Shear Rehabilitation of Damaged RC Beams Using Embedded Through-Section CFRP Bars Technique

Rafal A. Hadi; Raid A. Daud

doi:10.2478/cee-2026-0087

Shear Rehabilitation of Damaged RC Beams Using Embedded Through-Section CFRP Bars Technique

Civil and Environmental Engineering

AHEAD OF PRINT

By: Rafal A. Hadi and Raid A. Daud

Open Access

|Mar 2026

Abstract

Reinforced concrete (RC) beams often suffer from reduced shear capacity due to overloading or environmental deterioration, posing a significant challenge for maintaining structural safety and serviceability. Various strengthening techniques have been proposed in practice, including externally bonded (EB) laminates and near-surface mounted (NSM), to enhance the shear performance of damaged RC beams. However, these methods face limitations, such as susceptibility to debonding, limited effectiveness for heavily damaged beams, and uneven stress distribution. The present study investigates a novel shear strengthening technique known as embedded through-section (ETS) CFRP bars, which involves drilling holes through the beam section and inserting CFRP bars bonded with adhesives. The ETS technique effectively mitigates the debonding problem associated with conventional FRP strengthening methods. This research evaluates the shear efficiency of ETS-strengthened RC beams with 50% and 70% pre-damage under monotonic and repeated loading, considering the effect of CFRP bar location (centre vs. near longitudinal reinforcement) and inclination angle (45° vs. 90°). The results showed that embedding CFRP bars at 45° and near the longitudinal reinforcement significantly enhances shear capacity, with increases up to 63.66% for beams damaged under repeated loads, providing new insights for effective rehabilitation of damaged RC structures.

References

Lees, J. M., Winistörfer, A. U., & Meier, U. (2002). External prestressed carbon fiber-reinforced polymer straps for shear enhancement of concrete. Journal of Composites for Construction, 6(4), 249–256.
Search in Google Scholar Back to article
Kesse, G., & Lees, J. M. (2007). Experimental behaviour of reinforced concrete beams strengthened with prestressed CFRP shear straps. Journal of Composites for Construction, 11(4), 375–383.
Search in Google Scholar Back to article
Dirar, S., Lees, J. M., & Morley, C. (2013). Phased nonlinear finite-element analysis of precracked RC T-beams repaired in shear with CFRP sheets. Journal of Composites for Construction, 17(4), 476–487.
Search in Google Scholar Back to article
Breveglieri, M., Aprile, A., & Barros, J. A. (2014). Shear strengthening of reinforced concrete beams using embedded through-section steel bars. Engineering Structures, 81, 76–87.
Search in Google Scholar Back to article
Mostofinejad, D., & Tabatabaei Kashani, A. (2013). Experimental study on effect of EBR and EBROG methods on debonding of FRP sheets used for shear strengthening of RC beams. Composites Part B: Engineering, 45, 1704–1713. https://doi.org/10.1016/j.compositesb.2012.09.081.
Search in Google Scholar Back to article
Charalambidi, B. G., Rousakis, T. C., & Karabinis, A. I. (2016). Fatigue behavior of large-scale reinforced concrete beams strengthened in flexure with fiber-reinforced polymer laminates. Journal of Composites for Construction, 20, 04016035. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000689.
Search in Google Scholar Back to article
Aishwarya, R., Prabhakaran, P., & Divya, K. K. (2017). A review on shear strengthening of RC beams using embedded through-section (ETS) technique. [Conference paper/Report – no publication info available].
Search in Google Scholar Back to article
Kodur, V. R., Bisby, L. A., & Green, M. F. (2006). Experimental evaluation of the fire behaviour of insulated fibre reinforced polymer strengthened reinforced concrete columns. Fire Safety Journal, 41(7), 547–557.
Search in Google Scholar Back to article
Pham, H. B., & Al-Mahaidi, R. (2006). Prediction models for debonding failure loads of carbon fiber reinforced polymer retrofitted reinforced concrete beams. Journal of Composites for Construction, 10(1), 48–59.
Search in Google Scholar Back to article
Abdesselam, A., Merdas, A., Fiorio, B., & Chikh, N. E. (2023). Experimental and numerical study on RC beams strengthened by NSM using CFRP reinforcements. Periodica Polytechnica Civil Engineering, 67(4), 1214–1233.
Search in Google Scholar Back to article
Hawileh, R. A., Saleh, R. B., Saqan, E. I., & Abdalla, J. A. (2022). Contribution of longitudinal NSM-CFRP bars on the shear strength of RC beams with varying depths and concrete strengths. Journal of Composites for Construction, 26(3), 04022025.
Search in Google Scholar Back to article
Alwash, D., Kalfat, R., Al-Mahaidi, R., & Du, H. (2021). Shear strengthening of RC beams using NSM CFRP bonded with cement-based adhesive. Construction and Building Materials, 301, 124365.
Search in Google Scholar Back to article
Turki, A. Y., & Al-Farttoosi, M. H. (2023). Flexural strength of damaged RC beams repaired with carbon fiber-reinforced polymer (CFRP) using different techniques. Fibers, 11(7), 61.
Search in Google Scholar Back to article
Hawileh, R. A., Saleh, R. B., Saqan, E. I., & Abdalla, J. A. (2022). Contribution of longitudinal NSM-CFRP bars on the shear strength of RC beams with varying depths and concrete strengths. Journal of Composites for Construction, 26(3).
Search in Google Scholar Back to article
Valerio, P., & Ibell, T. J. (2003). Shear strengthening of existing concrete bridges. Proceedings of the Institution of Civil Engineers – Structures and Buildings, 156(1), 75–84.
Search in Google Scholar Back to article
Barros, J. A., & Dalfré, G. M. (2013). Assessment of the effectiveness of the embedded through-section technique for the shear strengthening of reinforced concrete beams. Strain, 49(1), 75–93.
Search in Google Scholar Back to article
Raicic, V., Ibell, T., Darby, A., Evernden, M., & Orr, J. (2017). Effectiveness of the Deep Embedment (DE) technique for shear strengthening of reinforced concrete continuous T-beams. In Advanced Composites in Construction (ACIC 2017), Proceedings of the 8th Biennial Conference on Advanced Composites in Construction (pp. 120–125).
Search in Google Scholar Back to article
Lateef, H. E., Al-Allaf, M. H., & Daud, R. A. (2024). Experimental study on bond-slip behavior of NSM-CFRP plate and recycled aggregates concrete substrate. Innovative Infrastructure Solutions, 9(10), 368.
Search in Google Scholar Back to article
Moradi, E., Naderpour, H., & Kheyroddin, A. (2020). An experimental approach for shear strengthening of RC beams using a proposed technique by embedded through-section FRP sheets. Composite Structures, 238, 111988.
Search in Google Scholar Back to article
Breveglieri, M., Aprile, A., & Barros, J. A. O. (2015). Embedded through-section shear strengthening technique using steel and CFRP bars in RC beams with different percentages of existing stirrups. Composite Structures, 126, 101–113. https://doi.org/10.1016/j.compstruct.2015.02.025.
Search in Google Scholar Back to article
Valerio, P., Ibell, T. J., & Darby, A. P. (2009). Deep embedment of FRP for concrete shear strengthening. Proceedings of the Institution of Civil Engineers – Structures and Buildings, 162, 311–321. https://doi.org/10.1680/stbu.2009.162.5.311
Search in Google Scholar Back to article
Barros, J. A. O., & Dalfré, G. M. (2013). Assessment of the effectiveness of the embedded through-section technique for the shear strengthening of reinforced concrete beams. Strain, 49, 75–93. https://doi.org/10.1111/str.12016.
Search in Google Scholar Back to article
Breveglieri, M., Aprile, A., & Barros, J. A. O. (2014). Shear strengthening of reinforced concrete beams using embedded through-section steel bars. Engineering Structures, 81, 76–87. https://doi.org/10.1016/j.engstruct.2014.09.026.
Search in Google Scholar Back to article
Van Hong Bui, L., Stitmannaithum, B., & Ueda, T. (2020). Experimental investigation of concrete beams strengthened with embedded through-section steel and FRP bars. Journal of Composites for Construction, 24(5), 04020052.
Search in Google Scholar Back to article
Mofidi, A., Chaallal, O., Benmokrane, B., & Neale, K. (2012). Experimental tests and design model for RC beams strengthened in shear using the embedded through-section FRP method. Journal of Composites for Construction, 16(5), 540–550.
Search in Google Scholar Back to article
Sogut, K., Dirar, S., Theofanous, M., & Faramarzi, A. (2023). Effect of shear span-to-effective depth ratio on the behaviour of RC T-beams shear-strengthened with embedded CFRP bars. (Publication details not available).
Search in Google Scholar Back to article
Azevedo, A. S., Firmo, J. P., Correia, J. R., & Almeida, J. (2025). Embedded through-section (ETS) technique for shear strengthening of reinforced concrete beams – Experimental and analytical study. Engineering Structures, 333, 120038.
Search in Google Scholar Back to article
Van Hong Bui, L., Ohno, T., Kurihara, N., & Sekiya, H. (2024). Experimental investigation of fatigue shear behavior of RC beams strengthened with FRP bars using embedded through-section technique. Journal of Composites for Construction, 28(5), 04024037.
Search in Google Scholar Back to article
Tuma, N. K., Al-Ahmed, A. H., & Al-Farttoosi, M. H. (2020). The shear strengthening of reinforced concrete beams by embedded through-section technique – Analytical study. IOP Conference Series: Materials Science and Engineering, 888(1), 012039.
Search in Google Scholar Back to article
Naqee, A. W., & Daud, R. A. (2024). Effect of CFRP bar diameter and concrete strength on shear performance of ETS-strengthened RC beams with recycled plastic aggregate: Validation and parametric study using Abaqus. (Publication details unavailable).
Search in Google Scholar Back to article
American Concrete Institute. (2015). Guide for the design and construction of structural concrete reinforced with FRP bars (ACI 440.1R-15). American Concrete Institute.
Search in Google Scholar Back to article
Godat, A., L’Hady, A., Chaallal, O., & Neale, K. W. (2012). Bond behavior of the ETS FRP bar shear-strengthening method. Journal of Composites for Construction, 16, 529–539. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000280.
Search in Google Scholar Back to article
Caro, M., Jemaa, Y., Dirar, S., & Quinn, A. (2017). Bond performance of deep embedment FRP bars epoxy-bonded into concrete. Engineering Structures, 147, 448–457. https://doi.org/10.1016/j.engstruct.2017.05.069.
Search in Google Scholar Back to article
Hamah-Ali, B. H. S., & Qadir, M. R. A. (2021). Effect of different levels of pre-damage loading on the strength and structural behavior of CFRP-strengthened RC beams: Experimental and analytical investigation. PLOS ONE, 16(12), e0261290.
Search in Google Scholar Back to article
Haddad, R. H., & Almomani, O. A. (2019). Flexural performance and failure modes of NSM CFRP-strengthened concrete beams: A parametric study. International Journal of Civil Engineering, 17(7), 935–948.
Search in Google Scholar Back to article
Hasan, A., & Al-Farttoosi, A. (2024). Investigation of the experimental shear resistance of RC T-beams after strengthening with CFRP bars. Engineering, Technology & Applied Science Research, 14(2), 1234–1242.
Search in Google Scholar Back to article
Murad, Y. (2018). The influence of CFRP orientation angle on the shear strength of RC beams. The Open Construction & Building Technology Journal, 12(1).
Search in Google Scholar Back to article
Turki, A. Y., & Al-Farttoosi, M. H. (2023). Investigation of the stiffness and ductility of pre-cracked RC beams after repairing with CFRP using different strengthening methods. Engineering, Technology & Applied Science Research, 13(6), 12423–12426.
Search in Google Scholar Back to article
Al-Mahaidi, R., & Kalfat, R. (2018). Rehabilitation of concrete structures with fiber-reinforced polymer. Butterworth-Heinemann.
Search in Google Scholar Back to article
Liu, F., Zhou, J., & Yan, L. (2018). Study of stiffness and bearing capacity degradation of reinforced concrete beams under constant-amplitude fatigue. PLOS ONE, 13(3), e0192797.
Search in Google Scholar Back to article
Ruiz, M. F., Zanuy, C., Natário, F., Gallego, J. M., Albajar, L., & Muttoni, A. (2015). Influence of fatigue loading in shear failures of reinforced concrete members without transverse reinforcement. Journal of Advanced Concrete Technology, 13(5), 263–274.
Search in Google Scholar Back to article
Obaidat, Y. T., Heyden, S., & Dahlblom, O. (2010). The effect of CFRP and CFRP/concrete interface models when modelling retrofitted RC beams with FEM. Composite Structures, 92(6), 1391–1398.
Search in Google Scholar Back to article
Chen, Z. B., Huang, P. Y., Li, Z. W., Guo, X. Y., Zhao, C., Zheng, X. H., & Yang, Y. (2018). Fatigue performance of RC beams strengthened with CFRP under overloads with a ladder spectrum. Sensors, 18(10), 3321.
Search in Google Scholar Back to article
Chen, H., Sun, Z., Zhang, X., & Zhang, W. (2024). Equivalent fatigue constitutive model based on fatigue damage evolution of concrete. Applied Sciences, 14(19), 8721.
Search in Google Scholar Back to article
Yi, W. J., Kunnath, S. K., Sun, X. D., Shi, C. J., & Tang, F. J. (2010). Fatigue behavior of reinforced concrete beams with corroded steel reinforcement. ACI Structural Journal, 107(5).
Search in Google Scholar Back to article
Bui, L. V. H., Stitmannaithum, B., & Nguyen-Thoi, T. (2024). Evaluation of shear strength models for ETS-FRP-retrofitted beams subjected to shear-critical failure. Engineering Structures, 321, 118954.
Search in Google Scholar Back to article
Alhilli, H. H., & Al-Farttoosi, M. H. (2023). Shear performance of reinforced concrete T-beams strengthened by carbon fiber-reinforced polymer bars. Civil Engineering Journal, 9(10), 2411–2429.
Search in Google Scholar Back to article
Aslani, F., & Jowkarmeimandi, R. (2012). Stress–strain model for concrete under cyclic loading. Magazine of Concrete Research, 64(8), 673–685.
Search in Google Scholar Back to article
Lin, H. B. (2025). Calculation of ultimate ductility index based on hysteretic energy analysis of the restoring force curve. Buildings, 15(17), 3152.
Search in Google Scholar Back to article
Jasim, N. R., & Daud, R. A. (2024, February). Behavior of hollow core slabs strengthened by NSM CFRP plates subjected to repeated loading. In AIP Conference Proceedings (Vol. 3009, No. 1, p. 030086). AIP Publishing LLC.
Search in Google Scholar Back to article
Daud, R. A. (2015). Behaviour of reinforced concrete slabs strengthened externally with two-way FRP sheets subjected to cyclic loads (Doctoral dissertation, The University of Manchester).
Search in Google Scholar Back to article
Applied Technology Council, Mid-America Earthquake Center, Multidisciplinary Center for Earthquake Engineering Research (US), Pacific Earthquake Engineering Research Center, & National Earthquake Hazards Reduction Program (US). (2007). Interim testing protocols for determining the seismic performance characteristics of structural and nonstructural components. Federal Emergency Management Agency.
Search in Google Scholar Back to article
Kopiika, N., Blikharskyy, Y., Selejdak, J., Khmil, R., Blikharskyy, Z., & Katunsky, D. (2024). CFRP materials for restoration of the bearing capacity of RC beams with damaged rebar. Journal of Engineering, 2024(1), 4915391.
Search in Google Scholar Back to article
Kopiika, N., Robery, P., Ninic, J., & Mitoulis, S. A. (2025). Remaining Life of Ageing RC Infrastructure for Sustainable development: Deterioration Under Climate Change. Case Studies in Construction Materials, 22, e04757.
Search in Google Scholar Back to article
Kopiika, N. S., Ninic, J., Cucuzza, R., & Mitoulis, S. A. (2024). Deterioration rate diagnosis to global climatic change: The case of Dnipro Dam in Ukraine. In Bridge Maintenance, Safety, Management, Digitalization and Sustainability (pp. 2603–2611). CRC Press.
Search in Google Scholar Back to article