A Comparison Between Empirical Procedures for the Definition of Vulnerability Classes of Masonry Buildings: Application to Five Historical Centres Struck by 2016 Central Italy Earthquake

Abstract

. The definition of seismic risk scenarios necessarily depends on the attribution of a vulnerability class to each building of a stock. In the macroseismic scale (EMS-98) the vulnerability class – from A to F – results from the combination between horizontal and vertical structures. On the basis of post-event surveys carried out in Italy after the earthquakes occurred in the last 50 years, many rules for converting the masonry quality and the stiffness of horizontal diaphragms into a vulnerability class have been proposed. However, despite the now high number of retrofitted or strengthened buildings in Italy, structural interventions are not mentioned in these procedures, except for metal tie rods and r.c. tie beams. The paper proposes a critical approach to the definition of vulnerability classes, by the means of applying the conversion rules to the same sample of 525 masonry buildings located in five historical centres struck by 2016 Central Italy earthquake: Acquasanta Terme, Campi Alto di Norcia, Castelsantangelo sul Nera, Muccia and Vezzano. They have been chosen due to the extensive strengthening campaigns that had been carried out after earlier seismic events. The preliminary recognition of the structural features of each building happens at the terms of the MUSE-DV Masonry, a rapid visual screening procedure recently proposed by the authors. The damage probability matrices (DPMs), obtained from each conversion, are compared to those from a theoretical model proposed for the EMS-98. Given the same poor masonry quality, the existing rules