She renamed the file before emailing it:
" cell, type the long AASHTO formula, referencing a temporary guess cell for cap S cap N Data > What-If Analysis > Goal Seek Set the "Calculated " cell to a equal to the log base 10 of of your actual cap W sub 18 cap S cap N guess cell. Final Answer
The equation is non-explicit; that is, the Structural Number ($SN$) cannot be easily isolated on one side of the equation. Solving for $SN$ requires iterative trial-and-error or complex logarithmic manipulation. Furthermore, because the Structural Number is a composite value derived from the thickness and material coefficients of the surface, base, and sub-base layers, engineers must balance these variables to achieve a cost-effective design. Performing these iterations by hand is time-consuming and prone to arithmetic errors, making computerized solutions a necessity.
Create a cell for the Estimated Structural Number ( SNestcap S cap N sub e s t end-sub ). Start with a placeholder value, like 1.0. Left-Hand Side (LHS) vs. Right-Hand Side (RHS): in one cell. aashto flexible pavement design excel spreadsheet
log10(W18)=ZRS0+9.36log10(SN+1)−0.20+log10[ΔPSI4.2−1.5]0.40+1094(SN+1)5.19+2.32log10(MR)−8.07log base 10 of open paren cap W sub 18 close paren equals cap Z sub cap R cap S sub 0 plus 9.36 log base 10 of open paren cap S cap N plus 1 close paren minus 0.20 plus the fraction with numerator log base 10 of open bracket the fraction with numerator cap delta cap P cap S cap I and denominator 4.2 minus 1.5 end-fraction close bracket 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 base 10 of open paren cap M sub cap R close paren minus 8.07 Key Components to Include in Your Spreadsheet: W18cap W sub 18
The predicted cumulative 18-kip Equivalent Single Axle Loads (ESALs) over the design life. Reliability (
: Combined standard error of the traffic prediction and performance prediction. : Present Serviceability Index loss over the design life ( MRcap M sub cap R : Resilient modulus of the subgrade soil (in psi). SNcap S cap N : Required structural number of the pavement. Structural Number and Layer Thicknesses Once the spreadsheet calculates the required SNcap S cap N She renamed the file before emailing it: "
Are you designing for a specific or state DOT?
Write out the long mathematical formula for the right side of the equation in an adjacent cell, referencing the SNestcap S cap N sub e s t end-sub cell and all other inputs.
variable appears on both sides of the equation, spreadsheets utilize the or Goal Seek feature to iteratively find the correct value. 🎛️ Essential Input Parameters for Spreadsheets Furthermore, because the Structural Number is a composite
): Relative strength of the materials used for the asphalt surface, base layer, and subbase layer. Standard values are 0.44 per inch for hot-mix asphalt (HMA) and 0.14 per inch for crushed stone base. Drainage Coefficients (
): The smoothness immediately after construction (typically 4.2 to 4.5). Terminal Serviceability (
Most spreadsheets generate a clean, standardised calculation sheet ready for inclusion in technical reports.