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Flexible Pavement Design Question

  1. May 13, 2007 #1
    1. The problem statement, all variables and given/known data

    Design a flexible pavement to last for 25 years. The initial PI is 4.2 and the terminal PI is 2.5. The subgrade has resilient modulus of 12,000 psi. The reliability is 95%, and the overall standard deviation is 0.4. The ADT is 25,000 light vehicles (two 2-Kip axels), 1,000 single unit trucks (one 8-Kip single axel and one 22-Kip single axel), and 500 semi-trailer trucks (one 10-Kip single axel, one 16-Kip tandem axel, and one 44-Kip triple axel). Use good drainage base and sub-base material.

    State your assumptions clearly. You need to do one iteration only even if your initial assumption(s) are not validated after solving the problem.


    2. Relevant equations

    http://training.ce.washington.edu/WSDOT/Modules/06_structural_design/06-3_body.htm

    3. The attempt at a solution

    i don't get how to get Zr in the empirical equation. i got .557 for my SN (after much algebra through that long equation to solve for SN) but when i used the nomograph (assuming SN=5) i got about 4.6 for my SN. my design came out to be:

    D1=4" D2=10" and D3=9.45" after using 4.6 as SN.
    am i doing this correctly? how do you know what coefficient to use for m2 and m3? i assumed 1, which i don't know if it that is correct to assume or not.

    i just received this problem and spent a good 2 hours or so on it; please forgive me but i need help soon!
    thanks! happy mothers day!
     
  2. jcsd
  3. May 13, 2007 #2

    Pyrrhus

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    Homework Helper

    Sorry, i can't help much. My knowledge on highways is upto the subgrade. I haven't designed a pavement, yet. Althought the website does reference a table for the value in an AASHTO guide, maybe that's the problem?
     
  4. May 13, 2007 #3
    thanks cyclovenom. i think i might just leave it at that, i followed the procedure the professor gave, so i just hope he won't have a fit.

    oh one more question, do you know how to calculate highway capacity? i'm not sure how to include a 6% grade into the factor of Level of Service and the highway capacity. thanks again!
     
  5. May 14, 2007 #4

    Pyrrhus

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    Funny thing, i'm taking that class now!, and we just started, so i can't help you now... :rolleyes:
     
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