PSI - Issue 66

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Domenico Ammendolea et al. / Procedia Structural Integrity 66 (2024) 396–405 Author name / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 4. Mixed-mode failure test of a notched concrete beam: (a) a comparison in terms of load (F) versus crack mouth opening displacement (CMOD) between the present method, the experimental data achieved by Gálvez et al. (Gálvez et al., 1998) and numerical predictions of Cervera et al. (Cervera et al., 2010) and Wu et al. (Wu et al., 2020); (b) snapshots of the damage profile of the beam gained by the proposed approach. It can be easily observed that the obtained curve are in excellent agreement with both the experimental findings and the numerical predictions of Wu et al. (Wu et al., 2020), thus denoting the reliability of the proposed approach in predicting the failure response of concrete structural members. For the sake of completeness, Fig. 4-b shows the snapshots of the damage profiles of the beam during the crack growth predicted through the present method at the

points of the F vs CMOD curve indicated by Roman numerals in Fig. 4-a. 4.2. A three-point bending test of a perforated beam with an eccentric crack

Fig. 5-a shows a schematic of geometry, boundary conditions, and loading scheme of a beam with an eccentric crack subjected to a three-point bending test, characterized by a regularly perforated microstructure. The repeating cell of this perforated microstructure consists of a square of side L cell = 2.2 mm with a centered hole having a diameter d f = 1.1 mm (Fig. 5-b). The beam has a total length of 120 mm, a height of 80 mm, and an initial vertical pre-crack of 13.3 mm. The Young’s modulus, Poisson’s ratio, tensile strength, and fracture energy are equal to E = 25 GPa, ν = 0.2, f t = 0.75 MPa , and G c = 1.2 N/m, respectively. Plane strain conditions are assumed. The internal length scale l 0 is equal to 2.2 mm and the Exponential softening curve is utilized to capture the material degradation during the crack propagation process. Finally, Fig. 5-c reports the mesh of a single perforated microstructure, which involves 187 nodes and 318 triangular elements arranged adopting, also in this case, the Delaunay scheme. Such a beam has been analyzed numerically by Khoei and Saadat (Khoei and Saadat, 2019). They have employed a nonlocal computational homogenization technique for reproducing crack propagation phenomena. At the beginning of the numerical simulation, the zone of interest consists of five micro-subdomains positioned around the initial crack tip. In the remaining part of the computational domain, micro-subdomains are replaced by macro-elements, which have the same dimensions of the adopted unit cell. It is important to note that homogenized moduli are used in the macro-subdomains to account for the presence of the hole.