PSI - Issue 44

Gaetana Pacella et al. / Procedia Structural Integrity 44 (2023) 1324–1331 G. Pacella, A. Sandoli, B. Calderoni, G. Brandonisio/ Structural Integrity Procedia 00 (2022) 000 – 000

1328

5

a)

b)

2D-shell with RS EF without WS (TD) EF with RS (TD) EF with RS (TR) EF without WS (TR) 2D-shell without RS

2D-shell with RS EF without WS (TD) EF with RS (TD) EF with RS (TR) EF without WS (TR) 2D-shell without RS

Fig. 5. (a) EF idealization of the Martoglio’s wall in Catania (southern Italy) and (b) force-displacement response

2.2. Flange effect The in-plane structural behavior of masonry buildings is influenced by the effectiveness of connection between the orthogonal and the longitudinal walls (pier-to-pier), also recognized in literature with ‘ flange effect ’ . Despite that first studies on this topic date back to 1990s (Tomazevic et al. 1993), it is still under studying in literature and represents a difficult task (Sajid et al. 2018, Cattari et al. 2022). For practical applications the main issue consists of identifying an effective flange length to include in the EF model, depending on the connection degree between the transverse walls (Ottonelli et al. 2022). Flange effect can be modelled by means of an enlargement of the transversal cross-section of masonry piers, obtaining L- or T-shaped sections. This means to add a portion of section (i.e., flange) to the original rectangular cross-section of the pier. Frequently, a flange length equal to that of the entire orthogonal pier is assumed within the commercial software: this choice can be not well representative for existing masonry buildings because it is related to the shear strength in vertical direction at wall-to-wall connection or, in other terms, to the capacity of withstanding the sliding at flange-to web intersection, often characterized with reduced interlocking among the stones. Any case, the introduction of a flange is often beneficial for the in-plane capacity of the walls because it increases ( i ) the axial force over the pier (and then its ultimate flexural and shear strength) and ( ii ) the global lateral stiffness of the wall (due to the modification of cross-section geometry). The effectiveness of the flange effect on the global seismic behavior of masonry constructions has been investigated in this paper, with reference of a real building (Fig. 6a) located in Pizzoli (central Italy). It is a two-story URM building, plus declared a basement, having an irregular U-like plan (Fig. 6b). The construction, which was the town hall building, was unusable following the 2016-17 central Italy seismic sequence. A spatial EF model of the building (Fig. 7) has been developed through the computer program SAP2000 v18 and linear and nonlinear static analyses both for X and Y directions carried out. The building has been modelled with in plane infinitely rigid diaphragms, with masses concentrated in the center of gravity at each story. The nonlinear behavior of piers and spandrels has been modelled through a lumped plasticity model (e.g., plastic hinges) with elastic perfectly plastic behavior, whose strength and deformation capacity are those defined in the ISR 2019.

a)

b)

Fig. 6. (a) Pizzoli’s building and (b) plan of the mezzanine floor