PSI - Issue 78

Carlo Rainieri et al. / Procedia Structural Integrity 78 (2026) 426–432

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Even if an effective modal-based SHM strategy can be implemented without explicit consideration of the structural response to seismic events, checks of the characteristics of the input ground motion in the case of an earthquake are also relevant for a thorough assessment of the structural health and performance of the structure. Collecting measured data as well as relevant information obtained from automated data processing supports the formulation of a more objective judgement about the overall health conditions and performance of the monitored structure and enhances the knowledge about the structural behavior. The present paper describes the modal-based SHM system recently installed at the School of Engineering Main Building of the University of Naples “Federico II”. This building has been for years the core of an experimental research in the field of structural monitoring aimed at the seismic risk mitigation and management (Rainieri et al. 2011). The building is indeed characterized by a relevant architectural value, and it is located nearby the Campi Flegrei, a large and active volcanic area generating frequent seismic sequences. After some renovation works carried out in the building in recent years, the old monitoring system installed in 2006 was decommissioned. However, the recent occurrence of several earthquakes in the area associated with bradyseism (e.g., Iervolino et al., 2024) motivated the design and installation of a new monitoring system in 2024. The present paper describes the implemented SHM system in detail, reporting some preliminary results, highlighting the primary role of OMA in the development of effective SHM technologies. 2. The new SHM system of the School of Engineering Main Building in Naples 2.1. Description of the SHM system and preliminary output-only modal parameter identification The School of Engineering Tower (Fig. 1) in Naples is part of a building complex designed by Luigi Cosenza in a way that a typological continuity with the blocks of preexisting public housing buildings designed in 1949 is observed. It consists of an 11-storey reinforced concrete frame structure built during the 1960s (Rainieri et al. 2011). The building dimensions in plan are approximately 60 m x 80 m from the ground to the third floor; at the upper floors the dimensions in plan are about 20 m x 80 m. The building plan is also characterized by a staircase, located approximately at one third of the larger dimension, and by a slight rotation (about 4°) of this smaller portion of the plan with respect to the remaining part.

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Fig. 1. (a) Satellite and (b) outdoor view of the monitored building.

The building has been recently equipped with a continuous, vibration-based SHM system aimed at timely detect possible structural anomalies induced by the frequent earthquakes occurring in the area due to bradyseism. The SHM system consists of fifteen IEPE accelerometers with the following technical features: 10 V/g sensitivity, ± 0.5 g full scale range, 0.000004 g rms resolution, and 0.10 μg/√Hz spectral noise. Twelve accelerometers have been installed in couples at opposite corners of the building plan at levels 3, 7 and 11 and along two orthogonal directions in order to ensure the observability of the fundamental bending and torsion modes. The remaining three accelerometers have been installed in triaxial configuration at the basement of the building, and they are aimed at recording possible seismic inputs. The sensors have been wired to a 24-bit data acquisition system, characterized by 120 dB dynamic range and embedded analog anti-aliasing filter. Vibration data are continuously collected and automatically processed by an industrial fanless computer, which has been installed into a rack at the basement. Data acquisition and storage is