Part 1 Pavement Design - Asphalt Facts

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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


• 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”

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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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No Escalation Clause for Labor Rates!

Layered Pavement with Drainage

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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

29

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

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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


Stra

in, (

10E

-06)

Endurance Limit

0

200

400

600

800

1000

1200

1000 100000 10000000 1.1E+08


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

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Thank You!

Part 2: Local Calibration

Next Webinar: Thursday, September 5th

Register at: AsphaltFACTS.com/webinars

Documents

Part 1 Pavement Design - Asphalt Facts