PSI - Issue 62

3

Mattia Zizi et al. / Procedia Structural Integrity 62 (2024) 430–437 M. Zizi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. The bridge San Ferdinando II in Mignano Monte Lungo (CE)

The abutments, adjacent to the wing walls of the structure, present the same geometrical characteristics, but with a width of 4.30 m. The bridge transversal length at the road level amounts to 8.7 m, with two cantilevered reinforced concrete slabs of 1.20 m, but the carriageway width is limited to about 6 m given the presence of lateral masonry parapets and sidewalks. The main constructive material is tuff masonry, widely adopted in this geographical area. Tuff piers are supported by limestone ashlar masonry elements, with units of significant dimensions. No information was instead available for the backfill material. Generally, the bridge is in a state of conservation compatible with its age. Nonetheless, it is invaded by weeds and an accurate reconnaissance of the structural defects was not possible. Such a situation is better shown in the photos of Fig. 2.

Fig. 2. Photographic survey of the bridge San Ferdinando II in Mignano Monte Lungo (CE)

2.3. Geometrical survey An accurate survey of the external geometry of the bridge was performed by using the digital photogrammetric methodology, through aerial acquisition. An Unmanned Aircraft System (UAS) was adopted by flying the drone (DJI Mavic 2 Enterprise Dual). Aerial acquisitions were processed by means of the open source DJI Pilot tool. 431 frames were acquired during the flight by guaranteeing appropriate overlapping between the frames. In particular, in order to obtain a reliable point cloud, it was necessary to respect the fundamental principle of photogrammetry (stereoscopy). This means that, considering a sequential acquisition, a horizontal overlap between 60 and 80% and a vertical sidelap