PSI - Issue 84

L. Pisani et al. / Procedia Structural Integrity 84 (2026) 1144–1150 L. Pisani et al. / Structural Integrity Procedia 00 (2026) 000–000

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Keywords: Post-tensioned cables; Non-destructive methods; X-Ray diffraction; Barkhausen Noise; Stress measurement; Special Inspections.

1. Introduction Prestressed Reinforced concrete structures may be subject to reduction of their bearing capacity and safety with the progressive degradation of the prestressing system, either determined by decay of the prestressing state or by corrosion. Although these two phenomena have different consequences at the structural level, corrosion can lead to prestressing wire breakage and therefore to tensile stress variation up to a certain distance from the breakage point. Therefore, measurement of the existing stress state is an important information in structural condition assessment. The measurement of the actual state of stress is, up to date, carried out mainly using destructive techniques such as stress release that, however, cannot be extensively or periodically used. Zanini et al. In order to avoid as much as possible destructive measurements, the possibility of using X-ray diffraction (XRD) has been investigated in the recent past years. X-Ray diffraction for stress evaluation is a technique widely validated in the mechanical, automotive, aeronautical and aerospace fields. In 1996, this technique was used to assess the stress state of decks at La Guardia Airport. It was considered very promising but difficult to use in the civil engineering field due to the instrumental dimensions.Carfagno et al. (1996). In 2021, as part of the initiatives undertaken in Italy following the collapse of the Morandi Bridge in Genoa, evaluation tests of XRD technique were conducted both in laboratories and onsite at selected bridges .Gennari Santori et al.( 2024) ,Chiaia et al.( 2023), Zanini et al. (2022) ,Mazzatura et al. (2023). XRD technique, as recommended method to assess stress state, it is already mentioned in some Italian national protocols such as: • PIARC: Piano Strategico 2020-2023 Tema Strategico 4 “Infrastrutture Resilienti” Comitato Tecnico 4.2 “Ponti” pp.59-61, https://www.piarc-italia.it/wp-content/uploads/2023/12/Quaderno-CT-4.2-127-pp.pdf • ANFISA: Istruzioni Operative per l’applicazione delle LINEE GUIDA PER LA CLASSIFICAZIONE E GESTIONE DEL RISCHIO, LA VALUTAZIONE DELLA SICUREZZA ED IL MONITORAGGIO DEI PONTI ESISTENTI www.mit.gov.it/nfsmitgov/files/media/normativa/2020 12/8_All_D_Scheda_ispezione_speciale.pdf The very first XRD tests have been done using a standard equipment model designed for multipurpose applications. Due to the necessity to have a more compact system to optimize measurement in bridges, a project was subsequently commissioned to further miniaturize the instrument for field use (Reference: SINA). Even if XRD has to be considered as the preferential method to assess the tensional state, to overcome some limitations due mainly to the use of ionising radiations, to measurement speed and setup at multiple nearby (e.g. parallel or twisted wires) or distant points (e.g. several point along the structure), this paper presents the preliminary results on the evaluation of a complementary technique based on the magnetic effect known as Barkhausen Noise Rautiohao et al. (1994), Behleda (2021), verifying its correspondence with XRD measurements both in the laboratory and in the field. 2. XRD and MBN technology recall A short recall of the two technologies used in this study is presented in the following. 2.1. X-Ray Diffraction (XRD) X-ray diffraction applied to the measurement of the stress state responds is based on to Bragg's law nλ=2dsinθ (1)