a) Why should the effective structural capacity of an existing pavement earmarked forrehabilitation to extend its service life be evaluated? O The following expression is associated with the use of

the Falling Weight Deflecto meter(FWD) on pavements earmarked for rehabilitation. d_{e}=\frac{1.5 p a}{M_{k}}\left\{\frac{1}{\left.\sqrt{1+\left(\frac{D}{a} \sqrt{\frac{E_{p}}{M_{k}}}\right.}\right)^{2}}+\frac{M_{R}}{E_{p}}\left[1-\frac{1}{\sqrt{1+\left(\frac{D}{a}\right)^{2}}}\right]\right\} What is the structural transformation required to make the use of the above expressionpossible? Which parameters in the expression relate to the transformation? Identify the parameters in the expression which are obtained from the FWD test and brieflydescribe how the setup of the test enables those parameters to be obtained. [You may useany relevant expression(s) or equation(s) to support your explanation.]