Anomaly detection and localization on masonry arch bridges using frequency data

Despite the age of construction, masonry arch bridges and viaducts have still an essential role in the European infrastructural network, so that implementing techniques to control their health state is of primary interest. To this purpose, masonry viaducts - often characterised by high piers - can be continuously monitored with Operational Modal Analysis (OMA): this technique provides reliable information on the natural frequencies of the structure and the possible appearance of structural anomalies. Nevertheless, due to the complexity of masonry viaducts, to move from damage detection to localisation with a relatively simplified distribution of sensors, a calibrated numerical model is needed. The paper summarises the development of a Structural Health Monitoring (SHM) methodology for the model-based damage assessment in masonry arch bridges using frequency data. The proposed methodology involves the following steps: (i) preliminary analysis including architectural research and OMA; (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 analysis of the continuously collected natural frequencies, and (v) localisation of the anomalies through the comparison between the experimentally identified variations of natural frequencies and the DLRM. The proposed SHM methodology is exemplified on the Olla bridge, Piedmont region, Italy. Pseudo-experimental monitoring data were generated and used to assess the reliability of the developed algorithm in identifying the damage location. The results show a promise toward the practical applications of the proposed strategy for the early identification of damage in masonry viaducts.