27
MEPDG 1 Lecture 1 Mechanistic Empirical Pavement Design Guide (MEPDG): Overview
MEPDG 1
Lecture 1
Mechanistic Empirical Pavement Design Guide (MEPDG):
Overview
MEPDG 2
Overview of Lecture
Pavement design guides
AASHTO Design Guide
o History
o Philosophy
o Key notes
o AASHO Road Test 1958
o Limitations
MEPDG
o Philosophy
o History
MEPDG 3
Overview of Lecture
Why MEPDG important?
AASHTO Design Guide vs. MEPDG
Why we are moving from AASHTO Design Guide to MEPDG
States MEPDG Implementation Plan
Improvements of MEPDG
Users of MEPDG
Benefits of MEPDG
Future work
Pavement Design State of the Art
Pavement design guides
For Concrete Pavement
American Association of State Highway and Transport Officials (AASHTO) Design Guide
Portland Cement Association (PCA) Design Guide
MEPDG
For Flexible Pavement
Asphalt Institute Guide
AASHTO Design Guide
MEPDG
MEPDG 4
AASHTO Design Guide: History
Empirical design came about the result of the AASHO Road Test in 1958.
Several Editions:
o 1961 Interim Guide
o 1972
o 1986
Resilient modulus, rehabilitation, reliability
o 1993 Improved rehabilitation
Current version
MEPDG 5
AASHTO Design Guide: Philosophy
Philosophy: This is based on the service performance concept, which provides a means of designing a pavement based on a specific total traffic volume and a minimum level of serviceability desired at the end of the performance period.
MEPDG 6
AASHTO Design Guide: key notes
Based on empirical methodology
Empirical design came about the result of the AASHO Road Test in 1958.
Since design guide based on AASHTO Road Test, limitations include one climate, one sub-grade, two years duration, limited cross sections, and 1950’s materials, traffic volumes, specifications and construction methods.
MEPDG 7
AASHTO Design Guide: AASHO Road Test 1958
Location: Ottawa, Illinois
MEPDG 8
AASHTO Design Guide: AASHO Road Test 1958, cont.
Construction methods
1950s vehicle loads
Single location
Single climate condition
MEPDG 9
AASHTO Design Guide: Limitations
MEPDG 10
Specific set of pavement materials and one type of roadbed soil.
Single environment
An accelerated procedure for accumulating traffic (a 2-year testing period extrapolated to 10 or 20-year design)
Accumulating traffic on each test section by operating vehicles with identical axle loads and axle configurations as opposed to mixed traffic
MEPDG: Philosophy
MEPDG: This is based on the Mechanistic-Empirical approach which uses computations of pavement responses such as stresses, strains, and deformations and then adjusts accordingly based on the performance models from the empirical approach.
* The ultimate goal for the future is to have pavement designed on a mechanistic approach only
MEPDG 11
MEPDG: History
Process initiated by Joint Task Force on Pavements
o Irvine, California: March 1996
Development of the Guide
o NCHRP 1-37A
o Awarded to ARA: February 1998
o Product Submitted: February 2004
o Cost $7 million Source: http://wwwcf.fhwa.dot.gov/exit.cfm?link=mms://conndot-video.ct.gov/mediapoint/FHWA/john_dangelo.wmv
MEPDG 12
Why MEPDG important?
Several pavement distresses such as fatigue, rutting, cracking reduce pavement life.
These distresses are analyzed in MEPDG
Optimize design and materials to minimize these distresses.
MEPDG 13
Why MEPDG important?, cont.
Design rehabilitation projects
Direct considerations of major factors
o Traffic-Direct consideration of over-weight trucks
o Climate
o Material-Different HMA, PCC, and Aggregate materials
o Support-Foundation and existing pavement
MEPDG 14
Why MEPDG important?, cont.
Compatible with superpave system
Most comprehensive approach for structural design
Provides link between structural design and material properties
Will include method for local calibration
MEPDG 15
AASHTO Design Guide vs. MEPDG
AASHTO Design Guide MEPDG
1. Empirical Methodology 1. Empirical and Mechanistic Methodology
2. Contains 5 inputs for flexible pavements and 10 inputs for rigid pavements, single environment
2. More then 100 total inputs with 35 or more for flexible pavements and 25 or more for PCC, more than 800 weather sites.
3. Depends on extrapolation of empirical relationships
3. No longer be dependence on extrapolation of empirical relationships.
4. Uses identical axle loads and axle configurations.
4. uses mixed traffic.
MEPDG 16
Why we are moving from AASHTO Design Guide to MEPDG
Legislative Mandate
Site specific climate and material properties considerations
o Material properties affected by climate
o PCC joint openings, Curl/Warping
In AASHTO Design Guide, pavement performances are predicted by extrapolating pavement performance from Ottawa, IL whereas in MEPDG pavement performances are predicted from 800 weather sites.
MEPDG 17
Why we are moving from AASHTO Design Guide to MEPDG, cont.
The use of updated “AASHTO Design Guide” produces conservative designs that are not optimally cost effective.
MEPDG incorporates mechanistic methodology along with empirical whereas AASHTO is based on only empirical methodology
AASOTO Design Guide does not provide performance of prediction of pavements (Coree, 2005)
MEPDG 18
Why we are moving from AASHTO Design Guide to MEPDG, cont.
AASHTO Guide cannot handle rehabilitation adequately
AASHTO Guide annot adequately consider all modern design features, materials, loadings
AASHTO Guide is thickness-centric
MEPDG 19
LEGEND
V & D V, Plan, R No Data Available
States MEPDG Implementation Plan
MEPDG 20
Source: http://www.cptechcenter.org/t2/documents/Crawford-MEPDG.pdf
Improvements of MEPDG
MEPDG 21
Predicts transverse cracking, faulting and smoothness for jointed plain concrete pavements, the addition of climate inputs, better characterization of traffic loading inputs, more sophisticated structural modeling capabilities, and the ability to model real-world changes in material properties.
Improvements of MEPDG, cont.
MEPDG 22
Modular system that allows for incremental enhancement
Produces a more reliable design
No longer dependent on the extrapolation of empirical relationships
Excellent for forensic analysis
Calibrate to local materials, traffic, climate..
Improvements of MEPDG, cont.
MEPDG 23
Provide more information about the development of pavement distresses during design life of the pavement.
Utilizes a user friendly software interface.
MEPDG Users
State DOT’s main user
o Pavement Designers
o Upper management
Academia
Industry
Consultant Designers
Designers
MEPDG 24
Future work on MEPDG
Maintain calibration-validation database along with input libraries
Periodically monitor test sections and input parameters and update database
Verify local calibration or agency specific factors for future DARWin-ME versions.
Source:http://www.cptechcenter.org/t2/documents/Crawford-MEPDG.pdf
MEPDG 25
Pavement Design State of the Art
MEPDG 26
AASHTO 93 MEPDG
Empirical Mechanistic
Future
Design
Guide
Questions?
MEPDG 27
