ESALCalculations.pdf

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Roadway  and  Pavement  Design  

References:  AASHTO  Guide  for  Design  of  Pavement  Structures,  1993      Huang’s  Pavement  Analysis  and  Design,  1993      

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m  =  number  of  axle  load  groups  F  =  the  equivalent  axle  load  factor  (EALF)  for  the  ith          axle  load  group  n  =  the  number  of  passes  of  the  ith  axle  load  group  during  the  design  period  

Class Description

1 Motorcycles (optional) 2 Passenger Cars 3 Other Two-Axle, Four Tire Single Unit Vehicles 4 Buses 5 Two-Axle, Six Tire, Single Unit Trucks 6 Three-Axle Single Unit Trucks 7 Four or More Axle Single Unit Trucks 8 Four or Less Axle Single Trailer Trucks 9 Five-Axle Single Trailer Trucks

10 Six or More Axle Single Trailer Trucks 11 Five or Less Axle Multi-Trailer Trucks 12 Six-Axle Multi-Trailer Trucks 13 Seven or More Axle Multi-Trailer Trucks

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80  kN  18,000  lb  

100  kN  22,000  lb  

18  kN  4,000  lb  

1  ESAL  

2.2  ESAL  

.002  ESAL  

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160  kN  36,000  lb  

Tandem  Axle  

160  kN  36,000  lb  Single  Axle  

1.38  ESAL   13.93  ESAL  

67  kN  15,000  lb  0.48  ESAL  

27  kN  6,000  lb  

0.01  ESAL  +   =  

151  kN  34,000  lb  

1.10  

151  kN  34,000  lb  

1.10  

+ =  54  kN  

12,000  lb  0.19  

+  

0.49  ESAL  

2.39  ESAL  

BIG  TRUCK  

Little  Truck  

Pavement  Type   Single  Unit   Multiple  Unit  

Flexible   0.600   1.300  

Rigid   0.900   2.000  

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  We  need  to  know:    Average  daily  traffic  (ADT)    Average  daily  truck  traffic  (ADTT)    Traffic  mixture  (number  of  vehicles  in  each  class)  

  Average  weight  of  the  vehicles  in  each  class  

  Given:  ADT  =  3500  VPD,  Class  9  –  30%,  Class  5  –  5%  

  Use  the  ESAL  data  from  earlier  slide  

ESALo  =  [(0.49)(0.05)  +  (2.39)(0.30)](3500)(365)    

     ESALo  =  947,266  

  Initial  traffic  in  two  directions   Must  correct  for  one  direction    Usually  a  factor  of  0.5  is  used    This  can  vary  depending  on  the  traffic  

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  100%  for  two  lane  highways    Outside  lane  is  design  lane  for  multilane  facilities  (truck  or  driving  lane)  

  AASHTO,  PCA,  and  Asphalt  Institute  all  recommend  slightly  different  methods  

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  Used  to  project  total  design  traffic  from  the  estimated  first  year  traffic  

  Multiply  initial  year  traffic  by  appropriate  growth  factor  

  Note  that  growth  factors  can  be  different  for  the  different  vehicle  classes  

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  Should  consider:    Expected  traffic  attracted  or  diverted  due  to  new/improved  facility  

  Normal  growth  due  to  increased  activity    Number  of  motor  vehicles  and  their  use    Future  development  (land  use)  

  Given      Four  lane  highway,  traffic  measured  in  two  directions  

  Flexible  pavement  with  pt  =  2.5  and  SN  =  5    Traffic  measurements  over  a  24-­‐hour  period    Traffic  data  as  previously  shown    Growth  factor  =  2%  

   Find    20  year  design  ESAL  ignoring  light  traffic  (eg.  passenger  cars)  using  AASHTO  method  

  Assumptions:    Traffic  volume  (all  vehicle  types)  will  increase  at  2%  per  year  

  Axle  weights  of  various  vehicle  types  will  remain  constant  over  design  period  

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ESALD  =  (947,266)(0.5)(0.9)(24.30)  

ESALD  =  10,358,354