Implications of Using Calibrated and Validated Performance Transfer Functions in the Mechanistic Empirical Pavement Design Procedure.

The Adoption of Mechanistic Empirical pavement design is growing steadfastly in many countries around the world. Australia and New Zealand adopted Mechanistic Empirical more than a decade ago. However, the success of the empirical design method depends on the use of well designed, calibrated and validated transfer functions. The transfer functions are the empirical component of the design procedure that relates pavement response with certain pavement performance indicators. In the Austroads Mechanistic Empirical pavement design, fatigue and rutting are the two performance indicators used in the design. Austroads guidelines adopted the Shell fatigue transfer function to predict the fatigue life of asphalt pavements. However, it was observed by many practitioners and confirmed by this study that Shell Transfer function significantly overestimates the design thickness or in other words underestimates the fatigue life of asphalt mixes. In this paper, calibration and validation of the Shell fatigue transfer function which is currently adopted in the Austroads design guidelines are demonstrated. The calibrated Shell fatigue performance model is integrated with the Austroads design method. A case study from the Christchurch Southern Motorway project has been analyzed using both the current design method and the suggested calibrated Shell performance model. The calibration factor based on the tested beams was found to be in the order of 5.6824. Using the calibrated Shell model produced a 26% to 27% thinner asphalt thickness compared to the current Austroads design guidelines. [ABSTRACT FROM AUTHOR]