PSI - Issue 10

M. Petrov et al. / Procedia Structural Integrity 10 (2018) 303–310

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M. Petrov et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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As can be seen from Fig.5, the transformation of spectra registered from samples with different types of reinforcement during compression tests has both common and distinctive features. For all reinforcement samples, shifting of spectrum toward low frequencies at the stage preceding the catastrophic destruction is observed. More significant changes in the spectra of electric signals registered from reinforced concrete are observed compared to the sample without reinforcement. a b

c

d

Fig. 5. Changing in the normalized spectra of electric responses registered from concrete (a) without reinforcement, (b) with single steel bar, (c) with two steel bars, and (d) with a steel reinforcing cage as a function of the compressive strains.

For the quantitative evaluation of the change in the shape of the amplitude-frequency characteristics of electric signals, a correlation analysis was used. Fig.6 shows the graphs of the changes regarding the maximum correlation coefficient between the signal spectrum registered during the compression test of concrete reinforced with a single steel rod, and the spectrum registered prior to the test, and in the frequency shift at which the maximum correlation coefficient is observed. These parameters for samples with other structural and strength characteristics under compression conditions behave similar to sample reinforced with single steel rod.

a

b

Fig. 6. Dependence of the (a) maximum correlation coefficient, and (b) shift for concrete reinforced with a single steel rod on the mechanical stress.