A Methodological Path to Assess the Out-of-Plane Vulnerability of Archaeological Walls in the Pompeii Archaeological Park

In archaeological contexts, isolated or poorly connected masonry elements are very common due to the absence of floors and weak connections between walls. As a result, under horizontal actions, vulnerability to out-of-plane (OOP) failures often becomes the most critical issue for their preservation. As is well-known, limit analysis-based approaches provide a reliable assessment of the expected OOP failure mechanisms and the associated acceleration capacity for existing masonry buildings. However, these approaches mainly refer to box-type buildings and cannot be directly applied to archaeological remains, whose morphology may differ significantly. With a specific focus on the Pompeii Archaeological Park (PAP), this study proposes a two-level classification of archaeological walls aimed at identifying their most likely OOP failure mechanisms and the most suitable analytical models available in the literature to predict their behaviour. The first level identifies recurring typologies based on the morphology of wall connections, relying on geometrical data that can be easily obtained from maps and/or on-site surveys. The second level then evaluates the effectiveness of these connections by investigating their construction techniques. The paper, therefore, proposes a general methodology for assessing the vulnerability of archaeological masonry walls to OOP failure mechanisms and discusses its application to some walls in the PAP.