PSI - Issue 64

Alessandra De Angelis et al. / Procedia Structural Integrity 64 (2024) 327–334 De Angelis et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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2.2. AVTs during the key stages of rehabilitation works (AVT n. 2 and 3) The AVTs, named AVT n. 2 and n. 3, were carried out during two key stages of the rehabilitation works that in the authors’ opinion are useful to highlight the role of external and internal masonry infill walls. In fact, the AVT n. 2 was carried out, during April 2023, after the emptying of the structure from all the furniture, the demolition of the internal masonry infill walls both in the longitudinal and transverse direction (Fig. 3) and the removal of the non structural floors and screed. Instead, the AVT n. 3 was performed on January 2024, after the demolition of the external masonry infill walls in the area of the staircase (Fig. 4a) and in some outer bays of the semi-basement (Fig. 4b). Moreover for the external perimeter infill walls, located in the transverse direction, which are double brick walls (Fig. 4c) the internal layer made of hollow clay bricks was removed (Fig. 4 d).

Fig. 3. Removal of a) longitudinal and b) transverse masonry partition walls

Fig. 4. Removal of a) infill walls at staircase, b) external transverse infill walls; c) detail of the external infill walls; d) removal of the internal layer of the infill wall.

For the dynamic tests at each key stage, the instrumentation employed included 12 accelerometers, a data acquisition device and a laptop equipped with a dedicated software for data storage and real-time tracking of the recorded time histories. In particular, the ambient vibration accelerations were measured using PCB Piezotronics 393B04 model uniaxial accelerometers, characterized by high sensitivity (1000 mV/g) and low background noise (0.13 µg/ √ Hz),