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Influence of Tire–Pavement Stress Distribution, Shape, and Braking on Performance Predictions for Asphalt Pavement

Advances in computing power and more realistic laboratory characterization of properties of pavement layers have resulted in a rational approach to predicting the performance of hot-mix asphalt (HMA) mixtures that takes into account pavement temperature, complex contact stress distributions, and rate of loading. A study was conducted to evaluate the effect of tire–pavement contact stress distribution and braking on flexible pavement responses while also considering moving loads and viscoelastic properties of the asphalt layer. The computed pavement responses were used to predict rut depth and bottom-up fatigue cracking in the asphalt layer following the Mechanistic–Empirical Pavement Design Guide approach for computation of pavement distresses. The comprehensive study used three pavement sections and laboratory-measured mixture properties for the HMA layer. The data for measured nonuniform contact stresses showed a much larger contact area and substantial variation in contact stress distribution than did the conventional uniform conditions often assumed in pavement analyses. Regardless of the asphalt layer thickness, mixture type, and braking condition, all three uniform contact stress distributions (circular, square, and elliptical) overestimated the maximum vertical strains and thus HMA rut depth by as much as 71% compared with those from a nonuniform contact stress distribution. For the nonbraking condition, an increase of 34% to 71% in HMA rut depth was observed for the uniform stress distributions compared with the nonuniform stress distributions. The HMA rut depth was three to four times larger for the pavements subjected to braking condition regardless of the type and shape of the tire–pavement contact stress distribution. Numbers of cycles to fatigue failure in nonbraking conditions for the uniform contact stress distributions were within 15% of those determined for the nonuniform stress distributions. Braking further increased the failure limit to as much as 27%, an indication of the importance of accounting for braking in pavement performance analyses.