Structural Behaviour of Umbrella Vaults Under Self-Weight: A Case Study

Masonry buildings belonging to the architectural heritage are often characterized by the presence of masonry arches, vaults, and domes. A thorough structural assessment of masonry vaults is essential from a conservation perspective, as these elements are often subject to damage, cracks, and, in some cases, collapse. In the literature, the structural behaviour of the most common vault types has been extensively investigated using a broad blend of techniques capable of capturing significant aspects of the complex behaviour of masonry. However, for some less common vault typologies, a comprehensive understanding of their structural response remains an open issue. In this multifaceted context, the present contribution aims to investigate the structural behaviour of a distinctive type of vault, namely the umbrella vault, in which a series of webs are arranged in an umbrella-like configuration. To this end, an iconic case study is selected for its geometric complexity, namely the umbrella vault of Masegra Castle (northern Italy). Peculiar aspects are manifold, the most important being the irregularity of the quadrangular plan. The analysis focused on the structural response of the vault under self-weight, in the presence and absence of supporting walls. During the modelling phase, an interdisciplinary approach was adopted, integrating historical and diagnostic information. Starting from the available data, the study proposes nonlinear finite element analyses, discussing the most appropriate modelling strategies, based on solid or plate/shell finite elements, and performing sensitivity analyses on the mesh used and the vault thickness.