Mechanistic-Empirical Design

Asphalt Institute Method

Mechanistic-Empirical Methodology

StructuralModel

PavementResponse

FailureCriteria

Trial LayerThicknesses

MaterialProperties

ClimateInformation

Final LayerThicknesses

Satisfactory

TrafficInformation

Unsatisfactory

ClimateModel

2

Asphalt Institute Methodology

StructuralModels

PavementResponse

FailureCriteria

Trial LayerThicknesses

MaterialProperties

ClimateInformation

Final LayerThicknesses

Satisfactory

TrafficInformation

Unsatisfactory

ClimateModels

DAMA(LEA)

max asphalt t max subgrade c

Nf (fatigue)Nd (rutting)

hachbs

Eac, Ebs, Esgac, bs, sg

MAAT(°F)

Final LayerThicknesses

ESALS

Freeze/ThawAsphalt Temp

3

Pavement Response

4

Pavement Response

5

h1 , E1 , 1

h2 , E2 , 2

, Esg , sg

h1 , E1 , 1

h2 , E2 , 2

h3 , Egb , gb

, Esg , sg

Pavement Response

6

h1 , E1 ,

h2 , E2 ,

, Esg ,

h1 , E1 ,

h2 , E2 ,

h3 , Egb ,

, Esg ,

Fatigue Failure Criterion

3.291 * 0.854f tN 0.0796 E

AsphaltTensileStrain

AsphaltFatigue

Life

AsphaltResilientModulus

7

Rutting Failure Criterion

4.4779d cN 1.365 10

SubgradeCompressive

Strain

SubgradeFatigue

Life

8

Traffic

fESAL ADT T T D L G 365

9

Climatic Regions

MAAT(ºF)

AsphaltGrades

Viscosity, (at 70ºF)

FrostEffects

45 AC-5, AC-10 600,000 Yes60 AC-10, AC-20 1,600,000 Possible75 AC-40 5,000,000 No

10

Mean Monthly Air Temperatures

Jan 45˚F May 56˚F Sept 78˚FFeb 38˚F Jun 70˚F Oct 73˚FMar 43˚F Jul 78˚F Nov 58˚FApr 45˚F Aug 81˚F Dec 54˚F

South Carolina (MAAT = 60°F)

11

Pavement Temperatures

-5

0

5

10

15

20

25

30

35

40

08/01/97 08/01/98 08/01/99 08/01/00 08/01/01

Tem

pera

ture

(C)

AsphaltAir

12

Pavement Temperature

1 341 64 4p aM M

z z

Mean monthlyair temperature (˚F)

Mean monthlyasphalt temp. (˚F) Depth (in)

13

Asphalt Modulus

3 7

9 10 13

*1 2 200 4 5 6

log0.58 11 12

log c ca

c c f cb

E c c P f c V c c f

c V T c c f

Vol. aircontent %

Asphaltviscosity

% passing#200 sieve

Vol. bindercontent (%)

Asphalttemp.

Loadingfreq.

14

Unbound Base Modulus

Source: WSDOT Pavement Guide Interactive CD-ROM

21 K

RM K

15

Unbound Base Modulus

0.471 0.041 0.139 0.287 0.8682 1 2 1 3 110.447E h h E E K

AsphaltThickness

EffectiveModulus

BaseThickness

AsphaltModulus

SubgradeModulus

16

Unbound Base Modulus

3 33

1

s s b b

s b

h E h EEh h

s = surface courseb = binder course

17

Subgrade Modulus

18

Subgrade Modulus2 Months 4 Months 5 Months1

January January

50,000 psi

4,000 psi12,000 psi22,500 psi

1,350 psi7,200 psi

18,000 psi

South Carolina(60°F MAAT)

19

Asphalt Institute Method

20

21

Asphalt Institute Method

22

23

24

Asphalt Institute Method

25

26

Stage 1

27

Stage 2

28

Unstaged