mechanistic empirical pavement design guide
TRANSCRIPT
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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
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Auburn and LSU Common Denominator
BEATBAMA
!!!!!
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Objectives
State Implementation Activities Status of MEPDG
Current State of the Practice
General Overview of ME DesignBenefits and Issues of Implementation
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What else happened in 1958 ?
Construction finished on the AASHO Road Test
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Whats Being Used (2003 survey)
Design Procedures DOTs1972 AASHTO Guide 3
1986 AASHTO Guide 2
1993 AASHTO Guide 26
Agencys own pavement design guide or combination of AASHTO/Agency design procedures
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1950s 1950s
ConstructionConstructionMethods...Methods...
(AASHO, 1961)
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Question ?z Why was the original AASHO Road Test conducted ?
How much did it cost ?
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Objectives
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The Big Picture
Climate Inputs
EICM
Material Properties
Transfer Functions
Predicted Performance Mechanistic Analysis
Traffic
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Loads and Layer Stiffness
Mechanistic AnalysisLayered Elastic Analysis
E*
Mr
Mr
Strain Calculations at Critical Locations
E = /
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Empirical Portion of MEPDGP
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Observed Performance
Line of
Equality
= Empirical Shift Factor
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Test Section Performance
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-4 -3 -2 -1 0 1 2 3
Log Damage (%)
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) Local Performance Data
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Local Calibration Benefits
Test Section Observations
National Data Set
Local Data Set
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Traffic
z Improved traffic characterizationz Ability to deal with changing load types
ESAL18k Load Spectra
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1950s Vehicle Loads...1950s Vehicle Loads...
Who drove these trucks ?
Extrapolati
ons beyond
these
total load a
pplications
should be u
sed with ca
ution.
Pg 7: AASHTO 72
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Materialsz Enhanced definition of material propertiesz Relate material properties to performancez Material Aging
LayerCoefficient Modulus
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0
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)
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Aging
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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
Pavement Age (month)
AC at 1/2" DepthAC at 5" DepthAC at 10" depth
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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
Pavement Age (month)
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What happened here ??
Granular Base
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0
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
Pavement Age (month)
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Granular Base
Soil
Input Value
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AASHTO Materials Characterization
z How do you Characterize your materials ??z SMAz Superpave HMAz Hveem HMAz Polymer Modifiedz Warm Mix Asphaltz RAP
Are they all ai = 0.44 ?
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Climatez Site specific climate considerationsz Material properties effected by climatez PCC Joint openings, Curl / Warping
Extrapolated fromOttawa, IL 800 Weather Sites
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Major Advantages
z Modular system that allows for incremental enhancement
z Produces a more reliable designz No longer dependent on the extrapolation of
empirical relationshipsz Excellent for forensic analysisz Answers What if. questions
z Calibrate to Local Materials, Traffic, Climate.
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Reasons for Changez Reduce Over-and-Under Design Costs z Legislative Mandatez Consider Alternative Designs/Unique Conditionsz Rational Basis for Warranties, LCCA, PRS,
QA/QC, Pay Factorsz Forensic Investigationsz Impact of Management Decisions on
Pavement Systemz Tie Design to Construction
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LCCA
Time
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Initial Construction
First Rehab
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PRS Example
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4 8 12
Air Voids (%)
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%
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8% Air Void Spec Limit
Contractor Builds 12% Va
$$$
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Pavement Design
Pavement Management Construction
Materials Selection
Communication
Integration
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Objectives
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Implementation Team
z Include In-House Experts; Pavements Materials and Traffic, PMS
z Consider Regional or Multi-State Effort; PFSz Contract with Consultant or Universityz Include Upper management Personnel
Develop a Team and Plan
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Data Collection - Traffic
z Most States Have Inadequate Dataz Some are Planning Regional Weight Data by
Roadway Classification (TRB Session 283)z Share Collection and Storage Efforts with
Other Offices Using Traffic Dataz Enhance WIM Quality and Magnitudez Integrate with PMS
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Data Collection - Materials
z Most States Need Additional Equipmentz Several are Determining Mr, FWD, DCP and
CBR Relationships for Catalogz Testing Equipment for CTE and E*z Predictive Equations for E*
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Practical Considerations
z You have to design before you buildz MEPDG is used for Design and Forensic
Evaluationz Dont need to use all distress predictions for
designz Do not need Level 1 for all Inputsz Do not throw out past experience
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Using MEPDG for Design
State specific guidance is necessaryz Pavement Design Manual z Distress criteria and limitsz Design parameters to change
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Implementation Timeframe
z Some DOTs Already Underwayz Others are Awaiting Other Efforts:z NCHRP Projectsz FHWA Research Projectsz Copy Other State Approachesz AASHTO Adoptionz Windfall from Gas Tax Revenuesz Hell Frozen
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Who will use the MEPDG?
z State DOTs Main Userz Pavement Designersz Upper Managementz Remaining Service Life, What if questions
z Academiaz Industryz Consultant Designersz Warranty, Design Build, PRS, PWL etc..
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Other WorkLead StateImplementation PlanBothUnknown
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Things to remember
z All pavement design systems need:z Quality Materials Characterizationz Quality Traffic Dataz Calibrated to local conditions
z The MEPDG is one tool for a designerz Focused on the structural design aspectsz Has limitations
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Version 1.0 Changes
z State DOTs will receive 2 copies soonz Batch Modez Model Recalibrationz Use of Volumetrics in rutting modelz Computer Program Stabilityz Perpetual Pavement Concept z Calculation of ESALs
NCHRP Draft Research Results Digest
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More Informationz www.trb.org/mepdg z www.fhwa.dot.gov/pavement/dgitz Webcast Workshopsz Traffic, Climate, Materials, Introduction
z ARA bugtracker website
z Local Calibration Guide and Users Manualz NHI Course: Hands on Application of MEPDG
zRead the book !!!
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Help Wanted
z Contact the DGITz Research Proposal Reviewz Training z Technical Assistance
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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
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Perspective1960 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
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"We can't solve problems by using the same kind of thinking we used when we created them."
PerspectivePerspective
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Questions ??
www.fhwa.dot.gov/pavement/dgit/
www.trb.org/mepdg
BEATBAMA !!!
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