Issue 51

F. Clementi et alii, Frattura ed Integrità Strutturale, 51 (2020) 313-335; DOI: 10.3221/IGF-ESIS.51.24 314 permitted to validate the selected approach. Finally, from results and conclusions provided by this case study, it is possible to affirm that the used methodology may be applied to a wide variety of historical masonry structure in Europe. K EYWORDS . Masonry Towers; Damage Assessment; Non-Smooth Contact Dynamics Method; Damage Cumulation. I NTRODUCTION he damage assessment of historical masonry buildings is one of the most difficult tasks to accomplish in structural mechanics, since this kind of structures is commonly heterogeneous, with complex geometries, irregularities and absence of a box behaviour due to defective connections between different structural parts, in particular walls and floors, that often play a fundamental role. However, the knowledge of the dynamical behaviour is crucial for a reliable seismic vulnerability assessment, which became more and more important due to recent catastrophic earthquakes that stroked Italy in the last few decades (Umbria-Marche 1997–1998, Abruzzo 2009, Emilia-Romagna 2012, Marche-Lazio- Umbria-Abruzzo 2016) [1–4]. Figure 1 : Geographical location of the civic bell tower of Amatrice (Rieti, Italy) and of the epicentres of the four main shocks of the Central Italy seismic sequence of 2016 on the Italian Macro seismic intensity map (https://emidius.mi.ingv.it/) Towers and belfries are peculiar structural type which characterizes Italian architectural heritage. These structures are distinguished by the poor-quality of local materials which were often deployed, i.e. brick masonry walls that in most cases are non-plastered and bound by poor mortar. Furthermore, these buildings were based on simple architectural forms, with a predominant vertical development. For these reasons, the primary aim is to develop a detailed analysis of interpretative models that can efficaciously predict the behaviour of these structures under seismic actions [5]. To investigate the mechanical behaviour of masonry structures, commonly finite element methods are used, often including very sophisticated constitutive laws taking into account post-elastic behaviours and damage [6–12]. These methods, while being very appealing, do not focus on the possible non-smooth nature of the dynamic response, which can come sliding and impacting between different blocks, a fact that turns out to be common both right before and during the collapse. T