PSI - Issue 78

Elisabetta Bonaguro et al. / Procedia Structural Integrity 78 (2026) 1016–1023

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Fig.6. Capacity curves ofthree different types ofunitary floor strengthening of the full cluster.

5. Unitary retrofit on a portion of the cluster Finally, the retrofit applied just in portions of the cluster is considered. The presented results (Fig. 7) refer to the two-units scenario (Fig. 1b), in which the taller unit is retrofitted in a unitary way, again with mixed brick and concrete slab, while the end one remains unreinforced. Also in this case, outcomes are equivalent for the two-units configuration and for the whole cluster. The base shear is computed by considering only the resultant horizontal forces developed atthebasenodesoftheunreinforced SU, in ordertoassesschangesinbaseshearanddisplacement capacitywhen the unit is paired with another retrofitted one; for this reason, the control node is located on its ridge rather than on the taller (retrofitted) unit.

Fig. 7.: Capacity curves of the unreinforced SU with retrofitted adjacent one, compared to its isolated response.

It is shown that the presence of a retrofitted adjacent SU excessively enhances the performance of the unreinforced one, showing almost a 100% increase in base shear with respect to the isolated condition; even the displacement capacity is unreliable, comparable to that exhibited by models with partial interventions (Fig. 3a,b). The juxtaposition of SUs leads to a 35% increase in base shear for the unreinforced one. These results are clearly unrealistic, astheywould implythat a SUbenefits from theretrofit of an adjacent one,highlighting a critical issue of continuous modelling, that is, the degree of connection between plate nodes.