Using Rocking Frequencies of Bridge Piers for Scour Monitoring

In this study, scour-based vibrations of bridge piers are investigated using a bridge model in a water flume. First, the eigenmode corresponding to the measured frequencies of pier-like structures is identified. Second, the effect of the pier-deck interaction is studied. Finally, a theoretical model is proposed to characterize the pier vibration and identify its input parameters. To this end, experiments were conducted and a laboratory-scale model pier was tested in two configurations: single piers and two piers in a bridge configuration. The experimental results enable the identification of the modal shape and indicate that the deck decreases significantly the pier's frequency. In parallel, a theoretical model was proposed to model the pier, where the soil was modeled with both lateral springs along the pier and a rotational spring at the base. The spring stiffnesses were then identified using a three-dimensional finite element model. The results obtained from the theoretical and numerical models are in good agreement with the experimental results with the bridge pier in the two tested configurations. The obtained theoretical, numerical and experimental results were compared to experimental data found in the literature for further validation.