# An Overview of the Historical Retrofitting Interventions on Churches in Central Italy
## 5 Conclusions  
Earthquakes have always marked the history of the affected territories and of their cultural heritage. Indeed, many of these events have not only caused losses of human lives but have also influenced the economy and the depopulation of several areas. Building reconstructions can be costly and challenging but are also a chance to explore new techniques, for both stylistic and structural modernization. In this paper, an overview of the structural features--relevant from a seismic viewpoint--of a significant sample of 600 churches located in Central Italy was presented, following the damage reconnaissance carried out in 2016 and 2017. The main post-earthquake interventions applied in the past to these heritage churches have been extensively described and their effectiveness discussed through comparative statistical analyses. The main fragilities that have threatened, and continue to threaten, this type of construction have been also identified. In the light of the findings from the post-earthquake survey conducted on the aforementioned sample of churches and of the extensive analyses performed hitherto, the following conclusions can be drawn:  
* The structural features of the surveyed churches, which soundly affected their seismic response, are often the result of past seismic events and subsequent post-earthquake reconstruction processes, whose knowledge is fundamental to provide reliable predictions of future damage scenarios;
* The seismic damage related to out-of-plane mechanisms was sufficiently reduced by the presence of transversal and longitudinal ties; conversely, churches with heavy RC roofs and ring beams, especially if placed on a poor-quality masonry, led to the worst seismic behavior, leading to 89% unusable churches in the area located at distance d < 25 km from the epicenter;
* Additions to the original plant represented a further source of vulnerability against horizontal actions;
* The lack of prompt temporary interventions after the first shock increased the proneness of the churches to undergo cumulative permanent damage during the aftershocks, which in some cases led to partial or complete failures. Figure 30: Masonry discontinuity: (**a**) San Rocco Church, Pietracamela; (**b**) S. Maria Immacolata Church, Isola Del Gran Sasso. The present work is not intended to be exhaustive, but it provides the first results from months of data collection and years of data storage, hierarchical classification and comparative analyses aimed at extracting valuable information to feed seismic fragility curves and predict future potential damage scenarios. In this sense, this work represents an important baseline reference for more accurate large-scale vulnerability assessments at the supra-regional scale. It is important to highlight that the variables affecting the severity of the seismic damage observed in the analyzed sample of churches are not only related to the magnitude of the seismic shake, the distance of the structure from the epicenter and the type of retrofitting/strengthening intervention. Indeed, local site effects can play a major role, ultimately altering the expected damage scenario. This aspect adds further complexity to the study and is currently the subject of extensive research by the authors. The obtained results will be ultimately exploited to identify archetypes of churches, namely church models featuring analogous (expected) seismic behavior, based on their typological characteristics and the interventions undertaken in the past. The definition of archetypes will enable in-depth empirical and analytical studies in order to quantify the seismic capacity improvement associated with different retrofitting solutions and to compare the costs and benefits of each intervention in historic churches for decision-making support at the governmental level. Conceptualization, G.C. and M.G.M. ; methodology, G.C. and M.G.M. ; validation, G.C. ; investigation, G.C. ; resources, C.V.; writing--original draft preparation, G.C. ; writing--review and editing, G.B. and M.G.M. ; supervision, G.B.