Seismic vulnerability assessment of the benedictine basilica typology in central Italy

The research deals with a methodology for the seismic vulnerability assessment of a set of historic churches characterized by a specific building typology and focuses on the mid-scale analysis which stands in between territorial level assessment and studies of single buildings. In particular, the proposed methodology allows to coordinate, connect and interpret apparently distant information, provided by accredited analysis tools from different scale of investigation on the seismic behaviour of historical constructions. A set of basilica churches, settled in central Italy, and stricken by the 2009 L'Aquila earthquake, has been analysed to uncover weaknesses related to the building typology by relating historical, environmental, geometrical, technological, and mechanical issues through a multi-discipline multi-scale innovative approach. All the churches belong to the Benedictine building culture and are built across a relatively limited territory; hence, they share the same architecture typology, while building technology can vary considerably due to the available environmental resources. Geometrical proportions and dimensions are investigated through appropriate morphological indexes, while masonry types through the Masonry Quality Index (MQI) method. First-level vulnerability indexes are determined on expeditious on site survey basis and most prone-to-activate kinematic mechanisms are hence deduced. Apse and facade constitute the macro-elements most prone to local mechanism activation. Also, the scale of the monument, associated to historical importance, quality of employed resources, and relevance of reworks, is central in determining homogeneity in the overall construction, quality of connections among the crucial macro-elements, and hence, their vulnerability. In the kinematic mechanism evaluation, the inclusion of frictional restraint forces simulating quality of connections between orthogonal walls proves effective in quantitatively translate observational data, although cautious calibration of the minimization procedure must be considered, especially for relatively small churches.