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Tran et al. Int J Concr Struct Mater (2026) 20:71https://doi.org/10.1186/s40069-026-00947-9RESEARCHOpen Access© The Author(s) 2026. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.International Journal of ConcreteStructures and MaterialsExperimental Study on Shear Strengthening of Reinforced Concrete Deep Beams with Both Embedded Through-Section GFRP Bars and Externally Bonded CFRP SheetsTrung Thanh Tran 1 , Linh Van Hong Bui 2,3* , Chanachai Thongchom 1* and Pitcha Jongvivatsakul 4,5 Abstract This study investigated the shear resistance of reinforced concrete (RC) deep beams strengthened with a combina-tion of embedded through-section glass fi ber-reinforced polymer (ETS-GFRP) bars and externally bonded carbon fi ber-reinforced polymer (EB-CFRP) sheets. Four-point bending tests were conducted on nine rectangular RC deep beams: one control beam with internal steel stirrups, two beams strengthened only with EB-CFRP sheets, and six beams retrof i tted with both EB-CFRP sheets and ETS-GFRP bars under various conf i gurations. The main design vari-ables were the ETS-GFRP bar diameter (10 or 13 mm), FRP sheet wrapping scheme (U-wrap or full wrap), number of sheet layers (one or two for U-wrap and one for full wrap), and the shear span-to-ef f ective depth ratio (a/d = 1.5 or 2.2). Experimental results indicate that RC deep beams with shear strengthening systems (EB-FRP combined with ETS-FRP) presented an increased peak load (i.e., beam capacity) and shear slope of the load?def l ection curve (i.e., beam stif f ness) compared with those of unstrengthened beams and those strengthened via only one strengthening method, with the shear capacity increasing by up to 13%. Notably, the use of the hybrid retrof i tting method helps delay premature debonding of the EB-FRP element and postpones the fi nal failure, as conf i rmed by higher debond-ing loads and extended strain development in the FRP systems. Increasing the ETS bar diameter enhances the shear strength of the beam. By contrast, increasing the a/d ratio reduced the shear strength by 14% approximately. Finally, predictions made by the existing design model aligned well with the test data.Keywords Deep beams, Embedded through-section, External bonding, Fiber-reinforced polymer, Hybrid strengtheningJournal information: ISSN 1976-0485 / eISSN 2234-1315.*Correspondence:Linh Van Hong Buibvhlinh@hcmut.edu.vnChanachai Thongchomtchanach@engr.tu.ac.th1 Thammasat University Research Unit in Structural and Foundation Engineering, Department of Civil Engineering, Thammasat School of Engineering, Thammasat University, Klongluang 12120, Pathumthani, Thailand2 Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City, Vietnam3 Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnam4 Center of Excellence in Innovative Construction Materials, Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand5 GreenTech Nexus: Research Center for Sustainable Construction Innovation, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand