In the framework of risk assessment at national and regional scale, the analysis of collapse mechanisms induced by seismic accelerations constitutes a useful tool to understand the behaviour of masonry structures and to plane mitigation strategies and rehabilitation interventions. In this perspective, the objective of the present study is the identification of the correlations among three factors: 1) structural-typologies which characterize Italian masonry buildings, 2) possible collapse mechanisms (in-plane and out- of-plane), 3) ground accelerations. The analyses developed concern a sample of 100,000 models representing the structural typologies of ordinary masonry buildings distributed on Italian territory. They have been derived through examination of structural characteristics (dimensions of structural elements, mechanical characteristics of material, typologies of horizontal structures and roofing, presence of vaults and/ or ties or ring beams, number of floors, etc.) collected by ‘in situ’ survey of about 250,000 buildings distributed along the Italian territory. For each model, the acceleration able to induce the first collapse mechanism has been calculated, adopting simplified limit state analyses. The results have been then elaborated to set, for different vulnerability classes (assigned combining typological- structural characteristics), the probability of occurrence of each collapse mechanism varying the peak ground acceleration (PGA) is analysed.
