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    AASHTO Design Example: (Rigid Pavements)

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    Laurence Samson
    This document provides an example of designing a rigid pavement using AASHTO 1993 methods. It describes a problem statement for designing a highway with 3 lanes in each direction and an expected traffic volume of 20,000-30,000 vehicles per day. It includes tables and equations for determining design properties like drainage coefficient, load transfer coefficient, modulus of subgrade reaction, and reliability. Graphs and tables are presented for selecting standard deviation and reliability values. Typical concrete properties and drainage quality ratings are also defined.

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    AASHTO Design Example: (Rigid Pavements)

    Uploaded by

    Laurence Samson
    212 views30 pages
    This document provides an example of designing a rigid pavement using AASHTO 1993 methods. It describes a problem statement for designing a highway with 3 lanes in each direction and an expected traffic volume of 20,000-30,000 vehicles per day. It includes tables and equations for determining design properties like drainage coefficient, load transfer coefficient, modulus of subgrade reaction, and reliability. Graphs and tables are presented for selecting standard deviation and reliability values. Typical concrete properties and drainage quality ratings are also defined.

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    This document provides an example of designing a rigid pavement using AASHTO 1993 methods. It describes a problem statement for designing a highway with 3 lanes in each direction and an expected traffic volume of 20,000-30,000 vehicles per day. It includes tables and equations for determining design properties like drainage coefficient, load transfer coefficient, modulus of subgrade reaction, and reliability. Graphs and tables are presented for selecting standard deviation and reliability values. Typical concrete properties and drainage quality ratings are also defined.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    212 views30 pages

    AASHTO Design Example: (Rigid Pavements)

    Uploaded by

    Laurence Samson
    This document provides an example of designing a rigid pavement using AASHTO 1993 methods. It describes a problem statement for designing a highway with 3 lanes in each direction and an expected traffic volume of 20,000-30,000 vehicles per day. It includes tables and equations for determining design properties like drainage coefficient, load transfer coefficient, modulus of subgrade reaction, and reliability. Graphs and tables are presented for selecting standard deviation and reliability values. Typical concrete properties and drainage quality ratings are also defined.

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    LAURENCE V.

    SAMSON
    CHAPTER 03: AASHTO 1993 DESIGN EXAMPLES
    C03-S02: EXAMPLE ON RIGID PAVEMENTS DESIGN USING
    GRAPHS AND TABLES.

    AASHTO Design Example

    (Rigid Pavements)
    Problem
    Statement
    We are going to design a limited-access highway in
    an exurban area. The predominate terrain is rolling
    hills. In order to accommodate expected commuter
    traffic of 20,000 to 30,000 vehicles/day, we require
    3 traffic lanes in each direction. The two-way ADTT
    is expected to be 1000 trucks/day in the first year of
    operation. Based on statewide averages, the average
    LEF for rigid pavements is 0.98. It is assumed that
    truck traffic will grow at a rate of 3% per year over
    the 25-year design life.

    2
    Design
    ESALs 1 n  1
    g
    ESAL  365  D  L   
    g
    ADTTTf
     

    3
    Problem
    Statement
    Local practice is to use a granular subbase that will
    drain within a few hours. The subbase has a resilient
    modulus of 15,000 psi when wet and 25,000 psi
    when dry. The roadbed soil has a resilient modulus
    of 3000 psi during the 7 months “wet” months and
    7000 psi the rest of the year. Based on rainfall data,
    we expect that the subbase will approach saturation
    one week per month during the wet season.

    4
    Problem
    Statement
    According to local practice, the pavement will be
    designed as JPCP with tied concrete shoulders. The
    slab length will be 30 feet and dowels will provide
    load transfer at the joints. The concrete slab is
    designed for a compressive strength of 5500 psi. We
    will assume that the initial pavement serviceability
    index will be 4.5. Based on the high traffic volume,
    we will select a terminal serviceability level of 2.5.

    5
    Design Equation

    log
     PSI 
    10  
    log10 W1  ZRS0  7.35 log10  D 1  0.06  4.5 1.57
    1.62 10
    8

    1.0 
    8.46
     D  1
     
     4.22  0.32p  
    1993
    log  Sc  C d  D0.75
     1.132  
    t 10 215.63 J  
     
    D0.75 18.42 
      6
    Design Equation
      
      4 Ec k  

    7
    Rigid Pavement
    Properties
    Zr= standard normal deviate
    So = standard deviation of
    W18

    Ec = concrete modulus of elasticity (psi)


    Sc = concrete modulus of rupture
    (psi) Cd = drainage coefficient
    J = joint load transfer coefficient
    LS = loss of support factor
    8
    Rigid Pavement
    Properties
    k = modulus of subgrade reaction (psi/in)

    9
    Rigid Pavement
    Properties
    Zr= standard normal deviate
    So = standard deviation of
    W18

    Ec = concrete modulus of elasticity (psi)


    Sc = concrete modulus of rupture
    (psi) Cd = drainage coefficient
    J = joint load transfer coefficient
    k = modulus of subgrade reaction (psi/in)
    1
    0
    Rigid Pavement
    Properties
    LS = loss of support factor

    1
    1
    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%

    1
    2
    Reliability, ZR
    Reliability Reliability
    ZR 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 -3.750
    Standard Deviation, So

    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 0.30 – 0.40

    11
    Rigid Pavement
    Properties
    Zr= standard normal deviate
    So = standard deviation of
    W18

    Ec = concrete modulus of elasticity (psi)


    Sc = concrete modulus of rupture
    (psi) Cd = drainage coefficient
    J = joint load transfer coefficient
    k = modulus of subgrade reaction (psi/in)
    12
    Rigid Pavement
    Properties
    LS = loss of support factor

    13
    Typical Concrete
    Properties
    S c  fc  psi
    8.4
    ft fc  psi
     6.7

    Ec  fc 57,000
    14
    Typical Concrete
    Properties
     psi

    15
    Rigid Pavement
    Properties
    Zr= standard normal deviate
    So = standard deviation of
    W18

    Ec = concrete modulus of elasticity (psi)


    Sc = concrete modulus of rupture
    (psi) Cd = drainage coefficient
    J = joint load transfer coefficient
    k = modulus of subgrade reaction (psi/in)
    16
    Rigid Pavement
    Properties
    LS = loss of support factor

    17
    Drainage
    Quality
    Water
    Quality
    Removed
    Within
    Excellent 2 hours
    Good 1 day
    Fair 1 week
    Poor 1 month
    Very Poor No drainage

    18
    Drainage Coefficient, Cd

    Percentage of Time Material Approaches Saturation


    Quality
    < 1% 1-5% 5-25% > 25%
    Excellent 1.25-1.20 1.20-1.15 1.15-1.10 1.10
    Good 1.20-1.15 1.15-1.10 1.10-1.00 1.00
    Fair 1.15-1.10 1.10-1.00 1.00-0.90 0.90
    Poor 1.10-1.00 1.00-0.90 0.90-0.80 0.80
    Very Poor 1.00-0.90 0.90-0.80 0.80-0.70 0.70

    19
    Load Transfer Coefficient,
    J
    Asphalt Shoulders Tied PCC Shoulders
    No No
    Dowels Dowels
    Dowels Dowels
    JPCP
    3.2 3.8 - 4.4 2.5 - 3.1 3.6 - 4.2
    JRCP
    CRCP 2.9 - 3.2 2.3 - 2.9

    NOTE: Use higher J values when you have (a) low k values, (b) lots of trucks,
    (c) high concrete thermal coefficients, or (d) large variations in temperature.

    20
    Rigid Pavement
    Properties
    Zr= standard normal deviate
    So = standard deviation of
    W18

    Ec = concrete modulus of elasticity (psi)


    Sc = concrete modulus of rupture
    (psi) Cd = drainage coefficient
    J = joint load transfer coefficient
    k = modulus of subgrade reaction (psi/in)
    21
    Rigid Pavement
    Properties
    LS = loss of support factor

    22
    23
    21
    22
    23

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