Pavement Structure

Chapter 5

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Life without Pavements

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Pavement Types

Flexible

Rigid

Load Distribution

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Rigid Pavements

“Simply supported beam”

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Rigid Pavements

“Beam on elastic foundation”

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Rigid Pavements

Source: WSDOT Pavement Guide Interactive CD-ROM

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Rigid Pavement Structure

Source: WSDOT Pavement Guide Interactive CD-ROM

Compacted Subgrade

Natural Subgrade

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Flexible Pavements

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Flexible Pavements

Source: WSDOT Pavement Guide Interactive CD-ROM

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Flexible Pavement Structure

Source: WSDOT Pavement Guide Interactive CD-ROM

Compacted Subgrade

Natural Subgrade

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Pavement Design Factors

Changes over Time

Subgrade Support ProvidedSeasonal Changes in Subgrade Support

Magnitude of Wheel Loads

Wheel Loads Applied to Pavement

Type of Wheel Loads (Single or Tandem Axles)

Number of Wheel Load Applications

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FHWA Vehicle Classes

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Damage Factors

1MM

dN

Curb weight = 2300 lb

Mazda Miata

1FF

dN

Curb weight = 6300 lb

Ford Excursion

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“Standard” Vehicle

1SS

dN

Curb weight = 4000 lb

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Equivalency Factors

MM

S

Mazda MiatadFd

FF

S

Ford ExcursiondFd

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Typical Axle Loads

12,000 32,000 32,000

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“Standard” Axle

Single Axle, Dual Wheels

9000 lb

9000 lb

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AASHTO Equivalency Factors

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Weigh Station

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Axle Load Histogram

0

50

100

150

200

250

6000-11999

12000-17999

18000-23999

24000-29999

30000-31999

32000-33999

34000-35999

36000-37999

38000-39999

40000-41999

Tandem Axle Load (lbs)

Freq

uenc

y

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Equivalent Single Axle Loads

12,000 32,000 32,000

ESAL = ??

FHWA Truck ClassesClass Type EALF1 Motorcycles negligible2 Passenger Cars negligible3 Other Two-Axle, Four-Tire Single Unit Vehicles negligible4 Buses 0.575 Two-Axle, Six-Tire, Single Unit Trucks 0.266 Three-Axle Single Unit Trucks 0.427 Four or More Axle Single Unit Trucks 0.428 Four or Less Axle Single Trailer Trucks 0.309 Five-Axle Single Trailer Trucks 1.2010 Six or More Axle Single Trailer Trucks 0.9311 Five or Less Axle Multi-Trailer Trucks 0.8212 Six-Axle Multi-Trailer Trucks 1.0613 Seven or More Axle Multi-Trailer Trucks 1.39