Fig. 1. Sensor structure

Fig. 2. Schematic diagram of long gauge FBG strain gauge sample section

Fig. 3. Schematic diagram of demodulation system composition

Fig. 4. Resolution test

Fig. 5. Spectral diagram of CH1（S1-S7）

Fig. 6. Experimental bridge and sensor layout

Fig. 7. First order modal analysis of test bridge

Fig. 8. On site testing of bridge and sensor layout

Fig. 9. Schematic diagram of overall strain of a river crossing bridge within 10 min

Fig. 10. Strain signals when different vehicles pass by

Fig. 11. Vehicle excitation signal and spectrum

Fig. 12. GWO-VMD decomposition diagram of vehicle excitation bridge signal

Fig. 13. First-order modal analysis of bridges

Fig. 14. Comparison of first-order modes of bridge with finite element simulation

Fig. 15. Modal frequency changes of CH1-CH4 corresponding to vehicle excitation

Fig. 16. Relationship between peak frequency of sensor and temperature change