An Object-Oriented System for Finite Element Analysis of Pavements

The calculation of displacements, stresses and strains caused by vehicle loads in pavements is not a simple task even when considering all layers formed by linear elastic materials. In reality, surface and granular layers present a complex constitutive behavior, with nonlinear and time-dependent effects. Such effects should be considered in mechanistic pavement design methodologies which make use of the pavement structural response into specific distress models [

1

]. Today, there is a trend in the pavement academic community to substitute pavement analysis based on the Multilayer Elastic Theory by analysis based on the Finite Element Method — FEM [

2

].

There are several different finite element programs for pavement analysis [

2

,

3

]. Most of these programs consider only axisymmetric models and the three-dimensional stress state due to vehicle loads is computed using superposition, which is not correct for nonlinear materials. Moreover, the existing pavement specific programs were developed for design purposes and do not allow the modeling of damage evolution (e.g., crack propagation in bituminous mixtures), which is an important topic in the pavement research community.

In this paper, a new computational system developed to be used in both pavement design and research is presented. The system is based on the FEM and is implemented using Object-Oriented Programming (OOP) techniques to make it easily extendable. It contains both 2D (axisymmetric, plane-strain and plane stress) and 3D analysis models and works with different element shapes (triangular, quadrilateral, bricks, etc.) and interpolation orders (linear and quadratic). It also provides an efficient and accurate modeling of different loading types, including time varying loads. Finally, the system provides different numerical algorithms to nonlinear and time-dependent analysis, as well as a set of constitutive models. In this work, the class hierarchy of the system is presented and its main features are thoroughly discussed.