PSI - Issue 62

Alessandro Bellini et al. / Procedia Structural Integrity 62 (2024) 315–322 A. Bellini et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The reliability and accuracy of the extraction method was evaluated calculating, for each test, the residual error and comparing the results in general and within the same group of samples. The effect of each parameter on the strain release has been discussed after the presentation of experimental results, concluding that the direction (parallel or orthogonal to the applied axial stress) and the penetration depth of any of the saw-cuts are the most important parameters. Prestress release tests carried out by varying the compressive axial load highlighted that results seem unaffected by the axial stress level, confirming the effectiveness of the technique. Of course, there may be an issue with strain gauge sensitivity when the prestress level is really low. The analysis of residual errors after the extraction of the samples showed a good accuracy of the method, with results generally included in the 6.0÷8.6% range and only a few cases of errors larger than 15%, obtained if the cutting procedure is based only on orthogonal saw-cuts (so without reaching the full detachment of the specimens); this confirms the need of gently detach the samples at the end of the procedure for obtaining reliable results. The experimental results presented in the paper could be considered as a first step towards the standardization of the method, with the aim of proposing a reliable procedure easily applicable during in-situ tests. Since the stress field generated during uniaxial compression tests on columns is simplified and different from that present in prestress RC beams subjected to bending moment and shear forces, additional tests on real-scale beams are currently in progress in order to obtain further results on the expected behavior in case of more complex stress and deformation regimes. Acknowledgements The financial support of Italian Department of Civil Protection (ReLUIS 2022-2024 Grant - WP3 Analysis, review and updating of the guidelines - Task 3.2) is gratefully acknowledged. References Bencivenga, P., Buratti, G., Cosentino, A., De Matteis, G., Morelli, F., Salvatore, W., Zizi, M., 2022. Evolution of Design Traffic Loads for Italian Road Bridges. Proceedings of the 1st Conference of the European Association on Quality Control of Bridges and Structures. C. Pellegrino, F. Faleschini, M.A. Zanini, J.C. Matos, J.R. Casas, & A. Strauss, Eds. Cham: Springer International Publishing. 1351-1358. 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