PSI - Issue 44

Francesca Ferretti et al. / Procedia Structural Integrity 44 (2023) 2254–2261 Ferretti et al./ Structural Integrity Procedia 00 (2022) 000–000

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edges involving both mortar and bricks. The failure mode of the sample CD_2 was characterized by a main diagonal crack on side A, strengthened with the reinforced repointing (Fig. 5 b ). The cracking appeared in the central part of the panel, mostly within the mortar joints, and it propagated towards the edges of the panel after the first triggering. On side B, strengthened with FRCM (Fig 5 c ), a more widespread cracking was observed at the end of the test, due to the presence of fibers and their redistributing capacity. It should be mentioned that first cracks, on both sides of the panels, appeared simultaneously in correspondence with the maximum load. In the post-peak branch, the asymmetry of the behavior of the sample due to the application of the different systems on both sides was evident, e.g., higher crack opening was detected on the side strengthened with structural repointing. Delamination of FRCM was observed at the end of the test, without fiber rupture. For the sample CD_3, strengthened with structural repointing and CRM, the failure mode was similar to the one described for CD_2 (Fig. 5 d, e ). The failure mode of the sample CD_4, having FRCM on both sides (Fig. 5 f ), was characterized by the appearance of first vertical cracks on both sides of the panel at the maximum load. In the post-peak phase, a slight load resumption and the progressive formation of further cracks were observed. Also in this case, delamination of FRCM was observed at the end of the test. The mechanical anchorages were effective for all the samples.

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Fig. 5. Representative failure modes: (a) CD_URM; (b) CD_2 – Side A; (c) CD_2 – Side B; (d) CD_3 – Side A; (e) CD_3 – Side B; (f) CD_4. In Fig. 6 and Fig. 7, the load vs displacement diagrams are shown for all the panels (elongations are considered positive, shortenings are considered negative). The CD_URM panel, after an almost linear elastic branch up to the peak load, was characterized by a brittle failure mode, as expected. The curves of the strengthened samples showed an initial branch that can be considered linear elastic up to the first peak, significantly higher than the peak load of the corresponding CD_URM sample, and a more ductile post-peak behavior. In particular, in Fig. 6, a comparison between CD_2 and CD_4 is reported to understand the behavior of different FRCM strengthening layout, i.e. symmetrical or not. The FRCM applied on both sides determined a greater increase in the capacity of the panel, also providing a greater pseudo-ductility in the non-linear branch.