Simulation of Falling Weight Deflectometer for In-Situ Material Characterization of Highway and Airport Pavements

Nondestructive evaluation of highway and airport pavements is performed by deflection testing, such as a falling weight deflectometer (FWD). Many agencies use FWD deflection data to backcalculate pavement moduli using subjective inputs and forcing the moduli within a pre-selected range for each material. The failure of many pavement projects can be attributed to the uncertainties in these material inputs. The use of static elastic layered analysis and two- dimensional static finite element analysis programs is inadequate to calculate pavement responses and to relate these to pavement performance. This paper presents some results of advanced three dimensional-finite element (3D-FE) computer simulations carried out on selected pavement-subgrade models of asphalt pavements, subjected to a standard FWD impact load. Good agreement is shown between simulated and measured FWD deflections. Examples of nonlinear FWD moduli for an aircraft wheel load are presented. Effects of viscoelastic material properties on pavement responses to dynamic FWD loading are discussed. The LS- DYNA contact surface definitions are applied for dynamic analysis of pavements. The paper demonstrates the use of advanced finite element dynamic analysis procedures for correctly simulating pavements subjected to dynamic loads produced by nondestructive evaluation equipment and dynamic wheel loads.