Let’s put trial SN in cell . Then in cell E20 , enter this monster formula (split into parts for clarity):
One click, and Excel solves for the required Structural Number instantly.
Using a spreadsheet over manual nomographs or expensive proprietary software offers several advantages:
You can instantly see how changing a layer thickness or material type affects the overall Structural Number.
Use a data table to show how SN changes with M_R or ESALs. This is critical for risk assessment.
A measure of the subgrade soil's stiffness.
Future research directions include:
Actually, careful: The full AASHTO equation predicts log₁₀(W₁₈). So:
), representing the total acceptable degradation in ride quality. Resilient Modulus ( Mrcap M sub r