PSI - Issue 44

Annalisa Rosti et al. / Procedia Structural Integrity 44 (2023) 91–98 Annalisa Rosti et al. / Structural Integrity Procedia 00 (2022) 000–000

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7. Conclusions

This paper focuses on the observational seismic vulnerability of Italian churches, evaluated by statistically processing post-earthquake damage data of 1843 masonry churches hit by the 2016-2017 Central Italy seismic sequence. In line with the key features of the Italian national seismic risk platform (Borzi et al. 2021), the peak ground acceleration was employed for punctual seismic input description. A PGA value, estimated from the latest INGV ShakeMaps (Michelini et al. 2020) and suitably accounting for the several main shocks of the earthquake sequence, was associated with each inspected church. Taking advantage of damage information from the post-earthquake survey form, global damage levels were defined based on the maximum level of damage detected on individual collapse mechanisms. Seismic vulnerability was quantified by deriving observational damage probability matrices for URM churches, then refined based on census parameters, such as plan area and construction age. Given its simplicity and immediacy, the binomial distribution was employed for providing a parametric representation of DPMs. Comparison of observed and expected frequencies of occurrence of damage levels pointed out the adequacy of the binomial model to reproduce the overall damage distributions. The effect of damage progression due to repeated ground shaking on the empirical seismic vulnerability of masonry churches was investigated by comparing damage data collected during the first and last post-earthquake inspections. Although the general tendency of the mean damage to increase from the first to the last post-earthquake survey, impact of cumulated damage on resulting DPMs was found to be limited, given that less than 10% of the available dataset was inspected multiple times. Results pointed out the tendency of seismic vulnerability to increase as a function of the experienced ground shaking. Despite their capability of capturing the peaks of damage, which is essential in case of territorial unusability impact scenarios (da Porto et al. 2021), approaches based on the maximum level of damage may underestimate the frequency of lower damage states. Based on this consideration, alternative damage metrics, either based on the mean damage level (e.g. Cescatti et al. 2020; Canuti et al. 2021) or accounting for the geometrical extent of each individual macroelement (e.g. Lagomarsino et al. 2019), will be explored in the future. Furthermore, the available post-earthquake dataset will be further statistically processed to derive observational fragility curves of Italian URM churches. Alternative seismic intensity measures may be also considered in the future for characterizing the severity of the earthquake shaking. Acknowledgements This work was developed under the financial support of the Italian Department of Civil Protection, within the ReLUIS-DPC 2019-2021 and ReLUIS-DPC 2022-2023 research Project, which is gratefully acknowledged. The Authors would also like to thank the team of colleagues, co-workers and students who voluntary participated to the post-earthquake surveys. Post-earthquake activities were conducted by the Italian Centres of Competence on Earthquake Engineering ReLUIS and EUCENTRE, under the coordination and supervision of the Ministry for Cultural Heritage and of the Department of Civil Protection. References Canuti, C., Carbonari, S., Dall’Asta, A., Dezi, L., Gara, F., Leoni, G., Morici, M., Petrucci, E., Prota, A., Zona A., 2021. Post-earthquake damage and vulnerability assessment of churches in the Marche region struck by the 2016 Central Italy seismic sequence. Int J Archit Herit, 15(7):1000 1021. Carbone, C., 2021. Processing of post-earthquake observations for the derivation of fragility curves of Italian churches”, MEng Thesis, University of Pavia, Faculty of Engineering, AY 2020/2021. In Italian. Cescatti, E., Salzano, P., Casapulla, C., Ceroni, F., da Porto, F., Prota, A., 2020. Damages to masonry churches after 2016-2017 Central Italy seismic sequence and definition of fragility curves. Bull Earthq Eng, 18(1):297-329. Cifani, G., Lemme, A., Podestà, S., 2005. Beni monumentali e terremoto. Dall’emergenza alla ricostruzione. ISBN-10: 8849615817. In Italian. D’Ayala, D., 1999. Correlation of seismic damage between classes of buildings: churches and houses. In: Seismic damage to masonry buildings. Proceedings of international workshop on measures of seismic damage to masonry buildings, pp 41-58. da Porto, F., Silva, B., Costa, C., Modena, C., 2012. Macro-scale analysis of damage to churches after earthquake in Abruzzo (Italy) on April 6, 2009. J Earthq Eng, 16(6): 739- 758. Borzi, B., Onida, M., Faravelli, M., Polli, D., Pagano, M., Quaroni, D., Cantoni, A., Speranza, E., Moroni, C., 2021. IRMA platform for the calculation of damages and risks of Italian residential buildings. Bull Earthq Eng, 19:3033-3055.