Evaluation of Representative Loading Frequency for Linear Elastic Analysis of Asphalt Pavements

Abstract

The mechanistic design of flexible pavement is usually done with linear elastic theory (LET); this process must use appropriate values of the equivalent asphalt concrete elastic modulus to evaluate stresses and strains in a linear elastic multilayer. The aim is to identify some relationships to estimate the value of loading frequency, representative of the real strain pulse frequency spectrum, to be used in calculating the stiffness modulus of the asphalt concrete layers. In this way, an equivalent linear elastic structural analysis can be conducted. To achieve this aim, many transient load simulations were performed with ViscoRoute software based on the viscoelastic model. After variables that affected the representative frequency value were detected, more than 215 variable combinations (representative of real conditions) were randomly generated. For each combination, viscoelastic analysis was conducted, and then the stiffness modulus and the corresponding loading frequency were backcalculated by minimizing the residuals between linear elastic and viscoelastic peak strains. The representative frequency values calculated for these configurations were related to the significant variables by means of a multivariate regression. The model was developed separately for each of the three directions according to the anisotropic behavior of pavement under moving loads. Finally, the procedure was validated by applying it to several climatic and load configurations of an existing pavement. A simple and useful tool is provided to take into account all significant parameters; the tool can be used in conjunction with LET for pavement design.