Mechanistic Pavement Design Considering Bottom-Up and Top-Down-Cracking

Abstract

Pavement design and pavement life-time estimation are generally realized by using mechanistic-empiric pavement design tools. In this paper an improved design procedure is presented that integrates bottom-up-fatigue-cracking and low-temperature-induced top-down-fatigue-cracking in a narrow time-scale. Considering a design period of decades (e. g. 30 years), traffic data and pavement temperature data are considered in every single hour. As time-variation curve of material stiffness is displayed, traffic loads are realistically superimposed in time by temperature-induced loads. Thus, inaccurate time-independent consideration of traffic and temperature loads is avoided, as usually realized in conventional mechanistic design procedures where crucial effects of extreme loading situations are more or less neglected because of simplification by statistic clustering and averaging of load input data. For the assessment of temperature input data, time variation of climate data – i. e. air temperature, humidity, wind velocity and solar radiation – may be obtained from routine meteorological observation, or from road data observation using sensor technology. These data are used in order to assess temperature profiles occurring in the pavement on an hourly time scale. For this purpose, the finite difference method is used, which is a simple numerical procedure based on the Fourier heat equation and which describes unsteady thermal processes in an iterative way. Consequently, temperature profiles considered in short time intervals can be calculated and used in the pavement design process. Using data of hourly pavement temperatures, critical temperature gradients are incorporated in the design process.