PSI - Issue 44

Brandonisio Giuseppe et al. / Procedia Structural Integrity 44 (2023) 1292–1299 Giuseppe Brandonisio et al. / Structural Integrity Procedia 00 (2022) 000–000

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Fig.4 gives a simplified plan scheme of the whole system, that indicates the location of the R.C: shear walls and rubber devices.

Fig. 4. Layout distribution of R.C. shear walls and rubber devices HDRB.

4.1 Structural analyses of the retrofitted school and comparison with the AS-IS configuration To evaluate the effectiveness of the hybrid solution for seismic retrofitting of the school building complex “R. Caccioppoli”, four different FEM model (by using SAP2000 – vers.23) have been analysed: model 1, that represents the school at the current state; model 2, that has been obtained from model no.1, by jointing the three portions at each floor level; model 3, that results inserting the shear walls in the model 2; model 4, that derives from model 3, introducing rubber devices at the base of the shear walls and pillars, to simulate the strengthen complex after the abovementioned structural interventions. In Fig.5 – Fig. 6 – Fig. 7, their dynamic characteristics are compared.

Fig. 5. Comparison between dynamic characteristics of the four models- 1 st vibration mode.

In detail, from Fig. 5 is visible that the fundamental period of the structure at the current state, T 1 =1.37s, is reduced to T 1 =0.37s for the model 3, i.e. for the fixed base model of the whole complex, having the three buildings connected at each level and strengthen by using shear walls; later, the introduction of BIS on the last model 3 leads to increase of vibration period to T 1 =3.82s (model no.4 – final design solution), recording a seismic isolation ratio of 3.82/0.37 = 10. Similar considerations refer to Fig. 6 and Fig.7, that look at the second and third vibration mode. Fig.8 shows a comparison between the cumulative mass percentage in x-direction (left) and y-direction(right), looking at the four models. It is visible that the model 4 (final design solution) has a regular structural behaviour: it is able to involve the 100% of the participating mass through the first three vibration modes (model 4 - red curve). On the contrary, the whole complex at the current state (model 1 – blue curve) needs 12 vibration modes to include 90% of the total seismic mass.