Variability characterisation of input parameters in pavement performance evaluation

Due to significant variability associated with the input parameters of pavement life and traffic repetitions, the performance evaluation in pavement design process becomes very uncertain. Uncertainty in performance evaluation can be handled using probabilistic design method. To calculate probability or reliability, it needs distributions and the parameters of distribution of the performance parameters, that is, pavement life and traffic repetitions. This paper attempts to establish these distributions and their goodness of fit based on statistical evidence. The uncertainty levels of traffic, pavement life and the pavement damage parameters are studied for the possible ranges of variations in different input parameters. Different possible combinations of distribution are considered, and it is observed that irrespective of the type of distribution of input parameters, the distributions of traffic, pavement life and damage parameters follow a lognormal distribution, with a wide range of coefficient of variation (COV). Sensitivity of COV parameters is also studied for reliability analysis in asphalt pavements. Finally, accounting the distributions and COVs as well, a factor of safety concept has been introduced towards a reliability-based deterministic design approach. Mechanistic-empirical (M-E) design method and, the fatigue and rutting failures are considered in the present work.