PSI - Issue 44

Carlo Vienni et al. / Procedia Structural Integrity 44 (2023) 2270–2277 Vienni et al. / Structural Integrity Procedia 00 (2022) 000–000

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a b Fig. 3. (a) Fem model; (b) capacity curves of reinforced and unreinforced wall: numerical (dotted lines) vs experimental curves (continuous lines)

Table 3. Mechanical properties for parametric analysis. Masonry typology f c [MPa] E [MPa]

Compression level ν = σ 0 /f c 0,05 - 0,15 - 0,30 - 0,50 - 0,75 0,05 - 0,15 - 0,30 - 0,50 - 0,75 0,05 - 0,15 - 0,30 - 0,50 - 0,76 0,05 - 0,15 - 0,30 - 0,50 - 0,77

Wall thickness [mm]

Existing brick Strong brick Regular tuff Uncut stone

4,30

2000 4000 1400 1440

120 - 250 120 - 250 250 - 400 250 - 400

14,00

3,00 2,00

Numerical capacity curves were drawn for both reinforced and unreinforced masonry walls. For each numerical model, it was possible to define the amplification coefficients in terms of stiffness α k , strength α V , and displacement capacity α dc provided by the reinforcement system as the ratio between the investigated parameter calculated on the reinforced and unreinforced wall . Considering the whole set of analyses, it was, therefore, possible to define the trend of the amplification coefficients according to masonry typology, thickness, and compression level. Fig. 4 shows the effect of the reinforced plaster as a function of compression level and masonry typology: for low compression, masonry shows a rocking behavior for which CRM has negligible influence; at increasing compression, panels are characterized by diagonal-cracking or toe-crushing failure, and the effectiveness of the plaster increases accordingly. Moreover, the influence is greater the worse are mechanical characteristics of the masonry and the lower its thickness. 4. Proposal of analytical formulations Common analysis procedures today available require considering the reinforced plaster effect through the use of amplification coefficients to be applied to the compressive and shear strength of URM and its Young modulus. According to the Italian Building Code NTC 2018 , these coefficients are differentiated with masonry typology but do not consider the mechanical characteristics of the masonry to be reinforced, its thickness, or the type of plaster used. In this section, a new analytical procedure has been developed for the definition of the equivalent mechanical properties to be assigned to reinforced masonry, able to correctly simulate the effect of CRM. The development of the procedure started from the definition of the bilinear response of masonry walls, characterized by a Timoshenko beam stiffness, a resistance equal to the minimum value between shear strength by diagonal cracking and flexural strength, and displacement capacity related to the compression level and panel aspect-ratio. 4.1. Shear strength The lateral strength of panels can be calculated as the minimum value between the shear and flexural resistance using the well-known formulations and .