PSI - Issue 36

Olena Stankevych et al. / Procedia Structural Integrity 36 (2022) 114–121 Olena Stankevych, Valentyn Skalskyi, Bogdan Klym et al. / StructuralIntegrity Procedia 00 (2021) 000 – 000

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signals. The results of the analysis of AE signals for the CWT and DWT in section C-D are similar to the previous section with the difference that the percentage of events that accompany the pull-out of the fiber increases to 12%. Fig. 4b shows the distribution of the number of AE events that accompanied the different fracture mechanisms at different stages of loading. It can be seen that the ratio between the different fracture mechanisms changes with increase of the bending load. At the initial stages there is an active micro- and macrocracking, then the percentage of events that were generated due to the pull-out/sliding of the fiber increases. Since the hooked-end fiber is used for reinforcement, its pull-out/sliding is accompanied by intense propagation of cracks from its ends in the concrete matrix. Therefore, although in the last stages of loading of SFRC these mechanisms traditionally dominate, we observe a large number of AE signals that accompany cracking in SFRC. The obtained results are consistent with literature (Li et al. (2018)). 6. Conclusions Reinforcement of concrete with hooked-end steel fiber increases its flexural strength and resistance to deflection; compared to plain concrete, the ultimate flexural strength of specimens is maximally improved by 12%, 50% and 100% for fiber volume fraction 1.5%, 2% and 2.5%, respectively. The parameters of the CWT and DWT of AE signals can be used to assess the damage to SFRC, which changes with time, and the characteristics of the stages and mechanisms of its fracture. The proposed method of identifying the types and mechanisms of SFRC fracture by the parameters of local pulses of the CWT of signals AE (dominant frequency, radiation duration and energy parameter) and energy distribution of the DWT makes it possible to assess in real time the degree of damage to structures made of such materials. References Bian, C., Wang, J.-Y., Gou, J.-Y., 2021. 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