High resolution operational modal analysis of Sant'Agata del Mugello in light of its building history
Résumé
The building history of a cultural heritage building and the after-effects induced by extreme loads
such as earthquakes have a durable impact on its modal parameters. This article aims to discuss the
peculiarities of some modal parameters extracted from ambient vibration measurements in light of the
complex history of Sant'Agata del Mugello. The Romanesque church located in the Mugello basin
(Tuscany, Italy) suffered from many earthquakes, at least from 1542. In this context, we carried out
two dense ambient vibration campaigns in March and June 2019. We extracted each mode's natural
frequency, mode shape, and damping using the Enhanced Frequency Domain Decomposition. We iden-
tified ten modes. Some modes highlight structural singularities related to the building history of the
church: rocking of the base of the bell tower; phase opposition between the bell tower and the nave;
bending of the walls of the nave. Since the instrumentation benefited from a vast number of recording
positions (83), we tested the impact of the sensor placement strategy on the resolution of the identified
modal parameters in the specific case of Sant'Agata del Mugello. The resolution of the higher-order
modes decreases strongly in case of degraded sensor placement strategy impacting the dynamic analysis
of the church.
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