Damage evolution in churches due to repeated earthquake shocks

Many ancient masonry churches reported considerable damage in the earthquakes that occurred in Italy in the last decades. In order to protect this heritage, dedicated research projects collected the effort of a large research community, producing methods for vulnerability assessment and damage classification, and criteria for seismic improvement. Considerations deriving from different surveys carried out by the authors on churches damaged in the recent Central Italy, 2016, earthquake are reported here. The surveys have been performed in the Region Marche at different times. Some churches inspected at the beginning of October 2016, after the first strong earthquake shocks, could be revisited in Spring 2017 after the strong events at the end of October and in January 2017. These surveys offered the opportunity of observing the evolution of damage and to assess some effects of the structural improvement interventions that had been carried out prior to the earthquake. In summary, the seismic events that arrived after the first surveys increased the damage on these already weakened structures, developing further the damage mechanisms that had been identified. In some instance the situation evolved into localized collapse, but in most cases the global stability was maintained. While further investigations including numerical modeling are in progress, observations confirmed that simple and low-impact interventions are effective in limiting some damage typologies; in some of these cases, however, damage developed moving to different elements, most likely for a higher level of action.