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The Asphalt Pavement Alliance Presents:A Five‐Part Webinar Series On Mechanistic Empirical Pavement Design Guide (MEPDG) Implementation Specific to Asphalt Pavements
The Asphalt Pavement Alliance Presents:A Five‐Part Webinar Series On Mechanistic Empirical Pavement Design Guide (MEPDG) Implementation Specific to Asphalt Pavements
• Today’s Webinar: Part‐1Pavement Design, Where We’ve Come From and What We’re Trying to Accomplish
•Speaker:David Newcomb, Ph.D., P.E.Senior Research Scientist with the Texas Transportation Institute
•Moderator:Mike Kvach, APA
Webinar Protocol:
• Audio Quality
• Headset Recommended
• External Speakers May Cause an Echo / Feedback
• Questions & Answers• Chat Box – Make sure to change the drop‐down
menu to “Organizer Only”
•Recorded Webinars• www.AsphaltFacts.com/webinars/• Click on: “Five‐Part Series on MEPDG
Implementation Specific to Asphalt Pavements”
9/5/2013
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The Asphalt Pavement Alliance Presents:A Five‐Part Webinar Series On Mechanistic Empirical Pavement Design Guide (MEPDG) Implementation Specific to Asphalt Pavements
Part 1: Pavement Design, Where We’ve Come From and What We’re Trying to Accomplish
Part 2: Local Calibration
Part 3: Individual Distress Models
Part 4: Major Inputs – Where Do They Come From & How Do We Get Them?
Part 5: Moving Beyond Data Input (Advanced)
• Speaker:David Newcomb, Ph.D., P.E.Senior Research Scientist with the Texas Transportation Institute
Pavement Design, Where We’ve Come From and What We’re Trying to Accomplish:
Kevin D. Hall, Ph.D., P.E.Professor and Head, Dept. of Civil Engineering
21st Century Leadership Chair in Civil Engineering
Dave Newcomb, Ph.D., P.E.Senior Research Engineer
TTI / Texas A&M University
Asphalt Pavement AllianceSeptember 2013
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Pavement Design: Where We’ve Come From and Where We Are Going
Overview of Pavement‐ME™Sensitivity of Models to Design InputsLocal Calibration: Pavement‐ME™Case Study: New Pavement DesignGetting the Most From Pavement‐ME™
Final Thoughts and Discussion
Dave NewcombTexas A&M Transportation Institute
Asphalt Pavement AllianceAASHTO Pavement M-E Webinar
2013
Pre-20th Century20th Century
• Early Patents• Early Design Approaches• AASHO Road Test
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50 mm (typical) Wearing Course Placed in One Lift (Coarse aggregate 50 to 80% between the ¼” and 3”)
Various Types of Base and Old Pavements
• First successful, reproducible asphalt concrete surfaces
• Maximum aggregate size 75 mm graded down to dust
• F.J. Warren patent issued 1903 (Patent No. 757505)
Warren’s primary patent of 1903—Patent No. 727505 which had the simple title of “Pavement”
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Soil is the important thing.Weather is handled according to local
observations.Pavements are designed for the loads
anticipated.• Airfields• Roads
Most asphalt pavements are:• 2 to 6 inches asphalt• 4 to 8 inches of granular base
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AASHO Road Test
Trucks
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LOOP
3 4 12 12
4 6 18 18
5 6 22 22
6 9 30 30
LANE 2
6 24 24
9 32 32
9 40 40
12 48 48
2 Years = 1.1 Million Applications
LANE 1
0
10”
20”ASPHALT surface
CRUSHED STONE base
SANDY GRAVEL subbase
2 3 4 5 6
0 3 6 9
0 4 8 12 16
MATERIAL THICKNESS
3
6
8
.44
.14
.11
4”
9”
16”
= 1.76
= 1.26
= 1.76
= 4.78
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LOOP 3 4 5 6
AC .44 .44 .47 .33
STONE .16 .14 .14 .11
GRAVEL .11 .11 .11 .11
34
07.8log32.2
1
10944.0
5.12.4log
20.01log36.9log
19.5
018
RR M
SN
PSI
SNSZW
36
•One Set of Materials
•Two Years of Weathering
•1.1 Million Axles
•Totally Empirical
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0
5
10
15
20
25
0.1 1 10 100 1000
HM
A T
hic
kn
ess
, in
.
Traffic, MESAL
AASHTO
PerRoad
Using 1960s performance equations1950s type of loadThin pavement structures (Max. 6” HMA)Meaning of structural coefficientsLimited reliability analysisSome movement to M-E
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Use stresses and strains to design roads, just like buildings.
Beam
Load
Deflection
Strain
Have to know loads, material properties, how pavement responses relate to failure• Loads Same as now – just stop short of ESAL calculation
• Material Properties Need modulus values How modulus changes with season/time
• Pavement responses Requires a model – layered elastic (for now)
• How pavement responses relate to failure Transfer function
Pavement
Beam
Load
Deflection
Strain
Asphalt
Base or Soil
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M-E Design Framework
Model ,
Transfer Function(s)
f
Materials, Layers
Loads
i
i
Nf
nDn
D>1?
D<<1?
Final Design
Traffic Load Spectra
No. Heavy Axles
Data from Traffic
W4 Tables
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Figure 1. Definitions of E and .
D
D/2
l
l
l = l/l
t = D/D
E =
= t / l
• bitumen viscosity (dynamic shear rheometer)
• loading frequency
• air voids
• effective bitumen content
• cum. % retained on 19-mm sieve
• cum. % retained on 9.5-mm sieve
• cum. % retained on 4.76-mm sieve
• % passing the 0.075-mm sieve
log . . . ( ) . .
.. . . . ( ) .
( . ` . log( ) . log( ))
E V
V
V V e
a
beff
beff af
1249937 0 29232 0 001767 0 002841 0 058097
08022083871977 0 0021 0 003958 0 000017 0 005470
1
200 2002
4
4 38 382
340 6033 3 0 313351 0 393532
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Flexible pavements consist of multiple layers Using physical principles, we can calculate stresses
beneath loads
Pa
H1, E1, 1
H2, E2, 2
En, n
zr
t
Horizontal Shear Stress, rz/p
De
pth
, z/a
1.0
Layer 1
Layer 2
0.0
x
Dep
th, z
Tension Compression
Layer 1
Layer 2
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Layer 1HMA
E1
Layer 3Subgrade Soil
E3
h1
h2
No bottom boundary, assume soil goes on infinitely.
Nohorizontalboundary, assumelayersextendinfinitely.
Tire has a total load P, spread over a circulararea with a radius of a, resulting in a contactpressure of p.
PavementReactions
Deflection ()
Tensile Strain (t)
Compressive Strain (v)
Layered Elastic Model Representation of a Pavement.
Layer 2Granular Base
E2
Ho
rizo
nta
l Te
nsi
le S
tra
in (
in./
in.1
0
)
Load Applications (N )f
3
10 10 10 10 10 103 4 5 6 7 8
10
100
1,000
10,000
log N = 15.947 - 3.291 log (––––– ) - 0.854 log (–––– )f t
10-6
E
10
-6
E = 200,000 psi(1,380 MPa)
E = 500,000 psi(3,450 MPa)
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Ver
tical
Co
mp
ress
ive
Str
ain
( in
./in.
10
)
N = 1.077 x 10 (–––)
10 10 10 10 10 103 4 5 6 7 8100
1,000
10,00
100,00
f
-6
4.484310 v
Load Applications (N )
18
f
-6
Asphalt Pavement Alliance - 2001 Design must be done by M-E
• Limiting strains – define criteria for perpetual design• Load spectrum – design for heaviest loads• Material properties – seasonal and long-term changes
M-E based design procedures for Perpetual Pavements• PerRoad• Illinois• Texas FPS-19W• Washington DOT – catalog• AASHTO Pavement M-E (formerly Darwin M-E) (formerly
MEPDG)• CalME?
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Normal Fatigue Testing Results VersusEndurance Limit Testing
0
200
400
600
800
1000
1200
1000 100000 10000000 1.1E+08
Number of Loads to Failure
Stra
in, (
10E
-06)
Endurance Limit
Normal Range forFatigue Testing
0
200
400
600
800
1000
1200
1000 100000 10000000 1.1E+08
Number of Loads to Failure
Stra
in, (
10E
-06)
Endurance Limit
0
200
400
600
800
1000
1200
1000 100000 10000000 1.1E+08
Number of Loads to Failure
Stra
in, (
10E
-06)
Endurance Limit
Normal Range forFatigue Testing
Resources• APA IM-40 – Perpetual Pavements: A Synthesis• TRB: Circular Number 503• SHRP 2: R-23 – Using Existing Pavement In-Place
and Achieving Long Life – Newt Jackson• International Conferences on Perpetual
Pavements
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Inputs – Use Average Inputs – Not Conservative!• Climate – Integrated Climate Model• Traffic - Load Spectrum• Materials – Modulus & Poisson’s Ratio• Reliability – This is the Conservatism
Models - Must Be Calibrated!• Cracking Bottom-Up Top-Down Thermal
• Rutting Any Layer
• Roughness
Output• Distress Development with Time – Example:
Alberta
Modern Materials• Polymer Modifiers• More RAP/RAS• New Mixes
More Efficient Designs• Stop Over-Design (Perpetual Pavement)• Engineer Materials for Pavement Layer
Greater Flexibility to Change• Adjust Models• Heavier Loads