ABSTRACT
In contrast to the Falling Weight Deflectometer (FWD), the Traffic Speed Deflectometer (TSD) operates without traffic safety measures, stressing the examined pavement by simply rolling over it. Measurements are usually performed at speeds of up to 80 km/h. Due to the horizontal speed of the truck, in contrast to other bearing capacity measuring methods, visco-elastic material behaviour and inertial effects can also be observed. This raises the question whether the horizontal speed of the truck influences the measurement results. The results are important for TSD data assessment as well as for operational issues in high-trafficked areas or in-town measurements.
For these purposes, various field tests were conducted with the BASt-owned TSD evaluating varying horizontal speeds (20-90 km/h, increments of 10 km/h). The measurements were performed at selected test sites with different bearing capacity levels. Based on these data, the effect of speed on various indicators related to bearing capacity, such as SCI300 and deflections has been assessed in detail. The study has been supplemented with an analytical parameter study using the 3D-Move algorithm. The results of the parameter study confirm the findings of the field test: In the speed range from 20 km/h to 90 km/h, the effects of the horizontal speed on the measurement results (for example the SCI300) are marginal. The analysis of the 10 m values showed no significant change in the SCI300 with respect to horizontal speed. The model calculations in 3D-Move showed that only from horizontal speeds below 20 km/h the applied load becomes almost static and thus a different material behaviour is addressed. It can therefore be assumed that measurement results that lie within the permissible horizontal speed window (40-80 km/h) specified by the manufacturer are nearly unaffected by the horizontal speed of the truck.
