Link between different bottom-up fatigue’s law coefficients of mechanical-empirical pavement design software

Abstract

Abstract Fatigue is considered the main pavement degradation phenomenon at medium temperature for bituminous pavements. Most mechanical-empirical pavement design (M-E PD) software used nowadays refer to the Wohler fatigue curve to predict the number of load repetitions needed to have fatigue cracking of asphalt mixtures. At the core of models used in M-E PD, three coefficients of this fatigue curve which allow the quantification of the specific fatigue performance of a given bituminous material are used. To provide an understanding of the different tools available for M-E PD methods, the main fatigue model parameters are examined in the present work, and the different coefficients found in these models are explained and connected together. It is shown that many aspects of fatigue tests have a major impact on the fatigue resistance, and in turn on the fatigue modelling and the pavement design. For instance, the strain amplitude selection of a fatigue test strongly influences the a1 coefficient of Wohler law. The influence of temperature, which is taken into account with the a3 coefficient, also has a major impact on the modelled fatigue performance. On top of that, the strain amplitude used in laboratory fatigue tests, the slope of the Wohler curve obtained from fatigue tests, and the risk, or reliability, used in pavement design do change the coefficients, which in turn significantly changes the design of the pavement.