COMPARISON OF VESYS IIM PREDICTIONS TO BRAMPTON/AASHO PERFORMANCE MEASUREMENTS

VESYS IIM is one of the most advanced models to date for simulation of a flexible pavement structure. However, this does not within itself imply its adequacy for practical use. Thus its ability to predict the performance of inservice pavements is of primary importanct to its eventual utilization for analysis and design. The paper provides comparisons of VESYS IIM predictions and measured performance of four sections of the Brampton Test Road and four sections of the AASHO Road Test. VESYS II M as currently configured normally requires 47 input variables, twelve of which include multiple values in arrays. For simplicity, these input variables may be classed into four categories having rational engineering significance when considered separately. These classifications include 1) pavement thickness dimensions, 2) traffic and wheel load data, 3) materials characterizations, and 4) control variables. The most important departure of VESYS IIM from more conventional analytical methods is in material characterizations. These material characterizations include creep compliance curves for viscoelastic responses, permanent deformation coefficients to describe permanent deformation potential for each layer, and the fatigue coefficient and exponent commonly used for the asphalt concrete characterized with respect to temperature. A very detailed contemporary test program has been conducted for the Brampton Test Road so much useful data was available. For the AASHO Road Test, however, it was necessary to obtain material samples and to conduct specialized testing to obtain the necessary material input. Comparisons of predicted and measured values show that performance predictions may not as yet be made at a sufficiently high confidence level. This is not surprising, however, considering the state-or-the-art for characterizing materials and inability of theoretical structural models in current use to deal with material changes with time. A significant finding of this study is that the calculated rut depth values approximated the measured rut depth for three of the eight sections when reasonably accurate input values were used. This success, even though limited, suggested that VESYS IIM holds considerable promise and may be expected to offer better predictive capabilities as improvements are made to both the program and to the material characterization procedures. While no definite conclusions can be made concerning predictions for cracking, present serviceability, and service life, these models do appear to function rationally and should also provide improved predictions as the state-of-the-art for materials characterizations and for the models themselves progress. /Author/

• Supplemental Notes:
  • Volume I of proceedings of 4th International Conference on Structural Design of Asphalt Pavements, Ann Arbor, Michigan, August 22-26, 1977.
• Corporate Authors:

  University of Michigan, Ann Arbor

  Department of Civil Engineering
  Ann Arbor, MI  United States  48109
• Authors:
  • Rauhut, J B
  • Haas, R
  • Kennedy, T W
• Conference:
  • Volume I of proceedings of 4th International Conference on Structural Design of Asphalt Pavements, Ann Arbor, Michigan, August 22-26, 1977.
• Publication Date: 1977-1

Media Info

• Features: Figures; References;
• Pagination: p. 131-138

Subject/Index Terms

• TRT Terms: Alternatives analysis; Asphalt concrete; Deformation; Flexible pavements; Forecasting; Foundations; Pavement design; Pavement performance; Pavements; Ruts (Pavements); Simulation; Thickness; Traffic loads; Viscoelasticity; Wheel loads
• Identifier Terms: AASHO Road Test
• Uncontrolled Terms: Pavement thickness; Rut
• Old TRIS Terms: Foundation investigations
• Subject Areas: Freight Transportation; Highways; Pavements;

Filing Info

• Accession Number: 00170210
• Record Type: Publication
• Report/Paper Numbers: Proceeding
• Files: TRIS
• Created Date: Mar 14 1978 12:00AM