PSI - Issue 44

Marta Del Zoppo et al. / Procedia Structural Integrity 44 (2023) 2158–2165 Del Zoppo et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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masonry and probably due to the opening of microcracks in the bed joints. In terms of capacity, the single side strengthening solution provided an increase of 18% with respect to the URM wall; conversely, the double side configuration reached a capacity enhancement of 82% with respect to the URM wall. The strong difference in terms of effectiveness can be partially justified by negative effects related to the eccentric reinforcement and partially to the effect of the cross-section enlargement in the double side configuration as well as to the uncertainties in the experimental result. Further experimental tests are needed to confirm the actual out-of-plane performance of single sided FRM strengthened walls. (a) (b)

Fig. 7. (a) Comparison of deformed shapes for P=30 kN, (b) comparison of capacity curves.

4. Conclusions This paper presented original experimental results on the out-of-plane performance of solid clay brick masonry walls strengthened with Fibre Reinforced Mortars (FRM). The FRM adopted for the study is a lime-based mortar with the addition of short glass fibres. An ad hoc experimental setup has been designed at University of Naples Federico II in order to simulate the condition of simply supported beam in a four-point bending test with an additional compressive axial load. Three specimen configurations have been presented herein: (i) as built wall, (ii) wall strengthened on one side with FRM and (iii) wall strengthened on both sides with FRM. The strengthening consisted in the application of a layer of FRM of thickness 15 mm. The out-of-plane performance of the three specimens has been presented and compared to point out the effectiveness of such strengthening system. The results of this preliminary experimental campaign showed that the failure mode of bare and strengthened specimens was quite similar. Indeed, all the specimens developed a flexural crack in the bed joints close to the upper loading roller. In all cases, the failure was governed by flexure. The FRM increased the out-of-plane capacity and reduced the out-of-plane deformation of the panels. Indeed, the capacity was enhanced by 18% for the single-side configuration and by 82% for the double-side configuration with respect to the bare wall. In terms of deformation, the comparison of deformed shapes and capacity curves clearly attested that the addition of the FRM on one or two sides changed the out-of-plane performance of the wall from nonlinear (due to the microcracking of the mortar) to linear elastic up to the development of a crack in the FRM. After the first cracking of the FRM, the short glass fibres crossing the crack start working according to the “bridging” effect . Hence, the FRM postponed the activation of the out-of-plane failure mechanism. From the analysis of these preliminary results, the FRM appears a sound technique for the out-of-plane strengthening of masonry walls. More experimental and numerical studies are needed to better assess the effectiveness of this solution for the seismic retrofit of masonry buildings, especially to evaluate the performance of single side strengthening solution.