Experimental in-situ characterisation of the damping properties of road pavements

Vibrations induced by tyre/pavement interaction may be of concern for the underlying structure and, due to propagation of waves, for surroundings buildings and facilities. In addition, they may cause discomfort to drivers and passengers of vehicles, as well as traffic noise pollution. Improving damping properties of roads may mitigate most of the harmful traffic-induced effects. Nevertheless, the evaluation of damping properties of road systems is still an open issue. The present paper aims to contribute to this matter by assessing the effectiveness of two procedures for the in-situ characterisation of road pavement damping. The first procedure (MDPE-SD) evaluates the damping properties of physical vibration modes by means of a modal parameter identification algorithm used in association with stabilisation diagrams. The second procedure (CWT-ED) applies a wavelet transform for frequency decoupling and estimates damping by evaluating the rate of signal decay. In-situ tests, in which an instrumented hammer and an accelerometer were used respectively to apply an impact load and to measure the vibration response, were conducted on flexible and rigid pavements. The reliability of the two experimental procedures was assessed and compared by examining the damping ratios estimated for the two pavements at different frequencies and for different excitation and sensing locations. The investigation indicated that the spectral response of the pavements was characterised by multiple closely spaced modes, thus affecting the reliability of their identification through the MDPE algorithm. The analyses also showed that the damping ratios provided by the MDPE-SD procedure may be greatly affected by the choice of the excitation and sensing locations. In contrast, the CWT-ED procedure was much more robust, at any of the frequencies considered for the two pavement systems tested, to changes in the excitation and sensing sites, thus highlighting its superior capability to estimate the damping properties of road pavements.