Condition of road bridges in central as well as eastern Europe is not excellent. Lack of funding for maintenance requires precise identification of road bridge in need of investment. Integration of permanent monitoring sensors during construction of new bridge is a tool for integrated diagnostics. While the integrated Fiber Bragg Grating (FBG) sensors can be used for strain measurement or crack detection, in meantime they could be the same sensors used for traffic load estimation. Two types of FBG sensors were installed in concrete road bridge during construction phase in 2017 Czech Republic. Two FBG sensors in steel body and 4 Glass Fiber Reinforced Polymer GFRP sensor chain was integrated in the concrete body of the pre-stressed reinforced concrete element. Sensors are measuring strain in longitudinal direction of the bridge close to the bottom edge of the bridge where load on the bridge is causing extension. The signal from FBG sensors is processed by interrogation unit FBGuard and since they are embedded in the concrete, they are well protected against vandalism as well as against outdoor weather conditions.
Weight in Motion (WIM) system together with measurement of acceleration was installed on the same bridge element as a reference system for accurate identification of vehicle type, speed, axle load measurement and bridge deflection under vehicles passed over the bridge element. Methods of fiber optic sensor (FOS) signal processing, mathematical processing to determine important traffic parameters, FOS system accuracy and reliability will be presented in this paper. Limitations of the system will be also discussed in the paper. Installed FOS system is used to determine vehicle number, speed, and weight estimation. Results of signal processing and calculation of traffic parameters from FOS system will be shown on real data obtained from the bridge load tests carried out in 2021.

Embeded diagnostics; Bridge Monitoring; FBG Optic sensors; Traffic monitoring