cell until the left side of the equation equals the right side.
is found by solving the following equation for a known traffic load ( cap W sub 18
: Used to calculate cumulative ESALs ( W18cap W sub 18 Reliability ( aashto flexible pavement design excel spreadsheet
: Layer coefficients (representing material strength for surface, base, and subbase). : Thickness of each layer in inches. : Drainage coefficients for the base and subbase layers. Must-Have Features in a Pavement Design Spreadsheet
| Layer | Modulus of Elasticity (psi) | Poisson's Ratio | Thickness (in) | | --- | --- | --- | --- | | Asphalt Concrete | 400,000 | 0.35 | | | Base Course | 30,000 | 0.40 | | | Subbase Course | 10,000 | 0.45 | | cell until the left side of the equation
log(W18)=ZRS0+9.36log(SN+1)−0.20+log(ΔPSI4.2−1.5)0.40+1094(SN+1)5.19+2.32log(MR)−6.24log open paren cap W sub 18 close paren equals cap Z sub cap R cap S sub 0 plus 9.36 log open paren cap S cap N plus 1 close paren minus 0.20 plus the fraction with numerator log open paren the fraction with numerator cap delta cap P cap S cap I and denominator 4.2 minus 1.5 end-fraction close paren and denominator 0.40 plus the fraction with numerator 1094 and denominator open paren cap S cap N plus 1 close paren to the 5.19 power end-fraction end-fraction plus 2.32 log open paren cap M sub cap R close paren minus 6.24 3. Determine Layer Thicknesses SNreqcap S cap N sub r e q end-sub
The predicted cumulative 18-kip Equivalent Single Axle Loads (ESALs) over the design life. Reliability ( : Drainage coefficients for the base and subbase layers
I tested a representative “AASHTO 1993 Flexible Design v4.2” spreadsheet from a public repository:
(Resilient Modulus): A measure of the in psi. 2. Converting SN to Layer Thicknesses
The road to better pavement starts with a single equation—and the right spreadsheet.