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S1D2_0830_David_Timm.. - Aapaq.org

What is a Perpetual Pavement

• No deep structural distress


Limit Cracking

to top-down


Goal of Perpetual Pavement Design

• Design so there are no deep structural distresses

– Bottom up fatigue cracking

– Structural rutting

• All distresses can be quickly remedied from surface

• Result in a structure with ‘Perpetual’ or ‘Long Life’


Do Perpetual Pavements Exist

• Perpetual Pavements are NOT a new concept

– Full-depth

– Mill and inlay

– Deep strength

• Perpetual Pavement Award

– 35+ years

– No structural failures

– 13+ year rehab interval


Designing Perpetual Pavements

Newcomb, 2001


M-E Perpetual Pavement Design

P

Log e

A

Threshold

Strain

e t

D 1

E 1

D 2

E 2

Log N

e v

No Damage Accumulation

D 3

E 3


Strain, (10E-06)

1200

1000

800

600

400

200

0

Normal Range for

Fatigue Testing

Endurance Limit

1000 100000 10000000 1.1E+08

Number of Loads to Failure

Normal Fatigue Testing Results Versus

Endurance Limit Testing


What is the Endurance Limit for HMA

• 1972 – Monismith estimates about 70 me

• 2001 – I-710 designed at 70 me

• 2002 – 70 me used by APA

• 2007 – NCHRP 9-38 Lab Study

– 100 me for unmod binders

– 250 me for mod binders

– More severe than field

• 2007 – MEPDG uses 100 to 250 me

• 2008 – Field measurements show higher

strains


N8 and N9

0.0

Lift 1

N8

Section

SMA

N9

2.3 PG 76-28

2.0

Lift 1

Depth From Pavement Surface, in.

5.0

10.0

15.0

20.0

25.0

Lift 2

Lift 3

Lift 4

2.9 PG 76-28

3.5

2.8

1.9

6.4

Dense Graded HMA

250 mm 350 mm

Moisture Content = 10.8%

Unit Weight = 133.4 pcf

Moisture Content = 18.0%

Unit Weight = 126.2 pcf

Dense Graded HMA

PG 64-22

Rich Bottom Layer

PG 64-22

Aggregate Base

(Track Fill)

Subgrade

(A-7-6 Soil)

3.1

2.6

3.2

8.4

Moisture Content = 12.9%

Unit Weight = 133.8 pcf

Moisture Content = 17.2%

Unit Weight = 126.9 pcf

Lift 2

Lift 3

Lift 4

Lift 5


Strain Measurements


Strain and Temperature

1200

120

Longitudinal Microstrain-Single Axle

1000

800

600

400

200

N8-Temperature

N9-Temperature

N8-Strain

0

01-Nov-06

31-Dec-06

01-Mar-07

30-Apr-07

29-Jun-07

28-Aug-07

27-Oct-07

26-Dec-07

24-Feb-08

24-Apr-08

100

80

60

40

20

Mid-Depth Pavement Temperature,F

N9-Strain

0

Date


Strain vs. Temperature

1200

Longitudinal Microstrain-Single Axle

1000

800

600

400

200

0

Section Axle Type C 1

C 2

R 2

Single 21.249 0.033 0.96

N8 Tandem 15.326 0.035 0.96

Steer 11.341 0.036 0.87

Single 11.136 0.029 0.93

N9 Tandem 8.600 0.030 0.92

Steer 5.901 0.030 0.93

N8 Strain = 21.249e 0.033*Temp

R 2 = 0.9584

N9 Strain = 11.136e 0.0293*Temp

R 2 = 0.9309

0 20 40 60 80 100 120 140

Mid-Depth Pavement Temperature, F


Strain Distributions

100%

90%

80%

70%

N9

N8

Percentile

60%

50%

40%

30%

20%

10%

0%

0 100 200 300 400 500 600 700 800 900 1000 1100 1200

Longitudinal Strain


End Result


NCAT Test Track Results

Percentile

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

No Fatigue

Fatigue

0 200 400 600 800 1000 1200

N1 2003

N2 2003

N3 2003

N4 2003

N5 2003

N6 2003

N7 2003

N1 2006

N2 2006

N3 2006

N4 2006

N8 2006

N9 2006

N10 2006

S11 2006

S13 2000

Microstrain


2003 Test Sections

4.5

4.0

3.5

Fatigue Cracking Occurred

Fatigue Ratio

3.0

2.5

2.0

1.5

1.0

0.5

Fatigue Cracking Absent

Max Ratio = 2.11

0.0

N1 2003 N2 2003 N3 2003 N4 2003 N5 2003 N6 2003 N7 2003

Section


2006 Test Sections

6

5

4

Fatigue Cracking Occurred

Fatigue Ratio

3

2

1

Fatigue Cracking Absent

Max. Ratio = 2.18

0

N1 2006 N2 2006 N3 2006 N4 2006 N8 2006 N9 2006 N10 2006 S11 2006

Section


Probabilistic Design – Monte Carlo Simulation

f

Axle Weight

f

Monte

Carlo

Random

Sampling

Mechanistic

Model

f

Material Properties

f

% Below Threshold

% Above Threshold

Thickness

Pavement Response


% Below Threshold

• Design should have high % below

threshold

f

% Below Threshold

How much

‘damage’ does this

area correspond to

Pavement Response


‘Damage Computation’

• For responses exceeding threshold, compute N

using transfer function

– User defined

• Calculate damage accumulation rate

– Damage / Maxles

f

% Below Threshold

Damage

Million Axles

Pavement Response


Estimated Long Life

• Convert damage rate into an estimated

time

– Use traffic volume and growth

– Calculate when damage = 0.1


PerRoad 3.5

• Sponsored by APA

• Developed at Auburn University / NCAT

• M-E Perpetual Pavement Design and Analysis Tool


f

Material Properties

f

Thickness


Performance Criteria


Traffic Volume

Types of Axles


Functional Classification


PerRoadXPress – For Low Volume Roads


Methodology - Overview

• Develop a set of boundary conditions

• Execute PerRoad analysis to determine

required thickness for each “design”

• Develop design regression equations

• Guiding Principles

– Limit number of required inputs

– Make design procedure simple/efficient


Structural Cross Section

Layer Stiffness

Poisson’s Ratio

HMA

400,000 to 1,000,000 psi

0.35

Variable

Aggregate Base

20,000 psi

0.40

0-10 in.

10,000 psi to 30,000 psi

Subgrade Soil

0.45

Infinite


Number of Simulations

# Simulations =

X

X

X

X

X

X

2 Highway Classifications

3 Traffic Volumes

3 Growth Rates

4 Percent Trucks

3 Soil Stiffnesses

3 HMA Stiffnesses

3 Base Thicknesses

1,944 Pavement Designs


Design Equation

HMA = C 0 + C 1 *AADT + C 2 *%Trucks +

C 3 *%Growth + C 4 *Soil Stiffness +

C 5 *Base Thickness + C 6 *HMA Stiffness


PerRoad

XPress

Traffic

Soil

Agg. Base

HMA


http://www.eng.auburn.edu/users/timmdav/Software.html

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