PSI - Issue 44

Gaetana Pacella et al. / Procedia Structural Integrity 44 (2023) 1324–1331 Gaetana Pacella et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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Fig. 7. Spatial EF frame model

Within the EF model, the flange effect has been taken into account considering different connection degrees between the transverse walls. In particular, the cross-sections of the piers have been modelled by assuming flanges with different length, and the amount of the axial force acting over the piers have been increased proportionally. In particular, the cases listed below have been considered to model the building (Fig. 8): (a) Without flanges : the contribution of the orthogonal walls has been neglected (i.e., the piers have a rectangular cross-sections) (Fig. 8a); (b) Small flange : the piers have L- or T-shaped cross-sections at wall-to-wall intersections. For L-shaped sections, the flange length is equal to two times the wall thickness, while for T-shaped sections the length is equal to three times the wall thickness (Fig. 8b); (c) Medium flange : for L-shaped sections, the flange length has been set equal to three times the wall thickness; while for T-shaped sections, the flange length has been fixed equal to five times the wall thickness (Fig. 8c); (d) Large flange : a flange length has been set equal to the half of the orthogonal wall (Fig. 8d). As for the case study of Petrucci Palace above discussed, two different limit behaviors have been considered for the spandrels, WS and RS. In particular, the case RS simulates the spandrel with a reinforced concrete ring, provided flexural and shear strength and stiffness. In the case WS, the structure has been modelled with a set of full- height cantilever walls connected by axially inextensible pendulums at each story (Configuration A - Fig. 9a). In the case of RS, the spandrels have been modelled by considering sub-configurations: ( i ) single horizontal beam-like element (Configuration B - Fig. 9b) and ( ii ) multiple horizontal elements. In latter case, the upper and lower elements represent the masonry sub- and upper-windows, while the horizontal one represents the reinforced concrete ring beam (Configuration C - Fig. 9c). According to ISR 2019, two different horizontal seismic action patterns have been adopted to carry out nonlinear static analyses: Uniform Patter-UP (horizontal actions proportional to the building masses at each story), and Modal Pattern-MP (horizontal actions are proportional to the first modal-shape of the structure). In Fig. 10, the pushover curves relative to the Configurations A and B, and for MP pattern, are showed. In each figure four curves have been plotted, representing the four geometries of flanges indicated in Fig. 8. The curves corresponding to the Configuration C have been not included in the figure because resulted practically coincident with those of the Configuration B. This leads to a first consideration: to model the spandrels by considering the configuration C can result time-consuming because gives rise the same result of the Configuration B. a) b) c) d)

Fig. 8. Different connection degrees between orthogonal walls: (a) without flanges, (b) small flange, (c) medium flange, (d) large flange