PSI - Issue 78

Mattia Zizi et al. / Procedia Structural Integrity 78 (2026) 1721–1728

1722

1. Introduction Historical surveys and post-earthquake assessments of masonry churches in Italy have repeatedly highlighted the vulnerability of curved structural elements, particularly vaulted systems, to seismic actions (D’Altri et al., 2017; De Matteis et al., 2019). Among these, cross vaults in transepts, often present in churches with Latin cross plans, emerge as critical components due to their complex geometry and structural configuration. Over the past decade, this topic has garnered growing attention within the scientific community, leading to a rich body of research involving analytical formulations and numerical simulations (Alexakis & Makris, 2015; Gago et al., 2011; Galassi & Tempesta, 2019; Zampieri et al., 2024), as well as full-scale or reduced-scale experimental investigations aimed at deciphering the seismic response of such masonry systems (Bianchini et al., 2022; Carfagnini et al., 2018; Fagone et al., 2016). One of the key factors contributing to the seismic fragility of vaulted structures lies in the intrinsic material properties of masonry and the pronounced deformability of vaults compared to adjacent structural elements. These issues are further exacerbate d in cases where the vault’s boundary conditions are asymmetrical, as often occurs in transept areas: three of the vault’s edges are commonly restrained by stiff masonry walls, while the fourth side remains open, supported by columns or arches connecting to the nave. This irregular support arrangement can lead to uneven displacement demands and shear-induced stress concentrations, ultimately triggering local or global collapse mechanisms during seismic events. This study is embedded within the wider framework of the GENESIS research initiative, which is devoted to the development of risk mitigation strategies and sustainable conservation methodologies for historic urban centres in Southern Italy. As a preparatory step for a future experimental test on a large-scale vault prototype inspired by a real case study, the present work focuses on preliminary numerical investigations of a representative masonry cross vault and the definition of the test set-up to be performed at the Structural Laboratory of the LEDA Research Centre (Fossetti et al., 2017). 2. The reference case study The vaulted structure examined in this study is located within the transept of the Church of San Michele Arcangelo (Rouhi et al., 2022), a Romanesque cathedral situated in the medieval village of Casertavecchia, approximately 4 km northeast of Caserta (Italy). The church represents a historically significant case study for the analysis of masonry cross vaults. Originally built in 1113 under Norman dominion and completed in 1153, the cathedral underwent substantial modifications during the early 13 th century, particularly under the episcopate of Bishop Stabile (1207 – 1217). This phase included the construction of the transept and central dome, leading to the current latin-cross plan with three semicircular apses. The cross vault under investigation is part of one of the lateral arms of the transept (Fig. 1) and is presumed to date from this construction phase. Its decorative features differ from those of the earlier basilican scheme, supporting the theory that it was added later. The lateral arms of the transept are covered by a vaulted system, which is the reference case of the present study. The examined vault is a pointed cross vault generated by the intersection of four ogival arches, two of which, those oriented along the transversal axis, follow rectilinear directrices, with the keystone located at an elevation of approximately 13.0 m. The remaining two arches, oriented orthogonally, have an oblique directrices and converge at the same vault keystone, though their own arch keys are positioned lower, at 12.5 m. The vault occupies a rectangular plan area of 8.70 m × 9.00 m and is defined by a diagonal rib system with trilobed cross-sections, whose extrados width is about 0.55 m. These ribs spring from an elevation of 8.0 m above ground and rest on free-standing masonry piers. In contrast, the lateral ogival arches are embedded into the perimeter walls, with springing levels at 9.3 m. The location and geometry of the transept vault are shown in Fig. 2. This architectural configuration finds parallels in the broader context of medieval ecclesiastical architecture in southern Italy. In fact, the vault of the transept of San Michele Arcangelo has remarkable stylistic and dimensional similarities with contemporary examples such as San Lorenzo Maggiore and Sant’ Eligio Maggiore, both located in Naples. In particular, the ratio between the major and minor spans of the transept arms (L max /L min ≈ 1.10) in these churches is comparable to that observed in Casertavecchia, suggesting a shared design approach. Furthermore, the presence of pointed arches, cross vaults and the composition of the openings in the walls highlights a common architectural vocabulary.