NCHRP 12-108 Guide Specification for Service Life Design of Highway Bridges
June 13,207| Spokane,WA
AASHTO 2017 SCOBS – T‐9 Committee Meeting NCHRP NATIONAL COOPERATIVE HIGHWAYRESEARCH PROGRAM
“This investigation was sponsored by TRB under the NCHRP Program. Data reported are work in progress. The contents of this presentation have not been reviewed by the project panel or NCHRP, nor do they constitute a standard, specification, or regulation.”
AASHTO T-9 June 2017
Presentation Outline
Project ObjectivesPhase I Work PlanPhase I ResearchUpdated ScheduleDiscussion/questions
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Phase I Research DiscussionScheduleWork PlanObjectives
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Firm POC EmailModjeski and Masters, Inc. Thomas Murphy
Ed WassermanMaria LopezTravis Hopper
Independent Consultant John Kulicki [email protected]
Rutgers University‐CAIT Frank MoonNick Romano
COWI Anne‐Marie Langlois
NCS GeoResources Naresh Samtani [email protected]
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Research Team Introduction
Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Develop an AASHTO Guide Specification for Service Life Design of Highway Bridges
Develop Case Studies to demonstrate the application of the proposed Guide
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Project Objectives
Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
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Phase I Planning
Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Task Primary Lead
1 ‐ Review Literature Frank Moon
2 – Synthesis of Literature Review Frank Moon
3 – Proposed Methodology Thomas Murphy
4A – Annotated TOC proposed AASHTO Guide Thomas Murphy
4B – Propose Case Studies Frank Moon
5 – Interim Report No. 1 Maria Lopez
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Phase II Methodology Development
Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Task Primary Lead
6 – Develop and Execute Methodology
7 – Sample Section Ready for Publication
8 – Interim Report No. 2
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Phase III Guide Specification Development
Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Task Primary Lead
9A – Guide Specification Development
9B – Case Studies Development
10 – Interim Report No. 3
Phase IV Final ProductsTask Primary Lead
11 – Revisions based on panel input
12 – Final Deliverables
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Literature Review| Task 1
Led By:
Supported By: All Team Members
Over 100 references on research topic were reviewed & summarizedThe literature synthesis focuses on
codes/standards technical reports from professional societiesgovernment reports
The literature review effort will continue throughout the project and, if needed, expand to include:
refereed journals, conference proceedingsReferences cited by review panel
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Synthesis of the Literature Review| Task 2
Led By:
Supported By: All Team Members
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Synthesis of the Literature Review| Task 2Full Probabilistic and Partial Factor Methods
For practical purposes these methods are limited to:
Carbonation‐induced depassivation(ISO 16240 and fib bulletin 34)Chloride‐induced depassivation(ISO 16240 and fib bulletin 34)
Although other limit states have been identified, no reliable models of the deterioration mechanisms are currently not availableExamples include:
corrosion‐induced crackingfreeze‐thaw scaling and cracking (with and without de‐icing agents)
Deemed‐to‐Satisfy MethodsConcrete material specifications – inclusive of acceptable types and classes of constituents, water/cement ratio, cement content, compressive strength, air‐content, etc.Concrete cover dimensionsCrack control approaches – inclusive of maximum rebar sizes and spacingCoatings – inclusive of steel coatings and membranes/overlays for concreteReplaceable elementsElement‐specific guidance
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Synthesis of the Literature Review| Task 2Exposure Classification Systems
Indicates the harshness of the environment that a bridge or element is exposed to Triggers specific “deemed‐to‐satisfy” provisions –harsher exposure leads to more stringent requirementsExamples
Eurocode – 3 to 4 categories for five deterioration mechanismsAustralian Code – 4 categoriesCanadian Bridge Design Code – informally classifies exposure for three deterioration mechanismsFDOT – 3 Levels for sub‐ and super‐structures
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Synthesis of the Literature Review| Task 2Example Deemed‐to‐Satisfy Provisions – Eurocode
Concrete Material Properties
Crack Width
Concrete Cover
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Synthesis of the Literature Review| Task 2Example approach to recognize a longer design life: Modify exposure classes
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Objective: to gather tacit knowledge along with owner‐specific documented practices and research regarding service lifeAudience: members of AASHTO Subcommittee on Bridges and Structures (SCOBS) and other Bridge OwnersProduct: 20 questions, format multiple selection and expanded answers (possibility of follow‐up questions)Questions included in this year’s State Bridge Engineer questionnaire for AASHTO SCOBS
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Questionnaire
Led By:
Supported By: All Team Members
Perhaps the most useful information gathered will be:
What practices should be encouragedin new designs based on experience?What practices should be avoided in new designs based on experience
We hope to have the opportunity to follow up with several owners
Opinions solicited on:Definition of service life (end of)Target service life values for permanent and replaceable itemsHow long bridges are currently lastingEffect of environment on deterioration ratesMost important factors on deterioration rates
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Questionnaire
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
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10
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40
107
86
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4
8
22
97
214
162
4
32
181
370
76
12
49
283
499
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1
24
94
459
553
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2
30
120
567
640
34
5
43
163
761
615
19
6
54
197
872
590
18
5
67
252
932
547
8
5
78
290
996
536
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1
6
110
337
1054
486
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1
1
11
141
368
1149
493
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2
20
156
426
1198
506
5
1
19
173
462
1275
522
7
2
26
197
506
1345
486
5
1
5
26
224
594
1482
471
6
5
33
258
675
1534
445
5
4
36
287
765
1628
435
4
8
45
335
885
1661
452
3
5
52
350
958
1740
472
5
60
389
1039
1791
453
9
76
422
1136
1825
435
2
1
9
86
469
1184
1824
397
3
1
13
103
498
1291
1818
370
3
1
17
118
504
1270
1751
319
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24
127
510
1281
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533
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831
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51
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479
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107
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0 5 10 15 20 25 30 35 40 45 50 55 60
NBI Con
ditio
n Ra
ting
Age (Year)
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Link to Deterioration Modeling
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Led By:
Supported By: All Team Members
Raw NBI Data (Steel Multi‐Girder Bridges post‐1960)
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2
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5
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7
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1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
NBI Con
ditio
n Ra
ting
Bridge Age
Steel (5%) Steel (50%) Steel (95%) PS (5%) PS (50%) PS (95%)
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Link to Deterioration Modeling
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
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Supported By: All Team Members
Deterioration Modeling (Weibull)
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2
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5
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7
89
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1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
NBI Con
ditio
n Ra
ting
Bridge Age
Steel (5%) Steel (50%) Steel (95%) PS (5%) PS (50%) PS (95%)
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Link to Deterioration Modeling
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Led By:
Supported By: All Team Members
Deterioration Modeling (Weibull) – Fundamental Limitations
Limited Data of Time‐in‐State for CR 5 and 4
Limited applicability to contemporary bridges
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1
2
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89
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1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
NBI Con
ditio
n Ra
ting
Bridge Age
Steel (5%) Steel (50%) Steel (95%) PS (5%) PS (50%) PS (95%)
Definition of End of Service Life
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Link to Deterioration Modeling
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Led By:
Supported By: All Team Members
Deterioration Modeling (Weibull) ‐ Service Life
β = 2.0 β = 1.0 β = 0.0
35 years 51 years 67 years
Majority of provisions and guidance are deemed‐to‐satisfyReinforcement corrosion in uncracked concrete can be treated probabilisticallyThe data just isn’t there to validate most deemed‐to‐satisfy provisions
The challenge is two‐fold:Lack of analytical predictive equations for deterioration mechanismsLack of field data to validate and/or calibrate predictive equations
Plenty of opportunities for future research
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Knowledge Gaps
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Led By:
Supported By: All Team Members
Deemed‐to‐satisfy and avoidance strategies will form the majority of the Guide SpecificationsCalibrated where possible by more rigorous approaches (concrete cover)
Base provisions on collective experiencesQuestionnaire is a startEvery owner has a slightly different approach to service life design provisionsMany rocky shoals to avoid
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Effect on Guide Specifications
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Design MethodsDeemed‐to‐satisfy
• Most common• Can be based on probabilistic
derivation
Avoidance of deterioration• Most straightforward• Generally most expensive
initially
Full probabilistic and Partial Factors method
• As an appendix to Guide Specs
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Proposed Methodology| Task 3
Led By:
Supported By: All Team Members
Goal of the Guide:Provide practical guidance to designers on service life design during the design phase.Utilize the currently available data as well as owner’s experiences to tie various design practices to service life targets.Allow for the incorporation of improved deterioration and service life models as they become available.
Retaining walls will be coveredThree tiered approach is the basis of the methodology, separating practice into:
GoodBetterBest
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Proposed Methodology| Task 3
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Example: DecksGood practices: low‐permeability concrete mixture, explicit curing requirements, concrete cover per LRFD specifications.Better practices: use of waterproofing membranes and/or low permeability overlays, prestressing of concrete, enhanced concrete cover dimensions.Best practices: combination of previous practices plus use of non‐corroding reinforcement and/or bi‐directional prestressing.
Many components driven by combination of factors
Cover, concrete type, reinforcing type all combine to determine deck service lifeConsider a scoring system, awarding points depending on components used, with specific target values for total score
Target service life:Normal = 75 years
Matches probabilistic basis of LRFD calibration
Enhanced = 100 yearsOften used in project specific criteria
Maximum = 125 yearsAt or beyond practical ability to predict
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Led By:
Supported By: All Team Members Proposed Methodology| Task 3
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Proposed Methodology| Task 3
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Environment classification:Different for Steel, Concrete, and GeosyntheticsComplicates use of specific target service livesNot currently well defined (splash zone)
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Proposed Methodology| Task 3
Category Criteria Limits (TBD – see below)
Steel Concrete Geosynthetics
Extreme (FDOT = Extremely Aggressive)
Examples: pH, Cl, SO4, Resistivity
Moderate (FDOT = Moderately Aggressive)
Mild (FDOT = Slightly Aggressive)
Major organization by material, then component
ConcreteDecksSteelFoundations & Retaining WallsRenewable elements
Initial chapters focusing on philosophy, approach, etc.Classification of target service life, environment, etc.General design guidance
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Annotated TOC| Task 4A
Led By:
Supported By: All Team Members
Life Cycle Cost Analysis chapterAppendix on probabilistic service life design framework (full and partial factors), and specifics related to concrete cover, concrete quality, type of reinforcement, and environment
Within each major chapter organization is as follows:
Deterioration mechanismsProtective measuresDetailingConstruction
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Annotated TOC| Task 4A
Illustrates the application of the guide specification to specific bridge designsTwo bridges will be investigated
Steel multi‐girderPrestressed concrete multi‐girder
Focus on changes in design process due to guide spec applicationThe bridge will then be “relocated,” and process repeated to highlight environment (exposure class effect)
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Case Studies| Task 4B
Led By:
Supported By: All Team Members
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Task Submission Review completed PhaseContract Signed ‐ Notice to Proceed September 1, 2016
5 – Interim Report No. 1 March 10, 2017 April, 2017 I6 – Develop and Execute methodology October 1, 2017 November, 2017 II7 – Complete Sample Section of the Guide October 1, 2017 November, 2017 II8 – Interim Report No. 2 October 1, 2017 November, 2017 II
9 & 10 – Develop Guide and Case Studies July 1, 2018 August, 2018 III11 & 12 – Revisions and Final Deliverables December 1, 2018 February, 2019 IVEnd of project February 28, 2019
Research Schedule
Quarterly Reports to Research Panel will be Submitted on March 31, June 30, September 30, and December 31
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Phase I Research DiscussionScheduleWork PlanObjectivesAASHTO T-9 June 2017
Questions?
NCHRP 12-108 Guide Specification for Service Life Design of Highway Bridges