MEPDG : Where are We Now? · PDF fileMEPDG : Where are We Now? Louisiana Transportation...

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MEPDG : Where are We Now?

Louisiana Transportation Engineering Conference

Baton Rouge, LAFebruary 12, 2007

Chris Wagner, P.E.FHWA – Resource Center

Christopher.Wagner@dot.gov

Auburn and LSU Common Denominator

BEATBAMA

Objectives

State Implementation Activities Status of MEPDG

Current State of the Practice

General Overview of ME DesignBenefits and Issues of Implementation

What else happened in 1958 ?

Construction finished on the AASHO Road Test

What’s Being Used (2003 survey)

Design Procedures DOTs1972 AASHTO Guide 3

1986 AASHTO Guide 2

1993 AASHTO Guide 26

Agency’s own pavement design guide or combination of AASHTO/Agency design procedures

1950s 1950s

ConstructionConstructionMethods...Methods...

(AASHO, 1961)

Question ?Why was the original

AASHO Road Test conducted ?

How much did it cost ?

Objectives

The Big Picture

Climate Inputs

Material Properties

Transfer Functions

Predicted Performance Mechanistic Analysis

Traffic

Loads and Layer Stiffness

Mechanistic AnalysisLayered Elastic Analysis

Strain Calculations at Critical Locations

E = σ/ε

Empirical Portion of MEPDGP

Observed Performance

Line of Equality

β = Empirical Shift Factorβ

Test Section Performance

-4 -3 -2 -1 0 1 2 3

Log Damage (%)

rea) Local Performance Data

Local Calibration Benefits

Test Section Observations

National Data Set

Local Data Set

Traffic

Improved traffic characterizationAbility to deal with changing load types

ESAL18k Load Spectra

1950s Vehicle Loads...1950s Vehicle Loads...

Who drove these trucks ?

“Extrapolations beyond these

total load applications

should be used with caution.”

Pg 7: AASHTO ‘72

MaterialsEnhanced definition of material propertiesRelate material properties to performanceMaterial Aging

LayerCoefficient Modulus

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

0 6 12 18 24 30 36 42 48 54 60

Pavement Age (month)

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

0 12 24 36 48 60 72 84 96 108 120

AC at 1/2" DepthAC at 5" DepthAC at 10" depth

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

0 6 12 18 24 30 36 42 48 54 60

What happened here ??

Granular Base

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

0 6 12 18 24 30 36 42 48 54 60

Granular Base

Input Value

AASHTO Materials Characterization

How do you Characterize your materials ??SMASuperpave HMAHveem HMAPolymer ModifiedWarm Mix AsphaltRAP

Are they all ai = 0.44 ?

ClimateSite specific climate considerations

Material properties effected by climatePCC Joint openings, Curl / Warping

Extrapolated fromOttawa, IL 800 Weather Sites

Major Advantages

Modular system that allows for incremental enhancement Produces a more reliable designNo longer dependent on the extrapolation of empirical relationshipsExcellent for forensic analysis

Answers “What if….” questionsCalibrate to Local Materials, Traffic, Climate….

Reasons for ChangeReduce Over-and-Under Design Costs Legislative MandateConsider Alternative Designs/Unique ConditionsRational Basis for Warranties, LCCA, PRS, QA/QC, Pay FactorsForensic InvestigationsImpact of Management Decisions on Pavement SystemTie Design to Construction

Initial Construction

First Rehab

PRS Example

4 8 12

Air Voids (%)

8% Air Void Spec Limit

Contractor Builds 12% Va

Pavement Design

Pavement Management Construction

Materials Selection

Communication

Integration

Objectives

Implementation Team

Include In-House Experts; Pavements Materials and Traffic, PMSConsider Regional or Multi-State Effort; PFSContract with Consultant or UniversityInclude Upper management Personnel

Develop a Team and Plan

Data Collection - Traffic

Most States Have Inadequate DataSome are Planning Regional Weight Data by Roadway Classification (TRB Session 283)Share Collection and Storage Efforts with Other Offices Using Traffic DataEnhance WIM Quality and MagnitudeIntegrate with PMS

Data Collection - Materials

Most States Need Additional EquipmentSeveral are Determining Mr, FWD, DCP and CBR Relationships for CatalogTesting Equipment for CTE and E*Predictive Equations for E*

Practical Considerations

You have to design before you buildMEPDG is used for Design and Forensic EvaluationDon’t need to use all distress predictions for designDo not need Level 1 for all InputsDo not throw out past experience

Using MEPDG for Design

State specific guidance is necessaryPavement Design Manual Distress criteria and limitsDesign parameters to change

Implementation Timeframe

Some DOT’s Already UnderwayOthers are Awaiting Other Efforts:

NCHRP ProjectsFHWA Research ProjectsCopy Other State ApproachesAASHTO AdoptionWindfall from Gas Tax RevenuesHell Frozen

Who will use the MEPDG?

State DOT’s Main UserPavement DesignersUpper Management

Remaining Service Life, “What if” questions

AcademiaIndustryConsultant Designers

Warranty, Design Build, PRS, PWL etc…..

Other WorkLead StateImplementation PlanBothUnknown

Things to remember

All pavement design systems need:Quality Materials CharacterizationQuality Traffic DataCalibrated to local conditions

The MEPDG is one tool for a designerFocused on the structural design aspectsHas limitations

Version 1.0 Changes

State DOT’s will receive 2 copies soonBatch ModeModel RecalibrationUse of Volumetrics in rutting modelComputer Program StabilityPerpetual Pavement Concept Calculation of ESAL’s

NCHRP Draft Research Results Digest

More Informationwww.trb.org/mepdg www.fhwa.dot.gov/pavement/dgit

Webcast WorkshopsTraffic, Climate, Materials, Introduction

ARA bugtracker website

Local Calibration Guide and Users ManualNHI Course: Hands on Application of MEPDG

Read the book !!!

Help Wanted

Contact the DGITResearch Proposal ReviewTraining Technical Assistance

AASHTO ImplementationJoint Technical Committee on Pavements

Subcommittee of Design &

Materials

Full AASHTO Balloting

Interim Guide – Spring 2008 ?

April 10-11, 2007MEPDG Roll Out Workshop

Irvine, CA

Perspective•1960 – Completion of Road Test Experiment

•1961-62 AASHO Interim Guide for the Design of Rigid and Flexible Pavements

•1972 AASHTO Interim Guide for the Design of Pavements

•1981 Revised Chapter III on Portland Cement Concrete Pavement Design

•1986 Guide for the Design of Pavement Structures

•1993 Revised Overlay Design Procedures

•1998 Supplement to Concrete Design Procedures

"We can't solve problems by using the same kind of thinking we used when we created them."

PerspectivePerspective

Questions ??

www.fhwa.dot.gov/pavement/dgit/

www.trb.org/mepdg

BEATBAMA !!!

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