nchrp 12-108 guide specification for national service … · aashto 2017 scobs –t‐9 committee...

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

3

Firm POC EmailModjeski and Masters, Inc. Thomas Murphy

Ed WassermanMaria LopezTravis Hopper

[email protected]

Independent Consultant John Kulicki [email protected]

Rutgers University‐CAIT Frank MoonNick Romano

[email protected]

COWI Anne‐Marie Langlois

[email protected]

NCS GeoResources Naresh Samtani [email protected]

3

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


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Phase I Planning


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


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


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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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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Synthesis of the Literature Review| Task 2

Led By:


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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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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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Synthesis of the Literature Review| Task 2Example Deemed‐to‐Satisfy Provisions – Eurocode

Concrete Material Properties

Crack Width

Concrete Cover

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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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Questionnaire

Led By:


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

1515151515


7

10

10

15

40

107

86

6

4

8

22

97

214

162

4

32

181

370

76

12

49

283

499

55

1

24

94

459

553

47

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

7

1

6

110

337

1054

486

6

1

1

11

141

368

1149

493

7

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

2

24

127

510

1281

1633

286

1

2

22

130

533

1329

1505

285

1

2

28

135

539

1333

1404

250

1

2

35

141

560

1346

1258

209

1

39

156

590

1302

1122

193

2

1

39

152

606

1285

987

187

3

1

42

163

611

1267

891

191

2

1

43

166

592

1193

808

152

1

1

36

150

550

1132

706

128

1

29

159

558

1059

615

96

1

24

143

542

970

538

78

26

145

503

900

458

63

25

130

496

831

383

51

25

113

479

776

321

42

26

107

453

705

277

35

25

101

421

621

247

32

1

22

92

370

536

214

22

1

16

96

327

450

178

21

15

87

299

363

148

19

14

75

252

307

124

14

10

72

213

255

104

10

7

67

190

210

88

9

8

62

161

162

72

8

5

54

142

131

55

6

5

44

111

108

37

6

1

4

30

85

83

24

5

3

20

59

59

22

3

1

11

43

42

17

3

9

28

31

11

1

4

12

17

4

1

1

2

3

4

5

6

7

8

9

10

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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Led By:


Raw NBI Data (Steel Multi‐Girder Bridges post‐1960)

0

1

2

34

5

6

7

89

10

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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Led By:


Deterioration Modeling (Weibull)

0

1

2

34

5

6

7

89

10

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


18


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Led By:


Deterioration Modeling (Weibull) – Fundamental Limitations

Limited Data of Time‐in‐State for CR 5 and 4

Limited applicability to contemporary bridges

0

1

2

34

5

6

7

89

10

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


Definition of End of Service Life

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Led By:


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

2020202020


Led By:


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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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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Proposed Methodology| Task 3

Led By:


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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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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Led By:

Supported By: All Team Members 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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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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Annotated TOC| Task 4A

Led By:


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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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:


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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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Questions?

NCHRP 12-108 Guide Specification for Service Life Design of Highway Bridges

nchrp 12-108 guide specification for national service … · aashto 2017 scobs –t‐9 committee...

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