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 summer cooling point was set at 26°C from 7AM to 10PM; during night hours the cooling system was supposed to be turned off, given the possibility of taking advantage of natural ventilation. 3.3. Structural and energy assessment – Retrofitted condition The retrofitted configuration foresees the application of the proposed system in connection to existing masonry walls in correspondence of RC curbs, with the aim – as said – of transferring only horizontal seismic actions. From a structural modelling point of view, this was realized through shell-type elements (representing the retrofitting system) connected using rigid link elements located at the beam-elements representing the concrete curbs. The presence of links ensures the transmission of horizontal actions only, while vertical ones continue to be carried by the existing masonry structure alone. For the thickness of the RC walls, as said ‘discontinuous’ due to the presence of the blocks’ ribs, an equivalent thickness, given by the total area of the concrete in the cross section of the infill wall, divided by the length of the wall itself, as prescribed by the Italian Guidelines (Linee Guida, 2011) was considered. Modal and linear dynamic analyses were performed on the new model, hereinafter referred to as 'design condition'. The retrofitted structure results, as expected, stiffener than the original one (Table 2) and therefore subjected to lower displacements. However, the fundamental period of the retrofitted structures still fell within the plateau of the response spectrum, leading to no variation in the related spectral acceleration.

Table 2. Modal analysis results for the "state of art" and the retrofit configuration. Model Mode Period ( s )

Modal Participation Mass ( % )

state of art state of art design state design state

1 2 1 2

0,307 0,255 0,255 0,219

M y M x M y M x

45 40 44 39

The introduction of the retrofitting system leaded to a mass increment: more specifically, the seismic weight highlighted an increment of 30% from the state of art configuration to the design state, with a corresponding increase of the seismic base shear of about 6%. The introduction of the retrofit system globally led to the increase of the safety level towards the design spectrum for the LS limit state: this increment has been measured in terms of ultimate in plane and out-of-plane bending moment (M u ) and ultimate shear strength to sliding (V su ) and diagonal cracking (V du ) in accordance with Italian Standard for existing buildings (D.M.17 gennaio, 2018).

Fig. 3 (a) Plan view of the ground floor - 'state of art'; (b) Plan view of the ground floor - 'design state'.

Results have been expressed with reference to the demand/capacity (D/C) ratio, excluding the elements not meeting the minimum criteria set by the regulations in terms of geometry and slenderness ratio. Safety checks were performed in correspondence of the most relevant sections of each masonry structural element, i.e., base and top sections for in plane actions and midpoint section for out-of-plane actions. With regard to the latter, the presence of perimetral curbs