Non-linear Finite-Element Analysis to Predict Permanent Deformations in Pavement Structures Under Moving Loads

Abstract

The structural analysis of pavement systems is quite a difficult problem; it involves a layered medium, usually modeled as unbounded in extent, subjected to moving loads. A principle concern is the permanent deformation remaining when the load exceeds design values; the so-called rutting phenomenon. A steady, moving load, assumed quasi-static, can be handled by employing a moving coordinate system to advantage; in essence converting the modeling problem to one with a stationary load. However, the unbounded domain is still problematical. The common practice of using rollers on the boundaries of a truncated domain will lead to a loss of accuracy, especially for points near the truncated boundaries. In a finite element approach to the steady-state problem in which a load moves at a constant speed on an elastic-plastic layered system “boundary effects” due to the inherent nonlinear boundary conditions are so obvious that it is almost impossible to evaluate residual displacements. In this paper, a method is proposed to treat the involved, nonlinear boundary conditions and to allow accurate prediction of the residual displacements. A modified iterative scheme is constructed and infinite elements are employed to treat the unbounded domain. The infinite element formulation involves the residual displacements and, therefore, must be used together with the modified iterative scheme. Numerical results indicate that the adoption of the infinite elements together with the modified iterative scheme completely eliminate the “boundary effects” and greatly improve the accuracy of calculated residual displacements.

Keywords:

• : Moving load
• Nonlinear boundary condition
• Infinite elements
• Pavement