Pavement foundation layers are typically non$-$linear materials comprising granular base, granular subbase, and granular or clayey subgrade. The objective of this project is to understand the differences between linear elastic and non$-$linear elastic analysis and its impact on pavement life.

Consider a flexible pavement with $6-$inch AC surface course having an elastic modulus of $0\mathrm{.}5{10}^6,$ a $12-$inch limerock base course, and a $18-$inch clay subgrade. Assume $18-$kip single axle$/$single tire load of $9000lb$ with a pressure of $100.$ Predicted number of ESAL on the roadway per year $=100,000$

Build a KENPAVE model with $AC$ as a linear elastic material and the foundations as non$-$linear materials. For the non$-$linear analysis, select appropriate model constants for resilient modulus.

Determine stresses, strains and deflections at the top, bottom and middle of each layer directly under the tire load.

Estimate and report average stresses in each foundation layer.

Calculate resilient modulus for the each layer using the average stress conditions.

Perform a completely linear elastic analysis using calculated values of the resilient moduli.

Predict pavement life as follows: Use strains from Step $5,$ transfer functions given in Equations $(3\mathrm{.}6)$ and $(3\mathrm{.}7),$ and damage ratio given by Equation $(3\mathrm{.}19).$

A well$-$known transfer function for $AC$ fatigue is given in the following graph. Predict pavement life using this transfer function based on strains obtained in Step $5$ and damage ratio in Equation $(3\mathrm{.}19).$

Compare pavement life in Steps $6$ and $7.$

Results obtained from KenPave

$\backslash$table$[[$RADIAL$,$VERTICAL.,VERTICAL,VERTICAL,RADIAL.,TANGENTIAL.,SHEAR$],[$COORDINATE$,$COORDINATE,DISPLACEMENT,$\backslash$table$[[$STRESS$],[($STRAIN$)]],\backslash$table$[[$STRESS$],[($STRAIN$)]],\backslash$table$[[$STRESS$],[($STRAIN$)]],\backslash$table$[[$STRESS$],[($STRAIN$)]]],[0\mathrm{.}00000,0\mathrm{.}00000,0\mathrm{.}02437,100\mathrm{.}000,257\mathrm{.}334,257\mathrm{.}334,0\mathrm{.}000],[($STRAIN$),,,-2\mathrm{.}117E-04,2\mathrm{.}288E-04,2\mathrm{.}288E-04,\mathrm{.}000E+00$