Write a simple VBA macro or enable iterative calculations in Excel options to find SNcap S cap N
in Excel, you must create a formula that calculates the "difference" between the left and right sides of the equation. Create a Cell for cap S cap N : Assign a cell (e.g., ) for the unknown cap S cap N . Input an initial guess (e.g., 3.0). Calculate the Left Side (LS) =LOG10(W18) Calculate the Right Side (RS) : Use the full AASHTO equation, referencing the cap S cap N ) and other input cells. Difference Cell : Create a cell for Use Goal Seek Data > What-If Analysis > Goal Seek . Set the "Difference Cell" to value by changing the cap S cap N Capitol Region Council of Governments (CRCOG) (.gov) 3. Determine Layer Thicknesses Once the required cap S cap N
Set a cell containing the AASHTO equation minus to a value of 0, by changing the
" 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 aashto flexible pavement design excel spreadsheet
Calculate the cumulative 18-kip loads over the 20 or 30-year design life.
Since the AASHTO equation is non-linear, you cannot solve for SN directly. An Excel spreadsheet typically uses:
The key inputs include:
Write a simple looping code to automate the Goal Seek process instantly when inputs change. Step 3: Layer Thickness Optimization Block Once Excel calculates the required total , the sheet must break down individual layer thicknesses (
“County Road 19 overpass approach,” Hank grunted, adjusting his hard hat. “Needs a new flexible pavement design. They want it by Friday.”
Assume three layers:
What are the specific (e.g., HMA, crushed stone) you plan to use?
This represents the total expected 18-kip (80 kN) Equivalent Single Axle Loads (ESALs). It spans the entire performance period of the pavement.
The total number of 18,000-lb equivalent single axle loads (ESALs). Write a simple VBA macro or enable iterative