A new set of Alpha Factor curves is derived for use in the CBR methodology for designing flexible airport pavements. The new Alpha Factor curves are compatible with the new Alpha Factors at 10,000 Coverages for 4- and 6-wheel gears proposed by ICAO for calculating the ACN of airplanes operatingon flexible pavements. The standard set of Alpha Factors at 10,000 Coverages for 1, 2, 4, 6, 8, 12, 18, and 24 wheels, as defined in the ICAO Pavement Design Manual, have the values: 0.995, 0.900, 0.825, 0.788, 0.755, 0.722, 0.700, and 0.689. These are replaced by a new set of values: 0.995, 0.900, 0.800, 0.720, 0.690, 0.660, 0.640, and 0.630. The new values for morethan six wheels were derived based on maintaining a consistent ranking ofdamaging effect. Analytic curves are defined so that Alpha Factors can becomputed at any number of coverages and for any number of wheels up to twenty four. Alpha factors computed with the analytic curves are compatible with the new ICAO values at 10,000 coverages and with existing full-scale test data. The new analytic curves are implemented in the computer programCOMFAA, which may be used to compute ACN for any arbitrary gear configuration. For the covering abstract see ITRD E139491.
Abstract