10 - aashto design equation (flexible) (2015) - aashto design equation... · the current ability of...

Pavement Performance

AASHO Road Test

Source: Highway Research Board Special Report 732

AASHO Road Test

Source: WSDOT Pavement Guide Interactive CD-ROM 3

AASHO Road Test

Source: http://www.fhwa.dot.gov 4

AASHO Road Test


Present Serviceability Rating

“The judgment of an observer as to the current ability of a pavement to serve the traffic it is meant to serve”

10

Present Serviceability Rating

11

Acceptable Ride Quality

PSR Acceptable?

3.0 88%

2.5 45%

2.0 15%

12

Measuring Roughness

Straightedge

Slope Profilometer

CHLOE Profilometer

13

CHLOE Profilometer

Source: State Library and Archives of Florida14

Slope Variance

22

6

1S SnSV 10

n 1

S = slope (radians)

15

Flexible Pavements

16

Rigid Pavements

17

Rut Depth

Source: www.halifax.ca/Works/AsphaltDefectGuide.html18

Flexible Pavements

19

Cracking

Source: www.asphaltrescue.com20

Patching

Source: www.asphaltrescue.com21

Flexible Pavements

22

Rigid Pavements

23

Present Serviceability Index

PC01.0RD38.1SV1log9.103.5PSI 2

PC09.0SV1log8.141.5PSI

Flexible Pavements

Rigid Pavements

24


Very good

Good

Fair

Poor

Very poor

5

4

3

2

1

0

PSI

ESALS (log scale)

Limit for Low-Volume Roads

Limit for High-Volume Roads

25


5

4

3

2

1

0

PSI

ESALS (log scale)

Acceptability Limit

75% Time

40%Drop

40%Drop

12% Time

Each $1 spent onmaintenance here

Ends up costing $4if delayed to here

26


5

4

3

2

1

0

PSI

ESALS (log scale)

Acceptability Limit

27

AASHTO Design Equation

(Flexible Pavements)


Wp 4.2 4.2 1.5

InitialConstruction

failure

4.2

1.5

W 29

p


Wt

terminal serviceability

tt 4.2 4.2 1.5 Wp

pt

InitialConstruction

failure

4.2

1.5

30

Flexible Performance

9.365.93 4.33

9.364.7918

10 1 1 0.64 118 1

SN SN

3.23

5.19 518 .193.23

0.081 18 1 10940.4 0.41 1 1

SN SN

31


Wt

terminal serviceabilitypt

InitialConstruction

failure

4.2

1.5

5.1910940.4

SN 118

9.t 36Wp 4

0..2

64.2 1.5

4 SN 1

32


Wt


InitialConstruction

failure

4.2

1.5

5.19

10940.4SN 1

t 189.36

4.2 p W4.2 1.5 0.64 SN 1

33


Wt


InitialConstruction

failure

4.2

1.5

t 18

10 105.19 9.364.2 p 1094 Wlog 0.4 log4.2 1.5 SN 1 0.64 SN 1

34


Wt


InitialConstruction

failure

4.2

1.5

t10

1810 9.36

5.19

4.2 plogW 4.2 1.5log 10940.64 SN 1 0.4

SN 1

35


Wt


InitialConstruction

failure

4.2

1.5

t10

9.3610 18 10

5.19

4.2 plog4.2 1.5log W log 0.64 SN 1 10940.4SN 1

36


Wt


InitialConstruction

failure

4.2

1.5

t10

10 18 10

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.4SN 1

37


t10

10 18 10

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.4SN 1

1966

38

AASHO Road Test

Average Mean Temperature (July) 24.5°C (76oF)

Average Mean Temperature (January) -2.8°C (27oF)

Annual Average Rainfall 837 mm (34 in)

Average Depth of Frost (for fine-grained soil) 711 mm (28 in)

Climate

39

AASHO Road Test

Soil Classification A-6

Percent Passing a #200 Sieve 82%

Liquid Limit 31%

Plasticity Index 16%

Average Degree of Saturation 85%

Average CBR 2.9

Subgrade

40


1972

t

10

10 18 10

5

i

.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.

1log 0.372 S 3.

S 1

0R4

N

41

SubgradeSupportFactor

RegionalClimateFactor

Regional Factor

42

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

Regional Factor

43

Soil Support Value

44


1986

10

t10

10 18 10

5.19

R

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.4S

2.32log M 8.07

N 1

45

SeasonallyAdjustedResilientModulus

Design Equation

18 TW w

PredictedTrafficLevels

PredictedPavement

Life

46

Design Equation

810 101log log TW w


PredictedPavement

Life

47

Predicted Pavement Life

t

10

10 10 10 R

5.19

T

4.2 plog4.2 1.5log 9.36log 1 0.20 2.32log M 8.071S 0940.4

1

N

SN

w

48

Reliability

Design Equation w/ FS

18 RTw FW


PredictedPavement

Life

Factorof

Safety

50

Design Equation w/ FS

10 10 10log log logTt RW w F


PredictedPavement

Life

Factorof

Safety

51

Reliability

wT Wt


PredictedPavement

Life

log10FR

52

Reliability

wT Wt


PredictedPavement

Life

log10FR

53

Reliability

wT Wt


PredictedPavement

Life

log10FR

54

Reliability

wT Wt


PredictedPavement

Life

55

Reliability

2 2 2o w nS S S

log10FR =

56

Reliability

2 2 2o w nS S S

P(fail)

log10FR =

57

Reliability

wT Wt

ZRSo

P(fail)


PredictedPavement

Life

log10Wt log10Wt 58

Design Equation

R 0

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.SN 1

Z S4

1993

59

Reliability

Recommended Reliability

Functional Classification Urban Rural

Interstate and Other Freeways 85 – 99.9% 80 – 99.9%

Principal Arterials 80 – 99% 75 – 99%

Collectors 80 – 95% 75 – 95%

Local 50 – 80% 50 – 80%

60

ReliabilityReliability

(%) ZRReliability

(%) ZR

50 -0.000 93 -1.476

60 -0.253 94 -1.555

70 -0.524 95 -1.645

75 -0.674 96 -1.751

80 -0.841 97 -1.881

85 -1.037 98 -2.054

90 -1.282 99 -2.327

91 -1.340 99.9 -3.090

92 -1.405 99.99 -3.75061

Standard Deviations

Source Flexible Rigid

AASHO Road Test Sn 0.35 0.25

AASHO Road Test So 0.45 0.35

Typical Range for So 0.40 – 0.50 0.35 – 0.40

62

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