Remote microtremor monitoring for scour assessment of railway bridge

This study aims to introduce an approach of scour detection for an in-service railway bridge in terms of a remote microtremor monitoring. Japanese railway companies make decisions on occurrence of scour by investigating changes in a target frequency, and it is very common to conduct the impact test on the railway bridge pier as a promising scour detection method to identify changes in frequencies. However, the impact test is a laborious and time-consuming method, and has difficulties in real time monitoring to make a proper decision on the train operation control during flood. This study investigates feasibility of scour detection from microtremor monitoring as an alternative method for the conventional impact test. A railway bridge has been being monitored utilizing a sensing unit including functions of vibration measurement, data processing and remote control. Observations from the microtremor data before and after a flood event showed that target frequency was slightly decreased under increase of water surface during flood. However, the slightly decreased frequency recovered once water surface level decreased after flood. Scour assessment following a Japanese guideline showed an extremely low probability of scour of the target bridge due to the flood.