fib 34 - model code for service life design

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Model Code for

Service Life Design

Model code prepared by

Task Group 5.6

February 2006


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Subject to priorities defined by the Steering Committee and the Presidium, the results of fibs work inCommissions and Task Groups are published in a continuously numbered series of technical publications

called 'Bulletins'. The following categories are used:

category minimum approval procedure required prior to publication

Technical Report approved by a Task Group and the Chairpersons of the Commission

State-of-Art Report approved by a Commission

Manual or

Guide (to good practice)

approved by the Steering Committee of fibor its Publication Board

Recommendation approved by the Council of fibModel Code approved by the General Assembly of fib

Any publication not having met the above requirements will be clearly identified as preliminary draft.

This Bulletin N 34 will be submitted to the General Assembly for approval as anfibModel Code in June 2006.

This report was prepared within Task Group 5.6,Model code for service life design of concrete structures:

Peter Schiessl (Convener, Technische Universitt, Mnchen, Germany)

Phil Bamforth (Principal Construction Consultancy, UK), Vronique Baroghel-Bouny (LCPC, France),

Gene Corley (Construction Technology Laboratories, Inc., USA), Michael Faber (ETH-Zrich,

Switzerland), Jim Forbes (Hyder Consulting, Australia), Christoph Gehlen (Ingenieurbro Schiessl,Germany), Paulo Helene (Univ. de Sao Paulo PCC/USP, Brazil), Steinar Helland (Skanska Norge AS,

Norway), Tetsuya Ishida (Univ. of Tokyo, Japan), Gro Markeset (Norwegian Building Research Institute,

Norway), Lars-Olof Nilsson (Lund Institute of Technology, Sweden), Steen Rostam (Cowi A/S,

Denmark), A.J.M. Siemes (TNO, The Netherlands), Joost Walraven (Delft Univ. of Technology, The

Netherlands)

Full address details of Task Group members may be found in the fibDirectory or through the online services onfib'swebsite, www.fib-international.org.

Cover images: The photos show the carbonation depth of a vertical concrete surface of an existing building after

8 years of exposure without shelter from rain. A phenolphthalein indicator distinguishes areas

with pH < 9.5 (not coloured) and areas with a higher pH (coloured). The graph shows the

development of the carbonation depth over time, xc(t), compared to the cover depth, a. Scatter of

both variables is also given.

fdration internationale du bton (fib), 2006

Although the International Federation for Structural Concrete fib- fderation internationale du bton - createdfrom CEB and FIP, does its best to ensure that any information given is accurate, no liability or responsibility ofany kind (including liability for negligence) is accepted in this respect by the organisation, its members, servantsor agents.

All rights reserved. No part of this publication may be reproduced, modified, translated, stored in a retrievalsystem, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, orotherwise, without prior written permission.

First published in 2006 by the International Federation for Structural Concrete (fib)Post address: Case Postale 88, CH-1015 Lausanne, SwitzerlandStreet address: Federal Institute of Technology Lausanne - EPFL, Section Gnie CivilTel +41 21 693 2747, Fax +41 21 693 6245, E-mail [email protected], web www.fib-international.org

ISSN 1562-3610

ISBN 2-88394-074-6

Printed by Sprint-Digital-Druck, Stuttgart


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fibBulletin 34: Model code for Service Life Design iii

Contents

Preface iv

0 Introduction 1

1 General 5

1.1 Scope 51.2 Associated codes 5

1.3 Assumptions 5

1.4 Definitions 6

1.5 Symbols 10

2 Basis of design 12

2.1 Requirements 12

2.2 Principles of limit state design 14

2.3 Basic variables 14

2.4 Verification 16

3 Verification of Service Life Design 20

3.1 Carbonation induced corrosion uncracked concrete 20

3.2 Chloride induced corrosion uncracked concrete 23

3.3 Influence of cracks upon reinforcement corrosion 24

3.4 Risk of depassivation with respect to pre-stressed steel 25

3.5 Freeze/thaw attack without de-icing agents 25

3.6 Freeze/thaw attack with de-icing agents 27

4 Execution and its quality management 29

4.1 General 29

4.2 Project specification 29

4.3 Quality management 304.4 Materials 31

4.5 Geometry 32

5 Maintenance and condition control 33

5.1 General 33

5.2 Maintenance 33

5.3 Condition control during service life 33

5.4 Action in the event of non-conformity 34

Annex A (informative)

Management of reliability for Service Life Design of concrete structures 36Annex B (informative)

Full probabilistic design methods 44

Annex C (informative)

Partial factor methods 83

Annex R (informative)Reliability management: from SLS to ULS 90

References 109


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fibBulletin 34: Model code for Service Life Design v

Preface

fiband its preceding organizations, CEB and FIP, have a long tradition in treating durability aspects and

to design for them. In 1978 CEB created a first working group, the Task Group Durability. Milestones in

the CEB and FIP work on durability are CEB Bulletins 148 Durability of concrete structures, 182

Durable concrete structures and 238 New approach to durability design. In the latter document the

framework for a probabilistic design approach was set. In 2002 fibestablished Task Group 5.6 Model codefor service life design of concrete structures with the objective to develop a model code document on

probabilistic service life design. The approach developed in this document is intended to be the basis for the

service life design approach of the newfibModel Code, currently under development. Furthermore it might

serve as a basis for further work in ISO (TC 71) and CEN (TC 104 and TC 250/SC2).

The following members of Task Group 5.6 actively contributed to the work (in alphabetic order):

Veronique BAROGHEL BOUNY

Phil BAMFORTH

Gene CORLEY

Michael Havbro FABER Christoph GEHLEN* (secretary)

Paulo HELENE

Steinar HELLAND*

Tetsuya ISHIDA

Gro MARKESET

Lars Olof NILSSON*

Steen ROSTAM

Peter SCHIESSL* (Convener)

*Members of the Drafting Board

The format of this Model Code follows the CEB-FIP tradition: the main provisions are given on the right-

hand side of the page, and on the left-hand side, the comments.

Peter SCHIESSL

Convener offibTask Group 5.6


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ulletin34:ModelcodeforServiceLifeDesign

1

0

Introduction

Thebasicideaofservicelifedesignaspresentedinthisdocumentisto

establishadesignapproachtoavoiddeteriorationcausedbyenvironmental

actioncomparabletoloaddesigna

sweareusedtohaveitinourdesign

codes(e.g.EC2).Thatmeansquantifiablemodelsontheloadside(theseare

theenvironmentalactions)andonth

eresistanceside(thisistheresistanceof

theconcreteagainsttheconsideredenvironmentalactions).Thedesign

approachwillbeexamplifiedfor

designagainstreinforcementcorrosion

causedbycarbonationofconcretewithoutloadorrestraintinducedcracks.

Thefirststepinthedesignap

proachistoquantifythedeterioration

mechanismwithrealisticmodelsd

escribingtheprocessphysicallyand/or

chemicallywithsufficientaccuracy(e.g.ingressofcarbonationintothe

concretedependingontheenviron

mentandtherelevantconcretequality

parameters).Suchamodelforingressofcarbonationisgiveninthe

document.Sufficientaccuracymean

sthatthemodelshouldbevalidatedby

realisticlaboratoryexperimentsand

bypracticeobservations,sothatmean

valuesandscatterofthematerialresistanceparametersareknownandcanbe

consideredinthemodel.Inthesa

mewaymodelsfortheenvironmental

actionswith

statistically

quantified

environmentalparameters(e.g.

temperature,relativehumidity,splashraineventsetc.)needtoexist.

Thesecondstepisthedefinitionoflimitstatesagainstthestructureshould

bedesignedfor.Appropriatelimitstateswouldbe

-

depassivationofreinforcementcausedbycarbonation

-

crackingduetoreinforcementcorrosion

-

spallingofconcretecoverduetoreinforcementcorrosion

-

collapseduetolossofcrosssectionofthereinforcement.

Theobjectiveofthisdocumentistoidentifyagreeddurabilityrelated

modelsandtopreparetheframeworkfor

standardizationofperformance

baseddesignapproaches.

ThisModelCodetreatsdesignforen

vironmentalactionsleadingto

degradationofconcreteandembeddedsteel.

Copyright fib, all rights reserved. This PDF copy of fib Bulletin 34 is intended for use and/or distribution only by National Member Groups of fib.


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2

0Introduction

Thethirdstepisthecalculation

oftheprobabilitythatthelimitstates

definedaboveoccur(determination

oftheprobabilityofoccurance).This

willbedonebyapplyingthemodelsdescribedinstep1above.Nowadaysit

iscommonlyacceptedthatthesafe

tyofstructuresshouldbeexpressedin

termsofreliability(reliabilityindex

!).Dependingonthetypeoflimitstate

(SLS,ULS)andtheconsequencesof

afailure,valuesfor!aregiveninEC0.

Thefourthstepisthedefinition

ofthetypeoflimitstate(SLS,ULS)of

thelimitstatesdescribedinstep2.Normallydepassivationwillbeclassified

asaSLSasthereisnoimmediate

consequenceonstructuralsafetyifthe

reinforcementisdepassivated.Therefore!-valuesintherangeof!

=1.0to

1.5maybeappropriatefordepassiv

ation.However,theownermayrequire

higher!-valuesforexampletosafelyensuretheaestheticqualityofthe

structure.Forthelimitstatecrackingandspallingthedesignerhastodecide

whichtypeoflimitstateisneeded

orshouldbechosen.If,forexample,

crackingandspallingoccursin

anchoragezoneswithoutsufficient

transversalreinforcement,spallingm

ayleadtocollapse.Inthiscasecracking

andspallingneedtobedefinedasULS.Inothercasesifcrackingand

spallingdoesnotinfluencetheloadbearingcapacityofthestructural

element,crackingandspallingmayb

edefinedasSLS.

TheModelCodeisdividedintofivechapters:

1.General

2.Basisofdesign

3.VerificationofServiceLifeDesign

4.Executionanditsqualitycontrol

5.Maintenanceandconditioncontrol

Theservicelifedesignapproachinthisdocumentiselaboratedforthree

differentlevels.Thefullprobabilisticapproach(level1)willbeusedonlyfor

exceptionalstructures.Basedonthefullprobabilisticapproachapartial

safetyfactorapproachcomparabletoloaddesignisgiven.Thepartialsafety

factorapproach(level2)isadeterm

inisticapproachwheretheprobabilistic

natureoftheproblem(scatterofmaterialresistanceandenvironmentalload)

istakenintoaccountbypartialsafe

tyfactors.Finallythedeemedtosatisfy

approach(level3),againderivedfromthefullprobabilisticapproachis

TheflowchartinFigure1.1-1illustrate

stheflowofdecisionsandthe

designactivitiesneededinarationalservicelifedesignprocesswithachosen

levelofreliability.Twostrategieshavebeenadopted,whereofthefirstis

introducedofthreelevelsofsophistication.Insum4optionsareavailable.

Strategy1:

Level1.

Fullprobabilisticdesignapproach,(option1)

Level2.

Partialfactordesignapproach,(option2)



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elaborated.Thistypeofapproachiscomparabletotheapproachwhichcanbe

foundinthestandardsnowadays.

Howeverdescriptiverulesoftodays

standardsarenotbasedonphysicallyandchemicallycorrectmodelsbut

moreonpractical(sometimesbad)experience.Inthefuturecurrentlyapplied

rulesurgentlyhavetobecalibrateda

gainstthefullprobabilisticapproach.

Anotheroptiongiveninthisdocu

mentistheuseofnonreactivematerials

(e.g.stainlesssteel,strategy2/option

4).

Othermethodsorlevelsbetween

thelevelschosenforthisdocumentmay

beappropriateforServiceLifeDesign(e.g.thedurabilityfactormethod

approach,[1]).

Level3.

Deemedtosatisfydesignapp

roach,(option3)

Strategy2:Avoidanceofdeteriorationdesignapproach,(option4)

Figure1.1-1:Flowchartservicelifedesign



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4

0Introduction

WithinChapter3variousdeteriorationmechanismsaretreated:

carbonation-inducedcorrosion;:

chloride-inducedcorrosion;

freeze/thawattackwithoutde-icing

agents;

freeze/thawattackwithde-icingagents.

Forthesemechanismsbroadacceptedmodelsexist.Otherdeterioration

mechanismsarenottreated,forexamplealkalisilicareaction,andsulfate

attack,mainlyduetothesituationthatbroad

acceptedmodelsdonotexistso

far.

Simultaneousdynamicloadingandcorrosionofsteele.g.intheregionof

loadorrestraintinducedcracks,willleadtoareductioninthefatigue

resistance.TheS-N-curvesasthebasisforfatiguedesignmaybeupto50%

lowerrelatedtothestressrangeco

mparedtoS-N-curvesofreinforcement

withoutcorrosionattack.

Besideabovementionedmechanismsa

lsofatiguecausedbydynamic

loadingandleadingtotimedependentmaterialdegradationandcorrosion

fatiguecausedbydynamicloadingandsimultaneouscorrosioncausedby

environmentalactionisnottreated.

Tomakethisdocumentcomplete,missingmodelshavetobedeveloped

whichhavetorespectthegeneralprinciplesofChapter2.

Theservicelifedesignapproachdescribedinthisdocumentmaybe

appliedforthedesignofnewstruc

tures,fortheupdateoftheservicelife

designifthestructureexistsandrealmaterialpropertiesand/orthe

interactionofenvironmentandstructurecanbemeasured(realconcrete

covers,carbonationdepths)andforthecalculationoftheresidualservicelife.

AttachedtotheMC-SLDare4informativeannexes.Thesearegiving

backgroundinformationaswellasexamplesofproceduresanddeterioration

modelsfortheapplicationinSLD.Othersufficientlyvalidatedproceduresfor

reliabilitymanagementandmodelsfordeteriorationmightbeused.



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1

General

1.1Scope

Traditionally,nationalandinternationalconcretestandardsgive

requirementstoachievethedesireddesignservicelifebasedonthedeemed-

to-satisfyandtheavoidanceofdeteriorationapproach.

Suchoperativerequirementshavetobecalibratedbytheresponsible

standardizationbody.Thisdocumentgivesguidanceforsuchcalibration.

(1)ThepresentModelCodeisapplicableforServiceLifeDesign(SLD)

ofplainconcrete,reinforcedconcreteand

pre-stressedconcretestructures

withaspecialfocusondesignprovisionsformanagingtheadverseeffectsof

degradation.TheModelCodeprovidesthe

basisforservicelifedesignof

concretestructures.Fourdifferentoptionsareoffered:

afullprobabilisticapproach

asemiprobabilisticapproach(partialfactordesign)

deemedtosatisfyrules

avoidanceofdeterioration

Themethodologydescribedinthisdocu

mentmightalsobeappliedfor

assessmentofremainingservicelifeofexistingstructures.

1.2Associatedcodes

CENEN1990Basisfordesign

isbasedonthegeneralprinciplesforthe

verificationofthereliabilityofstructuresgiveninISO2394:1998General

principlesonreliabilityforstructures

(1)Thepresentcodeisapplicableasdescribedunder1.1togetherwith

CENEurocode0(EN1990:2002)

Basisfordesign

ProbabilisticModelCode,Joint

CommitteeonStructuralSafety

(JCSSPMC:2000),www.jcss.eth.ch

CENENV13670-1:2000Executionofconcretestructures

ISO2394:1998(E),Generalprinciplesonreliabilityforstructures

1.3Assumptions

CENENV13670-1ispresentlythemainreferencedocumentforISOTC-

71/SC3whendraftinganinternation

alstandardfortheexecutionofconcrete

structures.

ThisCENstandardmightbereplacedbythecomingEN13670,orbythe

ISOdocumentwhenavailable,orw

iththeexecutionprovisionsinthenext

versionofthefibModelCode.

(1)InadditiontothegeneralassumptionsofEN1990thefollowing

assumptionsapply:

Structuresaredesignedbyappropriatelyqualifiedandexperienced

personnel.

Adequatesupervisionandqualityc

ontrolisprovidedinfactories,in

plantsandonsite.



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6

1General

Theexecutionstandardassumesthattheconstructionmaterialsbroughtto

thebuildingsitecomplywithrelevantproductstandardsdefiningtheir

minimumperformances.

Constructioniscarriedoutbypersonnelhavingtheappropriateskill

andexperience.

Theconstructionmaterialsandproductsareusedasspecifiedinthe

relevantmaterialorproductspecifications.

Thestructurewillbeadequatelymaintainedaccordingtothe

optionsgiveninthisdocument.

Thestructurewillbeusedinaccord

ancewiththedesignbrief.

Theminimumrequirementsforex

ecutionandworkmanshipgiven

inENV13670arecompliedwith.

1.4Definitions

(1)ThetermsanddefinitionsgiveninEN1990applywiththefollowing

amendments:

1.4.1Basicvariable1)8)

partofaspecifiedsetofvariablesrepresentingphysicalquantities,which

characteriseactionsandenvironmentalinfluences,geometricalquantities,

andmaterialproperties.

1.4.2Characteristicvalue(Xkor

Rk)2)

Inthisrespectanominalvaluemeansavaluefixedonnon-statistical

bases,forinstanceonacquiredexper

ienceoronphysicalconditions.

valueofamaterialorproductpropertyhavingaprescribedprobabilityof

notbeingattainedinahypotheticalunlimitedtestseries.Thisvaluegenerally

correspondstoaspecifiedfractileoftheassu

medstatisticaldistributionofthe

particularpropertyofthematerialorproduct.Anominalvalueisusedasthe

characteristicvalueinsomecircumstance.

1.4.3Characteristicvalueofageometricalproperty

(ak)2)8)

valueusuallycorrespondingtothedimensionsspecifiedinthedesign.

Whererelevant,valuesofgeometricalquantitiesmaycorrespondtosome

prescribedfractilesofthestatisticaldistribution.



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1.4.4Characteristicvalueofana

ction(Fk)2)8)

principalrepresentativevalueofanaction

.

1.4.5Designcriteria2)

quantitativeformulationsthatdescribefo

reachlimitstatetheconditions

tobefulfilled.

1.4.6Designservicelife3)8)

Thisdocumentappliestheterm

DesignServiceLife.Themeaningof

thistermisequivalenttothetermD

esignworkinglifeasusedbyCEN.

assumedperiodforwhichastructureor

apartofitistobeusedforits

intendedpurpose.

1.4.7Designsituations1)8)

setsofphysicalconditionsrepresentingtheexpectedconditionsoccurring

duringacertaintimeintervalforwhichthe

designwilldemonstratethatthe

relevantlimitstatesarenotexceeded.

1.4.8Designvalueofageometric

alproperty(ad)1)8)

generallyanominalvalue.Whererelevant,valuesofgeometrical

quantitiesmaycorrespondtosomepresc

ribedfractileofthestatistical

distribution.

Note:Thedesignvalueofageometricalpropertyisgenerallyequaltothe

characteristicvalue.However,itmaybetreateddifferentlyincaseswherethe

limitstateunderconsiderationisvery

sensitivetothevalueofthe

geometricalproperty.Alternatively,itcanbeestablishedfromastatistical

basis,withavaluecorrespondingtoamoreappropriatefractile(e.g.rarer

value)thanappliestothecharacteristicvalue

.

1.4.9Designvalueofanaction(F

d)2)9)

valueobtainedbymultiplyingtherepresentativevaluebythepartialfactor"f.

Note:Theproductoftherepresentative

valuemultipliedbythepartial

factor"F="Sd#"f

mayalsobedesignated

asthedesignvalueoftheaction

(SeeEN19906.3.2)



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8

1General

1.4.10

Designvalueofmaterialorproductproperty

(XdorRd)2)9)

valueobtainedbydividingthecharacteristicvaluebyapartialfactor"mor

"M,or,inspecialcircumstances,bydirectdetermination.

1.4.11

Inspection4)

conformityevaluationbyobservationandjudgementaccompaniedas

appropriatebymeasurement,testingorgauging.

1.4.12

Irreversibleserviceabilitylimitstates2)8)

serviceabilitylimitstateswheresomeconsequencesofactionsexceeding

thespecifiedservicerequirementswillremainwhentheactionsareremoved.

1.4.13

Limitstates2)8)

statesbeyondwhichthestructurenolo

ngerfulfilstherelevantdesign

criteria.

1.4.14

Maintenance5)

setofactivitiesthatareplannedtotakeplaceduringtheservicelifeofthe

structureinordertofulfiltherequirementsfo

rreliability.

1.4.15

Projectspecification7)

documentscoveringtechnicaldataandrequirementsformaterials,

execution,maintenanceandconditioncontrolforaparticularprojectprepared

tosupplementandqualifytherequirementso

fgeneralstandards.

1.4.16

Referenceperiod2)8)

chosenperiodoftimethatisusedasa

basisforassessingstatistically

variableactions,andpossiblyforaccidentalactions.

1.4.17

Reliability1)8)

abilityofastructureorastructuralmembertofulfilthespecified

requirements,includingthedesignservicelife,forwhichithasbeen



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designed.Reliabilityisusuallyexpressedinprobabilisticterms.

Note:Reliabilitycoverssafety,serviceabilityanddurabilityofastructure.

1.4.18

Reliabilitydifferentiation

2)

measuresintendedforsocio-economicop

timisationoftheresourcestobe

usedtobuildconstructionworks,takingintoaccountallexpected

consequencesoffailuresandthecostofthec

onstructionworks.

1.4.19

Repair2)

activitiesperformedtopreserveortorestorethefunctionofastructure

thatfalloutsidethedefinitionofmaintenance.

1.4.20

Representativevalueofa

naction(Frep)2)8)

valueusedfortheverificationofalimitstate.Arepresentativevaluemay

bethecharacteristicvalue(Fk)oranaccompanyingvalue($Fk).

Note:Theaccompanyingvalueofa

variableactionmaybethe

combinationvalue,thefrequentvalueorthequasipermanentvalue.

1.4.21

Resistance1)

capacityofamemberorcomponent,or

across-sectionofamemberor

componentofastructure,towithstandaction

sduetodeterioration.

1.4.22

Serviceabilitylimitstates(SLS)2)9)

SLSisthisdocumentonlytrea

tedinitsnarrowsense,i.e.durability

relatedlimitstates,andnotinitsgeneralwidersense,e.g.tocoverdeflection.

SLSmightbeassociatedwithanydurabilityrelatedconditionbeyond

whichtheownerfeelsuncomfortableandwhichareincludedinthedesign

criteria.

statesthatcorrespondtoconditionsb

eyondwhichspecifiedservice

requirementsforastructureorstructuralmem

berarenolongermet.

1.4.23

Serviceabilitycriterion2)

designcriterionforaserviceabilitylimits

tate.



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10

1General

1.4.24

Ultimatelimitstate(ULS

)2)9)

statesassociatedwithcollapseorwithothersimilarformsofstructural

failure

Note:Theygenerallycorrespondtothem

aximumload-carryingresistance

ofastructureorstructuralmember

1) ThedefinitionisbasedonthatinEN19

90

2)T

hedefinitionisidenticaltothatinEN1990

3)C

ENdocumentsareusingthetermDesignworkinglifewherethis

documentisapplyingDesignservicelife

4)T

hedefinitionisidenticaltothatinISO

9000

5)BasedonISO15686-1:2000BuildingandconstructionassetsService

lifeplanning,Part1:Generalprinciplesclause6.7

6)ThedefinitionisinaccordancewithJC

SSProbabilisticModelCode

Part1

7)BasedonCENENV13670-1

8)T

hedefinitionisbasedonthatinISO2394

9)T

hedefinitionisidenticaltothatinISO

2394

1.5Symbols

(1)Forthepurposeofthisdocument,thefollowingsymbolsapply:

F

Action

Fd

Designvalueofaction

R

Resistance

SLS

Serviceabilitylimitstate

ULS

Ultimatelimitstate

a

Distance,ageexponent

t

Thickness,timebeingconsid

ered



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"

Partialfactor

"c

Partialfactorforconcrete

"f

Partialfactorforactionswithouttakingaccountofmodel

uncertainties

"F

Partialfactorforaction,

alsoaccountingformodel

uncertaintiesanddimensiona

lvariations

"m

Partialfactorsformaterialproperty,takingaccountonlyof

uncertaintiesinthematerialproperty

"M

Partialfactorsformateria

lproperty,takingaccountof

uncertaintiesinthematerial

propertyitselfandinthedesign

modelused

"Sd

Partialfactorassociatedwiththeuncertaintyoftheaction

and/oractioneffectmodel

"Rd

Partialfactorassociatedwith

theuncertaintyoftheresistance

model,plusgeometricdeviationsifthesearenotmodelled

explicitly



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12

2Basisofdesign

2

Basisofdesign

2.1Requirements

2.1.1Basicrequirements

(1)TheSLDofconcretestructuresshallbeinaccordancewiththegeneral

rulesgiveninEN1990.

(2)Thesupplementaryprovisionsforc

oncretestructuresgiveninthis

documentshallalsobeapplied.

(3)ThebasicrequirementsofEN199

0Section2aredeemedtobe

satisfiedforconcretestructureswhenSLD

iscarriedoutaccordingtothe

requirementsgiveninsection2.1.2(2).

2.1.2Reliabilitymanagement

(1)ReliabilitymanagementshallfollowtherulesgiveninEN1990

Section2.

(2)Theservicelifedesignshalleither:

followthegeneralprinciplesforprobabilisticservicelifedesignof

concretestructuresoutlinedinthe

JCSSPMC,ISO2394:1998(E),

respectively.

usethepartialfactormethodgiveninthisdocument

usethedeemed-to-satisfymethodg

iveninthisdocument

bebasedontheavoidance-of-deteriorationmethodgiveninthis

document

2.1.3Design

service

life,durability

and

quality

management

(1)Therulesfordesignofservicelife,du

rabilityandqualitymanagement

aregiveninEN1990Section2.

(2)Thedesignservicelifeistheassumedperiodforwhichastructureor

partofitistobeusedforitsintendedpurposewithanticipatedmaintenance



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butwithoutmajorrepairbeingnecessary.

Thedesignservicelifeisdefinedby:

Adefinitionoftherelevantlimitstate

Anumberofyears

Alevelofreliabilityfornotpas

singthelimitstateduringthis

period

(3)Durabilityofthestructureinitsen

vironmentshallbesuchthatit

remainsfitforuseduringitsdesignservic

elife.Thisrequirementcanbe

consideredinone,oracombination,ofthefo

llowingways:

Bydesigningprotectiveandomitigatingsystems

Byusingmaterialsthat,ifwellmaintained,willnotdegenerate

duringthedesignservicelife

Bygivingsuchdimensionsthat

deteriorationduringthedesign

servicelifeiscompensated

Bychoosingashorterlifetimefor

structuralelements,whichmay

bereplacedoneormoretimesduringthedesignlife

incombinationwithappropriateinspectionatfixedorcondition

dependantintervalsandappropriatemaintenanceactivities.

Inallcasesthereliabilityrequirements

forlongandshort-termperiods

shouldbemet.

(4)Theserviceabilitycriteriashallbe

specifiedforeachprojectand

agreedwiththeclient.

Guidanceforthechoiceofserviceabilitycriteriacombinedwith

appropriatetargetvaluesofreliabilityaregiv

eninAnnexA.

TheConsequenceclasses,ReliabilityclassesandDesignsupervision

levelsareidenticaltothosedefinedinAnnexBofEN1990,whilethe

Inspectionlevelsduringexecution

ofEN1990areonlyoneelementinthe

Executionclassesdefinedinthepresentdocument.

(5)Asaguidancetoreliabilitydifferentiation,AnnexAtothisdocument

definesthefollowinggeneralclassifications:

ConsequenceclassCC3,CC2andCC1

ReliabilityclassRC3,RC2andRC1

DesignsupervisionlevelDSL3,DS

L2andDSL1

ExecutionclassEXC1,EXC2andEXC3



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14

2Basisofdesign

RobustnessClassROC1,ROC2andROC3

Forservicelifedesign,AnnexA,inaddition,classify4levelsofcondition

controlduringtheservicelife:

CCL3,CCL2,CCL1andCCL0

2.2Principlesoflimitstated

esign

Theperformanceofawholestructureorpartofitshouldbedescribed

withreferencetoaspecifiedsetoflimitstatesandassociatedlevelsof

reliabilitywhichseparatedesiredstatesofthestructurefromundesiredstates.

Itshallbeverifiedthatnoneoftheselimitstatesareexceededwithaless

degreeofreliabilitythangiveninthe

designcriteria.

ThedefinitionsofSLSandULSaregivenin1.4.22and1.4.24.

SLSrepresentsalllimitstatesexc

eptthatassociatedwithcollapseorother

similarformsofstructuralfailure.

ExamplesoflimitstatesassociatedwithSLSanddealtwithinthis

documentmightbe:depassivation

ofreinforcement,cracking,spallingof

cover,erosionofsurfaceduetofreez

e-thaw,etc.

(1)TherulesforlimitstatedesignaregiveninEN1990Section3.

2.3Basicvariables

2.3.1Actionsandenvironmental

influences

Rulesforactionsandenvironmen

talinfluencesarealsogiveninEN1990,

Section4.

(1)ActionsspecifictoSLDaregiveninrelevantsections.

Characteristicvaluesofactionsforusein

SLDshalleitherbe

basedondataderivedfortheparticularprojector

fromgeneralfield-experience

fromrelevantliterature

Otheractions,whenrelevant,shallbede

finedinthedesignspecification

foraparticularproject.



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2.3.2Materialandproductproperties

(1)Therulesformaterialandproductp

ropertiesaregiveninEN1990

Section4.

(2)Characteristicvaluesofmaterialsan

dproductpropertiesforusein

SLDshalleitherbe

basedondataderivedfortheparticularprojector

fromgeneralfield-experience

fromrelevantliterature

Materialsandproductpropertiestobe

determinedwilldependonthe

deteriorationmodelused.Ifdifferentmodels

withdifferentbasicassumptions

areoffered,acheckingprocessshouldbee

stablished,toavoidanincorrect

mixtureofdata.

(3)Materialpropertyvaluesshallbed

eterminedfromtestprocedures

performedunderspecifiedconditions.Aconversionfactorshallbeapplied,

whennecessary,toconvertthetestresultso

flaboratorycastspecimensinto

values,whichcanbeassumedtorepresent

thebehaviourofthematerialor

productinthestructure.

2.3.3Geometricdata

(1)TherulesforgeometricaldataaregiveninEN1990Section4.

Ofparticularrelevanceforservicelifedesign(SLD)areENV13670-1

clause10.6,figure3band3d

concerninglocationofordinaryand

prestressedreinforcement.

Forpracticalreasons,asimplifiedstatisticalapproachbasedon

maximumpermitteddeviationisoftenusedinprojectspecifications.This

isoftenthecasefortheconcretecovertoreinforcement.Thisisnormally

givenasanominalvalue(targetvalue)andmaximumpermittedminusand

plusdeviations.

WhenperformingafullprobabilisticSLD,thismaximumpermitted

deviationhastobetransformedtoagivenfractileofanassumedstatistical

distribution(seeclause4.5(2)).

(2)Designvaluesofgeometricaldatafor

SLDshallbeinaccordancewith

EN1990clause6.3.4oraccordingtom

easurementsonthecompleted

structureorelement.

(3)ENV13670-1Executionofconcretestructuresspecifiespermitted

geometricaldeviations.Ifthedesignassumesstrictertolerances,thedesign

assumptionsshallbeverifiedbymeasurementsonthecompletedstructureor

element.



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16

2Basisofdesign

2.4Verification

2.4.1Verificationbyfullprobabilisticmethod

Materialparametersderivedfrom

acceleratedshort-timetestsmighthave

aninherentuncertaintyconcerningth

eirapplicationforlong-termmodelling.

Therelevanceofsuchmaterialcharacteristicsshouldthereforebe

calibratedtolong-terminfieldperformance.

Theuncertaintyofmodelsand

parameterswillnormallyinfluencethe

resultoftheSLDtoagreaterdegreewhenusedfordesignofnewstructures

thanwhenassessingremainingservicelifeofexistingstructures.

(1)Thegeneralprinciplesforprobabilisticservicelifedesignofconcrete

structuresoutlinedintheJCSSPMCshallbe

followed.

Inparticularthefollowingfourprinciples

shallbeconsidered:

Probabilisticmodelsshallbeappliedthataresufficientlyvalidated

togiverealisticandrepresentativeresults.

Theparametersofthemodels

appliedandtheirassociated

uncertaintyshallbequantifiablebymeansoftests,observations

and/orexperience.

Reproducibleandrelevanttestmethodsshallbeavailabletoassess

theaction-andmaterial-parameters

.

Uncertaintiesassociatedwithmodelsandtestmethodsshallbeconsidered.

2.4.2Verificationbythepartialfactormethod

(1)Therulesforthepartialfactormethod

aregiveninEN1990Section6

andcanbeusedforSLDwithoutthelimitationsgiveninEN1990clause

6.2.

(2)Thesamemodelsasforthefullprobabilisticmethod,basedondesign

values,shallbeusedforthepartialfactormethod.Simplificationsonthesafe

sidearepossible.

(3)Thepartialfactorformatseparatesth

etreatmentofuncertaintiesand

variabilitiesoriginatingfromvariouscause

s.Intheverificationprocedure

definedinthisdocumentthedesignvaluesofthefundamentalbasicvariables

areexpressedasfollows:

Designvaluesofactionsaregenerally

expressedas

Fd="fFrep

(2.4-1)

whereFreparerepresentativevaluesof

action

"farepartialsafetyfactors



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Designvaluesofmaterialorproductpropertyaregenerallyexpressed

as

Rd=Rk/"m

(2.4-2)

Or,incaseuncertaintyinthedesignmodelistakenintoaccountby:

Rd=Rk/"M=Rk/("m#"Rd)

(2.4-3)

whereRkarecharacteristicvaluesofresistance

"misthepartialfactorformaterialproperty

"Rdisthepartialfactorassociatedwith

theuncertaintyoftheresistance

modelplusgeometricdeviationsifthesearenotmodelledexplicitly.

"M="m#"Rdisthepartialfactorform

aterialpropertyalsoaccounting

forthemodeluncertaintiesanddimensionalvariations.

Designvaluesofgeometricalquantitiestobeconsideredas

fundamentalbasicvariablesaregenerallydirectlyexpressedbytheir

designvaluesad.

Thetargetreliabilitylevelusedforthecalibrationshallbeinaccordance

withChapter2.1.3.(4)

(4)Whenusingthepartialfactormethod,

itshallbeverifiedthatthetarget

reliabilityfornotpassingtherelevantlimitstateduringthedesignservicelife

isnotexceededwhendesignvaluesforactionsoreffectsofactionsand

resistanceareusedinthedesignmodels.

Thepartialfactorsshalltakeintoaccount:

Thepossibilityofunfavourabledeviationsofactionvaluesfromthe

representativevalues

Thepossibilityofunfavourabledeviationsofmaterialsandproduct

propertiesfromtherepresentativevalu

es

Modeluncertaintiesanddimensionalv

ariations

Thenumericalvaluesforthepartialfactorsshallbedeterminedineither

oftwoways:

Onthebasisofstatisticalevaluation

ofexperimentaldataandfield

observationsaccordingtorequirementsofclauseVerificationbyfull



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18

2Basisofdesign

probabilisticmethod

Onthebasisofcalibrationtoalongtermexperienceofbuilding

tradition

2.4.3Verificationbythedeemed

-to-satisfymethod

Exposureconditionsinthedesignsituationsmightbeclassifiedin

exposureclasses.

Traditionally,deemed-to-satisfy

provisionsincluderequirementstothe

workmanship,concretecomposition,possibleairentrainment,cover

thicknesstothereinforcement,crackwidthlimitationsandcuringofthe

concrete.

However,otherprovisionsmight

alsoberelevant.

Examplesofthecalibrationof

deemed-to-satisfycriteriabasedona

close-tofullprobabilisticmethod

anddataderivedfrom1015yearsold

structuresaregivenin[2].

(1)Thedeemed-to-satisfymethodisaset

ofrulesfor

dimensioning,

materialandproductselectionand

executionprocedures

thatensuresthatthetargetreliabilityfo

rnotpassingtherelevantlimit

stateduringthedesignservicelifeisno

texceededwhentheconcrete

structureorcomponentisexposedtothedesignsituations.

(2)Thespecificrequirementsfordesign,materialsselectionandexecution

forthedeemed-to-satisfymethodshallbedeterminedineitheroftwoways:

Onthebasisofstatisticalevaluation

ofexperimentaldataandfield

observationsaccordingtorequirementsofclauseVerificationbyfull

probabilisticmethod

Onthebasisofcalibrationtoalongtermexperienceofbuilding

tradition

Thelimitationstothevalidityoftheprovisions,e.g.therangeofcement

typescoveredbythecalibration,shallbeclearlystated.

2.4.4Verificationbytheavoidan

ce-of-deterioration

method

(1)Theavoidance-of-deteriorationmethodimpliesthatdeterioration

processwillnottakeplaceduetoforinstance:

Separationoftheenvironmentalactionfrom

thestructureor

componentbye.g.claddingormembranes

Usingnon-reactingmaterials,e.g.certainstainlesssteelsoralkali-non-



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19

reactiveaggregates

Separationofreactants,e.g.keepingthestructureorcomponentbelow

acriticaldegreeofmoisture.

Suppressingtheharmfulreactione.g.byelectrochemicalmethods

Theassumedeffectivenessofthe

actualconceptshallbedocumented,for

instanceforproductsbycomplying

withrelevantminimumrequirementsin

productstandards.

(2)Thespecificrequirementsfordesign,materialsselectionandexecution

fortheavoidance-of-deteriorationmethodcaninprinciplebedeterminedin

thesamewayasforthedeemed-to-satisfymethod.

Thelimitationstothevalidityoftheprovisionsshallbeclearlystated.



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3VerificationofServiceLifeDesign

3

VerificationofService

LifeDesign

3.1Carbonationinducedcor

rosionuncracked

concrete

3.1.1Fullprobabilisticmethod

3.1.1.1

Limitstate:depassivation

Togetcorrosionanenvironme

ntthatiswetenoughisneeded.For

structuralelementssolelyexposedto

relativedryindoorenvironment,alimit

statedepassivationmaynotberelevantasnosignificantcorrosionwill

develop.

(1)Thefollowingrequirementneedstobefulfilled:

p{}=pdep.=p{a-xc(tSL)

fib 34 - model code for service life design

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