The calibrated mechanistic pavement performance prediction method developed in the SHRP A005 contract is an advance from the phenomenological prediction methods that have been used for the last two decades. The new methods make possible the use of material properties for specifications; simpler, more straight forward tests to determine these material properties; and permit the calibration of the models and specifications to local or regional conditions and materials; and are the basis of the new SHRP mix design procedure, SUPERPAVE. The concepts used in the predictions of pavement distress include the following: (1) microcracking in fatigue crack initiation; (2) shearing stress propagation of fatigue cracks; stress propagation of fatigue cracks; (3) rutting due to both volumetric and shearing plastic strains; (4) use of fracture mechanics and fracture properties to predict crack initiation and propagation; (5) use of plasticity theory and plastic properties including cohesion and friction angles to predict rutting; (6) use of system identification methods to calibrate the prediction models; and (7) both "forward" and "backward" calibration can be done. The "forward" calibration is to calibrate the model as illustrated in this paper. The "backward" calibration is to determine specification limits using observed performance and measured material properties. The material properties used in these models are few in number, simple to measure, and, in many cases, already familiar to engineers engaged in materials testing. (A)
Abstract