PSI - Issue 44

Sara S. Lucchini et al. / Procedia Structural Integrity 44 (2023) 2286–2293 Lucchini et al. / Structural Integrity Procedia 00 (2022) 000–000

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Table 5. Real residential building: mechanical properties considered in numerical and analytical models. Material E [MPa] f m [MPa] τ 0 [MPa] f v0 [MPa] f c [MPa] f ct [MPa] f Ft-0,25 [MPa] f Ftu [MPa] Masonry 600 1.10 0.07 0.15 - - - - SFRM 21000 - - - 25.40 1.82 1.55 1.40

Unstrengthened building Fig. 3a reports the designation and the in-plan dimensions of the ten piers of the ground floor oriented parallel to the X-direction. The Dolce’s (1991) approach was used to determine the effective height H eff , whose values are listed in Table 6. The average axial load N, calculated at half height, was considered for each pier. Furthermore, an axial load increase was also considered in piers X1, X4 and X7 to take into account the uplift of the adjacent transverse façade. The global resistance of the building was estimated as the sum of the resistances of the ten walls located at the ground floor. The analytical prediction was mainly governed by sliding shear: all piers failed due to this mechanism except piers X5 and X7 that exhibited a flexure failure. The analytical seismic resistance of the building before retrofitting was very close to the numerical one: 949.0 kN versus 939.1 kN (see Fig. 3b). Table 6. Unstrengthened real residential building: effective height and axial load of resisting masonry piers ( H =2700mm). Property Pier X1 Pier X2 Pier X3 Pier X4 Pier X5 Pier X6 Pier X7 Pier X8 Pier X9 Pier X10 H eff [mm] 2069 2700 2501 2700 2214 2700 2700 2339 2341 2645 Axial load N [kN] 148.28 180.85 182.44 127.77 113.71 191.16 104.69 128.12 146.36 79.33

(a)

(b)

Fig. 3. Real residential building: (a) length and effective height H eff of the ten resisting piers in X direction; (b) comparison between numerical and analytical results, in terms of global resistance, for both unstrengthened and retrofitted building. Retrofitted building Regarding the schematization of the retrofitted piers, the fracture lines expected in this case study after retrofitting are slightly different than those identified in the experimental building described in the previous paragraph. No steel rebars were used to connect SFRM coating to the RC foundation, so the lower critical section was always placed at the interface with the foundation, where the SFRM coating presents a discontinuity and therefore there is no tensile contribution. The only exception is represented by the piers between two windows, in which the lower critical section is the line that connects the lower edges of the openings. The upper critical sections remained unchanged. The sum of