PSI - Issue 84

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ScienceDirect

Procedia Structural Integrity 84 (2026) 231–239

© 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Conference Keywords: Prestressing force evaluation; x-ray diffraction; non-destructive testing; post-tensioned concrete structures. Abstract The assessment of residual prestressing force is of paramount importance for the structural safety assessment of existing post tensioned concrete structures. In fact, the effective tension present within the prestressing reinforcement is vital for the sustained structural integrity and comprehensive functionality of prestressed concrete elements, particularly within critical infrastructure such as bridges, thereby ensuring their durability and safety under diverse loading conditions. Given the concealed and embedded configuration of prestressing tendons, they remain inaccessible through traditional direct measurement methodologies. Thus, a variety of non-destructive testing (NDT) techniques have been proposed in literature to carry direct or indirect measurements of current stress level in steel strands and wires. Notably, amongst these techniques, X-ray diffraction (XRD) has emerged as a promising tool for direct stress evaluation, notwithstanding the practical challenge inherent on-site applications. This work shows the results of a large experimental campaign, aimed at evaluating the accuracy of the method under laboratory conditions. This study utilized both single wires and seven-wire strands, which were consistently tensioned under controlled conditions. The current stress was measured with a load cell and estimated with XRD, varying the operating conditions. Results obtained from the diffractometer, when compared with known stress values, indicated adequate measurement repeatability and low discrepancy among the NDT-estimated and measured values. III Fabre Conference: Existing Bridges, Viaducts, and Tunnels: Research, Innovation, and Applications Accuracy of X-Ray Diffraction as NDT technique for prestress force evaluation Silvia Manarin a , Flora Faleschini a* , Mariano Angelo Zanini a and Carlo Pellegrino a a Department of Civil, Environmental and Architectural Engineering, University of Padova, Via Marzolo 9, Padova 35131, Italy

* Corresponding author. Tel.: +39 049 8275585 E-mail address: flora.faleschini@unipd.it

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Conference 10.1016/j.prostr.2026.06.031