Comparative study on two analytical mechanical-based methods for deriving fragility curves targeted to masonry school buildings

Seismic events across several countries in the world have highlighted that strategic buildings, such as schools, may exhibit vulnerability levels that are in some cases higher than those of ordinary buildings. It follows the urgent need of reliable risk analyses to support the decision-making for large-scale mitigation policies. To this aim, the derivation of fragility curves, able to capture typological and constructive characteristics, constitutes an essential requisite. Within this context, the paper presents a comparative study on the use of two analytical-mechanical based methods for assessing fragility curves of Italian masonry school buildings. These are very often characterized by a number of stories rarely higher than three, presence of rigid floors, significant inter-story height, and great distance between transverse walls. Among the others, analytical approaches, either based on numerical or mechanical models, are more suitable to capture the effects of such features on the seismic vulnerability. The two methods discussed in the paper are “Vulnus Vb 4.0-2009”, developed at the University of Padova and based on the integrated use of mechanical and macroseismic approaches, and “DBV-Masonry (Displacement Based Vulnerability)”, a pure mechanical-based model developed at the University of Genoa. Both methods are applied to a stock of 14 masonry schools, selected as prototypes of Italian school masonry buildings. The critical review and comparative application of the two methods allow highlighting their similarities and differences in assessing the fragility associated to in-plane and out-of-plane failure mechanisms. Moreover, as some of the selected schools had been hit by the 2016-17 Central Italy earthquake sequence, the evidence of the real response allows assessing the actual reliability of the methods.