Falling weight deflectometer (FWD) – Measurement of structural road characteristics

The Belgian Road Research Centre has a falling weight deflectometer to measure the temporary deflection of roads under heavy traffic loads. A falling weight is dropped from a standing vehicle onto a metal disc laid on the road surface. A rubber interface on top of the metal disc damps the impact so as to simulate the passage of a heavily loaded wheel axle of a lorry. Nine sensors in the vicinity of the impact zone record the temporary deflection of the road surface. A deflection bowl can be determined from the measured data. The FWD is suitable for measurements on all types of pavement (from flexible to rigid) and for use on road networks. Usually one measurement is performed every 100 m. A single measurement takes less than two minutes.


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