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Improved Mechanistic–Empirical Continuously Reinforced Concrete Pavement Design Approach with Modified Punchout Model

The Mechanistic–Empirical Pavement Design Guide (MEPDG) makes available a mechanistic–empirical punchout prediction tool based on a comprehensive analysis of many design factors in continuously reinforced concrete (CRC) pavement. The punchout model is based on the idea that accumulated fatigue damage induces longitudinal cracking between two narrowly placed transverse cracks as a result of repeated loading, diminished load transfer, loss of support, and environmental stresses. Most factors are considered directly in the punchout prediction except those related to subbase support. For instance, stiffer support conditions reduce deflection, with smaller interfacial shear stresses than subbase shear strength as a result, and thus lower erosion. However, the MEPDG predicts a higher rate of punchouts with increasing k-value because a punchout is assumed to be analogous to longitudinal fatigue cracking. The unfortunate consequence of this assumption is that the predicted rate of punchout might increase as a result of greater curling and warping stresses because of stiffer sublayers or higher k-value situations. The probability of erosion was included to counteract this effect on punchout predictions. A modified mechanistic–empirical CRC pavement design approach is described in terms of a modified punchout model, subbase erosion model, and an enhanced traffic equivalency model. The modified design approach includes expressions for fatigue distress similar to those in the MEPDG. The design also considers partial-depth punchout distress as part of the assessment of punchout distress.