Mixed-SHM Strategies for the Dynamic Identification and Vulnerability Assessment of the San Francesco Basilica, Italy

The seismic assessment of historic masonry structures requires integrated methodologies that address the complexity of heritage buildings while respecting conservation constraints. In this context, dynamic identification techniques represent valuable tools for improving the understanding of structural behaviour and reducing uncertainties in seismic analyses. This study presents an integrated approach for the dynamic characterisation and seismic assessment of the Basilica of San Francesco in Arezzo, Italy. Ambient Vibration Testing (AVT) and Infrared Digital Holographic Interferometry (IR-DHI) were combined to obtain complementary information on the dynamic response of the monument, including structural components that are difficult to investigate using conventional instrumentation. The experimentally identified modal parameters were used to validate a finite element model and to support the assessment of local seismic vulnerability. The results demonstrate the effectiveness of combining contact and non-contact dynamic testing techniques to achieve a comprehensive characterisation of complex historic structures. Furthermore, the integration of experimental investigations, numerical modelling, and kinematic analyses proved essential for the identification and evaluation of local collapse mechanisms. While preliminary linear analyses highlighted potential vulnerabilities, non-linear assessments provided a more realistic estimate of the available safety margins, confirming an overall satisfactory seismic performance of the investigated macroelements. The proposed methodology highlights the benefits of a multidisciplinary, knowledgebased approach to the conservation and seismic risk assessment of historic masonry heritage.