PSI - Issue 84

Davide Caliò et al. / Procedia Structural Integrity 84 (2026) 513–520

514

Keywords: Multi-sensor UAV monitoring; Infrastructure resilience; Digital workflow; integration Non-invasive inspection.

1. Introduction Road infrastructures, and in particular bridges and viaducts, are today increasingly exposed to the combined effects geological, structural, and hydrodynamic processes. In Europe, a significant portion of the infrastructure stock was constructed more than fifty years ago and inevitably suffers from material ageing and design criteria that are no longer fully consistent with current standards (European Commission. Joint Research Centre., 2019). This condition is further compounded by the increasing frequency of extreme meteorological events, which contributes to accelerating degradation processes and the evolution of instability phenomena (Intergovernmental Panel On Climate Change (Ipcc), 2023; Duan et al., 2025). The stability of bridges and viaducts therefore results from the combined action of multiple factors. Geological and geomorphological processes, such as slope instability, landslides, and erosion, act together with hydrodynamic and morpho-dynamic processes, such as riverbed incision and both general and local scour during flood events, which can compromise foundation bearing capacity and pier stability (Federico et al., 2003; Liu and Li, 2012; Prolović et al., 2018), in addition to well-known mechanisms of structural deterioration, including reinforcement corrosion, cracking, and concrete cover detachment (Gabrieli et al., 2025; Pappalardo et al., 2024;). These phenomena often occur simultaneously, making traditional inspection approaches based on point observations and ground surveys insufficient. Consequently, a reliable assessment of infrastructure condition requires an approach that integrates structural, geotechnical, and hydraulic information within a unified interpretative framework (Gigli et al., 2014; Vaníček et al., 2018) . In recent years, UAV-based remote sensing technologies have assumed an increasingly important role in infrastructure diagnostics and associated geological risk assessment. The use of high-resolution RGB imagery, radiometric thermal data, multispectral sensors, and LiDAR systems enables non-invasive inspections even in hard to-access environments, such as bridge piers, intradoses, and riverbeds (Colomina and Molina, 2014; Feroz and Abu Dabous, 2021). In particular, Infrared Thermography allows the detection of moisture- and material-degradation related anomalies even at early stages (Frodella et al., 2017; Pappalardo et al., 2022) and has also seen significant development in geological applications (Mineo et al., 2025), while UAV photogrammetry enables detailed three dimensional reconstructions of both structures and the surrounding geomorphological context (Caliò et al., 2023). Despite the growing diffusion of these techniques, fully integrated approaches combining structural inspection with geological and geomorphological analysis within a unified 3D framework remain limited in practical applications ( Salciarini et al., 2024). This study proposes a multisensor UAV-based workflow for integrated viaduct inspection, combining structural, photogrammetric, thermal, and geological data within three-dimensional models aimed at multi risk assessment. The methodology is applied to the Cantera viaduct (Augusta, eastern Sicily), selected for its geological setting, potential interaction with flood events, and advanced structural degradation, to evaluate its operational effectiveness and transferability to similar infrastructural contexts.

2. Study area and infrastructure overview 2.1. Geological and geomorphological setting

The study area is located along the south-eastern margin of the Hyblean Plateau (eastern Sicily). From a structural point of view, the area belongs to a relatively stable foreland domain, only marginally affected by extensional tectonics related to the Hyblean–Maltese escarpment (Grasso and Lentini, 1982; Argnani and Bonazzi, 2005); therefore, regional structural controls are of secondary importance at the scale of the investigated infrastructure. The geological setting is instead dominated by the lithological characteristics of recent alluvial deposits and underlying carbonate bedrock. The youngest units are represented by fluvial alluvial deposits, consisting of poorly sorted coarse-grained