PSI - Issue 78

Marco Postiglione et al. / Procedia Structural Integrity 78 (2026) 984–991

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affect the structural-typological features of the school buildings, in this study the archetypes are classified mainly based on in-plan configurations (Figure 2), considered as an important discriminant of the structural behaviour. Figure 2a illustrates a representative sample of the surveyed building stock, highlighting the typical distribution of the volumes and the frequent adoption of courtyard-like or comb-shaped layouts mostly composed of simple rectangular geometry. These configurations reflect standard design practices from the mid-20th century. Figure 2b provides a schematic synthesis of the most recurrent plan geometries encountered during the survey highlighting the geometry composition through addiction, confirming the prevalence of regular modular arrangements based on repetitive RC frames. Together with on-site visual inspections and archival research activities, geometric, structural, and material data were collected. Based on these, the building configurations were condensed into four representative archetypes. 3.1. Representative structural archetypes Drawing on the above-described characteristics, several structural archetypes representative of the majority of mid 20th-century Italian RC school building archetypes are defined in the following (recalled in Figure 2d): • Archetype A : Low-rise rectangular-shape school. This archetype represents the most recurrent configuration among RC school buildings. It consists of low-rise building (typically two or three storeys) with a markedly elongated rectangular floor plan. The structural layout is defined by repetitive classroom modules aligned along the main longitudinal axis, usually flanking a central or lateral corridor. Frequent dimensions range for a classroom are between 6.0-8.0 m, with a corridor of range between 1.5-3.0 m. The lateral load-resisting system is composed of RC frames (in one direction, less frequent in two directions) with masonry infills, while floor and roof systems are cast-in-place RC slabs, ensuring in-plane diaphragm action. The regularity in plan and elevation generally results in a favourable seismic response in terms of loads distribution. Nonetheless, the presence of large window openings and limited reinforcement detailing (e.g., inadequate joint confinement, stirrups, etc.) can compromise the local behaviour of the structural elements, particularly in the transverse direction. Short-column effects can be pronounced. • Archetype B : L-shape school. This archetype encompasses buildings with irregular L or T-shaped plans, typically composed of two intersecting wings with differing lengths and/or orientations. The layout arises from functional or spatial constraints in urban contexts, with similar dimensions highlighted for Archetype A. These configurations introduce inherent torsional eccentricities and discontinuities between the wings, which are especially critical under earthquakes. Unless separated by seismic joints (rarely implemented these construction at the time), these buildings are prone to stress concentrations, differential displacements, and out-of-plane failures at re-entrant corners. While generally composed of two or three storeys, these buildings present irregularities both in plan and/or in elevation, depending on floor height variations between wings. • Archetype C : Courtyard or C-shaped school. This archetype is characterized by buildings with a C-shaped or partially enclosed courtyard plan. Typically developed on two to three storeys, this configuration results from the extension of classroom blocks around a central void or service zone. The re-entrant geometry inherently produces stiffness and mass asymmetries, generating complex seismic responses dominated by torsional modes. The points of discontinuity at internal corners are especially susceptible to cracking and failure of structural and non-structural elements, as for Archetype B. While such configurations may offer advantages in terms of natural lighting and functional zoning (even for the symmetrical position of the staircase), it represents a seismically vulnerable layout due to stress localization in the wing’s joints. • Archetype D : Compact block with central courtyard school. Though lesser common, this archetype comprises buildings with a nearly square or compact rectangular plan arranged around a central courtyard or lightwell, resembling an “O” shape in plan. These structures, generally mid -rise (three or four storeys, occasionally more). The surrounding perimeter frames enclose an internal void, concentrating lateral resistance along the outer envelope. This configuration can induce inward-acting diaphragm forces and potential in-plane discontinuities if not adequately detailed. Moreover, the increased building mass and vertical extension