PSI - Issue 44

Romina Sisti et al. / Procedia Structural Integrity 44 (2023) 1848–1855

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Romina Sisti et al./ Structural Integrity Procedia 00 (2022) 000–000

a systematic series of surveys of monumental buildings with two targets: churches and palaces. For both, a survey form has been adopted and in particular, for churches, the A-DC2006 is used. In the form are reported information about the item identification and principal geometries, the usability, the safety countermeasures suggested, the number and type of artworks present inside, and an evaluation of the damage. This essential tool acquires another relevant function in the research field since a large number of data of damage are recorded that, together with the information on the seismic intensities, may provide an estimation of the vulnerability of these structures. Indeed, assessing the vulnerability of buildings is a fundamental step in defining seismic risk and allowing the implementation of seismic risk mitigation actions. The creation of fragility curves for groups of buildings with homogeneous vulnerability is possible using different methodologies, one of which is based on the damage observed following a seismic event. For this reason and in order to intervene on damaged structures to prevent further damage, the Department of Italian Civil Protection (DPC) has developed survey forms to collect the damage reported by several types of buildings (residential buildings, long-span buildings, churches, historic buildings), in a standardized way. The systematic observation of the damage suffered by churches during the major Italian earthquakes of recent decades has shown how the seismic behavior of this type of buildings can be represented through a series of failure mechanisms related to separate and structural independent architectural portions of the church, called macro-elements (Doglioni et al. 1994, D’Ayala and Speranza 2003). The possibility of activating each mechanism occurs almost entirely related to the presence of specific macro elements constituting the building instead of the material or the rest of the church. Following the 1979 earthquake in Friuli region, several studies were undertaken to classify the damage and collapse modes of churches. The observation of post-earthquake damages led in 1987 to the formulation of a first damage survey form (GNDT - Model S3), which summarized the different ways of damage of churches through 18 typical collapse mechanisms. This form was tested, refined, and integrated over the years. The product of the integration process is the “A–DC form”, still in use today, officially approved by the Decree of the President of the Council of Ministers on February 23, 2006 (DPCM 2006) and adopted as damage survey form in emergency phase by the Ministry of Culture with the Directive of the April 23, 2015 (MiBACT 2015). The main purpose of the form is to give the usability outcome and the damage level of the churches in the post-earthquake emergency phase. The A-DC form is subdivided into two sections, each one containing a certain number of sub-sections. The first section is structured in 13 sub-sections (A1 – A13) and contains general information of the building and of its context. The second section is structured in 14 subsections (A14 – A27) and contains information related to the maintenance state, the damage assessment, and the evaluation of the usability outcome. The damage observed in churches during the 8 main earthquakes occurred in Italy starting from the 1997 (Umbria 1997, Molise Puglia 2002, Piemonte 2003, Salò 2004, L'Aquila 2009, Emilia 2012, Centro Italia 2016 - 2017, and Ischia 2017) were digitalized and collected in a database searchable on the IT-platform Da.D.O. Churches created by DPC (Calderini et al. 2022) (https://egeos.eucentre.it/danno_osservato/web/danno_osservato). This digitalization and collection of data aim at improving and better understanding the vulnerability models of churches in order to allow the study and creation of seismic risk maps. The analyses here presented concern the data of 225 churches inspected during the 2016-2017 Central Italy seismic sequence that severely affects also churches (Penna et. al 2019). The survey campaign has been activated after the 24 th of August earthquake M w 6.0 that stroke Amatrice but it has interrupted after the two events of the 26 th of October and restarted in a second phase after the other earthquake of the 30 th of October M W 6.5 which stroke Norcia. Moreover, another third phase of the surveys has activated after the events of January 2017. This subdivision, especially due to the main shock of Norcia, required checking some structures again. At the end of the survey campaign, this sequence of events produced that some churches have investigated by different technicians. The collection of the forms related to the churches inspected twice might allow an evaluation of the incremental damage due to the subsequent earthquakes, for example in the center of Amatrice. A first approach to this topic, related to a few cases of the same technicians provided encouraging results (Cescatti et al., 2020) but was too limited in the number of observations. The extensions of the form collection to a higher number of data (225 churches) gathered among six universities give the chance to evaluate also the form itself and the influence of the technician. Indeed, as introduced above, the form reports some general information about the church and also recognize the macro-elements present and the possible mechanisms. In this light, since these data related to the structural description of the church are not influenced by the damage, the forms should be the same contrary to what has been observed. Previous research has already highlighted some critical issues of the A-DC form like the lack of flexibility in considering mechanisms do not present among those listed in the form (Lagomarsino et al. 2019). This work aims to evaluate what are the situations in which technicians do not correctly identify the macro-elements in a church and the related possible mechanisms, including those already listed in the form. For this purpose, the two forms relating to the same church were compared for all 225 churches in the study and the aspects that affect the judgment of technicians are evaluated. The reduction of these critical issues would allow to have more accurate damage databases and therefore the improvement of risk assessment models