Usage of EB-CFRP for Improved Flexural Capacity of Unbonded Post-Tensioned Concrete Members Exposed to Partially Damaged Strands

Hayder Qays Abbas, Alaa Hussein Al‐Zuhairi


The study presents the performance of flexural strengthening of concrete members exposed to partially unbonded prestressing with a particular emphasis on the amount (0, 14.2, and 28.5%) of cut strands-symmetrical and asymmetrical damage. In addition to examining the influence of cut strands on the remaining capacity of post-tensioned unbonded members and the effectiveness of carbon fiber reinforced polymer laminates restoration, The investigated results on rectangular members subjected to a four-point static bending load based on the composition of the laminate affected the stress of the CFRP, the failure mode, and flexural strength and deflection are covered in this study. The experimental results revealed that the usage of CFRP laminates has a considerable impact on strand strain. In addition to that, the flexural stiffness of strengthened members becomes increasingly significant within the serviceability phases as the damaged strand ratios increase. The EB-CFRP laminates increased the flexural capacity by approximately 13%, which corresponds to strand damage of 14.28% and about 9.5% for 28.57% of strand damage, which represents one of the unique findings in this field. Additionally, semi-empirical equations for forecasting the actual strain of unbonded tendons were presented. The suggested equations are simple to solve and produce precise results.


Doi: 10.28991/CEJ-2022-08-06-014

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CFRP Laminate; Debonding; Post-Tensioned Girder; Strand Damage; Unboned Strands.


Slaitas, J., & Valivonis, J. (2021). Full moment-deflection response and bond stiffness reduction of RC elements strengthened with prestressed FRP materials. Composite Structures, 260, 113265. doi:10.1016/j.compstruct.2020.113265.

Ghaffary, A., & Moustafa, M. A. (2020). Synthesis of repair materials and methods for reinforced concrete and prestressed bridge girders. Materials, 13(18), 4079. doi:10.3390/ma13184079.

Kasan, J. L., Harries, K. A., Miller, R., & Brinkman, R.J. (2014). Limits of Application of Externally Bonded CFRP Repairs for Impact-Damaged Prestressed Concrete Girders. Journal of Composites for Construction, 18(3). doi:10.1061/(asce)cc.1943-5614.0000347.

Aljaafreh, T. (2019). Performance of Precast Concrete Bridge Girders with Externally Bonded Anchored CFRP. Ph.D. Thesis, The University of Texas, Arlington, United States.

Saeed, I. A. (2017). Flexural Performance of Reinforced Concrete Beams Strengthened with Near Surface Mounted Carbon fibre Reinforced Polymer Laminates and Bars under Elevated Temperature. Ph.D. Thesis, Building and Construction Department, University of Technology, Baghdad, Iraq.

Deng, Y., Li, Z., Zhang, H., Corigliano, A., Lam, A. C. C., Hansapinyo, C., & Yan, Z. (2021). Experimental and analytical investigation on flexural behaviour of RC beams strengthened with NSM CFRP prestressed concrete prisms. Composite Structures, 257, 113385. doi:10.1016/j.compstruct.2020.113385.

Kuntal, V. S., Chellapandian, M., Prakash, S. S., & Sharma, A. (2020). Experimental study on the effectiveness of inorganic bonding materials for near-surface mounting shear strengthening of prestressed concrete beams. Fibers, 8(6). doi:10.3390/FIB8060040.

Ganesh, P., & Murthy, A. R. (2019). Repair, retrofitting and rehabilitation techniques for strengthening of reinforced concrete beams - A review. Advances in Concrete Construction, 8(2), 101–117. doi:10.12989/ACC.2019.8.2.101.

Dawood, M. B., & Taher, H. M. A. M. (2021). Various methods for retrofitting prestressed concrete members: A critical review. Periodicals of Engineering and Natural Sciences, 9(2), 657–666. doi:10.21533/pen.v9i2.1849.

Deng, Y., Ma, F., Zhang, H., Wong, S. H. F., Pankaj, P., Zhu, L., Ding, L., & Bahadori-Jahromi, A. (2021). Experimental study on shear performance of RC beams strengthened with NSM CFRP prestressed concrete prisms. Engineering Structures, 235, 112004. doi:10.1016/j.engstruct.2021.112004.

Mohammed, A. M. Y., Ali, A. R. M., & Abdalla, H. A. (2021). Non-linear Behavior of Low Strength RC Beams Strengthened with CFRP Sheets. Civil Engineering Journal, 7(3), 518-530. doi:10.28991/cej-2021-03091670.

Wang, Q., Zhu, H., Zhang, B., Tong, Y., Teng, F., & Su, W. (2020). Anchorage systems for reinforced concrete structures strengthened with fiber-reinforced polymer composites: State-of-the-art review. Journal of Reinforced Plastics and Composites, 39(9–10), 327–344. doi:10.1177/0731684420905010.

Rafeeq, R. (2016). Torsional Strengthening of Reinforced Concrete Beams Using CFRP Composites, Master Thesis, Portland States University, Portland, Unite States.

Chai, H. K., Majeed, A. A., & Allawi, A. A. (2015). Torsional Analysis of Multicell Concrete Box Girders Strengthened with CFRP Using a Modified Softened Truss Model. Journal of Bridge Engineering, 20(8). doi:10.1061/(asce)be.1943-5592.0000621.

Kim, Y. J., Green, M. F., & Fallis, G. J. (2008). Repair of Bridge Girder Damaged by Impact Loads with Prestressed CFRP Sheets. Journal of Bridge Engineering, 13(1), 15–23. doi:10.1061/(asce)1084-0702(2008)13:1(15).

Peera, I., & Oukaili, N. (2021). Experimental Study on the Behaviours of Post-tensioned Concrete Members with Unbonded Tendons. IOP Conference Series: Materials Science and Engineering, 1067(1), 012033. doi:10.1088/1757-899x/1067/1/012033.

Barik, T., Parimita, S., & Pal, K. (2017). Parametric Study and Process Monitoring on Drilling of CFRP Composites. Proceedings of 10th International Conference on Precision, Meso, Micro and Nano Engineering (COPEN 10), 953–957. 7-9 December, Indian Institute of Technology Mardas, Chennai, India.

Li, X., Deng, J., Wang, Y., Xie, Y., Liu, T., & Rashid, K. (2021). RC beams strengthened by prestressed CFRP plate subjected to sustained loading and continuous wetting condition: Time-dependent prestress loss. Construction and Building Materials, 275, 122187. doi:10.1016/j.conbuildmat.2020.122187.

ACI 318-19. (2019). Building Code Requirements for Reinforced Concrete. American Concrete Institute, Farmington Hills, United States. doi:10.14359/51716937.

ACI 440.2R-17. (2017). Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structure. American Concrete Institute, Farmington Hills, United States.

El-Meski, F. M., & Harajli, M. H. (2013). Flexural Capacity of FRP Strengthened Unbonded Prestressed Concrete Members: Proposed Design Guidelines. 11th International Symposium on Fiber Reinforced Polymer for Reinforced Concrete Structures (FRPRCS-11), 26-28 June 2013, Guimarães, Portugal.

El-Meski, F., & Harajli, M. (2013). Flexural behavior of unbonded posttensioned concrete members strengthened using external FRP composites. Journal of Composites for Construction, 17(2), 197-207. doi:10.1061/(asce)cc.1943-5614.0000330.

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DOI: 10.28991/CEJ-2022-08-06-014


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