Thickness Design

1972 AASHTO Method

CIVL 3137 3

AASHO Road Test

CIVL 3137 4

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 5

AASHO Road Test

Source: http://www.fhwa.dot.gov

CIVL 3137 6

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 7

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 8

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 9

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 10

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM

CIVL 3137 11

AASHO Road Test

Source: http://www.fhwa.dot.gov

CIVL 3137 12

AASHTO Design Equation

LifetimeESALs

SubgradeSupport

Ride QualityThreshold

Structural Number(Flexural Rigidity)

t

10

10 18 10 i

5.19

4.2 plog14.2 1.5log W 9.36log SN 1 0.20 log 0.372 S 3.01094 R0.4

SN 1

RegionalFactor

1966

CIVL 3137 13

AASHTO Design Equation

LifetimeESALs

SubgradeSupport

Ride QualityThreshold

Structural Number(Flexural Rigidity)

t

10

10 18 10 i

5.19

4.2 plog14.2 1.5log W 9.36log SN 1 0.20 log 0.372 S 3.01094 R0.4

SN 1

RegionalFactor

1972

CIVL 3137 14

Ride Quality Threshold (pt)

Very good

Good

Fair

5

4

3

2

1

0

PSI

ESALS

Limit for Low-Volume Roads

Limit for High-Volume Roads

Failure

4.2

1.5 Poor

Very poor

CIVL 3137 15

Regional Factor (R)

Condition R value

Roadbed materials frozen to a depth of 5 in. or more (winter)

Roadbed materials dry (summer and fall)

Roadbed materials wet (spring thaw)

0.2 – 1.0

0.5 – 1.5

4.0 – 5.0

CIVL 3137 16

Regional Factor (R)

CIVL 3137 17

Soil Support Value (S)

CIVL 3137 18

AASHTO Design Equation

LifetimeESALs

SubgradeSupport

Ride QualityThreshold

Structural Number(Flexural Rigidity)

t

10

10 18 10 i

5.19

4.2 plog14.2 1.5log W 9.36log SN 1 0.20 log 0.372 S 3.01094 R0.4

SN 1

RegionalFactor

1972

AASHTO Design Nomograph

CIVL 3137 19

CAREFUL!

20-year Lifept = 2.5 only

CIVL 3137 24

AASHTO Pavement Design

Subbase

Base

Asphalt

D2

D3

D1

Source: NCEES FE Supplied Reference Handbook

AASHTO Layer Coefficients

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AASHTO Layer Coefficients

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AASHTO Layer Coefficients

CIVL 3137 27

CIVL 3137 28

Pavement Design

Sandy GravelSubbase

Crushed StoneBase

Dense-GradedPlantmix Asphalt

10"

12"

5"

SN = ??

CIVL 3137 29

Pavement Design

SandSubbase

Crushed StoneBase

Dense-GradedPlantmix Asphalt

6"

8"

?

SN = 2.7

CIVL 3137 30

AASHTO Design Equation

t

10

10 18 10 10 R

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN 1

LifetimeESALs

Seasonally AdjustedSubgrade Support

Ride QualityThreshold

Structural Number(Flexural Rigidity)

1986

CIVL 3137 31

AASHTO Design Equation

LifetimeESALs

Seasonally AdjustedSubgrade Support

Ride QualityThreshold

Structural Number(Flexural Rigidity)

1993

t

10

10 18 10 10 R

5. 9

0

1

R

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN

Z S

1

DesignReliability

CIVL 3137 36