Comportamento degli edifici in muratura nella sequenza sismica dell’Italia centrale del 2016 - Parte 1: Quadro generale

The seismic sequence of 2016-2017 in central Italy started on the 24th of August 2016. This event was followed by three other main events, the last of which occurred on the 18th of January 2017. This sequence induced severe damage in a very wide area of central Italy, spanning across the four regions of Lazio, Umbria, Marche and Abruzzi. Masonry structures constitute a significant percentage of the building stock in the affected area. This paper aims at describing and commenting the seismic behavior of residential unreinforced masonry buildings, starting from a critical analysis of the damages observed after the seismic events of the sequence. The existing building stock of the area is mainly characterized by stone masonry buildings with wooden floors and/or with vaults. Thanks to the occurrence of relatively frequent seismic events of significant intensity even in the recent past (Valnerina 1979, Umbria-Marche 1997, L’Aquila 2009), the damage in several buildings was limited by the presence of strengthening intervention or aseismic devices. However, in many sites, the seismic behavior was largely unsatisfactory, due to the use of very poor materials (mortar) and due to the inadequate maintenance conditions of old buildings. Along these lines, significant differences could be observed in the damage level occurred in nearby municipalities, belonging to different regions, with a different history. Similarly to what occurred in other recent events, very limited damage was instead observed in case of modern masonry buildings, although they are only few in the affected area