Unreinforced Masonry Italian Medieval Churches: A Holistic Framework for Seismic Risk Assessment from the National Scale to the Building Scale

On-site surveys were conducted of 72 unreinforced masonry (URM) medieval churches across Italy. Following a hierarchical approach for the surveys, each component of risk – hazard, vulnerability, exposure, and consequence – was defined throughout by the development of indices resulting in a holistic seismic risk assessment methodology. Regarding the risk component of vulnerability specifically, a “macro-block” analysis was applied to all 28 geometric components of each surveyed church that have been identified empirically as common collapse mechanisms in historic earthquakes. To improve the efficacy of subsequent assessments, an aggregation of commonly applied non-destructive testing (NDT) techniques was proposed to address the problematic acquisition of mechanical property of heritage URM buildings sans destructive testing. Finally, a case study church selected amongst the most critical churches was both geometrically and structurally modeled by applying photogrammetric techniques based on an unmanned aircraft system (UAS) survey, building information modeling (BIM) approach, and finite element model (FEM) analysis. The following goals of the seismic risk assessment were targeted in this study:

- Developing an appropriate and cost-efficient methodology for seismic risk assessments for large portfolios of churches;

- Quantifying the exposure and consequence components of risk by recording occupancy rates, heritage components, and equivalent replacement value of the churches;

- Developing a risk ranking of churches surveyed in order to assist stakeholders by prioritizing churches for futher detailed assessment and potentially retrofit intervention;

- Contributing to the innovation of engineering investigation techniques by introducing a rapid and reliable assessment methodology both on a regional or national scale, as well as on a higher resolution building scale;

- Recording in a rapid and dependable way the geometry and material properties with respect to complex URM churches when the lack of architectural and structural drawing represents a significant obstacle to assessment; and

- Developing a structural modeling approach for complex URM churches that is accessible by a significant portion of the practicing engineering community, based on the availability of the software utilized and the simplification of the robust analytical methods.