Issue 68

S. K. Kourkoulis et alii, Frattura ed Integrità Strutturale, 68 (2024) 440-457; DOI: 10.3221/IGF-ESIS.68.29

(a) (b) Figure 15: The entropic index and the applied load versus time-to-failure for notched beams made from concrete subjected to three point bending. (a) Plain beams and (b) Beams reinforced with metallic fibers [8]. However, this decreasing tendency is terminated about 10 s before macroscopic fracture, an instant corresponding to the initiation of fatal propagation of the front of a macro-crack (see ref. [8]) and therefore the damage process ceases being uniform and subsystems of damage nuclei are developed now around the reinforcing fibers located on either side of the propagating front which keep the two fragments in place. As a result, the values of q start increasing again up to the macro scopic fracture of the specimen given that the damage process remains spatially non-uniform. The specific response of q for the fiber reinforced concrete beam is quite compatible to the one described in the present study: The entropic index attains values well beyond the critical limit of unity (in the very narrow regime of 1.51

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