Structural Strengthening of Insufficiently Designed Reinforced Concrete T-Beams using CFRP Composites

Hasan Ehssan Alobaidi, Alaa Hussein Al-Zuhairi


This study aims to compare the response of reinforced concrete (RC) T-beams strengthened with carbon fibre-reinforced polymer (CFRP) composite with that of non-strengthened control beams when subjected to monotonic two-point loading until failure for flexural once and shear again. The experimental programme tested eight RC T-beams, which included two reference beams without strengthening and six strengthened beams. The eight beams were divided into two main groups according to strengthening (flexural and shear). Experimental analysis was performed to study the effect of the CFRP laminate width in the flexural group and the spacing of CFRP U-wrap sheets in the shear group on the ultimate load capacity, load-strain relationship, and load-deflection relationship. Results show that increasing the width of the CFRP laminate in the flexural group improves the ultimate strengths to approximately 9.5%, 35%, and 41% for beams with CFRP laminate widths of 50, 100, and 150 mm, respectively, compared with the reference non-strengthened beam. The stiffness of the beams increases in direct proportion to the width of the CFRP laminate. In the meantime, decreasing the spacing of the CFRP laminate in the shear group increases the ultimate strengths to approximately 13.2%, 17.7%, and 23.5% for beams with CFRP U-wrap sheet spacings of 166, 125, and 100 mm, respectively, compared with the reference non-strengthened beam. Therefore, the spacing of the CFRP sheet is inversely proportional to the stiffness of the beam.


Doi: 10.28991/CEJ-2023-09-08-05

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T-Beams; CFRP Composites; Bending Stresses; Shear Stresses.


Naqe, A. W., & Al-Zuhairi, A. H. (2020). Strengthening of RC Beam with Large Square Opening Using CFRP. Journal of Engineering, 26(10), 123–134. doi:10.31026/j.eng.2020.10.09.

Naqi, A. W., & Al-Zuhairi, A. H. (2020). Nonlinear Finite Element Analysis of RCMD Beams with Large Circular Opening Strengthened with CFRP Material. Journal of Engineering, 26(11), 170–183. doi:10.31026/j.eng.2020.11.11.

Abbas, H. Q., & Al-Zuhairi, A. H. (2022). Usage of EB-CFRP for Improved Flexural Capacity of Unbonded Post-Tensioned Concrete Members Exposed to Partially Damaged Strands. Civil Engineering Journal (Iran), 8(6), 1288–1303. doi:10.28991/CEJ-2022-08-06-014.

Jalil, A., & Al-Zuhairi, A. H. (2022). Behavior of Post-Tensioned Concrete Girders Subject to Partially Strand Damage and Strengthened by NSM-CFRP Composites. Civil Engineering Journal (Iran), 8(7), 1507–1521. doi:10.28991/CEJ-2022-08-07-013.

Mhanna, H. H., Hawileh, R. A., & Abdalla, J. A. (2019). Shear strengthening of reinforced concrete beams using CFRP wraps. Procedia Structural Integrity, 17(1), 214–221. doi:10.1016/j.prostr.2019.08.029.

Abdulkareem, B. F., & Izzet, A. F. (2022). Residual post fire strength of non-prismatic perforated beams. IOP Conference Series: Earth and Environmental Science, 961(1). doi:10.1088/1755-1315/961/1/012002.

Danraka, M. N., Mahmod, H. M., Oluwatosin, O. K. J., & Student, P. (2017). Strengthening of reinforced concrete beams using FRP technique: a review. International Journal of Engineering Science, 7(6), 13199.

Bizindavyi, L., & Neale, K. W. (1999). Transfer Lengths and Bond Strengths for Composites Bonded to Concrete. Journal of Composites for Construction, 3(4), 153–160. doi:10.1061/(asce)1090-0268(1999)3:4(153).

Ueda, T., Sato, Y., & Asano, Y. (1999). Experimental Study on Bond Strength of Continuous Carbon Fiber Sheet. SP-188: 4th Intl Symposium - Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures. doi:10.14359/5641.

De Lorenzis, L., Miller, B., & Nanni, A. (2001). Bond of fiber-reinforced polymer laminates to concrete. ACI Materials Journal, 98(3), 256–264. doi:10.14359/10281.

Nakaba, K., Kanakubo, T., Furuta, T., & Yoshizawa, H. (2001). Bond behavior between fiber-reinforced polymer laminates and concrete. ACI Structural Journal, 98(3), 359–367. doi:10.14359/10224.

Wang, Y. C., & Restrepo, J. I. (2001). Response of RC T-Beams Strengthened for Flexure with Staggered CFRP Plates. Journal of Composites for Construction, 5(3), 188–199. doi:10.1061/(asce)1090-0268(2001)5:3(188).

Zaki, M. A., Rasheed, H. A., Roukerd, R. R., & Raheem, M. (2020). Performance of reinforced concrete T beams strengthened with flexural CFRP sheets and secured using CFRP splay anchors. Engineering Structures, 210(1), 110304. doi:10.1016/j.engstruct.2020.110304.

Zaki, M. A., & Rasheed, H. A. (2021). Characterizing debonding strain in sand-lightweight high strength concrete T beams strengthened with CFRP sheets. Composite Structures, 262(1), 113630. doi:10.1016/j.compstruct.2021.113630.

ACI 440.2R-17 (2017). Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening of Concrete Structures. American Concrete Institute (ACI), Michigan, USA.

Ng, S. C., & Lee, S. (2002). A Study of Flexural Behavior of Reinforced Concrete Beam Strengthened with Carbon Fiber-Reinforced Plastic (CFRP). Journal of Reinforced Plastics and Composites, 21(11), 919–938. doi:10.1177/073168440202101104.

Mofidi, A., & Chaallal, O. (2011). Shear Strengthening of RC Beams with Externally Bonded FRP Composites: Effect of Strip-Width-to-Strip-Spacing Ratio. Journal of Composites for Construction, 15(5), 732–742. doi:10.1061/(asce)cc.1943-5614.0000219.

Belarbi, A., Bae, S. W., & Brancaccio, A. (2012). Behavior of full-scale RC T-beams strengthened in shear with externally bonded FRP sheets. Construction and Building Materials, 32(1), 27–40. doi:10.1016/j.conbuildmat.2010.11.102.

Ozden, S., Atalay, H. M., Akpinar, E., Erdogan, H., & Vulaş, Y. Z. (2014). Shear strengthening of reinforced concrete T-beams with fully or partially bonded fibre-reinforced polymer composites. Structural Concrete, 15(2), 229–239. doi:10.1002/suco.201300031.

ACI 318-19. (2019). Building Code Requirements for Structural Concrete. American Concrete Institute (ACI), Michigan, United States.

Mansur, M. A., Huang, L. M., Tan, K. H., & Lee, S. L. (1992). Deflections of reinforced concrete beams with web openings. ACI Structural Journal, 89(4), 391–397. doi:10.14359/3019.

Dong, J., Wang, Q., He, D., & Guan, Z. (2011). CFRP sheets for flexural strengthening of RC beams. 2011 International Conference on Multimedia Technology. doi:10.1109/icmt.2011.6003160.

Lee, S., & Moy, S. (2007). A method for predicting the flexural strength of RC beams strengthened with carbon fiber reinforced polymer. Journal of Reinforced Plastics and Composites, 26(14), 1383–1401. doi:10.1177/0731684407079372.

Alferjani, M. B. S., Samad, A. A., Elrawaff, B. S., & Mohamad, N. (2014). Behavior on shear strengthening of precraced / repair RC continuous beams using CFRP strips. International Journal of Engineering and Science, 4(5), 32-44.

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DOI: 10.28991/CEJ-2023-09-08-05


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