MEPDG Presentation - The University of Toledo - Engineering ...

By American Structurepoint, Inc.
Cash Canfield, PE ccanfield@structurepoint.com
Jason Koch, PE jkoch@structurepoint.com
614-901-2235

What is MEPDG?
Mechanistic-Empirical Pavement Design
Guide by AASHTO
Pavement analysis tool that uses project
specific traffic, climate, and materials data for
estimating damage accumulation over a
specified pavement service life
Design process based on predictive
performance of a pavement section designed
to predefined parameters identified as failing

Why use MEPDG?
FHWA considers implementation of MEPDG a high
priority as a critical element in improving the National
Highway System
Existing design procedures based upon 1950’s
AASHO Road Test and use empirical relationships
Current pavement designs often exceed the data
limits and conditions used in the AASHO Road Test
MEPDG provides a more realistic characterization of
in-service pavements and provides uniform
guidelines for designing in-common features of all
pavement types

AASHTO DARWin Method
“Required” Structural Number ≤ “Design” Structural Number
Inputs
1. Design life (analysis period)
2. Traffic (ESAL’s)
3. Foundation stiffness (M r or
CBR)
4. Performance criteria (ΔPSI)
5. Reliability (Z R and S o)
Output
1. Required Structural Number
≤
Inputs
1. Structural Layer Coefficients
2. Drainage Factor
3. Layer Thickness
Output
1. Design Structural Number

AASHTO DARWin Method
“Required” Structural Number ≤ “Design” Structural Number
(structural coefficient)
(drainage coefficient)

AASHTO DARWin Method
Benefits of Use
Quick calculation
Data requirements
Universal use
Drawbacks of Use
Not calibrated for
regional use
Climatic
Materials
Traffic
Layer Coefficients
Pass/Fail
Empirical design from one test track (Ottawa, IL) in the 1950’s

MEPDG Method
Climate
Response
Materials
Damage
Time
Damage
Accumulation
Structure
Traffic
Distress

MEPDG Overview
Mechanistic design – finite element analysis
Research grade software
Local calibration is the key
Does not “output” a design – your design is an
“input” for analysis
Expandable to new materials
Narrowing down design life deviations

MEPDG Overview
User Interface
General Inputs
Requirements from Designers
Inputs provided by INDOT
Traffic Inputs
Requirements from Designers
Inputs provided by INDOT
Climatic Inputs
Material Inputs
Requirements from Designers
Inputs provided by INDOT
Performance Criteria
Requirements from Designers
Inputs provided by INDOT
Outputs

MEPDG “Dashboard”

Inputs from Designer - General
Design life
expectancy
Critical milestones
Month of subbase
construction
Month of pavement
construction
Month that the road is
opened to traffic
Type of Design
◦ New pavement
◦ Restoration of JPCP
◦ Overlay (HMA or PCC)
Desired pavement type
◦ Flexible (HMA)
◦ Jointed Plain Concrete
Pavement (JPCP)
◦ Continuously Reinforced
Concrete Pavement (CRCP)

Inputs from INDOT - General
INDOT Design Life Expectancy
INDOT Traffic Groups
INDOT Assumed Milestones
Base/Subgrade Construction Month: May
Pavement Construction Month: July
Traffic Open Month: September

Inputs from Designer - Traffic
Roadway classification
Truck traffic data – AADTT (current, future, & growth rate)
Determination of Traffic Group (A, B, C, or D)
Traffic direction (north/south or east/west)
No. of lanes in design direction
Determination of % trucks in design direction
Determination of % trucks in design lane
Posted Speed (not design speed)

INDOT Inputs - Traffic
% Trucks in Design Lane
% Trucks in Design Direction
* Based on statewide WIM data
Bottom Line: Lots of data
collection & analysis by INDOT

Inputs from Designer - Climate
Project location (latitude, longitude & elevation)
Annual Average Water Table Depth
LTPP Weather Stations

Inputs from Designer - Materials
Soil Resilient Modulus (M R) –
NOT CBR
Untreated Subgrade – “Virgin”
Material
Treated Subgrade
AASHTO Soil Classification
FWD (Falling Weight
Deflectometer) Testing if
Structural Resurface
Modulus of Subgrade Reaction
(“k” value)
Subgrade Treatment Type
Underdrain Requirement
Initial Pavement Design

Inputs from Designer - Materials
Typical Sections - PCCP
Fig. 52-13F: PCCP Section with PCCP Shoulder
Fig. 52-13G: PCCP Section with HMA Shoulder

Inputs from Designer - Materials
Typical Sections - HMA
Fig. 52-13A: Full Depth HMA with Full Depth Shoulder
Fig. 52-13B: Full Depth HMA with Composite Shoulder

Inputs from INDOT - Materials
Subgrade Treatment as Determined by Geotechnical Engineer
Type I
14” of chemical soil modification, or
12” of subgrade excavated and
replaced with C.A. #53, or
24” of soil compacted to density and
moisture requirements
Type IA
14” of chemical soil modification, or
12” of subgrade excavated and
replaced with C.A. #53
Type IB
14” of chemical soil modification
Type IC
12” of subgrade excavated and
replaced with C.A. #53
Type II
8” of chemical soil modification, or
6” of subgrade excavated and
replaced with C.A. #53, or
12” of soil compacted to density and
moisture requirements
Type IIA
8” of chemical soil modification, or
6” of subgrade excavated and
replaced with C.A. #53
Type III
6” of soil compacted to density and
moisture requirements, or
6” of subgrade excavated and
replaced with C.A. #53
Type IIIA
6” of subgrade excavated and
replaced with C.A. #53
Type IV
9” of subgrade excavated and
replaced with C.A. #53 on geogrid

Inputs from INDOT - Materials
In DARWin, the strength value (resilient modulus) of Subgrade
Treatment and Subbase for PCCP were ignored
o Only CBR of “virgin soil” used
In MEPDG, subgrade & subbase are assigned strength values
◦ Chemical soil modification
◦ Compacted soil
◦ C.A. #53
◦ Virgin soil
◦ Subbase for PCCP
Subbase for PCCP
◦ 3” of #8’s for Drainage Layer (25,000 psi)
◦ 6” of #53’s for Separation Layer (30,000 psi)

Inputs from INDOT - Performance
HMA Criteria PCCP Criteria

HMA Performance Criteria
INDOT Criteria
Terminal Roughness (IRI)
Bottom-up Cracking / Alligator Cracking (Fig. 1)
Permanent Deformation – Rutting (Fig. 2)
Thermal Fracture (Fig. 3)
Dependant on Classification & Reliability
Fig. 1: Alligator Cracking Fig. 2: Rutting Fig. 3: Thermal Fracture

PCCP Performance Criteria
INDOT Criteria
Terminal Roughness (IRI)
Transverse Slab Cracking (Fig. 4)
Mean Joint Faulting (Fig. 5)
Dependant on Classification & Reliability
Fig. 4: Transverse Slab Cracking Fig. 5: Mean Joint Faulting

MEPDG Output