PSI - Issue 84

Donato Fiore et al. / Procedia Structural Integrity 84 (2026) 417–424

418

Keywords: Monitoring, interferometry, OMA, FEM

1. Introduction Structural Health Monitoring (SHM) involves the continuous assessment of a structure’s safety by detecting changes in its behavior caused by local damage, geometric deformations, or environmental degradation. Dynamic monitoring, although costly, enables fast assessments through sensors that measure the structure’s dynamic response. Advanced digital systems help define threshold values – based on standards like DIN 4150 and ISO 9916 – that trigger alerts when exceeded. SHM is useful for both routine management (tracking long-term degradation) and emergency situations (such as earthquakes or landslides, among others). However, monitoring data alone cannot completely determine safety; it must be interpreted through theoretical models and specific analyses. Key goals include early issue detection, optimized maintenance planning, improved safety, and systematic data collection. For bridges, dynamic monitoring links the structural response to natural frequencies and mode shapes, but interpretation is difficult if traffic loads, temperature effects, and permanent deformations are unknown. A calibrated Finite Element Model (FEM) is an effective tool to improve the analysis. Notably, local damage may not immediately affect global structural parameters. In the case of the Bisantis Bridge, included in a POR-Calabria project, SHM was conducted using a terrestrial interferometric system for operational modal analysis and 12 triaxial accelerometers for vibration frequency measurements and modal studies (Fig. 1).

Fig. 1. (a) location of the Bisantis Bridge; (b) interferometric data acquisition.

2. Theoretical background Operational Modal Analysis (OMA) is a structural monitoring technique that analyses the response to natural excitations like wind or traffic. In this study, OMA was performed using the IBIS-FS terrestrial interferometric radar (IDS Georadar), which differs from earlier systems (e.g., Farrar et al. 1999) by providing range resolution to distinguish targets within a radar beam of 0.75 m (Fig. 2).