A new set of Alpha Factor curves was derived for use in the CBR (California Bearing Ratio) methodology for designing flexible airport pavements. The new Alpha Factor curves are compatible with the new Alpha Factors at 10,000 coverages for four- and six-wheel gears adopted by International Civil Aviation Organization (ICAO) for calculating the Aircraft Classification Number (ACN) of airplanes operating on 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 more than six wheels were derived based on maintaining a consistent ranking of ACN compared to the old values. Analytic curves are defined so that Alpha Factors can be computed at any number of coverages and for any number of wheels, up to 24. 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 program COMFAA, which may be used to compute ACN for any arbitrary gear configuration. The source code of the function routine for computing the Alpha Factor in COMFAA is included in appendix A.
New Alpha Factor Determination as a Function of Numbers of Wheels and Number of Coverages
2008
39 pages
Report
No indication
English
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