An archetype-based automated procedure to derive global-local seismic fragility of masonry building aggregates: META-FORMA-XL

The paper presents an automated procedure for deriving fragility curves for typological masonry aggregates, named META-FORMA-XL (MEchanical-Typological Approach FOR Masonry Aggregates – X Local). The topic deals with the urban-scale seismic vulnerability analysis, which can provide powerful information for developing risk mitigation plans and implementing strategies for reducing expected losses. However, when masonry buildings in aggregate are analysed, many issues arise, related to the lack of data, the complexity of the structural configurations and the presence of uncertainties. To this scope, the proposed procedure aims to investigate the seismic behaviour of masonry aggregates, based on numerical analyses carried out on ideal representations of the existing building stock, indicated as archetypes, by modelling geometrical and mechanical uncertainties characterizing buildings in the studied area. The archetype buildings are made according to exposure analyses by combining typical inventory collection forms and information derived from freely available databases. By investigating the seismic response of numerical models for a high number of archetype buildings, fragility curves are derived for all limit-states and two main directions, accounting for global and local damage mechanisms. The procedure is tested on low-rise row masonry aggregates in Southern Italy. The output of the procedure is validated on a real case study, for which a near-full information on the geometrical and mechanical features is available, providing a critical comparison in terms of fragility curves. Results highlight several advantages of the proposed approach, such as the possibility of identifying the most likely collapse mechanism for a specific masonry aggregation, the simplicity and the celerity of the analyses despite the large number of archetype models, and the exhaustive consideration of the uncertainties. Finally, the proposed concept can be readily extended to other aggregation forms and structural typologies.