PSI - Issue 84

Luca Ranedda et al. / Procedia Structural Integrity 84 (2026) 1191–1197

1197

area scanning technique, thanks to the use of multi-antenna instruments and advances in software, is likely to become more advantageous in the future in terms of survey time and cost. Ultrasonic tomography is an extremely sensitive investigation method; potential defects in the grouting of prestressing cables can be easily detected and accurately reconstructed when present. On the other hand, the high sensitivity also results in a large number of “false positives” or, more accurately, the detection of minimal discontinuities such as a very thin layer of air at the interface between the concrete and the duct, or between the duct and the grout, which are difficult to detect using direct inspection techniques but cannot be classified as significant defects affecting the prestressing system. The possibility of comparing identified ultrasonic anomalies with known anomalies, such as reflections from the “back-wall,” or performing phase analysis, could help reduce the number of “false positives.” References Ministry of Infrastructure – DM 493 03.12.2021, “Adoption of the Guidelines for the Management of Risk in Existing Bridges and Operational Instructions for the Implementation of the Guidelines” . ANAS S.p.A. – In-depth inspection of bridge decks with prestressed concrete beams with post-tensioned cables , April 2020. W. Salvatore, F. Morelli, A. Piscini, I. Mazzatura, A. Mazzei, I. Panzera, M. Mori, M. Gammino – Special inspections on post tensioned cable bridges , Le Strade, May 2021. D. Testa – Structural diagnostics of road bridges: recent experiences at the ANAS Experimental Road Centre in Cesano – Special inspections of prestressed concrete bridges with post-tensioned cables , FOIR Conference 2023. A. Gennari Santori – Special inspection – traditional and innovative investigation techniques carried out on the “Passignano” viaduct , Fabre Conference 2024.