PSI - Issue 62

Giovanna Pappalardo et al. / Procedia Structural Integrity 62 (2024) 460–467 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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the landslide body. Based on this model, numerical modeling using Discrete Macro-Element Method (DMEM) was conducted to analyse the interaction of landslide thrust on the masonry arch bridge. In this context, the numerical model implemented in the advanced software HiStrA Bridge provides detailed insights into the structural response of the bridge.

Fig. 2. Detail of the foot of the landslide, portions in gray are represented by areas of stagnation.

3.1. UAV e IRT The digital data acquisition was conducted using a Parrot Anafi thermal quadcopter equipped with a dual sensor. Specifically, three aerial photogrammetric surveys were carried out. The first two surveys led to the reconstruction of two point clouds covering a total area of about 68,600 m². The first point cloud was generated from RGB digital images, while the second captured thermal data using an infrared sensor. The last survey, through the programming of three different flight plans, allowed for the geometric reconstruction of the bridge structure. The SfM (Structure from Motion) methodology used generated two sets of point data with different attributes in terms of precision and volume. The first set, focused on the bridge, had a resolution of 4.28 mm/pix and consisted of 63 million points. The second set, centered on the landslide, had a resolution of 4.13 cm/pix with a total of 13 million points. From the analysis of this last set, a digital elevation model (DEM) was obtained with a resolution of 8 cm/pix, along with a highly precise orthomosaic. The thermal cloud created using a Flir camera mounted on the drone, later processed through a polygonal mesh (Figure 3a), allowed the identification of negative thermal anomalies, represented by shades of blue, indicating cooler wet areas corresponding to incisions (1, 3 e 4 in Figure 3a). In particular, Area 3 shows the presence of water in the landslide scarp, and Area 4 indicates water stagnation between the bridge arches. Positive thermal anomalies are present in Sector 2, (Figure 3a), showing dry, widening lateral escarpments.

(a) (b) Fig. 3. (a) Digital model of the landslide slope with thermal cloud: 1 crowning; 2 right lateral boundary of widening landslide body; 3 foot of landslide with wet portion; 4 very wet landslide material. (b) Simulation of landslide plan and related volume calculation on point cloud.