USE OF THREE-DIMENSIONAL, DYNAMIC, NONLINEAR ANALYSIS TO DEVELOP LOAD EQUIVALENCY FACTORS FOR COMPOSITE PAVEMENTS

Abstract

Asphalt overlays are frequently used to improve the serviceability of a deteriorated concrete pavement. The asphalt overlay has a significant influence on the concrete pavement's behavior and response to loads. Most highway agencies approximate the behavior of composite pavements to that of asphalt or concrete pavements. In fact the 1993 AASHTO design guide suggests that concrete pavement load equivalency factors (LEFs) be used to assess the effects of traffic on composite pavements. This is an approximation and has not been validated with field measurements or realistic analytical procedures. From a structural point of view an asphalt overlay of a concrete pavement should have a significant effect on the response of the composite pavement. A logical approach for the development of composite pavement LEFs is presented. These LEFs were developed for a study of permissible overloads and are based on total deformation, elastic and plastic, at the pavement surface. A three-dimensional dynamic finite-element mesh (3D-DFEM) method of analysis was used to analyze the composite pavements. The 3D-DFEM was verified in two steps for asphalt and concrete pavements: first for static, linear elastic analysis and then for dynamic, nonlinear analysis. Moving loads and realistic material models were used in the analysis.