updates on mechanistic empirical pavement design guide mepdg
TRANSCRIPT
Updates onMechanistic Empirical Pavement Design Guide(MEPDG)
H. Thomas Yu, P.E.Federal Highway Administration
Office of Pavement TechnologyDesign and Analysis Team
WHAT IS MEPDG
Product of NCHRP 1-37A Started as NCHRP 1-37 (1996) – Development of the
2002 Guide for the Design of New and Rehabilitated Pavement Structures
NCHRP 1-37A was awarded in 1998
Evolution of name 2002 Guide 200X Guide 20XX Guide? MEPDG
The Big Picture
Climate Inputs
EICM
Material Properties
Transfer Functions
Predicted Performance Mechanistic Analysis
Traffic
The E in MEPDG
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1 10 100
Fatigue damage
Per
cen
t sl
abs
crac
ked Best-fit curve
E = mc2
MEPDGAASHTO 93
Pavement Design State of the Art
Empirical Mechanistic
Example 2,300-year-old empirical-design section
50-year-old modern pavement section
Reasons for switching to MEPDG
Legislative Mandate AASHTO design produces excessively thick
pavements for high-volume roads Design traffic is often well beyond the road test
traffic (1.1 million load applications) New materials are very difficult to relate back to
road test for layer coefficient
Climatic effects are not considered
Reasons for switching to MEPDG
“You have to ask yourself: Is it better than what we currently have?”
– John D’Angelo
FHWA Survey Results
42%
80%
0%
10%
20%
30%
40%
50%
60%
70%
80%
2003-42% Yes
2007-80% Yes
Does your state have an (MEPDG) Implementation Plan?
What’s Being Used (2007 survey)
How does the actual performance compare to design life?
12%
45%
10%
33%
More than design life
Similar to design life
Less than design life
Don't Know
Implementation Timeframe
Many DOT’s Already Underway Others are Awaiting Other Efforts:
NCHRP Projects FHWA Research Projects Copy Other State Approaches AASHTO Adoption Release of DARWin- ME Hell Freezes Over
Hawaii
Alaska
Timeframe for Implementation
Using 2
Hawaii
Alaska
Timeframe for Implementation
Using 2
1 – 3 yrs 17
Hawaii
Alaska
Does SHA Use or Plan to Use MEPDG?
N0 -12
YES - 40
Perspective
Current AASHTO Design Procedure 1960 – Completion of Road Test Experiment 1961-62 AASHO Interim Guide 1972 AASHTO Interim Guide for the Design of
Pavements 1981 Revised Chapter III on PCC Pavement Design 1986 Guide for the Design of Pavement
Structures 1993 Revised Overlay Design Procedures 1998 Supplement to Concrete Design Procedures
MEPDG NCHRP 1-37A completed in 2004 and software
released 2 States are using MEPDG and 17 plan to
implement within 3 yrs
DARWin ME Timeline
Intellectual rights transferred from NCHRP to AASHTO in December 2007 MEPDG referred as DARWin-ME v1.0 ARA appointed to provide support
Solicitation package finalized in July 2008 DARWin-ME Task Force was appointed in
February 2009 Contract sole-sourced to ARA
Development stared in March 2009 Development will take 15-18 month
Traffic input
Number of axles by:
• Axle type• Truck type• Axle load interval
Traffic inputs
Screen Inputs
Traffic growth
Traffic growth
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
Month of the Year
Urban CarsRural CarsRural Combination TrucksRural Single Unit Trucks
Seasonal traffic volume variation
Monthly adjustment factors
0.00%
1.00%
2.00%
3.00%
4.00%
5.00%
6.00%
7.00%
8.00%
9.00%
Hour of Day
Rural Cars
Business Day Trucks
Through Trucks
Urban Cars
Time of Day Truck Volume Variation
Hourly traffic distribution
Vehicle Class Distribution
13 FHWA Classifications Only concerned with trucks
Number of axles per truck
0
2
4
6
8
10
12
14
16
18
20
Axle load, lbs
Freq
uenc
y, %
Class 9 (Single Trailer)
Class 5 (Single Units Trucks)
Normalized axle load distribution
Vehicle Weight
0
2
4
6
8
10
12
14
3,00
05,
000
7,00
09,
000
11,0
00
13,0
00
15,0
00
17,0
00
19,0
00
21,0
00
23,0
00
25,0
00
27,0
00
29,0
00
31,0
00
33,0
00
35,0
00
37,0
00
39,0
00
41,0
00
Axle Weight, lbs
Dis
trib
uti
on
, %Axle load distribution – single axles
0
2
4
6
8
10
12
14
6,00
0
10,0
00
14,0
00
18,0
00
22,0
00
26,0
00
30,0
00
34,0
00
38,0
00
42,0
00
46,0
00
50,0
00
54,0
00
58,0
00
62,0
00
66,0
00
70,0
00
74,0
00
78,0
00
82,0
00
Axle Weight, lbs
Dis
trib
uti
on
, %Axle load distribution – tandem axles
MEPDG Input screen
Axle Configuration Parameters
Axle Width
Dual Tire Spacing
Axle Spacin
g
Tire Pressure
Wheel Base
Tube counters
Weigh in Motion Station
Data Collection Framework
MONITORING SITESMONITORING SITES
Continuous CountsShort Term Counts
VOLUME COUNTS
50 5051
48 H
r Vo
lum
es
48 H
r Vol
umes
and
Cla
ssifi
catio
n
2452299
Vehicle Classification (CVC)
31
Truck Weight (WIM)
$$$
$
365 days
Tandem axle load distribution – national ave.
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
Dis
trib
uti
on
14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Tandem axle load, kips
Overweights4.7% of total traffic
Effects of axle weight
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Tandem axle load, kips
Rem
ain
ing
Tra
ffic
, %
0%
1%
2%
3%
4%
5%
6%
7%
8%
Dam
age
Co
ntr
ibu
tio
n,
%
< 5% of traffic> 80% of total damage
Damage vs. axle weight
34k to 40k7%
> 40k5%
< 34k88%
Traffic distribution Damage distribution
34k to 40k17%
> 40k58%
< 34k25%
Effects of traffic wander and heavy loads
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
18 12 6 0
Mean wheel location, in from free edge
Rel
ativ
e am
ou
nt
of
crac
kin
g Default axle-load distribution
No heavy overloads
