Scour depth prediction of a railway bridge pier with shallow foundation using vibration monitoring

This study proposes a method for predicting the scour depth of railway bridge piers using microtremors. Scour has been one of the most critical threats to bridges crossing rivers worldwide. A novel technology for assessing ground conditions around a pier during a swollen river period involves identifying its natural frequency from microtremors. To enable fast and informed decisions for bridge operation during such periods, this study proposes a method for providing real-time, intuitively acceptable information on scour depth, predicted from identified frequencies and finite element models. Long-term vibration monitoring data from an in-service railway bridge pier during a high-water period were used to investigate the validity of the proposed method. This study presents the probabilities that scour reaches the bottom of the footing, and the results demonstrate an extremely low probability of scour progressing beneath the footing. To verify the behaviour of the proposed method under scour, artificial acceleration responses were generated by applying frequency shift processing and then used in the evaluation. The outputs clearly demonstrate the method's potential to identify scour depth at the bottom of the footing after heavy rainfall events.