A New French Rational Design Method for Airfield Pavements

Abstract

The current design procedure for airfield pavements used in France has shown limitations in the past decades. This empirical-based approach does not consider correctly new material performances, temperature effects, or new complex landing gear configurations. For flexible pavements, on which this paper is focused, the empirical California Bearing Ratio (CBR) is used to characterize the bearing capacity of the pavement for the design. These limitations, among others, led the STAC to make new developments to overcome them. Hence the development of a new method inspired by the rational approach which has been used for roads and highways for more than 30 years. This method is based on the computation of resilient stresses and strains in the pavement structure using a multi-layer linear elastic model. The calculation of a damage parameter in the pavement is made for all the materials, considering fatigue of bound materials and permanent deformations of untreated materials and soils. The cumulative effect of the loadings applied by the various aircraft of the design traffic mix is taken into account as well as the effect of complex landing gears and wheels interaction. The design thickness of the pavement structure is then determined so as to reach failure at one of the critical level in the pavement after all the aircrafts of the design traffic mix have passed. This corresponds to a damage parameter equal to one. The development of a specific version of the French software dedicated to airfield pavement design is in progress. This paper describes the basis of both design methods for flexible pavements and then a comparison of the input parameters that are taken into account is presented.