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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al. (2021). It consisted of four 200 mm thick hollow-clay block masonry walls supporting two floor diaphragms. The dimensions of the structure were 5.75 × 4.25 m 2 in plane with a total height of 6.7 m. After a pre-damaging test, the building was repaired by a 30 mm thick layer of SFRM provided with a series of local reinforcements (see the description below). The analytical prediction of the global seismic resistance of the building, before and after retrofitting, was compared with that resulting from the experimental tests. Table 1 reports the main mechanical properties of masonry and SFRM coating implemented in the analytical model. Fig. 1a reports the global envelope curves obtained from the experimental tests.

Table 1. Experimental building: mechanical properties considered in the analytical model. 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 2100 3.015 0.07 0.29 - - - - SFRM 21000 - - - 36.00 2.00 2.125 2.23 * Secant Elastic Modulus

Unstrengthened URM building First, the global resistance of the unstrengthened building was analytically calculated. The weakest mechanism between diagonal shear (D), sliding shear (S) and flexure (F), according to NTC (2018), provided the capacity of each of the six longitudinal piers located at the ground floor (Fig. 1b-c). The piers were schematized by using the approach proposed by Dolce (1991) to determine their own effective height H eff (see Table 2).

Table 2. Unstrengthened experimental building: effective height and axial load of resisting masonry piers. Property Pier 1 Pier 2 Pier 3 Pier 4 Pier 5 Pier 6 H eff [mm] 2096 1733 2096 2420 1933 2096 Axial load N +X [kN] 44.24 48.26 33.15 45.18 49.20 33.15 Axial load N -X [kN] 33.15 48.26 44.24 34.09 49.20 44.24

100 200 300 400 500 600 700

605.5 kN

Unstrengthened, experimental Retrofitted, experimental Unstrengthened, analytical Retrofitte, analytical

437.5 kN (-28%)

180.0 kN

129.1 kN (-28%)

-700 -600 -500 -400 -300 -200 -100 0

129.7 kN (-27%)

Base shear [kN]

-178.6 kN

479.0 kN (-18%)

-584.6 kN

-20 -18 -15 -13 -10 -8 -5 -3 0 3 5 8 10 13 15 18 20

2nd floor lateral displacement [mm]

(a) (c) Fig. 1. Experimental building: (a) comparison between experimental and analytical results, in terms of global resistance, for both unstrengthened and retrofitted building; experimental crack pattern at the end of the test on retrofitted building: (b) external East façade; (c) external West façade. The average axial load N, calculated at half height, was considered for each pier. Furthermore, the two loading (b)