EMI-FREE MONITORING OF A RAILROAD BRIDGE FOR ELECTRIC POWERED LIGHT WEIGHT RAIL TRANSIT

This paper investigates a prestressed concrete girder railroad bridge using FBG based sensors to monitor the dynamic response of the bridge with a test train which passes over the bridge at different speeds ranging from 10km/h to 50km/h. A test train made up of 2 cars is the Korean-standardized rubber-tired AGT (K-AGT) and it is powered by high-voltage of 22,900V. One FBG strain sensor and another FBG based accelerometer are attached on the surface of the bridge. For the comparison of measured data, an electric strain gage and an accelerometer are also attached near each FBG sensor. The results show that the measured data from FBG based sensors are free from EMI, though electric sensors are not, especially in the case of electric strain gage, which is crucial in the health monitoring of structures including high voltage power feeding systems.