COMPARISON BETWEEN MEASURED AND CALCULATED STRESSES AND STRAINS IN FLEXIBLE ROAD STRUCTURES

At two full-scale flexible road structures of a test track extensive measuring programmes were carried out to determine stresses and strains in structures under controlled dynamic load conditions. A rail guided load vehicle, driven automatically, enabled the application of defined rolling loads of a single lorry wheel in the range between 0.5 and 2.0 tons. For testing the influences of loading time (speed) and environmental conditions, the load device was run on each test structure in the speed range between 5 and 50 km/h, and during all seasons of the year at asphalt temperatures between 0 deg C and 30 deg C. Radial strains (longitudinal and transverse) and vertical strains in the asphalt layer, and vertical stresses in the unbound base and the soil were measured at different levels of depth in the structures. The applied transmitters (strain gauges, pressure cells) had been tested successfully in situ for years. The two investigated road structures with a total thickness of the asphalt of 22 cm differed only in the stability properties of the asphalt base materials. Therefore direct comparisons could be made between the two structures under the same conditions. As a general result, the differences between radial strains in the asphalt were bigger than the differences between the vertical stresses in the unbound base and in the soil For the comparisons between measured and calculated values a so-called values a so-called effective dynamic stiffness modulus of the asphalt materials was introduced which accounts for the material properties, the temperature and the "effective" loading time. The numerical data were calculated by the computer programme BISTRO, which is based on the theory of elasticity for multilayer systems. The dynamic moduli of the materials were determined in the laboratory by a known vibration method, and in situ by the wave porpagation method. The best correlations between measured and calculated values were found for strains in the lower part of the asphalt layer and for the stesses in the unbound base and the soil, even when the stiffness conditions for the asphalt layer were low at asphalt temperatures of 30 deg C. When asphalt temperatures exceeded 25 deg C, maximum tensile strains were observed in the middle part of the asphalt pavements at the interface of two layed asphalt courses.

  • Supplemental Notes:
    • Presented at the Third International Conference on the Structural Design of Asphalt Pavements, Grosvenor House, Park Lane, London, England, Sept. 11-15, 1972.
  • Corporate Authors:

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Divil Engineering
    Ann Arbor, MI  United States  48104

    Interrational Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104
  • Authors:
    • Dempwolff, R
    • Sommer, P
  • Conference:
  • Publication Date: 1972-9

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 786-794
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00261920
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 22 1974 12:00AM