On the estimation of the fundamental modal properties of Italian historical masonry towers

The preservation of historical structures is a very challenging problem that requires strong interdisciplinary efforts, in particular in those countries where seismic risk is relevant and the integration between conservation and protection can be very difficult. Recent Italian earthquakes hit many valuable masonry structures marking the urban and rural landscape. Among those, masonry towers are often impressive signs of past cultures and folks. Non-destructive testing of such structures has been widely investigated and discussed in the technical literature. In the present paper, some aspects related to output-only modal identification of tower-like masonry structures for their non-destructive characterization in view of seismic performance assessment are discussed. Specific attention is paid to the role of Operational Modal Analysis in the seismic analysis of masonry towers and the development of empirical predictive correlations.