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Chapter 4Figure 4.65 - Truck tyre on the shaker table actuator.The shaker table was used in order to excite dynamic movements of the instrumentedvehicle, one axle at a time. For the dynamic wheel load calibration and the DLC (DynamicLoad Coefficient) calculation, three real longitudinal road profiles measured by theFinnish Road Surface Monitoring Vehicle were used as input. Each profile consists of fivehundred metres data of vertical road displacements at 0.23 metre spacing. The profiles,having average IRI values of 1.6, 3.3 and 5.4 respectively, represent three road comfortclasses, namely a fair, poor and bad road.4.7.3.4 Virttaa test siteThe Virttaa test site of VTT is located about 200 kilometres Northwest from Helsinki onNational Highway 41. It is a highway section, widened to 40 m for use as a jet fighterairstrip. The instrumented test pavements are located in the shoulder of the road, so theyare loaded only during VTT experiments. For these tests, a section with 150 mm thicknessof bituminous layers was used, constructed in 1987. Thicknesses and materials of the testsection pavement are shown in Table 4.28. Seven strain gauges in line at the bottom of thebituminous layers and three pressure cells have been used for these measurements.version 29 November 2001125