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!