Modification of Load-Repetition Factors for Airfield-Pavement Design

Abstract

The new generation of aircraft will require more landing-wheels to be packed into basically the same space. This move increases concern that current pavement-design procedures do not accurately predict load interaction for the type of closely spaced landing gears on the new generation of aircraft. In response to the requirement for developing valid pavement-design procedures, the American Federal Aviation Administration (FAA) constructed and operated a National Airport Pavement Test Facility (NAPTF) with the cooperation of the Being Company. The data from the NAPTF tests, recently made available, gave an opportunity to run a comprehensive analysis that included both the data of the old USACE full-scale trafficking tests (known as the Multiple-Wheel, Heavy-Gear Load tests, also called the MWHGL tests) and the data from these new NAPTF tests. This comprehensive analysis led two conclusions: (a) the load-repetition factor for the 10,000 coverage’s derived NAPTF data. The new value (0.720) was identical to that introduced by the ICAQ-CAN Study Group; (b) the engineering consequence of the combined old MWHGL and new NAPTF data is that it is necessary to consider the effect of the new NAPTF data on changing the load-repetition factor for all other wheel configurations. Thus, using these combined data in a combined analysis leads to new values of load-repetition factors for various wheel configurations possessing the number of wheels used to compute Equivalent Single Wheel Load (ESWL) of 6 and above. Finally, the design equations based on these new load-repetition factors lead to 6% to 10% smaller values of total thicknesses than do those derived from the COMFAA program.