PAVEMENT DAMAGE FUNCTIONS FOR COST ALLOCATION, VOLUME 3 FLEXIBLE PAVEMENT DAMAGE FUNCTIONS DEVELOPED FROM AASHO ROAD TEST DATA

Flexible pavement damage functions for rutting and serviceability loss were developed from a representative subset of AASHO Road Test data consisting of 76 test sections. The primary purpose of this limited project was to check out and validate the use of a combined mehcanistic and empirical modeling approach to develop damage functions that were used in the recent cost allocations studies. As the damage functions developed from AASHO Road Test data predicted the measured data from the AASHO Road Test reasonably well, the procedures used are considered to be valid. Attempts to develop a damage function for fatigue cracking were frustrated by the nature of the data. Virtually all cracking failures occurred during spring thaw periods, resulting in clustered data for which meaningful regression analyses are not possible. Load equivalence factors were also developed from the damage functions and compared to other LEF's from previous studies. The LEF's vary grossly for equations with essentially equal predictive capabilities for the AASHO Road Test data. The implications from this are discussed. (FHWA)