PSI - Issue 64

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ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000 Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 64 (2024) 1287–1294

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Detection of internal tendon breaks by fiber-optical measurements – influence of the re-anchoring behavior Aeneas Paul a, *, David Sanio a , Peter Mark a a Institute of Concrete Structures, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany Abstract Unannounced tendon breaks belong to the most dreaded failure mechanisms in prestressed concrete bridges. Failure of single wires or tendons does not necessarily cause concrete cracking. Hence, such damage cannot always be detected by visual inspection. In the case of tendons bonded in concrete, re-anchoring after breaking induces characteristic local strain fields: tensile strains occur between the separated extremities, while compressive strains develop around the tendons, until the initial prestressing strain is reached again. On the more distant concrete surface, these strains are rather small and depend on multiple factors, e.g., the depth of the tendon, the transfer length or the concrete stiffness. Nevertheless, such strain fields can be detected by fiber-optical sensors attached to the surface in two-dimensional grids. By evaluating the backscatter of emitted light, minimal strain changes (uncertainty: ± 1 µm/m) can be recorded in quasi-continuous resolution (0.65 mm pitch). An experimental investigation of artificial tendon failure in two prestressed concrete beams is presented. The tendons were mechanically cut to simulate failure, while strains were measured on the concrete faces. The failure can be localized within a few centimeters by monitoring. The bond to the tendon mainly depends on the concrete strength. To investigate its effect on the surface strain a normal strength concrete is compared to a high-performance concrete. Better bond conditions result in lower expansion of the strain field and smaller strains in general. The results show potential to detect the position and quantity of broken tendons, solely from the strain signal on the concrete surface. © 2024 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 SMAR 2024 Organizers Keywords: Fiber-optics, DFOS, monitoring, prestressed concrete, re-anchoring, tendon break, bond stress SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Detection of internal tendon breaks by fiber-optical measurements – influence of the re-anchoring behavior Aeneas Paul a, *, David Sanio a , Peter Mark a a Institute of Concrete Structures, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany Abstract Unannounced tendon breaks belong to the most dreaded failure mechanisms in prestressed concrete bridges. Failure of single wires or tendons does not necessarily cause concrete cracking. Hence, such damage cannot always be detected by visual inspection. In the case of tendons bonded in concrete, re-anchoring after breaking induces characteristic local strain fields: tensile strains occur between the separated extremities, while compressive strains develop around the tendons, until the initial prestressing strain is reached again. On the more distant concrete surface, these strains are rather small and depend on multiple factors, e.g., the depth of the tendon, the transfer length or the concrete stiffness. Nevertheless, such strain fields can be detected by fiber-optical sensors attached to the surface in two-dimensional grids. By evaluating the backscatter of emitted light, minimal strain changes (uncertainty: ± 1 µm/m) can be recorded in quasi-continuous resolution (0.65 mm pitch). An experimental investigation of artificial tendon failure in two prestressed concrete beams is presented. The tendons were mechanically cut to simulate failure, while strains were measured on the concrete faces. The failure can be localized within a few centimeters by monitoring. The bond to the tendon mainly depends on the concrete strength. To investigate its effect on the surface strain a normal strength concrete is compared to a high-performance concrete. Better bond conditions result in lower expansion of the strain field and smaller strains in general. The results show potential to detect the position and quantity of broken tendons, solely from the strain signal on the concrete surface. © 2024 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 SMAR 2024 Organizers Keywords: Fiber-optics, DFOS, monitoring, prestressed concrete, re-anchoring, tendon break, bond stress © 2024 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 SMAR 2024 Organizers

* Corresponding author. Tel.: +49-234-32-27860. E-mail address: aeneas.paul@rub.de * Corresponding author. Tel.: +49-234-32-27860. E-mail address: aeneas.paul@rub.de

2452-3216 © 2024 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 SMAR 2024 Organizers 2452-3216 © 2024 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 SMAR 2024 Organizers

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