Review of the long-term pavement performance backcalculation results : final report

Details

• Creators:
  Stubstad, R. N. ; Jiang, Y. J. ; Lukanen, E. O.
• Corporate Creators:
  Applied Research Associates ; Long-Term Pavement Performance Program (U.S.)
• Corporate Contributors:
  United States. Department of Transportation. Federal Highway Administration. Office of Infrastructure Research and Development
• Subject/TRT Terms:
  • Pavement performance
  • Statistics
  • Backcalculation
  • Modulus of elasticity
  • Concrete tests
  • Deflection
  • Deflection tests
  • Pavements, flexible
  • Pavements, Asphalt concrete
  • Testing
  More +
• Publication/ Report Number:
  HRT-05-150
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report
• Contracting Officer:
  Larry Wiser
• Corporate Publisher:
  United States. Department of Transportation. Federal Highway Administration. Office of Infrastructure Research and Development
• Abstract:
  A new approach to determine layered elastic moduli from in situ load-deflection data was developed. This “forwardcalculation” ; approach differs from backcalculation in that modulus estimates come directly from the load and deflection data using closed-form ; formulae rather iteration. The forwardcalculation equations are used for the subgrade and the bound surface course for both flexible ; and rigid pavement falling weight deflectometer (FWD) data. Intermediate layer moduli are estimated through commonly used ; modular ratios between adjacent layers. ; The entire LTPP set of backcalculated parameters was screened using forwardcalculated moduli. Any assumed or fixed modulus ; value was left as is and not further screened (e.g., hard bottom). Further, any back- or forwardcalculated values outside a broad range ; of reasonable values were not further screened, but flagged as unreasonable. Finally, a set of broad range convergence flags (0 = ; acceptable, 1 = marginal, 2 = questionable, and 3 = unacceptable) were applied to the backcalculated dataset, depending on how ; closely the pairs of back- and forwardcalculated moduli matched. Since both techniques used identical FWD load-deflection data as ; input, the moduli derived from each approach should be reasonably close to each other (within a factor of 1.5 to qualify as acceptable, ; for example). ; Although backcalculated values cannot be rejected merely because they are outside a reasonable or acceptable range, the ; complementary forwardcalculated values were usually more stable on a section-by-section basis. The exception was the portion of the ; database based on slab-on-dense-liquid or slab-on-elastic-solid theory, where the correspondence between the two approaches was ; excellent and very stable. Therefore, it is recommended that the backcalculated database be retained as is, with the addition of checks ; and flags so the database user can choose the best method, depending on the application.
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• Format:
  PDF
• Funding:
  DTFH61-02-D-00138
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/781/dot_781_DS1.pdf
• File Type:
  [PDF - 819.55 KB]
• Collection(s):
  Federal Highway Administration
• Main Document Checksum:
  urn:sha-512:a194e8d4d32e2b157568d29e402b8224a6d7cbd2546754de5a928cab57edecb8e325b1b1b3bc3c98385cd3e73ac069b6eeefc49a89a5fb848e15c6b147ebdc81