PSI - Issue 78

Francesco Bencardino et al. / Procedia Structural Integrity 78 (2026) 1396–1403 Author name / Structural Integrity Procedia 00 (2025) 000 – 000

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Conversely the lowest increase in strength has been observed in tests conducted on the specimen strengthened with M1 mortar and basalt fabric on only one side, even though cyclic response got enhanced if the reinforcement was applied on both sides. 4.2. Failure modes Failure modes occurring in specimens strengthened with M1 or M2 matrix have looked quite different. The general trend exhibited by specimens strengthened with M1 was the delamination of the whole FRCM system from the masonry substrate which, in some cases, was quite sudden (see Fig. 5c). Conversely, the M2 matrix showed a more gradual detachment of the matrix from the fabric, therefore damages in the external reinforcements were less abrupt than those observed in the previous case (see Fig. 5b). For instance, as regards BM-B1-M1#1, the first cracks in the matrix happened at relatively high displacement level (about 24 mm), almost at the center of the façade of masonry wall; after that, cracks started to get numerous and directed along both diagonal directions. The same cracks were observed on the unreinforced side of the wall, which exhibited the typical cracking pattern due to shear forces (Garcia Ramonda et al. 2022). As already said, failure occurred due to the detachment of B-FRCM systems from the masonry substrate, while basalt fabric appeared almost undamaged at the end of the test (see Fig. 5a). On the other hand, BM B1-M2#1 exhibited quite premature failure, since this test exhibited the lowest increase in terms of strength and ductility, if compared to BM-UR specimen. The first damage in B-FRCM system was observed at 13 mm horizontal displacement equal, when the detachment of the overlapped layer of basalt fabric occurred (see Fig. 5b). Furthermore, cracks in the masonry of the unreinforced side were observed too, at the same displacement values.

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Fig.5. BM-B1-M1#1 (a), BM-B1-M2#1 (b), BM-B2-M1#1 (c) and BM-S-M1#1 (d) mode of failure.

Concerning the influence of the strengthening layout of B-FRCM systems, experimental evidence and failure modes showed that negligible differences occurred in specimens where basalt fabric was coupled with M1 mortar, since peak values of both load and displacements were almost the same. The modes of failure observed were also quite similar, given that in the case of BM-B2-M1#1 specimen, B-FRCM systems remained almost uncracked until high values of displacements were achieved. Minor cracks formed when a horizontal displacement equal to 20 mm was reached. In this case, the specimen was relatively intact until the sudden detachment of the reinforcement from the masonry occurred (see Fig. 5c). A similar behavior was also observed in BM-S-M1#1 tests, in which the typical cracks due to shear forces were observed along diagonal direction at the reaching of 16 mm, but no significant damage on the reinforcement was recognizable until about 30 mm, when the detachment of steel fabric from mortar M1 started to occur (see Fig. 5d). Despite that, the specimen was still able to bear further horizontal actions, since forces continued to get increased in both directions. The complete loss of resistance was quite sudden and reached when steel cords started to divide from matrix and the masonry got completely broken; indeed, sensible ruptures of bricks and mortar joints were perfectly recognizable.