Seismic empirical fragility curves of the Marche Region churches after the 2016 Central Italy seismic sequence

2016 Central Italy seismic sequence seriously damaged many historical buildings of the Italian cultural heritage, especially churches. The damage of churches is due to intrinsic peculiarities of their structural systems, not capable to develop an efficient box-like resisting mechanism. Teams of technicians coordinated by the Department of Civil Protection and the Ministry of Cultural Heritage and Tourism carried out a substantial survey of churches to assess the occurred damage and their usability by registering occurred damages in a specific survey form. In this paper, a methodology for processing damage data collected in the survey of Marche Region churches is addressed in order to propose a probabilistic response model. Descriptions of the seismic sequence of Central Italy 2016 and of main characteristics of the church sample are illustrated. Churches are grouped into homogeneous typologies characterised by similar structural response, in order to derive empirical fragility curves and damage index functions. The fragility model, generally adopted to describe the response of different types of structures, is proposed for the considered dataset by evaluating relevant parameters using the Maximum Likelihood Estimation. Finally the global damage index function is derived from the defined fragility curves and compared with the curve obtained by fitting data registered on field with a Sum Square Estimation technique.