Vibration-based assessment and model calibration of a heritage masonry church after post-earthquake strengthening

The preservation of historical masonry structures in seismic-prone regions increasingly re-lies on vibration-based techniques for assessing structural integrity and supporting model-driven vulnerability analyses. Within this framework, the present study investigates the dynamic behaviour of the Church of SS. Trinità in Popoli Terme (Italy), a significant heritage building that sustained severe damage during the 2009 L’Aquila earthquake and was subsequently repaired and strengthened. The work has been developed in the context of the GENESIS project – Seismic risk management for touristic valorisation of the historical centres of Southern Italy, aimed at integrating seismic risk management with the enhancement of cultural heritage. An extensive ambient vibration test campaign was performed to characterize the dynamic properties of the structure through Operational Modal Analysis (OMA). The identified modal parameters - natural frequencies and mode shapes - were used to calibrate a detailed finite element model of the church developed in the NOSA-ITACA code, which implements the constitutive equation of no-tension materials for simulating the mechanical response of historic masonry structures. The model updating process proved particularly challenging due to the structural complexity of the building as well as to uncertainties in boundary and soil conditions. Nonetheless, it led to a consistent representation of the current structural state after the post-earthquake strengthening works. The updated model provides a robust basis for subsequent seismic vulnerability assessments and demonstrates the effectiveness of OMA-based model updating in improving the reliability of numerical simulations of complex non-conventional heritage structures.