PSI - Issue 62

Stefano Grimaz et al. / Procedia Structural Integrity 62 (2024) 161–168 S. Grimaz et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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one bridge, the on-site survey activities required about one hour of drone flight (preceded by the plan and preload flight activities). Regarding data processing time, based on current knowledge and usage conditions, high-resolution data processing typically involves a waiting time of at least 3 to 4 hours (for small structures, with longer times for larger structures) before it can be made accessible for the assessment team. These values are highly dependent on the computer processing capabilities and on the number of captured photographs. The TG modality involved the use of drones in direct support of ANSFISA inspectors. The inspection was conducted organizing a command post in which a monitor allowed the inspector to see the images captured by the drone, and contemporary permitted to inspector to communicate with pilots to address specific requirements. Pictures and videos were recorded upon inspector request. Also infrared camera was used during the survey, to improve the inspection. Details or specific aspects to investigate were requested by the inspectors directly to the pilot team both locate closely in a safe and strategic command position. On-site activities required about one-two hours. These times could be reduced, considering that it was the first test of the methodology and many aspects required to be defined and improved during the activity. As result the two methodologies of survey were completed, taking note of problems, time, positive and negative aspects for the subsequent evaluation. 6. Conclusions from the collegial final debriefing The experiment concluded with a debriefing involving all participants (inspectors, researchers, drone operators) to highlight strengths and weaknesses of the two ways of using drones and the aspects to improve the effectiveness of the investigation. Furthermore, it allowed the recognition of specific issues that require further attention in inspection activities. Below, key debriefing conclusions are summarized regarding various factors (e.g., timing, equipment, technical capabilities). For surveillance purpose, the rapidity and reliably of identification of the most critical safety aspects are crucial. Despite technological advancements, creating 3D models via TC drone surveys still requires significant processing time compared to surveillance needs. All participants indicated the TG modality as most appropriate for surveillance. However, a systematic visual analysis procedure must be defined to ensure full structural inspection and proper evidence localization. Regarding the drones and their equipment, the TG technique only requires a “ small ” drone for capturing unreachable areas, acting as an inspector's remote eyes. Standardizing communication between inspectors and pilots becomes essential to expedite surveys and minimize misunderstandings. The TC survey modality necessitates drones with specialized cameras and adequate computational power to process 3D models and data. Notably, the volume of data may hinder achieving the required synthesis for surveillance. For inspection activities, establishing an isolated, safe base near the structure is important. In any case, highly qualified pilots must conduct the drone surveys alongside inspectors. Defining a flight plan beforehand allows organized reconstruction of flight paths, and establishing a common language between pilots and inspectors facilitates the survey activities. Experts agreed the TG modality is most suitable for ANSFISA surveillance with the VISIT methodology, indirectly implying that third-party drone operation without inspector’s on-site presence is inadvisable. If third-parties drone pilots must be involved, ANSFISA inspectors should still work shoulder-to-shoulder to conduct on-site surveillance. Nevertheless, 3D models can provide a useful assistance in preliminary desk evaluations for on site planning. Finally, in the debriefing, a common conclusion emerged: even with the availability of a detailed 3D survey, in-person inspection is indispensable for achieving essential surveillance results. Acknowledgements The authors thank all colleagues who provided helpful discussions in developing the methodology and organizing the field application, particularly Eng. F. Daneluz for her operational support. Special thanks to Prof. A. Morassi, Prof. A. Beinat, and Prof. N. Baldo of the University of Udine for their valuable knowledge exchange. We also extend our gratitude to the RPAS team of the Italian National Fire Corps from Veneto and Trentino Alto Adige Interregional Directorate for performing the drone surveys during the comparative field tests.