Fatigue life prediction of an asphalt pavement subjected to multiple axle loadings with viscoelastic FEM

A model for determining bituminous pavement degradation due to multiple-axle moving traffic loads is presented. The developmental work has been based on a viscoelastic finite element method (FEM) dedicated to bituminous pavements subjected to multiple-axle traffic loads, through reliance on the following variables: pavement structure, load speed, load configuration, and bituminous material temperature. The Load Equivalent Factor (LEF) relative to various axle configurations is approximately proportional to the number of axles within a given axle group. For flexible pavements, the fatigue life predictions using the Homsi model exceed the other two models (i.e. the French standard fatigue law, developed by LCPC–SETRA [7], and the interface fatigue law developed by Diakhaté et al. [31]). Results obtained indicate that the design concept based on bending fatigue in bituminous layers is insufficient to realistically predict the degradation of a bituminous pavement structure. The phenomenon of shear at bituminous interfaces must also be taken into account, as revealed by simulation results for the degradation of two pavement structures from the French design code [8] (i.e. flexible pavement and thick asphalt pavement). For the thick asphalt pavement structure, the main damage mode is of the “bottom-up cracking” type, whereas “interface cracking” damage is typically displayed for flexible pavements. Even before determining life expectancy by means of fatigue models, the LEF clearly indicates in every pavement structure the spot where degradation was most severe (at either the interface or bottom of asphalt layers).