Implementation of a User Material Routine in 3D-FE Codes for Viscoelastic Modeling and Simulation of Highway and Airport Pavements

Traditional static analysis procedures using linear elastic pavement properties may lead to incorrect structural response analysis of pavements. Many of these procedures do not appropriately consider the effects of dynamic loading and pavement nonlinearities such as joints and cracking. It is imperative to use appropriate and correct material properties for meaningful advanced computer simulations. This paper presents some results of traditional analysis and three dimensional-finite element simulations carried out on selected pavement- subgrade models of highway pavements. Results of static and dynamic analysis are presented using measured falling weight deflectometer (FWD) load pulses and deflections. Effects of viscoelastic material properties on pavement responses to dynamic FWD loading are investigated. A user defined material subroutine UMAT is described. The UMAT material routine incorporates a generalized Maxwell viscoelastic model and microcracking propagation methodology. The UMAT material routine is being implemented in the LS-DYNA code.