Load Spectra–Incorporated Fatigue Cracking Model Implementation and Case Study

Traffic loading is one of the key factors that may cause asphalt concrete pavement fatigue cracking. Axle load spectra input provides an opportunity for evaluating the pavement response under real traffic loads throughout the pavement design life. This paper describes the methodology of incorporating axle load spectra into the mechanistic–empirical fatigue cracking model that uses a fracture mechanics method to determine crack propagation. The paper also presents the incorporation of the method into the Texas mechanistic–empirical flexible pavement design system. Several load spectra cases were studied, and the percentages of the corresponding fatigue cracking areas were predicted and compared. The comparison results confirmed the necessity of load spectra analysis. Overall, the implemented load spectra–incorporated asphalt concrete fatigue cracking model generated rational results. Further research is continuing on field validation and calibration.