PSI - Issue 72

Andrey Yu. Fedorov et al. / Procedia Structural Integrity 72 (2025) 453–457

457

Table 1. The relative values of strains at different loads and defect depths h h = 0 h = 5 h = 9

h = 12

h = 15

ε1/ε2 ε1/ε3 ε1/ε4 ε1/ε5

0.909 0.852 0.862 1.219

0.807 0.829 1.017 1.252

0.642 0.589 0.915 1.239

0.581 0.435 0.936 1.237

0.541 0.391 0.890 1.220

The results presented in the table show that the ratio ε1/ε5 retains its value under different loads and when cuts of different depths occur. The ratios ε 1 /ε 2 , ε 1 /ε 3 , ε 1 /ε 4 change when a cut occurs, and the largest change occurs for the ratio ε1/ε3 . The invariance of the ratio ε1/ε5 allows for the conclusion that there are no defects in the vicinity of these sensors. A change in the ratios ε 1 /ε 2 , ε 1 /ε 3 , ε 1 /ε 4 indicates the appearance of a defect (cut) in the vicinity of these sensors, and the largest change in the value ε 1/ε 3 indicates that the defect is closer to this sensor. 4. Conclusions The reliability of measured quantitative strain values and the possibility of recording technological strains in con crete by fiber-optic sensors embedded in the volume of the material at the stage of its formation from the concrete mixture are demonstrated. Variants of the method for detecting defects under loads that differ from each other by a constant factor are pre sented based on the results of measuring strains in different zones of the observed object and the results of its testing on a sample of cement mixture. 5. Acknowledgments This work was supported by the Russian Science Foundation (Project No. 19-77-30008). References Biswas, P., Bandyopadhyay, S., Kesavan, K., Parivallal, S., Arun Sundaram, B., Ravisankar, K., Dasgupta, K., 2010. Investigation on packages of fiber Bragg grating for use as embeddable strain sensor in concrete structure. Sensors and Actuators A: Physical 157(1), 77 – 83 Leung, C.K., 2001. Fiber optic sensors in concrete: the future? NDT and E International 34(2), 85 – 94 Mao, J., Xu, F., Gao, Q., Liu, S., Jin, W., Xu, Y., 2016. A monitoring method based on FBG for concrete corrosion cracking. Sensors 16(7), 1093 Slowik, V., Schlattner, E., Klink, T., 2004. Experimental investigation into early age shrinkage of cement paste by using fibre Bragg gratings. Cement and Concrete Composites 26(5), 473 – 479 Stepinski, T., Uhl, T., Staszewski, W. (Ed.) 2013. Advanced Structural Damage Detection: From Theory to Engineering Applications. John Wi ley & Sons, Ltd.