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

Abstract

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.

Short continuously reinforced concrete pavement design recommendations based on non-destructive ultrasonic data and stress simulation.

“…The use of more rigid non-erodible bases helped mitigate the punchouts problem -usually connected to slab support loss. However, as reported by Jung et al (2012), in these improved structures, longitudinal cracks started to appear at the longitudinal reinforcement position connecting two closely spaced cracks. To this problem was given the name partial punchout.…”

“…This may be an indicative that most non-visible cracks show a similar development patter to the visible crack, as expected. It is assumed that for the short CRCP, most cracks begin at the reinforcement and develop up and down with time in a similar behavior than traditional CRCP as seen in Jung et al (2012).…”

“…Also, it is possible to observe that the current version of MEPDG brings considerable improvements incorporating a punchout prediction model based on fatigue damage associated with the formation of longitudinal cracks between closely spaced transverse cracks (less than 0.8 m crack spacing). However, according to Jung et al, (2012) Friction between slab and base has a direct impact on crack spacing as comment by Rao et al (2004). Table 2.4 shows the variation of the slab/base friction coefficient for different materials.…”

“…6 presents the basic differences between deep and partial punchouts. a) Deep punchout and (b) partial punchout(JUNG et al 2012) …”

“…Figure 2.7 shows a comparison between the MEPDG (a) and a model created by the authors (b). Results are very conflicting, indicating MEPDG ineffectiveness to consider the non-erosion potential of stiffer bases(JUNG et al, 2012).Momeni (2013) also points out additional advantages of having stabilized bases with more uniform material. According to the author, in the early stages of concrete contraction, changes in the friction coefficient between slab and base may cause direction variations of the stresses that are under development.…”