A series of models have been developed that are designed to predict physical distress in asphalt pavements. The two computer programs, referred to as PDMAP (Probabilistic Distress Models for Asphalt Pavements) and COLD (Computation of Low-Temperature Damage), predict when and how much fatigue cracking and rutting will occur and when low-temperature cracking can be expected. The PDMAP program is designed to predict fatigue cracking and rutting in asphalt-type pavements and includes the following features: seasonal variations in material properties; long-term changes in material properties; daily variation in traffic (e.g., difference between daytime and nighttime truck traffic); traffic growth on a yearly basis if required; uncertainty in measuring material properties; conversion, by simple iteration, of the prediction models to design models for the selection of material and thickness; and distress predictions considering untreated or treated materials, including asphaltic concrete, asphalt emulsion mixes, and soil-cement. The COLD program is designed to predict if and when low-temperature cracking is likely to occur, given that a specific layer of asphaltic concrete and asphalt binder is to be placed in a known location for which reasonable temperature data are available. The pertinent features of this program are as follosw: (1) computes temperature in the asphaltic concrete; (2) computes the thermally induced stress in asphaltic concrete at 2-hour intervals; (3) provides a comparison of tensile strength with thermal stress at various levels of reliability in order to predict the probability of low-temperature cracking.
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