AASHTO Rigid Pavement Design Equation Study

In 1986, a revised rigid pavement design equation was introduced by the American Association of State Highway and Transportation Officials. The revised equation contains new input parameters such as: reliability, R, to introduce risk analysis into the design process; standard error, $S_0$, to represent variability in design input values; and drainage coefficient, $C_d$, to represent variability in drainage of water from the pavement structure. The final input parameter is joint transfer coefficient, J, to represent the type of joints used in the construction process. This paper summarizes the results of a significance study performed using the revised rigid pavement design equation. The study demonstrates the relative importance of design equation input parameters and provides insights into the relative change in required pavement thickness resulting from variations or errors in input parameter values. Study results show that variation in the concrete modulus of rupture, $S{\prime }_c$, and the concrete modulus of compressibility, $E_c$, have the most pronounced effect on pavement thickness. Variations in modulus of subgrade reaction, k, has the least pronounced effect on pavement thickness.