Seismic vulnerability of the nave arcade in three-aisled churches

Seismic events have shown the significant risk of collapse faced by traditional masonry churches during earthquakes, highlighting the need for a reliable structural assessment and effective strengthening interventions. In historical churches, seismic damage is typically associated with the activation of local mechanisms, rather than a global structural behavior. Among the recurrent local mechanisms observed in multi-aisled churches, there is the collapse of the nave arcade. This architectural feature is typically used to separate the central nave from the side aisle and is composed of arches placed at the top of columns or slender piers, creating a sense of openness and enhancing the architectural quality of the interior. The arches are usually characterized by large spans and limited restraints (both in the longitudinal and transverse directions), which makes the nave arcade highly vulnerable to seismic actions. This research investigates the seismic vulnerability of the arcade in a three-aisled, case study church characterized by a traditional open timber truss roof (i.e. without cross-vaulted roofing). The local failure mechanisms (both in-plane and out-of-plane) are examined through Finite Element numerical analysis. The effect of a roof bracing intervention using diagonal steel ties for the prevention of the local collapse of the arcade is also analyzed. The results provide valuable insights into the seismic behavior and vulnerability of these complex monumental structures.