Objectives of the project:Develop practical service life design ‘system’
Guidance and toolsAllow comparison of different approaches toachieving a structure that is durable for itsrequired service life
Facilitate the minimisation of whole life costs
Consistent with existing codes & standardsOverall framework intended to be genericConcrete-specific at lower levels
Objectives
Ultimately to produce simple, user-friendlycomputer-based system to lead user throughprocess using:
• Simple flow diagrams and/or decision trees• Prompts/questions at key stages• Focused ‘digest-type’ guidance documents• Links to existing guidance• Tools to assist:
•Service life forecasting•Reducing whole life costing
‘The assumed period for which a structure isto be used for its intended purposes withanticipated maintenance but without majorrepair being necessary’.
prEN 1990: Basis of design
Service life
‘Deemed to satisfy’ durability design
‘Deemed to satisfy’ has served industry well inmajority of cases but:
• Does not define service life or end of service life• Risk of premature deterioration in aggressive
exposure conditions• Fails to acknowledge that structures deteriorate
progressively• Limited account of impact of conceptual and
detailed design, construction quality and method.• Limited flexibility
Drivers for service life design
• Whole life costing
• Improved knowledge of degradative processesand other factors contributing to failure
• Improved ability to specify durable concretes
• Additional protective measures
• Development of predictive models
• Sustainability
Incr
easi
ng s
usta
inab
ility
Overdesign andspecification
Zone of sustainableconstruction
Too littlequality
Increasingquality
Present practice
Plateau of sustainablepractice
Plateau of sustainable construction(from Somerville)
Factors affecting service life
• Design
• Construction method
• Materials
• Workmanship
• Repair and maintenance
• Environment
Approach
The main elements of the service life designframework are:
• Client Brief (project brief)• Determination of environmental loads• Definition of performance requirements under
environmental loads• Conceptual design• Detailed design• Execution• Maintenance and management issues in use
Approach
Other key elements in framework include:• Quality• Communication throughout process• Feedback• Tools
• Service life forecasting• Whole life costing
• BRE Durability review
Definition of requiredperformance under defined
‘loads’
Client BriefDefine function and type of structure
Clients basic needs Determine performance requirements
Safety and serviceabilityImportance of continuing of function
required service life and end of service life Management and maintenance strategy
Likelihood of future changes of use LoadsAssessment of:
Dead and imposed loadingAssess & define exposure environment
Aggressive actionsExposure class
Moisture, rainfall, chemicalstemperature, sunlight
etc
Conceptual design (see separate diagram)Construction method and quality issues
Ease of maintenance, upgrade, replacement, deconstruction and reuseBuildability
Assess level of workmanshipAppropriate materials selection based on known performance of materials and components & materials compatibility
Define structure/element criticality (and replacability) and identify durability critical areasEstablish basic defence strategy
Forecasts of structure and element service lifeConduct initial whole life cost assessments
Review of Durability Brief
Review of Detailed Design
Review of Conceptual Design
Structural designCalculations for limit states
DetailingMaterials specifications and QC
Durability/design life optionsDevelopment of basic defence strategy from conceptual design
Revision of whole life costsBuildability assessment
Detailed design (see separate diagram)
Apply best practiceaddress workmanship issues inspection, quality assurance
Communication
Ensure materials specification is achievedE.g. conduct trial castings for concrete
Reviews of Pre-Execution Planning andExecution
Reviews of Specification & Supply ofMaterials and Products
Execution
Review of handover and commissioning
Reviews of refurbishment & demolition
Schematic diagramshowing the main
components of servicelife design
Conduct (ongoing) durability assessments to confirm properties match expectations
Apply maintenance strategy , inspect & repair
Use
End of life -decisions on refurbishment, re-use, demolition
BR
E D
urab
ility
Rev
iew
Qua
lity
issu
esC
omm
unic
atio
nan
d fe
edba
ck
Serv
ice
life
fore
cast
ing,
who
le li
fe c
ostin
g +
sust
aina
bilit
y to
ols
Client Brief
Assessment of loads
Detailed design
Conceptual design
Execution
Maintenance and management issues
Define performance Requirements under environmental loads
Definition of requiredperformance under defined
‘loads’
Client BriefDefine function and type of structure
Clients basic needs Determine performance requirements
Safety and serviceabilityImportance of continuing of function
required service life and end of service life Management and maintenance strategy
Likelihood of future changes of use LoadsAssessment of:
Dead and imposed loadingAssess & define exposure environment
Aggressive actionsExposure class
Moisture, rainfall, chemicalstemperature, sunlight
etc
Conceptual design (see separate diagram)Construction method and quality issues
Ease of maintenance, upgrade, replacement, deconstruction and reuseBuildability
Assess level of workmanshipAppropriate materials selection based on known performance of materials and components & materials compatibility
Define structure/element criticality (and replacability) and identify durability critical areasEstablish basic defence strategy
Forecasts of structure and element service lifeConduct initial whole life cost assessments
Review of Durability Brief
Review of Detailed Design
Review of Conceptual Design
Structural designCalculations for limit states
DetailingMaterials specifications and QC
Durability/design life optionsDevelopment of basic defence strategy from conceptual design
Revision of whole life costsBuildability assessment
Detailed design (see separate diagram)
Apply best practiceaddress workmanship issues inspection, quality assurance
Communication
Ensure materials specification is achievedE.g. conduct trial castings for concrete
Reviews of Pre-Execution Planning andExecution
Reviews of Specification & Supply ofMaterials and Products
Execution
Review of handover and commissioning
Reviews of refurbishment & demolition
Schematic diagramshowing the main
components of servicelife design
Conduct (ongoing) durability assessments to confirm properties match expectations
Apply maintenance strategy , inspect & repair
Use
End of life -decisions on refurbishment, re-use, demolition
BR
E D
urab
ility
Rev
iew
Qua
lity
issu
esC
omm
unic
atio
nan
d fe
edba
ck
Serv
ice
life
fore
cast
ing,
who
le li
fe c
ostin
g +
sust
aina
bilit
y to
ols
Assessment tools
Durability review
Quality communication
Feedback
Service life designframework
Clients basic needsType of structure
FunctionLocation
Site investigationExposure class
Aggressive agents
Wind direction & strengthRain
Temperature (including degreeand frequency of changes)
Definition ofenvironment
Review of data
Further environmentaldata needed?
Performance requirementsSafety and servicability
Importance of continuity of functionSpecify required design life
Specify what constitutes end ofservice life
‘Sustainability’ requirementsRestrictions to design that may affect
durabilityManagement and maintenance
requirementsLikelihood of changes of use and
upgrading
Statement of requiredperformance under defined
environmental loads
Conceptual design
Clarification ofperformance
requirements needed?
Audit of clientbrief
Identification of intended(and possible future) use
and consequent loads
Schematicdiagram for
client brief andstatement of
requiredperformance
Clients basic needs
Performancerequirements
Definition of environment
Required performance under defined environmental
loads
To conceptual design
Client brief & statementof requiredperformance
Site investigation
Client BriefClient’s basic needs including:
• Type of structure• Function• Location• Appearance
Performance requirements including:• Service life and end of service life• Potential changes of use• Maintenance (planned or reactive)• Balance between initial and running costs• Sustainability issues• Restrictions affecting durability
Definition of exposure environment
General environmental conditionsExposure class and aggressive agentsWind direction & strength,RainTemperatureGround conditions
Specific location/orientation of structure
Potential interaction between structure andenvironment
Statement of required performanceunder defined environmental loads
Starting point for the Service life designprocess developed from:
Client briefPerformance requirementsClients basic needs
AndDefinition of exposure environment
Conceptual design How best to resist environment
• Choice of structural form to minimise deterioration• Identification of vulnerable areas• Basic protection strategy (Design-out, Provide resistance)
• Appropriate approach depends on type of structure:• Durability and design life issues differ• Consistent with formal consensus guidance documents• Concept of service life design at different stages of
development• Economic options are different⇒Sub-divide design system according to type of structure
Conceptual design Also consideration of:
• Buildability• Health & safety• Quality issues (materials, workmanship)• Initial service life forecasting• Initial whole life costing
Yes
Detailed design
Assess basic defence mechanism forstructure/elements (based on guidance) see
figures
Provide resistanceDesign out
Classification of structure/elementcriticality (and replacability) and
identification of durability critical areas
Generate ‘outline’ options and conduct buildabilityand whole life cost assessments
(see Figure ?)
Envi
ronm
enta
lLo
ads
Choice of structural form to minimisedeterioration
Construction method and quality issues
Determine appropriate Maintenance approach(see Figure ?)
Are initial and whole life costs acceptable toclient?
Can performance requirements bemet?
Qua
lity
(wor
kman
ship
,m
ater
ials
avai
labi
lity
etc.
)
No
Yes
No
Choice of structural form to minimisedeterioration
Initial buildability assessment
Buildability assessment - are design & maintenance strategies
feasible?
No
Yes
Client brief and performance requirements
under defined loads
Planned replacement
Forecast service life ofelement in its environment
Predict replacementfrequency
Can performancerequirements be met
using different defencemechanism orcombination?
Yes
No
List optional Design strategies + repair,maintenance strategies
Conduct whole life cost (& sustainability)assessment. Select most cost effective option
Schematicdiagram forconceptual
designAudit of
conceptual design
Service life forecasting,whole life costing +sustainability tools
Feed
back
from
per
form
ance
of e
xist
ing
stru
ctur
es
Client brief &Performance requirements
Buildability
Selection of basic defence
strategy
Maintenance strategy
Whole life costing
Quality issues
Environment
ConceptualDesign
Buildability
Identify and quantify materialsdegradation processes, impact of macro
and microenvironment etc.
Selection of appropriate basic protection strategy
Assess secondary processes and selectappropriate additional protection strategies
Design out
Concrete deterioration
(e.g. ASR, sulfate attack,freeze-thaw, etc).
Controlling early age effects
Avoidance of factors such asthermal cracking, plastic shrinkage
& settlement through controllingpeak temperature, appropriate
materials selection, curingconditions etc.
Design out: Use appropriateconcrete parameters based on
codes and standards andassociated guidance
Is risk of deteriorationunacceptable or is multi-layer
approach required?
Select additional protectionstrategy in accordance with
guidance or considerplanned repair or
replacement
Designmaterials
List and assess options usingwhole life costing tools etc.
Concrete
Select most appropriateoptions based on guidance
Yes
No
EnvironmentalLoads
Performancerequirements
Develop design out strategiesfurther under detailed design
Reinforcement corrosion(see separate diagram)
ProvideresistancePlanned
repair orreplacement
Multi-layer
Singlelayer
Selection of basicdefence strategies
Identification of deterioration
Processes Reinforcement
corrosion
Avoidance of concrete
deterioration
Controlling early age
effects
Whole life costing of
options
Structural design•Design calculations•Selection of initial concrete parameters•Reinforcement arrangements•Detailing
Development of durability options selected inconceptual design stage
Also:•Service life and whole life costing•Buildability•‘Life care plan’
Detailed design
Design calculations
DetailingShapes and profiles
JointsDrainage & water
Outer fabric treatmentProvision for inspection &
maintenance
SpecificationsMaterials and products•Concrete•Reinforcement•Joint materials•Etc.Quality control
Structural designDurability/design life
options
Provide designresistance
Multi-layerprotection
(see separatediagram)
Single layerprotection
(see separatediagram)
Design outapproach
(see diagram)
Planned replacement
Forecast service life ofelement in itsenvironment
Predict replacementfrequency
Develop basic defence strategy selectedin conceptual design for each component
Revise whole life cost andbuildability assessments
NO
Can/must structural aspects ofdesign be revised?
Are costs acceptable to the client?
YES
Is design still feasible?
Does design meet clients needs? YES
YES
Execution stage
NO
NO
Reviews of durability design,specification of materials and
products, pre-construction plan andlife-care plan
NO
YES
Service life forecastingwhole life costing
sustainability tools
Conceptual design
Preparation of life-care plan
Preparation of pre-constructionplan
Durability &design lifeoptions
Development of defence strategy
Detailed design
Detailing
Specifications for concrete
cover, QC etc
Structural design
AcceptabilityBuildabilityService life
costs Life care plan
Execution2 approaches to addressing variability.
• Raise standards to acceptable & repeatable level by:• Encouraging better design• Improved communication• Education & training• Benchmarking• Method statements & certification etc.• Durability Review
• Assume current variability & standards, relying on:• Multi-layer protection• Design out approaches• Durability Review
Maintenance and Use
Ongoing assessmentsAppropriate inspection, maintenance and repair(particularly of key areas)End of life decisions
Ensure that further work such asrefurbishment doesn’t impair durabilityDeconstructionEtc.
Design for service life - materials properties
Tools (models) and guidance on their use,benefits, limitations etc.A number of possible approaches including:
! Knowledge and experience! Performance of similar materials! Accelerated testing! Modelling! Combinations of these
Whole life costing
Where several options are available to meetclients requirements
! Use of whole life costing principles to assessoptions
! Select most cost effective option and that mostappropriate to clients needs
! Use sustainability concepts?
Whole life costing ‘tool’ and guidance onuse, limitations etc.
Summary
The main elements of the service life designframework are:
• Client Brief• Determination of environmental loads• Definition of performance requirements
under environmental loads• Conceptual design• Detailed design• Execution• Maintenance and management issues
Summary
Other key factors include:• Quality• Communication throughout process• Feedback• Tools
• Service life forecasting• Whole life costing• Sustainability
• BRE Durability review
Next Steps
Development of computer-based version
Develop individual elements:Key factors to be addressed.Developing interactions within and betweenelements
Preparation of guidance documentsInitially Information papers
Develop interactions and overall frameworkDigests and design system
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