Dynamic Structural Identification of a Portion of the Medieval Defensive Walls of Verona, Italy, Through Ambient Vibration Test

The study focuses on the results of the analysis of data recorded during Ambient Vibration Tests (AVT) conducted on a portion of the Medieval Walls of Verona (Northern Italy). Seismometric stations were installed both at the top and at the base of the walls, recording the free vibrations of the structure. Spectral analyses provide information about the principal modal frequencies, which are compared with the results obtained through Operational Modal Analysis (OMA) techniques. Numerical models were developed to describe the elastic behavior of the walls and to support the interpretation of the experimentally identified modes. Seismic noise measurements were also performed on the ground to characterize the spectral response of the soil and to estimate the soil–structure interaction. The combined use of AVT data, OMA procedures, and numerical modeling allowed for a robust identification of the fundamental dynamic properties of the walls, highlighting the predominance of out-of-plane modes and the limited dynamic coupling with the underlying soil. The study demonstrates the effectiveness of this non-invasive approach for improving the knowledge of structural assessment, reducing uncertainties in mechanical parameter calibration, and supporting informed conservation, maintenance, and risk-mitigation strategies for historic defensive masonry structures.