Evaluation of Predicted Pavement Response with Measured Tire Contact Stresses

Abstract

A uniform circular vertical contact stress is commonly assumed in representing wheel loads in pavement analysis procedures. However, experimental measurements have shown that actual loading conditions are nonuniform and depend on tire construction, tire load, and tire inflation pressure. Predicted pavement response from three-dimensional (3D) finite element (FE) and layered elastic programs were compared to establish guidelines for modeling wheel loads in current layered elastic pavement analysis programs to provide a better approximation of pavement response parameters for design and evaluation. Tire contact pressure was measured with the stress-in-motion pad. In addition, tire contact pressure measurements from a previous study conducted at the University of California at Berkeley were obtained. Available contact pressure measurements on four tires were used to predict pavement response with a 3D FE program, which permitted input of measured tire contact pressures at various tire loads and tire inflation pressures. Horizontal strain at the bottom of the asphalt layer, compressive strain at the top of the subgrade, and principal stresses at different depths were predicted. Similar predictions were generated with layered elastic theory with two different representations of contact pressure and contact area. From predicted strains, service life for a range of pavements, tire load, and tire inflation pressures were estimated with limiting strain criteria. In addition, Mohr-Coulomb (MC) yield function values were calculated from predicted principal stresses at different depths. The MC yield function values and pavement life estimates from 3D FE and layered elastic analyses were compared with established guidelines for modeling wheel loads using existing layered elastic procedures.