Fatigue Shift Factors to Predict HMA Performance

Imad L. Al-Qadi, Walid N. Nassar

Research output: Contribution to journalArticlepeer-review


Hot-mix-asphalt (HMA) fatigue failure is achieved much faster under a laboratory setting than in the field. The difference between laboratory and field conditions is related to loading, material properties and specimen preparation. This difference has typically been accounted for by using a single shift factor based on engineering experience. Four shift factors can be identified: stress state, traffic wander, HMA healing and material properties. In this paper, approaches are presented to determine the stress-state and traffic-wander shift factors. Both field-measured critical strains and strain energy exerted during truck loading were used to determine the stress-state shift factor. Strain measurements for truck-loading distribution (wander) were used to determine the wander shift factor. Although the derived shift factors utilize the measured stresses and strains at the Virginia Smart Road, the approach may be used to determine the stress state and traffic wander shift factors utilizing appropriately calculated strains and stresses.

Original languageEnglish (US)
Pages (from-to)69-76
Number of pages8
JournalInternational Journal of Pavement Engineering
Issue number2
StatePublished - Jun 2003
Externally publishedYes


  • Critical strain
  • Field-laboratory correlation
  • Flexible pavement instrumentation
  • HMA fatigue
  • Shift factors

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Mechanics of Materials


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