A damage localisation procedure for masonry towers based on frequency data

The structural health conditions of masonry towers can be monitored with a few dynamic sensors (e.g. accelerometers or seismometers) placed at the top of the structure. This cost-effective setup provides continuous and reliable information on the natural frequencies of the structure; however, to move from anomaly detection to localisation with such a simplified distribution of sensors, a calibrated numerical model is needed. The paper summarises the development of a Structural Health Monitoring (SHM) procedure for the model-based damage localisation in masonry towers using frequency data. The proposed methodology involves the subsequent steps: (i) preliminary analysis including geometric survey and Ambient Vibration Tests (AVTs); (ii) FE modelling and updating based on the identified modal parameters; (iii) creation of a Damage Location Reference Matrix (DLRM) from numerically simulated damage scenarios; (iv) detection of the onset of damage from the continuous monitoring system performed with state-of-art techniques, and (v) localisation of the anomalies through the comparison between the experimentally identified variations of natural frequencies and the above-defined location matrix, called DLRM. The proposed SHM methodology is exemplified on the ancient masonry tower of Zuccaro in Mantua, Italy. Pseudo-experimental monitoring data were generated and employed to assess the reliability of the adopted algorithm in identifying the damage location. The results show a promise toward the practical applications of the proposed methodology in the monitoring of real structures.