Reliability-Based Model for Predicting Pavement Thermal Cracking

Thermal cracking of asphalt pavements is a serious problem in Canada and the northern parts of the United States. On many occasions, either at the design stage or during service, highway agencies demand a forecast of pavement performance rating, which is highly sensitive to the intensity of cracking. There are two failure modes of thermal cracking: low-temperature cracking and thermal-fatigue cracking. Low-temperature cracking is caused by accumulated thermal stresses in the pavement layer during cold winters or spring thaws. Thermal-fatigue cracking is caused by daily cyclic thermal loading. Classical probabilistic approaches have been applied to pavement design systems, including thermal cracking predictions, during the past three decades. Advances in reliability analysis, however, have proven that classical reliability methods are inconsistent, and mandate that current design procedures should be revised accordingly. This paper presents an improved reliability model for predicting thermal cracking. The proposed model accounts for the variability in the component design variables and the correlation between the two failure modes. The model results were verified using Monte Carlo simulation, and the sensitivity of the predicted intensity of cracking to various design variables was examined.