Full-scale test of a concrete box girder using FBG sensing system

For the structural monitoring of railway bridges, electromagnetic interference (EMI) is a significant problem as modern railway lines are powered by high-voltage electric power feeding systems. Fibre optic sensing systems are free from EMI and have been successfully applied in civil engineering fields. This study presents the application of fibre Bragg grating (FBG)-based sensing systems to precast concrete box railway bridges. A 20 m long full-scale precast concrete box railway girder was fabricated and tested in order to identify its dynamic and static performance. The experimental programme involved two phases. First, the dynamic characteristics of the test were identified using a digitally controlled exciter. An FBG-based accelerometer was installed on the surface of the structure. The second phase involved the measurement of the nonlinear static behaviour until failure. Multiplexed FBG strain sensors were embedded along the length of steel rebar and a strain-induced wavelength shift was measured in order to monitor internal strains. The measured values from the FBG-based sensors are compared with the results using electric signal-based sensors. The results show that the FBG sensing system is promising and can improve the efficiency of structural monitoring for modern railway bridges.