chart guide

Code Total Depth mm

Precast Panel mm

Topping mm

Void Depth mm

UpperSpanLimit Single Continuous mmmm

AD150 150 60 90 N/A 3500 4500

AD175 175 60 115 N/A 4000 5200

AD200 200 60 140 50 4500 6000

AD225 225 60 165 100 5000 6500

AD250 250 60 190 120 5500 7300

AD275 275 60 215 145 6000 7750

AD300 300 90 210 130 6700 8500

AD350 350 90 260 160 7750 10200

AD400 400 90 310 210 8750 11500

Table 2 shows span to depth ratios for residential application of Austral Deck.

Astandard250mmthickslabhasa23%weightsavingofthestructure, withonly7.5%lossofstiffness

AUSTRAL PRECAST

/ 12 / / 13 /

Austral Deck TECHNICAL GUIDE

Atypicallayoutofplanksaroundasquarecolumnisshown

below in Figure 4.

Thefigureshowsa600x600squareconcretecolumn,withthe

precastplanksstoppingshortofthecolumnby20mmall

round.

Thereisminimum500mmclearancetothecolumninone

direction,and675mmintheorthogonaldirection.Note,

675mmallowsthevoidstoremaininlineandwouldnot

interferewiththereinforcementorrebartrusslayout.

To calculate the effective or average self-weight for this

example,anaverageshouldbetakenoverseveralcolumn

grids.

Note:thepositioningofthe500mmclearancearound

columnsandotherloadbearingelementsisconsideredthe

minimumtoallowforgeneraldetailingofthecolumn-slab

joint.Itdoesnotconsideranypunchingshearperimeter,

whichmayrequirealargersolidregionaroundthecolumn

than depicted in Figure 4. Refer to Section 4.7 for further

details on Punching Shear.

AnexamplecalculationisshownoppositeinSection2.2.3.

2.2.3. Multi-Span Weight Calculation Example

The basic self-weight calculations take into account the

generalproposedlayoutfora2.5mx7.8mplank,including

200mmsolidsectionslongitudinallyand400mmsolidplank

ends.

TheexampleshowninFigure5showsaslabof2x2gridbays

of7.5mx7.8meach.

The250mmslabhas9columnseachof600x600.

Usingatypicalcasewheretheslabbeneathacolumnis

includedintheslabvolumesthetotalvolumeofthisslabis:

15 × 15.6 × 0.25 = 58.5m3

Excludingthevoidfreeareasaroundthecolumnsthenormal

reductionof24.4%equatestoatotalvolumeof44.2m3.

Howeverthereareanumberofsmaller600x550voidsaround

thecolumns.Thetotalvoidvolume:

[16 × 0.4 × 0.55 + ( 12 × 18–16) × 1 × 0.55] × 0.12 = 13.62m2

Volume Reduction = 13.62 = 23.2%

58.5

Iftheslabweretohavesetdowns,wallsandfolds,asislikely

foraresidentialapartmentcomplex,thevolumereduction

maywellreduceto20%orbeyond.

2.2.4. Calculations Using Software

Itispossibletouse3Dmodellingsoftwaretocalculaterough

slabvolumesandthereforeself-weights,includingTekla,

Autodesk Revit or Bentley Microstation.

Whenusinganymodellingsoftware,thedesignerand

draftspersonshouldalwayshaveinmindtheadditional

complexityofmodellingvoids,andtakecarenottouseany

volumeoutputswithouthandcheckingtheresults.

Figure 4 – Plan of Austral Deck Around Column

2.2 Calculation of Austral Deck Weight Reduction

The accurate calculation of the weight reduction is critical to

the design of the structure.

Structuralself-weightmustbeincludedforallcalculationson

slabperformance.Iftheself-weightreductionduetothevoid

formersisignoredthentheslabwillbecomeneedlessly

conservative both for strength and serviceability calculations.

Asadesigner,onemustalsorememberthatforanyconcrete

spanningelement,serviceability(i.e.stiffness)effectsare

multipliedandamplifiedwiththeadditionaleffectsofcreep

andshrinkage.Insomecases,thiscancausesignificantover

orunder-estimationoverthelongtermlifeoftheproject.

Self-weighthasflow-oneffectstotheverticalandlateral

supportingelementsofthestructure.WhilsttheAustralDeck

designernormallywouldonlyconcernthemselveswiththe

designofthesuspendedslabs,anymaterialchangetothe

self-weightoftheslabswillhaveflow-oneffects,byincreasing

(ordecreasing)thecolumns,foundationsandtransferbeams

providing vertical support and cores and shear-walls

providing lateral support.

Generally,over-estimatingtheself-weightofthestructure

would provide a conservative design, however for lateral

elements,particularlyfortallandslenderbuildings,the

designershouldalsobecarefulasunder-estimationofthe

building weight would put excessive tensile loads on the lateral

supportsystems,bynotprovidingenoughtie-downforceto

counteract overturning effects.

Lastly,andpossiblymostimportantly,ifAustralDeckis

adoptedonaprojectafterthepreliminaryandconceptdesigns

have already taken place, the designer should be careful not to

increasetheweightoftheslabs,causingaflow-onincreasein

thecostsofalltheverticalandlateralelementsabove.

2.2.1 Basic Self-Weight Calculations

Calculate self-weight based on an average slab thickness and

average reduction due to the voids.

Forexample,takingatypical2.5mx7.8mplankina250mm

thickconcreteslab,theconcretevolumeis:

2.5×7.8×0.25=4.875m3

Overtheplankarea,thereare18voids,in6rowsx3columns.

Each void is:

550mmx1000mmx120mm,or0.066m3 per void.

Intotaltheconcretevolumefortheplankistherefore:

2.5×7.8×0.25–18x(0.55×1×0.12)=3.687m3

The total average reduction in the concrete slab is:

1 – 3.687

=24.4%

4.875

Fromastartingpointofa250mmslab,thisistheweight

equivalentofa189mmslab.

2.2.2. Refinements to the Self-Weight

The basic self-weight calculations take into account the

generalproposedlayoutfora2.5mx7.8mplank,including

200mmsolidsectionslongitudinallyand400mmsolidplank

ends.

However,therearemanymoreareaswhereitmaynotbe

possibletoachievethemaximumandmostefficientvoid

arrangement.

Itisadvisedthatthereisaminimumof500mmclearance

aroundallloadbearingelementsandconnectionsonatypical

slab.Thatincludesloadbearingcolumns,wallsandcores,as

wellastransfers,steps,foldsandbathroomsetdowns.

Insomecases,itmaynotbefeasibleorpracticaltousevoid

formersatall,usuallyoncetheslabdepthnarrowstounder

175mm.

TypicalAustralDeckdimensionsandcrosssectionsareshowninFigure3.

Figure 3 – Austral Deck Cross Sections

AUSTRAL PRECAST

/ 14 / / 15 /

Austral Deck TECHNICAL GUIDE

2.3 Calculation of Austral Deck StiffnessThe elastic stiffness of a suspended slab (or any structural

element)issolelydependentontwoproperties;

•Materialproperties,E,theYoung’sModulus

•Geometricproperties,I,theSecondMomentofInertia

Theeffective,transformedstiffnessofasuspendedslab

dependsonanumberofnon-linearandbehavioural

propertiesoftheconcretematerialandlayoutwithinthe

structure,including;

•Extentofcracking,influencedbyreinforcementratio,

concretematerialandhorizontalprestressasperAS3600

sections8.5.3and9.3

•Loadduration(ψfactors)andDeadtoLiveLoadratios

•Creep,influencedbyenvironmentalconditions,concrete

strength and hypothetical slab thickness as per AS3600

section3.1.8

•Shrinkage,influencedbyenvironmentalconditions,

concrete strength and hypothetical slab thickness as per

AS3600 section 3.1.7

Generally in the case of Austral Deck slabs, the calculation of

stiffness is no different, however the designer should also take

the precast concrete panel joints into consideration. For

example,stiffnessacrosspaneljointsevery2.5mona10m

spanmaywellbereducedby10%,asindicatedinsection

2.3.3.

Ingeneral,weignoreanychangestotheYoung’sModulusof

the section, as the concrete is usually a relatively standard

strengthmix,withwell-knownproperties.Concrete

specificationisdiscussedfurtherinthisdocument.

Thegeometricstiffnessdependsonthelayoutandpositionof

thevoidformsandforfullytransformedsections,thelocation

ofthereinforcement.

Forcomputermodellingpurposes,thevoidsareconsidered

usingatraditionalelasticmoduluscalculation.

FortheexampleinSection2.2.3thestiffnessofaplankis

calculated below:

2.3.1. Calculation of the Neutral Axis – Elastic Section

The neutral axis of the cross section is found as follows:

Q = ∑y∙dA

= (2.5 × 0.25m) × 0.125 – 3 × (0.55 × 0.12) ×0.120)

(2.5 × 0.25m) – 3 × (0.55 × 0.12)

= 127.3mm

2.3.2. Calculation of the Moment of Inertia

TheMomentofInertiaofthecrosssectionisfoundusingthe

parallelaxistheoremasfollows,assuminganelastic,

uncracked section.

Ixx = ∑y2∙dA

= bd3 12

+ Ay2 (Concrete minus voids)

= 2.5 × 0.253 0.55 × 0.123 12

+ 2.5 × 0.25 (0.125-0.1273)2 – 3 12

– 3 (0.55 × 0.12) (0.12 - 0.1273)2

= 3010 × 106 mm4

Withoutvoidformers,theMomentofInertiaoftheequivalent

section would be:

Ixx = 2.5 × 0.253

= 3255 × 106 mm4

12

The reduced stiffness in this case is only:

3010 3255

= 92.47%

Inotherwords,forastandard250mmthickslab,thereisa

23-24%weightsavingofthestructure,withonly7.5%lossof

stiffness.

( )

Figure 5 – Typical Multiple Span Austral Deck LayoutNote: Refer to 2.1 about Theoretical Weight Reduction. Some voids might be required to be removed to place the splice bars.

AUSTRAL PRECAST

/ 16 / / 17 /

Austral Deck TECHNICAL GUIDE

3.1 Design PrinciplesThischapterprimarilydiscussestheuseofcomputer

modellingsoftwaretoanalyseanddesignAustralDeckina

varietyofprojectsettings.Thechaptermostlyusesexamples

andspecificsettingsfromRAMConcept,byBentleySystems,

however the general principles can be applied to any internally

recognised software package, including SAFE/ETabs (by

ComputersandStructuresInc),RAPT(byPCDC),Slabs(by

Inducta),Strand7,SAP2000,DIANAandotherFiniteElement

Analysis packages.

Ingeneral,thedesignoftheAustralDeckconsistsoftwo

design stages

1st Stage : Design as formwork

Must be designed for

•Liftingduringmanufacturing

• Transport

•Liftingduringinstallation

•Constructionloadsduringuseasformwork

2nd Stage: Final in-use slab design

• Must be designed for strength and serviceability for

in-servicesituationasperconventionalreinforcement

concrete suspended slab

3.2 General ModellingThe concept and general properties of Austral Deck can be

analysedanddesignedusingregularmethods,conceptsand

codesthatwouldnormallybeemployedtodesignareinforced

concrete suspended slab.

Ingeneral,thedesignerneedstotakeaccountofthefollowing

properties and changes:

•Structuralmass–changingtheconcretematerialproperties

toaccountforvoidformers.

• Structural stiffness – changing the slab shape properties to

accountforvoidformers.

• One vs Two-way spanning – changing the shape properties

to account for non-isotropic properties of the precast joints

andvoidformershapes.

3.2.1. Outputs from Modelling

Just like an ordinary suspended concrete slab, Austral Deck

canbemodelledusing1-D(striprun),2-D(areaplan)or3-D

(fullbuilding)software.

Thedesignercanusethenormalsoftwareoutputssuchasload

run-downs,bendingmomentsanddeflectionstodesignand

design-check the suspended slab.

Somesoftwarehasalsobeenspecificallydevelopedtooutput

detaileddesigns,includingstrip-runanalysis,reinforcement

design and detailing and even bar bending schedules. Any

outputrelatedtothereinforcementandstripanalysisof

AustralDeckshouldbecarefullychecked,assomeofthe

detailingrequirementsaredifferenttoanormalsuspended

reinforced concrete slab.

3.2.2. Code Compliance

AustralDeckhasbeendesignedsuchthatitiscodecompliant

with all of the standard design and construction codes that

exist around the world. These include:

• AS3600-2009 – Concrete Structures

•AS3610-1-2010–FormWorkforConcrete

• Eurocode 2 – 1992-1-1 - Design of Concrete Structures

(Europe)

•BS8110–StructuralUseofConcrete(UnitedKingdom,now

supersededbyEurocode2)

•ACI318-BuildingCodeRequirementsforStructural

Concrete(NthAmerica)

•NZS-3101–ConcreteStructuresStandard(NewZealand)

Thedesignershouldmakethemselvesfamiliarwiththe

particularcoderequirementsforanalysis,designand

detailingfortheregionthatismostrelevanttotheproject.

Inaddition,thedesignershouldalsomakethemselves

familiarwithadditionalcoderequirementsformaterialsand

testingofreinforcement,concrete,formwork,temporary

works and propping that is relevant to the project location.

3.3 Using Ram ConceptRAMConcept(byBentleySystems)isatwo-wayanalysis

package,usingFiniteElementAnalysis(FEA)todetermine

loadsandactionsforasuspendedconcreteslab.Itcanbe

customisedandcanbeusedtodesign,checkanddetail

concrete slabs, including Austral Deck slabs.

3. MODELLING AUSTRAL DECK

Figure 6 – Elastic Analysis of Panel Joints

2.3.3. Calculation of Elastic Stiffness Allowing for Joints

The calculation of a reduction of stiffness based on the precast

concretejointscanbeestimatedbasedonsimplelinearelastic

calculations,butadetailedfiniteelementmodelmaybemore

useful.

Forexample,Figure6belowaretwospans,approximatinga

280mmthick,1000mmwideconcreteslabspanning10m.The

lowerspanhasthreejointsat2500mmcentres,wheretheslab

thicknessisreducedby60mm.

Thejointsaresettobe20mmwideandtheslabinthejointis

raisedsuchthatthetopofslabremainsconstant(i.e.elastic

neutralaxisisraisedby30mm).

Thedeflectionforthemodelbelowhasincreasedbybetween

1%and2%overallatthemidspan.

Itshouldbenotedthatthebelowcaseisforasolid,elastic

section only, and does not include effects for voids,

transformedsections,creep,shrinkageetc.Onlytheimpactof

thepaneljointsaremodelled.

Whilstthejointlocationmayseemtrivial,theoverimpacton

deflectionmaybecritical,andthelocationofjointsshouldbe

positionedwherepossibletoproduceminimalimpactonthe

slab, such as the one-quarter to one-third points of the slab

whereapointofinflectionexists.

0.000 -0.1030.000 -0.1110.000 -0.1030.000 -0.0790.000 -0.043 0.000 -0.079

0.000 -0.043

0.000 -0.1020.000 -0.1100.000 -0.1020.000 -0.0790.000 -0.043 0.000 -0.079

0.000 -0.043

0.000 0.000

0.000 0.000

0.000 0.000

0.000.0.000

AUSTRAL PRECAST

/ 18 / / 19 /

Austral Deck TECHNICAL GUIDE

3.3.2. Average Slab Thickness

Designers should also take care when calculating the average

density for highly variable slabs, such as residential slabs with

bathroomandwet-areasetdowns,balconiesandclosely

spacedloadbearingelements.

Eachoftheseitemswouldaltertheaverageslabthicknessand

density reduction.

The designer should always err on the conservative side of

judgementwhencalculatingaverageweightreductions.For

theexampleshowninFigure23,aresidentialslabmayhavea

reductionof10-12%,withanequivalentdensityof2112–

2160kg/m3.

Forlargefloorareas,itisalsopossibletoaddmultipleslab

typeswithmultipledensities,asperTable4.

3.3.3. Reduced Concrete Stiffness

Different software packages have the ability to directly

influenceconcretestiffnesseithergloballyorlocallyincertain

areas of the slab.

Structuralstiffnessisproportionaltobothmaterial(Young’s

ModulusE)andgeometricstiffness(MomentofInertiaI).

Thematerialstiffnessvalueswereunmodifiedinthematerial

settingsabove,astheconcretematerialisnotactually

changing when using Austral Deck.

RAMConceptcanmodifygeometricstiffnessbyalteringthe

slabthicknessordirectlywithmodificationcoefficients.

Itisthedesigner’sprerogativeastowhichoptionismodified,

butoneshouldalwaysremembertheflow-oneffectsofeach

option. For instance, reducing the slab thickness in RAM

Concept would directly reduce the structural self-weight, and

dramaticallyreducethecapacitycalculationsforBending

Moment,BeamShearandPunchingShear.

Itisrecommendedtoreduceonlythebendingstiffness

coefficientsasperFigure8.ForRAMConcept,thecoefficients

arefoundintheSlabPropertiesoftheMeshInputwindow.

Table 4 – Reduced Austral Deck densities for regular and bathroom slab areas

Figure 8 – Slab properties showing Austral Deck concrete mix and custom reduced stiffness

MIX NAME Density (kg/m3)

Density For Loads(kg/m3)

f 'ci (N/mm2)

f 'c (N/mm2)

25 MPa 2400 Density 15 20

32 MPa 2400 Density 20 25

40 MPa 2400 Density 20 32

40 MPa 2400 Density 20 40

50 MPa 2400 Density 20 50

65 MPa 2400 Density 20 65

40 MPa Austral Deck Bathroom Setdown 2400 Density 20 32

RAMConceptcanundertakeanalysesandcodecompliant

detailingforavarietyofcountryspecificconcretestandards.

OnlyrelativelyminoradjustmentsarerequiredtoenableRAM

ConcepttobecompatiblewithAustralDeck,whichare

detailedbelow.Itisimportanttonote,howeverthatthereare

manyotheroptionsinRAMConceptthattheAustralDeck

designer can be used to adjust or “tweak” the analysis or

design.Designersshouldalwaysfamiliarisethemselveswith

thelimitationsofthesoftwareandundertakesensitivity/

varianceanalysisrunstoascertainthemagnitudeofimpact

on any of these options.

Note:Thefollowingexamplesarebasedoncurrentmenusand

screenshotsfromRAMConceptCONNECTEdition,

v6.00.01.006x64.Otherversionsmayhaveslightlydifferent

menuconfigurations.

3.3.1. Adjustment for Structural Weight

Oncreatinganew“ElevatedSlab”model,thedesignershould

selectthe“Materials”screenfromthenavigationmenu,

Figure 7:

FromtheMaterialsscreen,thedesignershouldselecta

concretestrengthmostlikelytobeused–generallythiswould

be32MPaor40MPa(N32orN40)gradeconcrete.

Select“AddConcreteMix”andnameittoappropriatelyreflect

theAustralDeckmix,e.g.:“50MPa(AustralDeck).

Copytheconcretemixproperties,ensuringthatthestrength

andstiffnesspropertiesremainthesameastheordinary

concretemix(refertoTable3).

ReducetheconcreteDensitybyafactorcalculated/estimated

tobetheslabaverage,allowingforweightreductionsfrom

voidformers.

Forexample,forarectangular,regularcarparkslabin

Figure4themaximumdensitymightbe24.4%,butthe

averagereductionmightbe20%.Conservatively,thedesigner

mayevenuse17%asaninitialassumption.

For this case, the density would be:

2400kg/m3×(1-0.17)=1992kg/m3

Note:thedesigndensityofnormalconcreteisspecifiedby

AS3600-2009,Section3.1.3as2400kg/m3.Inpractice,the

actual density of concrete changes with the concrete and

aggregatespecifications,quantityofreinforcementandother

properties.

The designer should also take care to check if the density

properties are used in calculation for any other structural

propertiesthatmightimpacttheresultsoftheanalysis.

InthecaseofRAMConcept,itispossibletospecifyaseparate

DensitypropertyfromDensityForLoadscalculation.Itis

highlyrecommendedthatthedesignerruntheanalysisfor

both options and check if any differences in the results are

significanttothecalculations.

Itisalsoimportantthattheconcretestrengthandstiffness

characteristics,suchasf’ci,f’

c, E

ci and E

cremainthesameas

thetraditionalconcretemix–thesewillbealteredlater.

Figure 7 – RAM Concept Menu

Table 3 – RAM Concept Concrete Mix Properties

MIX NAME Density (kg/m3)

DensityForLoads (kg/m3)

f 'ci (N/mm2)

f 'c (N/mm2)

f 'cui (N/mm2)

f 'cu (N/mm2)

Poisson's Ratio Ec Calc User Eci

(N/mm2)User Ec (N/mm2)

20 MPa 2400 Density 15 20 18.75 25 0.2 Code 21000 25000

25 MPa 2400 Density 20 25 25 30 0.2 Code 25000 27000

32 MPa 2400 Density 20 32 25 40 0.2 Code 25000 31000

40 MPa 2400 Density 20 40 25 50 0.2 Code 25000 34000

50 MPa 2400 Density 20 50 25 60 0.2 Code 25000 38000

65 MPa 2400 Density 20 65 25 80 0.2 Code 25000 43000

32 MPa (Austral Deck) 2400 Density 20 32 25 40 0.2 Code 25000 31000

AUSTRAL PRECAST

/ 20 / / 21 /

Austral Deck TECHNICAL GUIDE

3.3.7. Austral Deck and RAM Concept Design Strips

RAM Concept uses Design Strips to integrate design actions

suchasbendingmoments,shearsandsupportreactionsand

createaone-dimensionalspan.Thedesignorspanisthen

split into several regular cross sections which are analysed.

Reinforcementquantities(inmm2)aredeterminedforthe

design load envelopes over the design cross section. Finally,

the software takes all the design sections along a particular

spanandappliescodecompliantdetailingrulestolayoutthe

reinforcement.

3.3.8. RAM Concept and AS3600-2009 Implementation

The designer should be aware of the various inclusions and

exclusions that RAM Concept applies and ensure that

adequatehand-checksareperformedtomakesurethereisno

areasoftheslabthatareexcludedfromtherun.

For instance, RAM Concept does not apply all the various

requirementsfromAS3600-2009,orappliesitsown

interpretationsofsomeofthevariousdesignrequirements.

ThisisdetailedintheRAMConceptmanual.

SomeofthedesignlimitationsthatRAMConceptappliesare

pertinent to Austral Deck designs, as follows:

Initial Service Load Case

RAM Concept does not take into account the differential age

between the precast plank and topping portion of Austral

Deck.

Concrete modulus

RAMConceptusestheformulaforEcandEciasspecifiedby

the equations in AS3600-2009 Section 3.1.2, not the values

specifiedbyTable3.1.2.

f 'cmvaluesusedintheequations,however,aretakenfrom

Table 3.1.2. in AS3600.

Low Ductility Rebar

RAMConceptdoesnotapplythelowductility(ClassL)rules

thatwereupdatedaspartofAmendment#2ofAS3600-2009.

Thisisparticularlyrelevantforthemeshreinforcementplaced

within the precast section of Austral Deck.

Minimum Reinforcement

RAMConceptusesAS3600-2009Section8.1.6andSection

9.4.3.2forminimumreinforcementinspandirections.

Section9.1.1isimplementedviaSection8.1.6.1forspanning

reinforcement.Thismayresultindifferentreinforcement

quantities in Austral Deck planks.

Crack Control

AS3600-2009Section9.4.1(c)and(d)areignoredwhenthe

slabenvironmentisspecifiedas“protected”,whichisthe

typicalsettingforinternalslabs.Thismaybeunconservative

forAustralDeckslabsandshouldbecheckedmanually.

Axial Forces

Axialforcesaresometimestakenintoaccount,dependingon

thedesignstripsettings,howeverfor“T”,“L”,or“Z”beams,

Austral Deck designers should take care that the design strips/

sectionsincludetheentirebeamflangearea,otherwise

significantout-of-balanceaxialforceswillbeappliedintothe

plankzonesoftheAustralDeckslab.

Reinforcement depth

Austral Deck designers should carefully specify the design

locationandactuallocationoftheLayer2reinforcement,i.e.

thebarsplacedonthebottomofthein-situslab,sitting

directlyonthebottomoftheprecastplank.Insomecases,

thesebarsmaynotbeproperlyincludedasbottomface

reinforcement.

3.3.9. Austral Deck and RAM Concept Deflection Analysis

Accuratepredictionofslabdeflectionscanbeadifficulttask

andisdependentonbothanalysisanddesignparameters

including:

•Loadingandloadhistoryestimatesovershortterm(days)

andlongterm(years)

•Estimationofslabcrackingandeffective/transformedslab

section properties

•Tensionandcompressionreinforcementratios

•Interactionbetweencrackedconcreteslabsand

reinforcement

•Estimationofcreepandshrinkageproperties

•Estimationofshortandlongtermconcretestrengthand

stiffness(asdesigncomparedtoas-constructed)

•Estimationofconcreteratesofstrengthgainover24hours,

30 days and 30 years.

• Slab age at de-propping and loading

RAM Concept provides load history calculations which are

then reconciled to the cracked section analysis in orthogonal

directions.(Figure10).

Figure 10 – RAM Concept load history options

3.3.4. Isotropic vs Orthotropic Stiffness

Whenmodellingasuspendedslabinafiniteelementsoftware

environment,itisoftenpossibletoadjusttheindividual

stiffnesscoefficientsseparately.

InthecaseofRAMConcept,Figure7showsthe6degreesof

slabmovement,asfollows:

•KMr Bendingstiffnessaboutprimarydirection

(aboutRaxis)

•KMs Bendingstiffnessaboutsecondarydirectory

(aboutSaxis)

•KMrs Torsionalstiffness

•KFr In-planeaxial/membranestiffnessinprimary

direction

•KFs In-planeaxial/membranestiffnessinsecondary

direction

•KVrs In-planeshearstiffness

Wherecustomcoefficientsareused,theorientationofthe

R-axis is critical.

For Austral Deck slabs, it is good practice to orientate the

R-axis in the direction of the Austral Deck plank. Whilst

Austral Deck has been designed to be a two-way suspended

slabsystem,theplanks,voidsandjointsinteractsuchthatthe

direction of the deck is considered the stronger and stiffer

direction.

ForRAMConcept,ifallcoefficientsare1,theslabisperfectly

isotropic, or two-way spanning. Whereas, for an idealised

one-way slab, RAM Concept defaults to

KMr=0.001andKMrs=0.5.

3.2.5. Austral Deck and Orthotropic Stiffness

Inanidealdesign,AustralDeckisconsideredtobealmost

isotropic. As Table 1 indicates, the difference between strong

andweakaxisreductionsissubtle.InthecaseofAD250the

differenceis93%comparedto91%.

Inpractice,forlongerAustralDeckspans,plankdimensions

maybe8-9mx2.5m.Thisresultsin3-4timesmoreplank

jointsinthesecondarydirectionthantheprimarydirection.

Forproperly(andideally)laidoutslabplans,thecumulative

impactofthejointsmayreducestiffness(andincrease

deflection)byasmuchas5%overlargerspans.Thisalsohas

theeffectofredistributingprimaryandsecondarydirection

momentswhichwillalterthereinforcementdesignand

placement.

3.3.6. Orthotropic Stiffness and Australia Code Compliance

Itisimperativethatanyvariationtotheslabstiffnesstakes

into account both the actual, real-world differences in the

structuralpropertiesoftheslab,butalsothelimitations

imposedbyanyrelevantdesigncodesandstandards.

For instance, Australian Standards AS3600-2009 describes

methodsforstructuralanalysisinSection6.Inparticular,

Section6.9describestheuseofIdealisedFrames,whereby

positiveandnegativemomentsinbothprimaryandsecondary

axesareapportionedtocolumnandmiddlestrips.

RAM Concept enables the designer to split the suspended

slabintovariousdesignstrips.Ifdesignstripsaresetup

automatically,RAMConceptwilldefaulttousing“CodeSlab”

layout rules, which generally apportion the strips in

accordance with AS3600, Section 6.1.

ForAustralDeckdesigns,theuseofprimaryandsecondary

stiffnessmodifierswillsignificantlyinfluencethe

apportionmentofloadandthereforebendingmomentintothe

columnandmiddlestrips.

Thedesignershouldtakecaretoensurethatthemoment

redistributiondoesnotexceedthelimitsofredistributionthat

is allowed by the code. For instance, AS3600-2009 Table

6.9.5.3limitsthemomentdistributionasfollowsinTable5:

Table 5 – Design strip distribution from AS3600-2009 Table 6.9.5.3

Figure 9 – Design column and interior strips as defined by AS3600-2009 Section 6.1.

AS 3600—2009 78

© Standards Australia www.standards.org.au

FIGURE 6.1.4(A) WIDTHS OF STRIPS FOR TWO-WAY SLAB SYSTEMS

FIGURE 6.1.4(B) SPAN SUPPORT AND SPAN LENGTHS FOR FLAT SLABS

Acce

ssed

by

R O

BIR

D A

ND

ASS

OC

IATE

S PT

Y LT

D o

n 21

Dec

200

9

Distribution of Bending Moments to the Column Strip

Bending Moment Under Consideration

Strength Limit State

Servicability Limit State

Negativemomentinaninteriorsupport 0.60 to 1.00 0.75

Negativemomentinanexteriorsupportwithspandrelbeam 0.75 to 1.00 0.75

Negativemomentinanexteriorsupportwithoutspandrelbeam 0.75 to 1.00 1.0

Negativemomentinaninteriorsupport 0.50 to 0.70 0.6

AUSTRAL PRECAST

/ 22 / / 23 /

Austral Deck TECHNICAL GUIDE

3.4 Austral Deck Design Strip Layout in RAM Concept

Thissectiondiscussessomeofthemodellingoptionsavailable

to Austral Deck designers using RAM Concept.

The layouts are only suggested for various designs, and could

easilybereconfiguredtosuittheAustralDeckdesigner’sown

preferences.

Theexampledesignusedinthissectionhasbeenchosento

demonstratesomedesignstriplayoutoptions,anddoesnot

representareal-worldmodel.

ToensuretheterminologyofRAMConceptremains

consistent,wewillrefertotheslabaxesasLatitude,running

horizontallytothepage,andLongitude,runningverticallyto

the page.

Theslabcontains3spansof8m,6.5mand8mrespectivelyin

theLatitudedirection,and2spansof6.5mintheLongitude

direction.(Figre11–12)

Theoverallflooris250mmthickAustralDeck,with40mm

bathroomset-downs.Thereare200mmwide,1000mmdeep

upstandbeamsontwosidesofthemodel.

3.4.1. Example Design

Figure 11 – RAM Concept strip layout example

Figure 12 – RAM Concept strip layout - 3D render

ItisimportantforthedesignerofAustralDecktotakeinto

accountsomeparticulardeflectioncharacteristicswhichmay

influencethedeflectioncalculation,asfollows:

•TheRAMConceptcreepandshrinkagemodelsarederived

fromACIreport209R-92.Thereissignificantliterature

onlineforthisdeflectionmodel,howeveritisimportantto

notethattheACImodelassumestheinitialloadingtimeis7

days,whereasAS3600assumesinitialloadingis28days.

DesignersshouldeitherusetheACImodelandspecifythe

actualtimeofloading,orusetheAS3600-2009finalcreep

factorsfromTable3.1.8.3,andthenmultiplyby1.326,which

is(k3-7days/k3-28days).

• Designers should also note that the creep factor includes

elastic strain + creep strain.

•ShrinkageRestraintplaysanimportantroleindeflection.

OnlineguidancefromRAMConceptisasfollows:

>0%-unrestrainedorverylightlyrestrainedslabs

(flexiblecolumnsonly,singlestiffelement)

>10%-normallyrestrainedslabs(morethanonestiff

element,someflexibility)

>20%-completelyrestrainedslabs(basementwalls

aroundentireperimeter,etc.causingahighdegreeof

restraint)

• Generally, shrinkage restraint for Austral Deck should be set

between10and15%dependingonthelevelofconservatism

requiredfordeflectioncalculations.

• Whilst designers usually ignore the live load reduction

factorssettingsinRAMConcept,itisimportanttosetlive

loads to their correct load case (Reducible, Unreducible,

Storage,Parking,Roof).RAMConceptusesthesecasesto

determineshortandlongtermcombinationfactorsin

accordance with AS1170.0 Table 4.1. These are then used for

theloadhistory.Forexample,settingresidentialloadingto

“unreducible”wouldapplyψL=0.6andψS=1,ratherthan

ψL=0.4andψS=0.7.Thiswouldobviouslyincreasethe

deflectionoverthelongterm.

•RAMConceptdefaultstousing5000days(132/3years)for

longtermdeflection,butAS3600conventionssuggest30

years, or 10950 days.

Table6isasetofloadhistorysettingsthatmightbetypicalof

aresidentialslab(average250mmthick,32MPa,coastal

environment).

Variationinthesesettings,combinedwithanabundanceof

localisedenvironmentaleffectswillgiverisetodifferencesin

real-worldexperiencesofdeflection.Itishighlyrecommended

that conservative values are chosen, and that the designer

undertake sensitivity analyses with different values to check

thattheslabdesignissufficientlyconservative.

3.3.10. Example – Austral Deck Load History Settings

Table 6 – Typical load history settings for a residential Austral Deck slab

Setting Value Comments

Live Load 1.5kPa(reducible) AsperAS1170.1,toensureshortandlongtermfactorsarecorrect

Load History –Sustained 10950 days Equalto30yearsfortotallongterm

Initial Load Application 7 days AsperRAMConceptRecommendations

Shrinkage Restraint 15%Forexample,aresidentialslab,precastconcretepartywallsandasheercore,

but free to shrink on the edges

Creep Factor 3.8DesigncreepfactorfromAS3600-2009using:

F'c + 32, t

h=250,t=10950,k2=1.127,k3=1.463φ*

cc=2.8,Designcreep=1+φ*

cc

Shrinkage Strain 0.000462FromAS3600-2009,usingbasicshrinkageε*ccsd,b=1000µε,

basedonaggregatesupplyfrom"elsewhere'

AUSTRAL PRECAST

/ 24 / / 25 /

Austral Deck TECHNICAL GUIDE

Figure 14 – Example plank layout #1

Figure 15 – Example plank layout #2

Flatplateslabscanbemodelledasindividualstripsoras

individual Austral Deck planks.

Inthiscasethe250mmAustralDeckslabwasmodelledwitha

17%reductionallowanceforvoids,butthebathroomswere

modelledwith11%reduction,using210mmthickslabs,

roughlybasedonthereductionfactorsfromTable1.

Figure13presentsareasonablemeshforAustralDeck,

however does not provide a very cost effective plank layout, as

seeninFigure14.ThereareeightprimaryAustralDeck

planksand18secondaryplanks,whicharequiteshort.

Figure15removesoneoftheprimaryplanksandextendsthe

secondaryplanks,reducingthetotalplankcountto18,saving

eight planks in total.

TheAustralDeckdesignermustconsiderthatextraplanks

requireextrapropping,transportandliftingrequirements,

andincreasethenumberofjointsvisibleinthesoffitofthe

slab.

RAMConceptprioritynumberswereused(higherpriority

numbersaremeshedinpreferencetolowernumbers),as

follows:

•Upstandbeams,fulldensity,priority5,meshedasslab

elements

•Bathroomareas,latitudeorientation,priority3

•Generalprimaryspans,longitudeorientation,priority2

• General secondary spans, latitude orientation, priority 1.

3.4.2. Flat Plate

Figure 13 – Example model showing mesh area layouts

AUSTRAL PRECAST

/ 26 / / 27 /

Austral Deck TECHNICAL GUIDE

SomeoftheothercharacteristicsofthestripsinFigures16

and 17 are:

•Alllatitudestripshavetheirreinforcementcoverssetto

minimum–i.e.thedesignedreinforcementallowsfor

bottombarstobelocatedintheplank.Thedesignershould

note, however, that the planks in the latitude direction stop

shortbythewidthofthecolumnplanksspanninginthe

longitudedirection.Bottomlayerreinforcementatthispoint

would not be in the critical section, but needs to be checked

nonetheless.Furtherdetailingrulesforthesecircumstances

are shown in Section 4.

•Latitudestripshavebeensettoroughly2.4mwide,

mirroringtheplanklayout,howeverthestripsareshifted

suchthattheyarecentredonthecolumnslines.Thismeans

thattheedgedesigns(span1-1to1-4and7-1to7-4)would

actually be “half-strips”. The designer could either bear this

inmindwhendetailingthereinforcementonstructural

drawings,orcouldadjustthestripboundariesmanuallyto

exactlymirrortheplanklayout.

•LongitudestripsfollowthetraditionalColumnStrip/Middle

StriplayoutasspecifiedbyAS3600.Thesestripswouldbe

stiffer as they are generally shorter spans and as such the

designer should take advantage of AS3600 detailing

guidelines for positioning of rebar within the effect

compressionwidthofthecolumnstrips.Furtherdetailsare

shown in Section 4.

•Longitudestripsfortheupstandplanksaresetas“Inverted

L”beams,howeverthedesignershouldconsiderusing

manualdesignsectionstoensurethetopdimensioniscutoff

to200mmabovetheslabsurfacelevel.ThisenablesAustral

Deck to provide the upstand plank with a short hob and the

remainderoftheupstandasaprecastwallelement.

Figure 17 – Longitudinal sections generated from design strips

Figure 16 – Latitude and longitude design strips

The design strip layouts in Figure 15 follow the plank layouts

at left for latitude and longitude strips. They are all designed

as “slab rectangle” strips, with the exception of the upstand

beams.

AUSTRAL PRECAST

/ 28 / / 29 /

Austral Deck TECHNICAL GUIDE

The design strips in Figure 20, particularly in the longitudinal

direction are not altered in layout, however designating the

stripsas“beam”adjuststheeffectivestripwidth,in

accordancewithAS3600-2009Section8.8.

Themaximumslabdeflectioninthiscaseis32-35mm,which

isSpan/295fora10mspan.Thisisconsideredreasonableas

farasspan-to-deflectionratios,butgenerallywouldbe

considered5-10mmtoolargeinabsolutedeflectionterms.

Whenproperlyreinforcedanddetailed,theabovedesignproducesadeflectionprofileasfollows:

Theadjustmentalsoremovestheupstandsontheedgesfrom

the concrete section calculations, in favour of the downstand

band. Note that the stiffening effect of the upstands, including

bendingmomentdistributionisstilltakenintoaccount.

Figure 21 – Banded slab deflection profile

Figure 20 – Longitude strip layout for banded slab

Abandedslab(Figure18&19)representsamorespecificuse

ofAustralDeck,mostlikelytobefoundincarparks,

commercialbuildingsortransferfloors.

Thedeeperbandseffectivelyconfiguretheslabintoaseriesof

one-wayspanningbeamsandone-wayspanningslabs.Ifthe

spansbetweenthebeamsaresufficientlylong,AustralDeck

provideanidealdesigntolimitformworkandproppingand

speed up construction cycles.

Thedeeperbands(usuallyintheorderoftwotimestothree

timestheslabdepth)arestillsufficientlywidetoenable

flexuralcapacityintheirtransversedirection,howeverthere

would not usually be any voids present in the bands. The

bands,therefore,arespecifiedwithnormal,ratherthan

reduceddensity,concretematerials.

3.4.3. Banded Slab

6.5

6.5

8 6.5 6.5

RRS

SRR

S

S

RR

S S RRS

S

Figure 18 – Banded slab layout

Figure 19 – Banded slab 3D render (viewed from below)

AUSTRAL PRECAST

/ 30 / / 31 /

Austral Deck TECHNICAL GUIDE

4.2 Ductility Requirements in Flexural Reinforcement

Ductilityrequirementsareoneofthefundamentalconcernsof

well designed, conservative concrete structures in accordance

withAustralian(andmostinternational)codesandstandards.

The general ductility principle requires structures that have

beenloadedbeyondthepointoffailuretodeflectsignificantly

withoutcollapse,soastoprovidesufficientwarningtotheir

occupants to evacuate.

AS3600-2009specificallyaddressessomeductilityconcerns.

The changes to the code should be carefully considered in all

Austral Deck designs.

AS3600-2009 section 1.1.2 requires:

ReinforcingsteelofDuctilityClassLinaccordancewithAS/

NZS 4671—

(i)maybeusedasmainorsecondaryreinforcementinthe

formofweldedwiremesh,oraswire,barandmeshin

fitments;but

Whilstthereinforcementlayingsequencewillprimarilybe

definedbytheplankspandirection,thesequenceofthetop

reinforcementlayersaresomewhatmoreflexible.

For Austral Deck slabs, layers 1 and 2 are cast into the precast

concrete plank. Splice bars on layer 3, along with any

additionalsecondaryreinforcementisplacedonthesurfaceof

the plank once the Austral Deck has been positioned on site.

ReinforcementisusuallyreferredtoasLayers1through5,

orB1/T1,dependingonthenormalnamingconventionsofthe

Austral Deck designer. These are detailed in Figure 23:

These bars are usually threaded through gaps in the trusses.

Finally, layers 4 and 5, are placed and tied in the top layer in

thesamemannerasatypicalin-situpouredconcreteslab.

(ii)shallnotbeusedinanysituationwherethereinforcement

isrequiredtoundergolargeplasticdeformationunder

strengthlimitstateconditions.

Generally, throughout the code, the use of low ductility

reinforcement,suchasSLandRLgrademeshesisexpressly

forbidden.However,Section6ofAS3600-2009provides

designguidanceastotheuseof“L”gradereinforcement.

Essentially,positivedesignmomentsareincreasedbyupto

10%,(forexamplewL2/16becomeswL2/14),andmoment

redistribution is not allowed.

AustralDeckusesacombinationoflowductility(L)and

normalductility(N)reinforcementfortheprimarypositive

(mid-span)bendingmoments,andnormalductility

reinforcementforthenegativebendingmoments,over

supports.

ItistheAustralDeckdesigner’sresponsibilitytodetermine

theratioofLtoNductility.Onesuggestionistoprovide

sufficientNgradereinforcementtocomplywithultimateloads

under“fire”or“earthquake”loadconditions.Thisistypically

W*=DL+0.3xLLinaccordancewithAS1170.0.

4.3 Reinforcement Laying Sequence

Figure 23 – Reinforcement bar laying sequence

Figure 22 – Cover requirements for Austral Deck planks

Table 7 – Extract from AS3600-2009, Table 4.3 - Concrete Exposure Classification

Table 8 – Extract from AS3600-2009 Table 4.10.3.3 - Concrete Cover

Thefollowingchapterdiscussessomeofthemorespecific

requirementsofAS3600-2009,ConcreteStructures.The

standardhasspecificdesignanddetailingrequirementsthat

alldesignersarerequiredtocheckaspartofthenormal

design process.

Thischapterwilldiscussthoserequirements,andhowthey

impactthedesignofAustralDeckslabs.

4.1 Concrete Cover4.1.1. Code Requirements

ThecoverrequirementsforAustralDeckslabsarethesame

asforanynormalreinforcedconcreteelement,withone

exception.

Minimumcovertothebase(soffit)andsidesoftheAustral

DeckprecastplankcanbetakenfromAS3600-2009,Table8

inthisguide,ratherthanTable4.10.3.2.Thisisjustifiedasthe

Austral Deck planks are cast on rigid steel casting beds,

off-siteinaprecastconcretefactory.Itisassumed(andshould

alwaysbecheckedbythedesignengineer),thattheprecast

factorywillemployrigorousqualitycontrolandchecking

procedures.

Theminimumcoverrequirementsforenvironmental

conditions,asdetailedinAS3600-2009Table4.8.1andTable

4.8.2shouldalwaysbeadheredto,forAustralDeckslabsclose

to or in contact with the ground, especially in aggressive soils.

Carefulreinforcementlayingdirectionsshouldbefollowedfor

thegeneralmesh,especiallywiththestandard60mmAustral

Deck biscuit thickness. These are represented in Figure 22.

The Austral Deck designer should also check the exposure and

durabilityrequirementsfortheAustralDeckplanks,

especiallyforthesoffitsofexternalelementssuchas

balconies.

Table4.3ofAS3600-2009,(Table7)inthisguide,detailsthe

exposureclassificationforvariousconcreteelements.Section

4oftheStandardindicatesthemostcommonelementsthat

would be used for Austral Deck planks.

ReferencingtheabovetablesfromAS3600-2009,AustralDeck

projectsintropicalclimaticzones,oranyAustralDeckplanks

locatedexternallyandwithin50kmofthecoastwouldbe

definedasB1.Theserequireminimum25mmcoverfor40MPa

concreteinaccordancewithAS3600.Note:tropicalzonesare

alsodefinedinAS3600,andgenerallyrefertoareasNorthof

20°S in Western Australia and Northern Territory, North of 23°

in Queensland.

4. AUSTRAL DECK AND AS3600 DETAILING REQUIREMENTS

Surfaces of members in above ground exterior environments in areas that are:

(a)Inland(>50kmfromcoastline)environmentbeing: (i)Non-industrialandaridclimaticzoneA1 (ii)Non-industrialandtemperateclimaticzoneA2 (iii)Non-industrialandtropicalclimaticzoneB1 (iv)IndustrialandanyclimaticzoneB1 (b)Near-coastal(1kmto50kmfromcoastline), anyclimaticzoneB1 (b)CoastalandanyclimaticzoneB2

Required cover where repetitive proceedures and intense compaction or self-compacting concrete are

used in rigid formwork

Exposure classification

Requiredcover,mm

Characteristic strength (f 'c)

20 MPa 25 MPa 32 MPa 40 MPa ≥50 MPa

A1 20 20 20 20 20

A2 (45) 30 20 20 20

B1 – (45) 30 25 20

B2 – – (50) 35 25

C1 – – – (60) 45

C2 – – – – 60

AUSTRAL PRECAST

/ 32 / / 33 /

Austral Deck TECHNICAL GUIDE

The calculation of splice bar quantity and length is required to

becarefullydeterminedforAustralDeckslabs,astraditional

“lappedsplices”arenotusuallyapplicable.(Figure25)

4.7 Punching Shear4.7.1 General Design Issues

Punching shear for Austral Deck slabs needs to be carefully

designedandchecked,especiallywithlarger,flat-platetype

slab designs.

InAustralia,itisgenerallyaccepteddesignpracticetoeither

use AS3600 Section 9.2 or to use the Eurocode EN 1992-1-1

Section 6.4.4

Bothoftheabovedesignmethodshavesignificantbodiesof

researchbehindthem,andarenotcomparedspecificallyinthis

manual.

Ingeneral,AustralianStandardAS3600treatspunchingshear

usingclosedreinforcementtieslaidinatorsionaldesignstrip

acrossthecolumn.Thedetailingrequiresthetiestobeplaced

overaquarter-spanineachdirectiontoadjacentcolumns.

TheEurocode(andtheoldBritishStandard8110)modelsa

series of concentric shear planes or rings progressing outwards

fromthecolumninquestion.Verticalshearreinforcementis

placedinacruciformorradialpatternoutwardsfromthe

columnuntilthepunchingshearperimeterissufficientlarge

enoughtocarrytheload.Thereinforcingisusuallyintheform

of individual hooks or “S” shape rebar, or proprietary studs

tack-welded on to light bars such as Ancon Studrail.

4.7.2 Punching Shear Reinforcement and Austral Deck

ForAustralDeckslabs,itisusuallysimplertousethe

Eurocode to both check and design for punching shear, and

the use of shear studs rather than closed ligatures is certainly

easier for installation.

Where required, the punching shear studs can be installed

into the precast biscuit in the factory to a precisely laid out

position, and generally do not interfere with the trusses or

bottomreinforcing.

Itiscriticallyimportantthatallvoidformersareremoved

fromthepunchingshearperimeter,howeverwidethatmay

be.Thisinturnwillimpactthetotalslabweightandmay

requirerecalculationofrun-downloadstocolumnsand

foundations, all of which should be taken into account by the

Austral Deck designer.

4.7.3 Basic Punching Shear Checks

Prior to undertaking detailed checks and design, it is often

usefultodetermineabasicpunchingshearcapacityaround

thecolumns.ForthispurposeeitherAustralianorEuropean

codes can be used.

The Austral Deck designer should establish the capacity of the

toppingcomponentoftheAustralDeck,excludingtheprecast

biscuit.Thisisconsideredtheabsoluteminimumcapacityasit

ignoresupto60mm(or90mm)oftheconcretedepth.

4.6 Calculation of Splice Bars

Figure 25 – Splice bar calculation of forces

4.4 Detailing of Span Direction Reinforcement

PrimaryreinforcementdetailinginaccordancewithAS3600is

specifiedinsection9.1.3.1forsuspendedslabs.Thisincludes,

amongothers,thefollowingkeyrequirements:

•Requirementforanchorageofpositive(bottom)flexural

reinforcementatendsupports–generallyatleast50%ofthe

totalflexuralreinforcement,anchoredtoatleastthelarger12

bardiametersorD,theslabthickness.

•Requirementofatleast25%ofthepositive(bottom)flexural

reinforcementtoextendpastthenearfaceofaninternal,

continuous support point, typically to full anchorage of 25 bar

diameters.

4.4.1 End Supports

For Austral Deck planks supported by a precast concrete wall,

thefirstrequirementcanbemetbythefollowing:

1. Provide screw-in ferrules, rip-boxes or other proprietary

reinforcementequivalenttoatleast50%oftheflexural

reinforcement.

2.Provideafulllapofferruleswiththebottomreinforcement,

asperAS3600Section13.2,toaminimumlengthofLsy.t.lap

Forplankssupportedbymasonryorbrickwork,thiscanbe

achievedbyprovidingcogsontheprimarybottom

reinforcement,asthecogswillprovide50%anchoringin

accordance with AS3600 Section 13.1.2.6

4.4.2 Internal Supports

Atinternalcolumnsorwalls,atleastonequarteroftheflexural

bottomreinforcementshouldbeextendedpastthefaceofthe

support. This will require additional splice bars to be added to

the Austral Deck once it has been installed on site. Refer to

Section 4.6 in this guide for notes on calculation of splice bars.

Figure 24 below shows a typical splice bar detail at an internal

columnlocation.Notethatonly25%oftheflexuralbarsare

required to be spliced.

4.4.3 Negative Reinforcement

Standarddetailingrulesremainapplicableforthe

conventionallylaid,negativeortoplayersofreinforcement.

One critical such rule is AS3600-2009, Section 9.1.2,

Reinforcementandtendondistributionintwo-wayflatslabs.

Intwo-wayflatslabs,atleast25%ofthetotalofthedesign

negativemomentinacolumn-stripandadjacenthalfmiddle-

stripsshallberesistedbyreinforcementortendonsorboth,

locatedinacross-sectionofslabcentredonthecolumnandof

a width equal to twice the overall depth of the slab or drop

panelplusthewidthofthecolumn

GiventhatthemajorityofAustralDeckslabsaretwo-way,

withgenerallyflatsoffits,theaboverequirementwillmost

likely apply.

4.5 Detailing of Cross Direction Reinforcement

IftheAustralDeckdesignerreducesthestiffnessofatwo-way

slabto50%orless,thenitislikelythatthesecondary

directionreinforcementrequirementwillbealmostentirely

metbythecrossrodsofthemeshcastintotheprecastplank.

Typically,forSL92*mesh,thisis287mm2/m,orthe

equivalentofN12rebarat400mmcentres.

Thedesignerwillneedtobemindfulofductilityrequirements

(refertosection4.2).

Thenumberofsplicebarsrequiredforthecrossdirection

reinforcementwouldthenbecalculatedasaproportionofthe

crossdirectionreinforcement.Forinstance,if180mm2/m

reinforcementisrequiredand287mm2/misprovided,then

splicebarstheequivalentofN12at600mmcentreswouldbe

required,providing183mm2/m.Thisisequivalenttosplicing

everythirdrodfromSL92*(8.55mmbars).

* The common mesh size used for manufacturing Austral Deck is SL72.

Figure 24 – Typical internal support splice bar locations

AUSTRAL PRECAST

/ 34 / / 35 /

Austral Deck TECHNICAL GUIDE

4.8 Longitudinal ShearInzonesofhightransverseloads,longitudinalshearcan

becomesignificantforanycompositestructure,including

Austral Deck.

InthecaseofAustralDeck,theshearcanberesistedbythe

friction interface between the in-situ topping slab and the

precast biscuit or by the rebar trusses, or both.

Calculationofthelongitudinalshearfollowstheformulafor

Shear Flow:

q = V* Q

I

Where: qisthelongitudinalshear,orshearflow,inkN/mm

V*isthetransverseshearforce(kN)

Qisthefirstmomentofareaattheshearinterface

(mm3)

Iisthemomentofinertiaabovethenaturalaxis

(mm4)

Forinstance,takingtheexamplefromSection4.7.3.wherethe

totalloadontheslabis10.47kPa,andweassumeasinglespan

of7.5mandtributarywidthof6m.

V* = wL

= 10.47 × 6 × 7.5

= 235.5kN

2

2

Ixx = BD3

= 6000 × 0.275 3

= 7812.5 ×106 mm 4

12 12

Q60mm = (60 ×6000) × 250

– 60

= 34.2 × 106 mm 3

2 2

q = 235.5 × 34.2 × 106

= 1.031kN/mm

7812.5 × 106

Ifthelongitudinalshearforcefromtheabovecalculationis

resistedover6mwidthby9rebartrusses,eachwith2xN6

rebarat100mmcentresthentheshearresistanceprovidedby

the trusses is:

ØVlong = 0.8 × 500MPa × 28mm2 × 18 bars

= 2.02kN/m resistance

100 mm spacing

Inthiscasetheshearresistanceoftherebarissufficientto

resist any longitudinal shear forces at the in-situ/precast

interface.

( )

Ifpunchingshearbecomestoogreattobeabletobesupported

bythetoppingslabalone,andshearties/studsareimpractical,

itmayalsobepossibletopouralocalised“mushroomhead”

(Figure26)aroundthecolumn,wheretheprecastslabiscut

backroughly100mmandtheentiredepthofconcreteisused.

Forinstance,takingthepreviousexample,ifdom

were

increasedby60mmto239mm,thentheshearperimeteru

becomes4(500+239)=2956mm.Punchingshearcapacityis

increasedbyapproximately45%

ØVuo=0.7×2956×239×2.15=1063kN

Figure 26 – Punching Shear Setback

4.7.5 Alternatives for Punching Shear

Thedesignercanthendeducethatthecolumntributaryload

areaisapproximately731.7/10.47=69.9m2 that could be

carried by the topping portion of the slab alone with no

punching reinforcing.

IfusingAS3600section9.2.4,therearefurtherreductions

duetothetorsionalmomentsacrossthecolumn,

approximatelyequaltouMv* which need to be considered.

8V* adom

4.7.4 Punching Shear Using Rebar Trusses

ItispossibletoconsiderthefulldepthoftheAustralDeckslab

for punching shear, using the rebar trusses as shear ties.

Generally, the design for this should be undertaken using the

Eurocode provisions, and would require careful checking.

Usually, however, the spacing of the trusses and lack of truss

continuityovercolumnsupportsprecludestheirinclusionin

the punching shear calculations.

Forinstance,a500x500concretecolumnsupportinga

275mmthickN40AustralDeckslabhasthefollowingcapacity

in accordance with AS3600.

ØVuo = Øudom (fcv + 0.3σcp )

fcv = 0.17 1 + 2

√ f’c ≤ 0.34 √ f’c

βh σcp = 0 (slab is not tensioned)

βh = 1 (square column aspect ratio)

fcv = 0.34√40 = 2.15MPa

dom = 179mm 275mm – 30 cover – 12mm

– 60mm planket

2

u = 4 ×(500 + dom ) = 4 × (679) = 2716mm

ØVuo = 0.7 × 2716 × 179 × 2.15 = 731.7kN

Fora275mmAustralDeckslab,carryingresidentialloads

(1kPaSDLand1.5kPaLL)withself-weightof5.85kPa

(basedon15%voidratio),thetotalultimateslabweightis

1.2(5.85+1)+1.5(1.5)=10.47kPa.

(

(

)

)

AUSTRAL PRECAST

/ 36 / / 37 /

Austral Deck TECHNICAL GUIDE

5.2 Design Criteria and Specifications5.2.1 Strength

ThePanelmustresistthebendingandshearactioneffects

fromalltheappropriateloadcombinations.Inthecaseofa

simplysupportedpanelthefollowingloadcombinationsare

appropriate.

StageI–priortoplacementofconcrete

1.25G+1.5Quv

+1.5M1 (1)

StageII–duringplacementofconcrete

1.25G + 1.25Gc + 1.5Q

uv + 1.5M

2 (2)

1.25G + 1.25Gc + Q

c (3)

StageIII–afterplacementofconcrete

1.25G + 1.25Gc + 1.5Q

uv + 1.5M

3 (4)

Ifthepanelisconsideredaprimarymemberasper

AS3610–1995,thentheseloadsmustbemultiplied

byafactorof1.3.Forexample:

StageI–priortoplacementofconcrete

1.3(1.25G + 1.5Quv

+ 1.5M1)

(5)

5.2.2 Stiffness

Thepanelstiffnessmustbesuchthatthedeformationunder

theappropriateloadcombinationdoesnotexceedchosen

limits,usingeitherthelimitsspecifiedinAS3610.1–2010,

Table3.3.2(Formfacedeflection)orotherwisechosen.In

thecaseofasimplysupportedpanelthefollowingload

combinationsareappropriate:

StageII–duringplacementofconcrete

G + Gc + Q

uv (6)

StageIII–afterplacementofconcrete

G + Gc + Q

uv + M

3 (7)

While AS 3610 – 1995 does not require the addition of Quv

, it

has been added to be in line with the intentions of AS 1170.0

– 2002.

5.2.3 Surface Finish

Thesurfacefinishofthepanelsoffitconformswiththe

physicalqualityofa“Class2”surfacefinishasspecifiedin

AS 3610.1 – 2010. The surface class chosen for the in situ

slabisalsousedtodefinethemaximumallowabledeflection

limits.

5.2.4 Panel Capacity

The strength and stiffness of the panel is dependent on the

truss,panelsizeandgeometry.Duringconstructionthe

appliedloadsareresistedbytheactionofthetrussmembers

andpanelconcrete.Theresistanceprovidedbyanymeshor

additionalreinforcementbarsisignored.

Thefollowingstructuralchecksareperformed:

Themaximumallowablespaniscalculatedforeachcase.

STRENGTH

a)TopChordCompression

b)TopChordTension

c)BottomChordCompression

d)BottomChordTension

e)ConcretePanelCompression

f)DiagonalCompression

g)ConcreteTensileStrength

SERVICEa)Deflection

b)Cracking

5.1 Stage one: Design as formworkTheprecastelementofAustralDeckmustbedesignedas

formworkforconstructionloadssinceitisutilisedas

permanentformwork.Thestrengthoftheprecastelement

requiredtospanbetweentemporaryandpermanentsupports

duringconstructionisgainedfromthelatticegirdertype

reinforcementthatispartiallyembeddedintheprecast

concrete.

Thetopchordofthelatticegirdertypereinforcementisnot

embeddedintheprecastconcretesoAustralDeckmustbe

designedasformworkusingacombinationoftheAustralian

StandardforConcreteStructures(AS3600-2009)andSteel

Structures(AS4100-1998)alongwiththeAustralianstandard

forloading(AS1170)andformwork(AS3610-2010).

Itisrecommendedthatthedesignengineerusesstrict

deflectioncriteriawhendesigningasformworkfor

constructionloadstoalleviateanysignificantcracking.

ThissectionistodemonstratetheprocessofdesigningAustral

Deckasformworkcomplyingwiththestability,strengthand

serviceabilitylimitstagecriteriaspecifiedinAS3610-1-2010

FormworkforConcrete–Part1Documentationandsurface

finish.

Theprocessisusedtodeterminethemaximumspanning

capacity of Austral Deck based on the structural properties

andconstructionloadsinordertodefinethetemporary

proppingrequirementofaconcreteslabconstructedusing

Austral Deck.

Thespecifccalculationsinthisdocumentapplytoasimply

supported double span Austral Deck panel for the variable

structural properties and construction loads listed on 5.3.1.

Howeverthecalculationsalsoprovideguidanceforother

situations.

Charts2and3in5.4.8and5.4.9canbeusedasaguidefor

AustralDeckasformworkunderconstructionloadsfor

variousslabthicknessandsteellatticegirderreinforcement

con gurations.

AustralDeck–ConstructionLoadAnalysissoftwarecanbe

usedtodeterminepropspacingforavarietyofstructural

properties and construction loads.

The software can be downloaded via the Austral Precast

websitewww.australprecast.com.au

5. AUSTRAL DECK DESIGN AS FORMWORK

Figure 27 – Interior Support During Construction

EQUAL SPAN EQUAL SPAN

AUSTRAL PRECAST

/ 38 / / 39 /

Austral Deck TECHNICAL GUIDE

5.3 Panel PropertiesOverallSlabThickness,d= 250 mm

MinimumCoverto

BottomReinforcement= 20 mm

Concrete Density, r = 2400 kg/m3

ConcreteStrengthatLoading,ƒcm= 20 MPa

Concrete Modulus of Elasticity, Ecj= 22,610 MPa

PanelWidth,b= 2,500 mm

Precast Panel Thickness, tp= 75 mm

NumberofTrussperPanel,nt= 10

NumberofVoids,nv= 0

Void Width, bv= N/A mm

Void Thickness, tv= N/A mm

ClassofSurfaceFinish= 2

NumberofSpans(basedonsupports)= 2

The panel concrete properties (ƒcm, Ecj)areatthetime

ofliftingfromcastingbeds.

5.3.1 Construction Loads

PanelDeadLoad,G= 1.87 kPa

In-situSlabDeadLoad,Gc= 4.29 kPa

ConstructionLiveLoad,Quv = 1 kPa

ConcreteMoundingLoad,Qc= 3 kPa

Stacked Materials, M1= 4 kPa

Stacked Materials, M2= 0 kPa

Stacked Materials, M3= 4 kPa

* Although AS 3610 – 1995 states that the concentrated load Qc

willapplyoveranareaof1.6x1.6m,ithasbeenappliedover the full area of the panel.

** Theloadsfromstackedmaterials,M, mayapplytoonespanonly.

5.3.2 Load Combinations

5.3.3 Design Load

Therefore the design loads are as follows:

Strength,w*= 19.76 kPa

Service, ws= 11.16 kPa

5.3.4 Truss Properties

AustralDeckTrussType,T= T190/12

Average Truss Spacing, Ts= 250 mm

TrussHeight,Th = 192 mm

Truss Bar Yield Strength, fsyt= 500 MPa

5.3.5 Top Chord

BarDiameter,dt= 11.9 mm

Area, At= 1,112.2 mm2

StrutLength,Lt = 200 mm

EffectiveLength,It= 180 mm

Radius of Gyration, rt= 2.98 mm

5.3.6 Bottom Chord

BarDiameter,db= 6.3 mm

Area, Ab= 623.4 mm2

StrutLength,Lb = 200 mm

EffectiveLength,Ib= 200 mm

Radius of Gyration, rb= 1.58 mm

5.3.7 Diagonal Lacing

BarDiameter,dw= 6.3 mm

Area, Aw= 623.4 mm2

Angle ofWeb,q= 62.5 degrees

StrutLength,Lw = 216.5 mm

EffectiveLength,Iw= 151.5 mm

Radius of Gyration, rw= 1.58 mm

5.3.8 Mesh

Mesh= SL72

WireDiameter,dm= 6.8 mm

Area, Am= 448 mm2

STAGE LOAD COMBINATION LOAD UNIT EQUATION

l 1.3 (1.25G + 1.5Quv + 1.5M1)** 12.78 kPa

(5)ll 1.3 (1.25G + 1.25Gc + 1.5Quv+ 1.5M2)** 11.96 kPa

ll 1.3 (1.25G + 1.25Gc + Qc)* 15.86 kPa

lll 1.3 (1.25G + 1.25Gc + 1.5Quv + 1.5M3)** 19.76 kPa

STIFFNESS

ll G + Gc + Quv 7.16 kPa (6)

lll G + Gc + Quv + M3** 11.16 kPa (7)

5.2.5 Maximum Span

Themaximumspanisselectedonthebasisthatthedesign

action,calculatedfromthefactoredloadcombinations,does

not exceed the capacity of the panel.

Asummaryofthecalculationsshowingthemaximumspan

for each action is given in the table below:

DESIGN ACTION MAX SPAN (m)

POSITIVE BENDING

TopChordCompression 3.41

BottomChordTension 3.37

NEGATIVE BENDING

Top Chord Tension 3.95

BottomChordCompression 1.33

ConcretePanelCompression 5.59

SHEAR DiagonalLacingCompression 5.13

CRACKINGConcrete Tensile Strength 2.23

Flexural Cracking 3.96

DEFLECTION ServiceabilityDeflection 3.05

Themaximumspanforthegivenconfigurationistherefore:

Thebottomchordcompressionlimitcanbeignored

ifthebottomchordiscompletelyembeddedinthepanel

concrete for its full length. Control for concrete tension can

also be ignored as it is based on the uniaxial tensile strength

oftheconcretepanelratherthantheflexuraltensile

strength.Thisimpliesthattheconcreteisallowedtocrack

butiscontrolledbythelimitssetoutinSection9.4.1of

AS3600-2009.

5.2.6 Stacked Materials

ThemaximumspanloadingsincludefactorsM1,

M2 and M

3fortheliveloadingsofstackedmaterials.

AS 3610 – 1995 gives these values as 4.0 kPa for before and

aftertheplacementofconcrete(M1 and M

3),and0kPafor

duringtheplacementofconcrete(M2).

Themaximumspanmaybeincreasedbydecreasingthese

loads.Insuchacase,thisloweredloadlimitmustbeclearly

indicatedintheformworkdocumentationandconstruction

controlput in place to ensure it is not exceeded.

5.2.7 Assumptions

1) Verticalandhorizontalactioneffectsfromenvironmental

loadshavebeenignored(e.g.winduplift,rivercurrents).

Ifrelevant,appropriatestrengthandserviceloadsshould

be calculated with reference to AS 3610 – 1995, Table

4.5.2.

2) ThevalueforstackedmaterialsduringStageI(M1)applies

alsotoStageIII(M3)andduringStageIIthevaluefor

stackedmaterials(M2)is0kPa.

3) Theeffectsofformfacedeflectionandconstruction

tolerances can be ignored.

4) Thedeviationsspecifiedforformfacedeflection,

in AS 3610.1 – 2010, Table 3.3.2, will be interpreted

asthedeflectioncriteriaforthepanelasperthefollowing

extract:

5) Theweldsconnectingdiagonalwirestothetop

andbottomchordofthetrussarecapableoftransmitting

the full design action effects.

6) Trussgeometryisasperthefollowingtable:

SURFACE CLASS DEFLECTION LIMIT

1 Lesserof2mmorspan/360

2 Lesserof3mmorspan/270

3 Greaterof3mmorspan/270

4 Greaterof3mmorspan/270

5 N/A

TRUSS TYPE

WIRE SIZE (mm)

TOP BOTTOM DIAGONAL HEIGHT

T90/10 9.5 6.3 6.3 92

T110/10 9.5 6.3 6.3 111

T150/10 9.5 6.3 6.3 154

T190/10 9.5 6.3 6.3 191

T110/12 11.9 6.3 6.3 112

T150/12 11.9 6.3 6.3 155

T190/12 11.9 6.3 6.3 192

MaximumSpan 3.05m

AUSTRAL PRECAST

/ 40 / / 41 /

Austral Deck TECHNICAL GUIDE

5.4 Panel Properties5.4.1 Diagonal Lacing CompressionWhere Φ= 0.90

FormFactor,kf= 1.00

Section Capacity, Ns=k

fA

nf

y= 311.72 kN

λn= 136.07

aa= 13.93

ab= 0.50

λ= 143.03

η= 0.42

ξ= 0.78

ac= 0.32

LimitStateCapacity,ΦacN

s = 89.21 kN

MaximumSpanbasedonshear

CapacityofDiagonalLacing,Lds= 5.13 m

Themaximumspanuscalculatedfromthegreatestshearat

any point along the slab:

V*=j3w*L L=

Where j3 is a constant that depends

onthenumberofspans.

Steel Elastic Modulus, Es= 200,000 MPa

Concrete Elastic Modulus, Ecj= 22,610 MPa

ModularRatio,n= 8.85

DistancefromSoffittoTopChord= 221.9 mm

TransformedTopChordArea= 9,838 mm2

DistancefromSoffittoBottomChord= 29.9 mm

TransformedBottomChordArea= 4,891 mm2

PanelConcreteArea= 187,500 mm2

Distance to the Neutral Axis, yg= 46.29 mm

SecondMomentofInertia,Ig= 4.07E+08 mm4

NO. OF SPANS j3

1 0.5

2 0.625

≥3 0.6

Largestreinforcementdiameter,db= 6.8 mm

SteelStressLimit,σsteel= 362.3 MPa

AreaofBottomChordSteel,Ab= 623.4 mm2

Area of Mesh Steel, Am= 447.5 mm2

TotalAreaofBottomSteel= 1,071 mm2

EquivalentAxialForce,N*= 387.99 kN

TrussHeight,Th= 192 mm

Limitstatemoment

capacity for Steel Stress, M*pf.s= 74.49 kN.m

MaximumSpanbased

onFlexuralCracking= 3.96 m

InaccordancewithAS3600–2009ConcreteStructures,

Clause8.1.3:

ConcreteStrengthatLoading,f'c= 20 MPa

Concrete Strength Factor, a2= 0.85

CompressiveAreaFactor, γ= 0.85

Φ= 0.60

Effective Cross Section Depth

(equal to panel thickness tp),d= 75 mm

yg= 46.29 mm

ku= 0.62

LimitStateCapacity,ΦNc= 1,003 kN

TrussHeight,Th= 192 mm

LimitStateMomentCapacity,M*pc= 192.6 kN.m

MaximumSpanbasedonmoment

capacityofTopChordintension,Lpc= 5.59 m

5.4.5 Crack Control for Flexure

AS3600–2009,Clause9.4.1statestherequirementsfor

crackcontrolinflexuretobedeemedcontrolled.Part(c)

providesalimitbasedonthesteelstress,whichisusedto

defineanothermaximumspanlimit.

5.4.3 Control for Concrete Tensile Strength

AS3600–2009,Clause3.1.1.3definesthetensilestrengthfora

givenconcretemember,thishasbeenusedtoensurethatthe

deflectioncalculationsareaccuratewithoutusingthecracked

secondmomentofarea.

M*pt

= wheref'ct.f=0.6√ f'

c

f'ct.f= 2.68 MPa

LimitStateMomentCapacityfor

concrete strength, M*pt= 23.61 kN.m

MaximumSpanbasedoncontrolling

toconcretetensilestrength,Lpt= 2.23 m

V*j

3w

f'ct.f

'Ig

yg

5.4.2 Concrete Panel Compression

Transformed Section:

Forserviceabilitylimitstate,thepanelisanalysedasan

uncrackedsectionusingtheTransformedAreamethodto

determinethestressesinthesteelandconcrete.

5.3.9 Capacity Calculations

Thenumberofspans(basedonthenumberoftemporary

supports)affectsthecoefficientsusedwhencalculatingthe

maximumspans:

M*=jw*L L=

5.3.10 Top Chord Compression

InaccordancewithAS4100–1998SteelStructures,

Clause 7.1 – N*≤Φag N

2

NO. OF SPANS j1, POSITIVE MOMENT

j2, NEGATIVE MOMENT

1 0.125 N/A

2 0.096 0.125

≥3 0.101 0.121

WhereΦ= 0.9

FormFactor,kf= 1

Section Capacity, Ns=k

f A

nf

y = 556.1 kN

λn= 85.57

aa= 18.77

ab= 0.50

λ= 94.95

η= 0.27

ξ= 1.07

ac= 0.58

LimitStateCapacity,ΦacNs = 288 kN

TrussHeight,Th = 192 mm

LimitStateMomentCapacity,M*tc = 55.28 kN.m

MaximumSpanbasedon

MomentCapacityofTopChord

incompression,Ltc = 3.41 m

WhereΦ= 0.9

FormFactorkf= 1

Section Capacity, Ns=k

f A

nf

y = 311.7 kN

λn= 179.6

aa= 11.05

ab= 0.50

λ= 185.11

η= 0.56

ξ= 0.68

ac= 0.20

LimitStateCapacity,ΦacNs = 56.88 kN

TrussHeight,Th = 192 mm

LimitStateMomentCapacity,M*bc

= 10.92 kN.m

MaximumSpanbasedon

MomentCapacityofTopChord

incompression,Lbc

= 1.33 m

WhereΦ= 0.9

LimitStateCapacity,ΦAgf

y= 500 kN

TrussHeight,Th = 192 mm

LimitStateMomentCapacity,M*tt= 96.09 kN.m

MaximumSpanbasedonMoment

CapacityofTopChordintension,Ltt= 3.95 m

5.3.11 Top Chord Tension

InaccordancewithAS4100–1998SteelStructures,

Clause 7.1 – N*≤ΦAgf

y

5.3.13 Bottom Chord Tension

InaccordancewithAS4100–1998SteelStructures,

Clause 7.1 – N*≤ΦAgfy

5.3.12 Bottom Chord Compression

InaccordancewithAS4100–1998SteelStructures,

Clause 6.1 – N*≤ΦacNs

Where Φ= 0.9

LimitStateCapacity,ΦAgf

y= 281 kN

TrussHeight,Th = 192 mm

LimitStateMomentCapacity,M*bt= 53.87 kN.m

MaximumSpanbasedonMoment

CapacityofTopChordintension,Lbt= 3.37 m

M*jW*

2

AUSTRAL PRECAST

/ 42 / / 43 /

Austral Deck TECHNICAL GUIDE

5.4.8 Single Span

Variables:75mmprecast,fcmi20MPa,SL72mesh,20cover,Class2finish.

0

50

100

150

200

250

300

350

400

450

500

00.5 1 1.5 2 2.5 3.53

Maximum Distance between Supports (m)

T80/10, 250 spacing

T80/10, 565 spacing

T110/10, 250 spacing

T110/10, 565 spacing

T150/10, 250 spacing

T150/10, 565 spacing

T110/12, 250 spacing

T110/12, 565 spacing

T150/12, 250 spacing

T150/12, 565 spacing

T190/12, 250 spacing

Tota

l Co

nc

rete

Sla

b T

hic

kne

ss (

mm

)

0

50

100

150

200

250

300

350

400

450

500

00.5 1 1.5 2 2.5 3.53

Maximum Distance between Supports (m)

T90/10, 250 spacing

T90/10, 565 spacing

T110/10, 250 spacing

T110/10, 565 spacing

T150/10, 250 spacing

T150/10, 565 spacing

T110/12, 250 spacing

T110/12, 565 spacing

T150/12, 250 spacing

T150/12, 565 spacing

T190/12, 250 spacing

T190/12, 565 spacingTota

l Co

nc

rete

Sla

b T

hic

kne

ss (

mm

)

0

50

100

150

200

250

300

350

400

450

500

00.5 1 1.5 2 2.5 3.53

Maximum Distance between Supports (m)

T80/10, 250 spacing

T80/10, 565 spacing

T110/10, 250 spacing

T110/10, 565 spacing

T150/10, 250 spacing

T150/10, 565 spacing

T110/12, 250 spacing

T110/12, 565 spacing

T150/12, 250 spacing

T150/12, 565 spacing

T190/12, 250 spacing

Tota

l Co

nc

rete

Sla

b T

hic

kne

ss (

mm

)0

50

100

150

200

250

300

350

400

450

500

00.5 1 1.5 2 2.5 3.53

Maximum Distance between Supports (m)

T90/10, 250 spacing

T90/10, 565 spacing

T110/10, 250 spacing

T110/10, 565 spacing

T150/10, 250 spacing

T150/10, 565 spacing

T110/12, 250 spacing

T110/12, 565 spacing

T150/12, 250 spacing

T150/12, 565 spacing

T190/12, 250 spacing

T190/12, 565 spacingTota

l Co

nc

rete

Sla

b T

hic

kne

ss (

mm

)

5.4.9 Two Span

Variables:75mmprecast,fcmi20MPa,SL72mesh,20cover,Class2finish.

** TheinformationinthegraphshasbeengeneratedinaccordancewithAustralianStandard™.Formworkforconcrete.AS3610AS3610-1995FormworkforConcreteandAS3610.1-2010Formworkforconcrete–Part1Documentationandsurfacefinish

* Theinformationinthegraphsareindicative,shouldbeusedasaguideonlyanddoesnotreplacetheneedforqualifiedstructuraldesignengineer.

Chart 2 – Maximum distance between supports for single span

Chart 3 – Maximum distance between supports for multi span

5.4.6 Deflection

Themaximumdeflectionofthepanelcanbecalculatedfrom

either of the following questions:

Foranabsolutevalueofadeflectionlimit,

∆= L=√Where j

4isavaluethatvariesbasedonthenumberofspans

and ∆isthedeflectionlimit.Foraspan:deflectionratio

limit,

= L=√Where j

4isavaluethatvariesbasedonthenumberofspans

and βisthespan:deflectionrationlimit.

Astheprecastslabinassumedtobecrackedfordeflection

calculation,onlythesteeltrussmembersareusedforthe

values of E and I.Anyreinforcingmeshisnottreatedas

contributingtodeflectioncontrolasitisnotassumedtobe

sufficientlyattachedtothetrussframes.

NO. OF SPANS j4

1 0.0130

2 0.0092

≥3 0.0099

Surfacequalityclass= 2

Maximumdeflection(absolute)= 3 mm

Maximumdeflection(ration),ß= 270

Area of tensile steel, Ast= 623.4 mm2

Distance of tensile steel, dst= 29.9 mm

Areaofcomprehensivesteel,Asc= 1,112.2 mm2

Distancetocomprehensivesteel,dsc= 221.9 mm

Neutral axis height for

steel truss only, dsn= 152.9 mm

Secondmomentofinertia

forsteeltrussonly,Is= 1.47E+07 mm4

Maximumspanbased

onabsolutelimit,Ldef.abs

= 3.05 m

Maximumspanbased

onrationlimit,Ldef,rat

= 4.74 m

Maximumspanbased

onserviceabilitylimits,Ldef= 3.05 m

5.4.7 Maximum Spans Summary

Topchordcompressionlimit= 3.41 m

Topchordtensionlimit= 3.95 m

Bottomchordcompressionlimit= 1.33 m

Bottomchordtensionlimit= 3.37 m

Diagonallacingcompressionlimit= 5.59 m

Concretepanelcompressionlimit= 5.13 m

Concretetensioncontrollimit= 2.23 m

Flexuralcrackinglimit= 3.96 m

Deflectionlimit= 3.05 m

Governing limit = 1.33 m

Governing limit, ignoring bottom chord compression and flexural cracking = 3.05 m

Whenchoosingthemaximumallowablespan,thebottom

chordcompressionlimitmaybeignoredinsomesituations.

Thebottomchordcompressionlimitcanbeignoreifthe

bottomconcretepanelisassumedtoprovidesufficient

restrainttopreventbuckling.Whenchoosingthemaximum

allowablespan,theconcretetensioncontrollimitmaybe

ignored.Thislimitmaybeignoredasitisbasedonthe

uniaxial tensile strength of the concrete panel, as opposed to

theflexuraltensilestrength.Astheprecastpanelisnot

typically going to be axially loaded, this is not relevant.

Thehorizontalloadingoftheframework(AS3610–1995,

Clause4.4.5)mustalsobeprovidedfor.Thiswilltypicallybe

aroleoftheedgeformdesigner.

j4w

sL ∆EI

EI j4w

s

4

j4w

sLL

EIβ

EI

βj4w

s

3

AUSTRAL PRECAST

/ 44 / / 45 /

Austral Deck TECHNICAL GUIDE

Figure 29 – Primary positive moment (about R axis)

Figure 30 – Primary negative moment (about R axis)

Figure 31 – Secondary positive moment (about S axis)

Figure 32 – Secondary negative moment (about S axis)

6.1 Sensitivity Analysis of Two-Way Slabs – Example 1

Theexamplebelowisanexampleofthechangesforasimple

two-wayslabspanningmultiplegrids.Threecasesforthe

exampleareproduced:

•Case1:Idealised2-waystiffness(KMr=KMs=1)

•Case2:75%two-waystiffness(KMr=1,KMs=0.75)

•Case3:50%two-waystiffness(KMr=1,KMs=0.50)

Theexampleuses:

•2x2spansof6.5mbetweencolumns

•300x300concretecolumns

•3kPaLiveLoadand1.5kPaSuperimposedDeadLoad(SIDL)

•250mmAustralDeckslabswith17%weightreduction

•Defaultvaluesforcreepandshrinkagecoefficients

•30yearloadhistoryforcrackedsectiondeflection

calculations

TheslabisorientatedsuchthatRisLeft-RightandSis

Up-Downonthepage.ReducingKMseffectivelyreduces

stiffness about the S direction. This is the equivalent of the

planksorientatedintheUp-Downdirection.Forthisexample,

theremightbe2plankspansintheup-downdirection,but

5-6spansintheLeft-Rightdirection.

The results indicate the following:

Astheaboveexampleisonly2x2spans,thereisonlylimited

optionsformomentredistribution,buttheresultsstill

indicateincreaseddeflectionsupto50%andredistributionof

secondarymomentsintoprimarymoments.

Resultswouldalsobemorepronouncedforrectangulargrid

layouts,suchas6mx8.5m,ratherthansquaregridlayouts,

whichdonotnaturallylendthemselvestoprimaryand

secondary span directions.

The following screen captures are results on the above

options.

6. EXAMPLE MODELS AND CALCULATIONS

Table 9 – Differential stiffness results for Three Austral Deck slabs

Figure 28 – Long term (30 year) deflection for 100%, 75% and 50% secondary stiffness

Design Case Idealised 2-way 75% Secondary Stiffness 50% Secondary Stiffness

Mid-span Deflection 31.5mm 36.1mm 46.7mm

Primary +ve Moment 38.1kNm 41.1kNm 44.6kNm

Primary -ve Moment -117kNm -120kNm -138kNm

Secondary +ve Moment 38.1kNm 37.8kNm 36.6kNm

Secondary -ve Moment -120kNm -104kNm -101kNm

AUSTRAL PRECAST

/ 46 / / 47 /

Austral Deck TECHNICAL GUIDE

6.2.1 Strip 1 – Vertical Span

Theabovestripis230thick,with2equalspansof6.5.It

carriestributarywidthofapproximately7.5m,butinpractice

thisamountisreducedduetothesemi-two-waynatureofthe

slab.

Thebendingmomentdiagramfortheaboveslabisasfollows:

Themaximumpositivestripbendingmomentforthedesign

stripis110kNmoverthe2.5mplankwidth,or44.0kNm.

Tosatisfythismoment,reinforcementof630mm2/mis

needed, as follows:

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2 ∙ 0.85 ∙ b ∙ f 'c

= 0.8 ∙ 800 ∙ 500 ∙ (194 - 630 ∙ 500

2 ∙ 0.85 ∙ 1000 ∙ 40

= 47.72kNm > 44.0kNm

630mm2/mcanbesuppliedasN12barsat200mmcentres

(565mm2/m)laidontopofSL92mesh(287mm2/m),ortotal

852mm2/m.

Theneutralaxisdepth,194mm,isbasedonthetotalslab

depth:

d = 230 - 30 (cover) - 6 N12 bar

= 194mm

2

Negativemomentoverthecolumnsis243kNm/mover2.5m

width.

Thiscanbeprovidedwith3450mm2reinforcinginasimilar

way,withatraditionalreinforcinglayoutover2.5m:

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2 ∙ 0.85 ∙ b ∙ f 'c

= 0.8∙ 3350 ∙ 500 ∙ 194 - 3350 ∙ 500

2 ∙ 0.85 ∙ 2500 ∙ 40

= 244.08kNm > 243kNm

3,350mm2canbesuppliedby17xN16bars,orN16at150mm

centresover2.5mwidth.

Figure 34 – Example Slab

(

(

((

()

)

))

)

6.2 Worked CalculationsUsingtheexamplemodelfromsection3.3,somefurther

workedcalculationsaretakenbelow.Inthiscase,the

bathroomsetdownsareremovedforsimplicity.

The design loads and slab features are as follows:

Twofulldesignstripswillbetakenasexamples,highlighted

above in Red.

Figure 33 – Example Slab

Design Properties Value

GeneralLoading Residential

SuperimposedDeadLoad 1.0kPa

LiveLoad 2.0kPa

Slab Thickness 230mm

Precast Thickness 60mm

Columns 400x400

Shrinkage Restraint 11%(Minimalwalls)

AUSTRAL PRECAST

/ 48 / / 49 /

Austral Deck TECHNICAL GUIDE

6.2.5 Check on Punching Shear

Punchingshearchecksarefirstcompletedagainstthein-situ

portion of the slab.

Inthecaseofthecentralcolumnintheaboveexample,the

punching shear forces are:

Firstcheckthein-situportion(D=160mm,dom=125mm)in

accordance with AS3600:

f 'cv = 0.17 1 + 2

√f 'c ≤ 0.34 √f 'c (but βh = 1)

βh f 'cv = 0.34 √f 'c = 2.15MPa

dom = 125, u = 4 ∙ (400+125) = 2100mm

ØVuo = 0.7 ∙ 125 ∙ 2100 ∙ 2.15 = 395kN < 584kN (fail)

Nexttrythefulldepth(D=230mm,dom=195mm):

dom = 195, u = 4 ∙ (400 + 195) = 2380mm

ØVuo = 0.7 ∙ 1 95 ∙ 2380 ∙ 2.15 = 698kN > 584kN (OK)

Checktorsionstripreduction,(a=400+195=595mm)

ØVu = ØVuo 1.0 + u ∙ Mv*

8V* ∙ a ∙ dom ØVu = ØVuo 1.0 +

1.0 + 2380 ∙ 32.3 584 ∙ 595 ∙ 195

ØVu = 698 1.0 +

2380 ∙ 32.3 × 103 8 ∙ 584 ∙ 595 ∙1 95

ØVu = 698 1.1418 = 611.3kN (OK)

As punching shear fails on the in-situ portion alone, but

passes when including the precast portion, the designer

should ensure that the total reinforcing bars in the trusses are

sufficientto“hangup”theloadbetweentheprecastand

in-situportionsoftheslab.Ifnot,thenshearstudsshouldbe

considered.

(

(( (

)

) ) )

Punching Shear Reactions Value

V* 584kN

Mr* 0.02kNm

Ms* 32.3kN

Ms* 32.3kN

6.2.2 Strip 2 – Horizontal Span

SimilartoStrip1,thepositivemomentsare100,50.9and

65.7kNminthedesignstripspans1to3respectively.

WetakeSpan1asanisolatedplank,andachievethemoments

thus:

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2 ∙ 0.85 ∙ b ∙ f 'c

= 0.8 ∙ 1350 ∙ 500 ∙ 194 - 1350 ∙ 500

2 ∙ 0.85 ∙ 2500 ∙ 40

= 102.6kNm > 100kNm

1350mm2isprovidedbyN12at250mmcentresplusSL92

mesh.

Forspans2and3,weuse65.7kNmasthecriticalmoment,

whichisachievedwithN12at300mmcentres.

Thenegativemomentforthehorizontalspanis210kNmand

151kNmatthetwointernalcolumns.

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2∙ 0.85 ∙ b ∙ f 'c

= 0.8 ∙ 3350 ∙ 500 ∙ 180 - 3350 ∙ 500

2∙0.85∙2500∙40

= 228.06kNm > 210kNm

Notethereducedcoverd=180mm,forthesecondlayerof

rebar.

Thismomentisresistedby3,350mm2orN16at150mm

centresover2500mm.

Inthecentralportion,thewidthis2xD+Column,

=2x230mm+400mm=860mm.

Over860mm,N16-150mmis1152mm2,whichprovides

momentof

ØMuo = 78.5kNm < 84.5kNm.

This fails clause 9.1.2.

The designer can choose either to increase the reinforcing in

thislocation,ortoclosethebarcentresoverthecolumn.

6.2.4 Check on Secondary Moment Direction

Thesecondarynegativemomentsarenotaddressedinthis

example,asthereinforcingbarsarelaidtraditionallyatthe

top and 2nd layers.

Thesecondarypositivemoments,however,canonlybe

resistedbytheSL92meshcaseintheprecastplank,plusextra

barslaidontopoftheprecastatreducedcover(60mm).

Inthisexample,thesecondarymomentis40.8kNmover

2.5m.

ThemomentcapacityintheplankusingSL92mesh

(287mm2/m)is:

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2 ∙ 0.85 ∙ b∙ f 'c

= 0.8 ∙ 287 ∙ 2.5 ∙ 500 ∙ 194 - 287 ∙ 2.5 ∙ 500

2∙0.85∙2500∙40

= 55.6kNm > 40.8kNm

However,therearebreaksintheplanksevery2.5m.

To account for the breaks, “cracker” bars are placed over the

breaks,whichhavecoverofapproximately70mmtothebar

centre(d=230-65-12/2=159mm)

ThecrackerbarsshouldbeN12at400mmcentres(700mm2

over2500mm):

ØMuo = 0.8 ∙ Ast ∙ fsy ∙ d - Ast ∙ fsy

2 ∙ 0.85 ∙ b ∙ f 'c

= 0.8 ∙ 700 ∙ 500 ∙ 159 - 700 ∙ 500

2 ∙ 0.85 ∙ 2500 ∙ 40

= 44kNm > 40.8kNm

SocrackerbarsofN12at400mmcentresareplaced,centred

over the plank joints.

The cracker bars should be at least one splice-length each side

ofthejoint,orapproximately1200-1500mmintotal.

6.2.3 Check on Column Strip Width

Asalloftheabovestriprunsareconsideredcolumnstrips,

check that the strip width allocation is appropriate with

AS3600.

Inthiscase,thebottomreinforcingissuitable(withthe

columnstripbeing2500mmwide)butthetopreinforcingwill

fail clause 9.1.2, which states:

In two-way flat slabs, at least 25% of the total of the design negative moment in a column-strip and adjacent half middle-strips shall be resisted by reinforcement or tendons or both, located in a cross-section of slab centred on the column and of a width equal to twice the overall depth of the slab or drop panel plus the width of the column.

Forthisexample,inthehorizontalspan,thetotalcolumn

momentrequirementis:

(

(

( (

(

((

()

)

))

)

))

)

(210 + 64 + 64) × 25% = 84.5kNm

AUSTRAL PRECAST

/ 50 / / 51 /

Austral Deck TECHNICAL GUIDE

7.1 Fire Resistance Period7.1.1. Austral Deck ProfileAnyconcreteslabmustbedesignedtoachieveafire

resistance period(1)(FRP)forstructuraladequacy,integrity

andinsulationofnotlessthantherequiredfireresistance

level(2)(FRL)asspecifiedinTheNationalConstructionCode

–BuildingCodeofAustralia(NCC-BCA).

Chart 4 shows FRP for insulation of various slab thicknesses

constructed using Austral Deck. The FRP has been

calculated in accordance with Australian Standards:

Concrete Structures, AS3600-2009, Clause 5.2.1 –

Insulationforslabs,andmodifiedtakingintoaccount

AustralDeckprofile–Figure35and36.

Chart 4 – Fire Resistance Period(3) for insulation for solid slabs constructed using Austral Deck profile.

30min

50mm

100mm

150mm

200mm

250mm

60min 90min

FRP “minutes”

Min

imu

m S

lab

Thic

kne

ss “

mm

”

120min 180min 240min

30min

50mm

100mm

150mm

200mm

250mm

60min 90min

FRP “minutes”

Min

imu

m S

lab

Thic

kne

ss “

mm

”

120min 180min 240min

Figure 35 – Austral Deck side profile.

Figure 36 – Effective thickness for FRP calculation Austral Deck profile.

Effective thicknessfor FRP Calculation

Min

sla

bth

ickn

ess

Austral Deck

20

10

2410

16

60, 7

5, 9

0

Effective thicknessfor FRP Calculation(without joint sealant)

Austral Deck Flat pro�le

Min

sla

bth

ickn

ess

Effective thicknessfor FRP Calculation

Min

sla

bth

ickn

ess

Austral Deck

20

10

2410

16

60, 7

5, 9

0

Effective thicknessfor FRP Calculation(without joint sealant)

Austral Deck Flat pro�le

Min

sla

bth

ickn

ess

7.1.2. Thermal ResistanceAustral Deck, as part of the concrete slab can be designed to

achieveenergyefficiencyprovisionsasspecifiedinThe

NationalConstructionCodeVolumeTwo–BuildingCodeof

Australia(BCA).

TheThermalresistancecoefficient“TheR-Value”(4)ofthe

Austral Deck slab is affected by the precast panel thickness,

overall slab thickness, the use of slab voids, the use of other

insulationmaterials,flooringandceilingmaterial.

TheNationalPrecastConcreteAssociationofAustralia(5)

“NPCAA” has developed a software to calculate the R Value

of Austral Deck considering all the above factors. Copy of the

software can be downloaded via the NPCAA website:

www.nationalprecast.com.au/r_value_calculator/

7.1.3. Definitions and References(1)Fireresistanceperiod(FRP)

Time,inminutes,foramembertoreachtheappropriate

failure criterion (i.e., structural adequacy, integrity and/or

insulation)iftestedforfireinaccordancewiththe

appropriate Standard. Source Australian Standards,

Concrete Structures, AS3600-2009, Clause 5.2.5

(2)Fireresistancelevel(FRL)

Fire resistance periods for structural adequacy, integrity and

insulation, expressed in that order.

NOTE: Fire resistance levels for structures, parts and

elementsofconstructionarespecifiedbytherelevant

authority,e.g.,intheBuildingCodeofAustralia(BCA).

Source Australian Standards, Concrete Structures, AS3600-

2009, Clause 5.2.4

(3)Section5ofAS3600-2009outlinestherequirementsfor

thefireresistanceofslabs.Itisassumedthatthecriteriafor

integrityisconsideredtobesatisfiedifthedesignmeetsthe

criteria for both insulation and structural adequacy for that

fireresistanceperiodasperclause5.3.1ofAS3600-2009

(4)TheR-valueofasubstanceisitsdirectmeasureofits

resistancetotransferringenergyorheat;RValuesare

expressedusingthemetricunits(m2.K/W).Theamountof

degreeskelvintemperaturedifferencerequiredtotransfer

onewattofenergyperonesquaremeterofasubstance.

(5)PublishedwithanapprovalfromNPCAA

7. FIRE AND THERMAL RESISTANCE

AUSTRAL PRECAST

/ 52 / / 53 /

Austral Deck TECHNICAL GUIDE

8.1.3. End Support to Internal Precast Wall

8.1.2. End Support to External Precast Wall – Option 2

8. TYPICAL INSTALLATION DETAILS

8.1.1. End Support to External Precast Wall – Option 1

8.1 Typical Wall Connection – End Support

Figure 37

Figure 38

Figure 39

AUSTRAL PRECAST

/ 54 / / 55 /

Austral Deck TECHNICAL GUIDE

8.3.2. Mid Span – Internal Precast Wall Above

8.3.3. End Support – Double Wall Connection

8.4.1. Beam Reinforcement within Slab Thickness

8.4 Typical Beam Configuration

8.2.1. Longitude Side to External Precast Wall

8.2.2. Side Joint Details

Austral Deck side profile.

Effective thicknessfor FRP Calculation

Min

sla

bth

ickn

ess

Austral Deck

20

10

2410

16

60, 7

5, 9

0

Effective thicknessfor FRP Calculation(without joint sealant)

Austral Deck Flat pro�le

Min

sla

bth

ickn

ess

Effective thicknessfor FRP Calculation

Min

sla

bth

ickn

ess

Austral Deck

20

10

2410

16

60, 7

5, 9

0

Austral Deck

Onsite caulking if required (by others)

Min

sla

bth

ickn

ess

8.3.1. End Support – Internal Precast Wall Under

8.2 Typical Wall Connection – Longitudinal Side

8.3 Typical Wall Connection – Internal Precast Wall and Double Wall

Figure 40

Figure 41

Figure 42

Figure 43

Figure 44

AUSTRAL PRECAST

/ 56 /

Austral Deck TECHNICAL GUIDE

85.1. Balcony and Cantilever Arrangement

8.5.2. External Precast Wall with Balcony

8.5 Balcony and Cantilever Arrangement

/ 57 /

8.4.2. Precast Beam

8.4.3. Band Beam formed by Austral Deck

Figure 45

Figure 46

Figure 47

Figure 48

AUSTRAL PRECAST

/ 58 / / 59 /

Austral Deck TECHNICAL GUIDE

Theproppingdesignisprovidedandshallbecertifiedbythe

supplieroftheprops.Thepropswillbecertifiedtocarrythe

definedconstructionloads.

Precast Shell BeamAustral Deck

Precast Shell Beam

Span Direction

Austral Deck

8.6 Proposed Propping Arrangement

Figure 49

Sydney CBD

Ground Floor 50 Carrington Street, Sydney NSW 2000

Melbourne

490 Swan Street Richmond VIC3121

Adelaide

Ground Floor 70HindmarshSquare , Adelaide SA 5000

Brisbane

27JamesStreet Fortitude Valley QLD4006

Perth

67KingStreet Perth WA 6000

Hobart

9 Franklin Wharf Hobart TAS 7000

brickworksbuildingproducts.com.au | 13-brick

follow brickworks building products on

Partners in Design 11/2017

DESIGN STUDIOS