Prediction of Pavement Fatigue Life with Simulated Temperature Profile from Hourly Surface Temperatures

Abstract

ABSTRACT A typical model for predicting the fatigue life of an asphalt pavement involves mid-depth temperature and the elastic horizontal strains at the bottom of the asphalt layer. Strains are studied at the bottom of the asphalt layer as cracks are assumed to originate there. Pavement temperatures naturally experience daily fluctuations as a result of varying air temperature and solar radiation. The amplitude of the oscillation decreases with depth and maximum temperature is reached later in the day at greater depth. During warming up, strain levels under loading increase as stiffness decreases, while the bottom of the asphalt layer is rather cold and thus sensitive to strains. At cooling down, strain decreases and the bottom layer is warm and withstands strains more easily. It is therefore proposed in this paper to use the temperature at the bottom of the asphalt layer instead of the mid-depth temperature when calculating fatigue damage. It is also proposed to use the complete temperature profile to improve the calculation of strain levels under loading. As the fatigue damage caused each hour will vary with temperature during the course of the day, it is also pointed out that the calculations might be improved by relating the distribution of traffic to the distribution of incremental fatigue damage. A simulation model calculating the temperature profile and strain levels was developed and run for three different pavements with different thicknesses of asphalt layer. It was found that the distribution of incremental fatigue damage over a typical summer day could be completely different for different pavements.