An Evaluation of the Effects of Nonlinear Load-Strain Behavior on MEPDG Analysis of Flexible Pavements

This study describes how the Mechanistic-Empirical Pavement Design Guide (MEPDG) employs the JULEA layered elastic analysis procedure for the structural analysis of flexible pavements. JULEA is utilized at each time increment within the design period, to compute strains within the pavement structure in response to traffic loading. The computed strains are then used to accumulate damage and distresses over the design period. To minimize computing time, the MEPDG makes the assumption that the computed strains are linearly proportional to the applied load and exploits this assumption to extrapolate strains from an 18 kip single axle load and the specified tire pressure to the entire load spectrum in the traffic composition. The load-strain linear proportionality assumption is valid only if the contact area remains the same as load varies, resulting in similar variation in the contact pressure. However, in reality, for truck loads of interest, the contact (tire inflation) pressure remains within a narrow range whereas the contact area changes with axle load. This paper analyzes the effect of the load-strain linear proportionality assumption on MEPDG rutting predictions. It quantifies the effect of the load-strain linearity assumption and the expected deviation in MEPDG distress predictions in flexible pavements. The MEPDG rutting models were coded and incorporated along with JULEA in to a ‘stand-alone application’ to conduct independent analyses for comparison with MEPDG predictions. The stand-alone application utilizes the MEPDG computer climatic and material properties. It was used to analyze pavement sections with consideration of constant tire pressure, representing the field conditions more closely, and constant tire contact area, assumed in the MEPDG, for strain computations. The distress values computed using the two criteria (constant tire pressure and constant contact area) showed higher deviations within top several inches (up to 6 in. deep). As expected, the deviation in calculated strains diminishes with increase in depth. The study revealed that the load-strain linear proportionality assumption can lead to significant error in the predicted permanent deformation. A viable alternative scheme has been identified by extrapolating the strain values from three axle loads (3-Point extrapolation) instead of a single load as currently implemented in the MEPDG. The distress predicted from 3-Point extrapolation matches well with those computed with constant tire pressure.

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  • Authors:
    • Thyagarajan, Senthilmurugan
    • Sivaneswaran, Nadarajah
    • Muhunthan, Balasingam
    • Petros, Katherine
  • Conference:
  • Publication Date: 2009

Language

  • English

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  • Accession Number: 01158637
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 11 2010 12:05PM