Sensing performance assessment of twisted CFRP with embedded fiber Bragg grating sensors subjected to monotonic and fatigue loading

Cable force monitoring plays a key part in structural health monitoring (SHM) of long-span bridges. Long-term stability and durability of monitoring method is a major problem of bridge cable, which often suffers from fatigue loads. An in-situ and efficient monitoring method for cable force was proposed by using smart twisted carbon fiber reinforced polymer (CFRP) bar with embedded fiber Bragg grating (FBG) sensors. Sensing performance of smart twisted CFRP bar was evaluated through static and fatigue tests. Elastic modulus, sensitivity, reflection intensity and spectra were utilized comprehensively to characterize stability and durability of FBG sensor under fatigue loading. Then, smart steel strand and smart cable were produced with embedded smart twisted CFRP bar. Stretching tests were carried out to obtain their sensing performances. In addition, experiments were conducted for comparison of smart CFRP bar with strain gauges mounted on surface of smart cable. The results show the good stability of measurement and excellent durability of sensors based on smart CFRP bar. Meanwhile, the feasibility of proposed method is validated basically to monitor bridge cable force from the perspective of online production and bearing capacity. In final, field test of the developed smart cable in bridge engineering was presented.