Backcalculation of Raptor (RWD) Measurements and Forward Prediction of FWD Deflections Compared with FWD Measurements

Rolling wheel deflectometer (RWD) devices are increasingly being used for structural condition evaluation. However, the response of a pavement to a moving load generated by an RWD is different from the response to an impact load as generated by the commonly used falling weight deflectometer (FWD). Thus in order to fully understand deflections obtained by an RWD device, it is important to establish a proper comparison between the two types of equipment. This research presents a dynamic and viscoelastic finite element model able to simulate both impact load and moving load. The model is used for backcalculation of RWD measurements and then forward simulation of an impact load to obtain the corresponding FWD deflections. The “corresponding FWD deflections” refer to the deflections an FWD would have measured at the same location on a pavement as the RWD measurements were conducted. Experimental tests were conducted on a 10 km highway using both a Dynatest Raptor (RWD) and an FWD for measuring. The experimental data from the Raptor measurements was given as input to do backcalculation of pavement parameters, followed by a forward simulation of corresponding FWD deflections. The corresponding FWD deflections compared well with the experimentally measured FWD deflections.