PSI - Issue 44

Silvia Caprili et al. / Procedia Structural Integrity 44 (2023) 1030–1037 Silvia Caprili et al. / Structural Integrity Procedia 00 (2022) 000–000

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the presence of blocks’ ribs (Fig. 1b): it can be compared to a weakly armed extended wall according to the definition provided by Italian Standards for Construction (D.M.17 gennaio, 2018) and – till now - reference for dimensioning, detailing, modelling and analyzing the system can be made only to the Italian “ Linee guida per sistemi costruttivi a pannelli portanti basati sull’impiego di blocchi cassero e calcestruzzo debolmente armato gettato in opera ” (Linee Guida, 2011). The above-mentioned guidelines, otherwise, were developed for new constructions adopting such a system: given the innovative character of present proposal – i.e. applied to existing constructions for retrofit and therefore used for horizontal loads - their applicability shall be validated, through both numerical analyses and experimental tests, actually ongoing within a strict collaboration between PAVER S.p.A. and Pisa University.

Fig. 1 (a) Vertical section of the retrofitting system; (b) Detail of the expanded-clay block.

3. Application to case study 3.1. Description of the selected case study building

A two-story masonry building is considered as a case study. Such a building is a good example of the Italian building stock of the second half of the 20 th century (Fig. 2a). Despite its simplicity, the study of this building appears to be useful since it allows the generalization of the results of the structural and energy performances obtained after retrofitting. The building is located in the municipality of Altopascio (Lucca, Italy) and has a rectangular plan with dimensions 15 x 11 m and a height of about 9 m, and it is made of hollow bricks and Italian-standard "doppio UNI" bricks. The floors are made of reinforced brick concrete slabs, connected to the walls by means of concrete curbs. The RC foundation is large enough to allow it to be connected to the retrofitting system. Mechanical and thermal properties of the external bearing walls are summarized in Table 1.

Table 1. Bearing walls’ mechanical and thermal properties. Element f m ( Mpa ) f v0 ( Mpa )

E m ( Mpa )

λ ( W/mK )

R ( m²k/W )

Ground floor bearing wall First floor bearing wall

5.8 5.3

0.2 0.2

4800 5300

- -

0.858 0.625

Plaster

-

-

-

0.700

-

The retrofit system is planned to be applied on all perimeter walls, except for that of the stairs (Fig. 2b). C25/30 concrete was chosen for the structural infill wall, reinforced with ϕ10 mm vertical rebars with a spacing of 250 mm and with ϕ6 mm horizontal rebars with a spacing of 200 mm. Rebars used for the RC walls are B450C, according to