Vulnerability Evaluation of Historical Masonry Structures: Italian Churches and Towers

The evaluation of the seismic vulnerability for historical masonry structures like churches and towers (medieval defense towers, bell towers and city gates) is paramount for developed countries. This is particularly true for Italy, a high seismicity country where it is esteemed that more than 5% of the total architectural heritage is located (UNESCO source). Consistently with the need of a sound protection of such kind of structures against seismic events, specific Guidelines for the built heritage have been conceived, which provide useful hints to practitioners for an assessment, but still leave important open issues. The present paper reviews the existing numerical approaches used for churches and towers. For churches, a guidebook for a reliable evaluation of the seismic vulnerability is proposed, relying into a broad blend of different approaches ranging from the easiest ones –usually available to practitioners- to the most sophisticated, like for instance Non-Linear Dynamic Analyses with damaging materials. A simplified procedure of FE upper bound limit analysis with coarse mesh adaptation is finally reviewed, which is sufficiently simple for common use but at the same time allows a realistic prediction of the most vulnerable macro-elements and the collapse acceleration. For towers, a straightforward approach based on the vulnerability evaluation by means of five probable (observed) failure mechanisms is proposed to overcome the limitations of a too simplistic cantilever beam approximation and to avoid demanding non-linear computations with 3D FEs.