Scour Repair of Bridges Through Vibration Monitoring and Related Challenges

Abstract

AbstractScour in railway bridges is often an important problem, especially for old bridges. In this regard, the assessment of full-scale bridges to establish scour repair adequacy or efficiency is an important question. Typically, scour weakens the bridge structure by modifying its boundary conditions. Such changes, when significant enough, can lead to changes in modal properties and in vibrations measurements with respect to the ideal baseline. On the other hand, a repair attempts to restore the release in boundary conditions. Consequently, a repair also changes the modal properties and the dynamic responses. This indicates that significant and consistent changes of bridges before and after repair can indicate the adequacy and efficiency of scour repair. This paper addresses this idea by carrying out a full-scale test on scour repair of a train bridge in Ireland. The bridge is monitored on two abutments with several wireless accelerometers while the bridge is operational. Both ambient and train passage events are considered in terms of collection of vibration data. While it is not possible to discern the difference between repaired and scour-damaged conditions, it is observed that time domain markers may be more consistent in indicating repair efficiency as compared to its frequency domain counterpart. This full-scale demonstration is expected to act as a full-scale example for vibration-based repair monitoring and performance criteria for future detection algorithms. The approach does not require the bridge to be closed down and can be relevant for other sensors as well.KeywordsBridgeScourInstrumentationMonitoringDamageRailwayTrainVibrationMode shapeFrequency-DomainTime-DomainMahalanobis distance