On the Dynamic Performance of the Santa Maria Maddalena Church, Ischia Island (Italy): Numerical and Experimental Comparative Analysis

After the seismic event of August 21st, 2017 that hit the Ischia Island (Italy), in-situ surveys were carried out on several masonry churches located in the island in order to assess the damage induced by the earthquake. Among the inspected churches, a very interesting case study is represented by the Santa Maria Maddalena Church, located on the hill of Casamicciola Terme, close to the epicentre. The church was built in 1896 with a ‘mixed’ structure, made of yellow tuff masonry walls strengthened by iron profiles in its main body and by wooden elements in its back part. After the seismic event, in addition to a detailed survey of the church, thermography imaging and in-situ dynamic tests under operational conditions were carried out. The paper describes the experimental procedures adopted during the tests and the results in terms of experimentally identified fundamental modal parameters. An attempt of correlating the experimental results with those obtained from a finite element numerical model of the only church façade is carried out. The comparison evidences some discrepancies between the dynamic features of the single façade and the whole church. This confirms that the church is characterized by a ‘box behaviour’, most likely favoured by the presence of the iron frames, and, thus, the behaviour of the single façade cannot be considered independent of that of the whole church.