Experimental and Numerical Analysis of CFRP-Strengthened Reinforced Concrete Beams at Various Temperatures

Abstract

This study investigates the effects of various temperatures on the performance of reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymer (CFRP) using both experimental and numerical methods. A total of 24 beam specimens with dimensions of 10×15×60 cm were cast using C25/30 concrete. Half of the specimens were strengthened by CFRP wrapping, while the remaining half served as the control group. A total of 24 specimens were divided into three groups: 8 specimens were tested at 24 °C (room temperature), 8 specimens at 120 °C, and 8 specimens at 240 °C after being exposed to these temperatures for two hours. The experimental results showed that CFRP strengthening provided approximately 15% higher flexural strength at room temperature. In addition, while no significant strength loss was observed up to 120 °C, an approximate 8% reduction in strength occurred at 240 °C due to the adverse effect on the CFRP layer. The findings were further validated through finite element analyses conducted using Ansys Workbench. Numerical results were largely consistent with the experimental data, confirming that CFRP strengthening maintains its effectiveness up to elevated temperatures. At the same time, performance degradation becomes evident once the critical temperature threshold is exceeded. Overall, the results highlight that CFRP strengthening offers significant advantages in terms of post-fire performance, although its efficiency is clearly limited under high-temperature exposure.

Keywords

• Carbon fiber reinforced polymer
• Strengthening
• High temperature
• Flexural strength
• Reinforced concrete beam

References

1. Al-Rousan, R. Z. (2021). Integration of CFRP strips as an internal shear reinforcement in reinforced concrete beams exposed to elevated temperature. Case Studies in Construction Materials, 14, e00508. https://doi.org/10.1016/j.cscm.2021.e00508
2. Al-Rousan, R. Z., & Alkhawaldeh, A. (2021). Behavior of heated damaged reinforced concrete beam–column joints strengthened with FRP. Case Studies in Construction Materials, 15, e00584. https://doi.org/10.1016/j.cscm.2021.e00584
3. Al-Rousan, Z. A., & Alnemrawi, B. A. (2025). Nonlinear finite element analysis for the torsional and bending behavior of heat-damaged RC beams strengthened with CFRP composites. International Journal of Structural Integrity, 16(6), 1529-1556. https://doi.org/10.1108/IJSI-03-2025-0064
4. Arslan, Ş., & Aydın, F. (2023). Yüksek sıcaklık etkisindeki CFRP donatıların dayanım kayıplarının matematiksel yöntemlerle tespiti. Karadeniz Fen Bilimleri Dergisi, 13(3), 926-942. https://doi.org/10.31466/kfbd.1273294
5. Assad, M., Hawiled, R. A., & Abdalla, J. A. (2022). Modeling the behavior of CFRP-strengthened RC slabs under fire exposure. Procedia Structural Integrity, 42, 1668–1675. https://doi.org/10.1016/j.prostr.2022.12.210
6. Azevedo, A. S., Firmo, J. P., Correia, J. R., Chastre, C., Biscaia, H., & Franco, N. (2022). Fire behaviour of CFRP-strengthened RC slabs using different techniques – EBR, NSM, and CREatE. Composites Part B: Engineering, 230, 109471. https://doi.org/10.1016/j.compositesb.2021.109471
7. Calis, M., Uygunoglu, T., & Kara, A. F. (2024). Effect of heat aging on pull-off strength of FRP epoxy bonded concrete: An experimental study and fire modelling. Construction and Building Materials, 439, 137290. https://doi.org/10.1016/j.conbuildmat.2024.137290
8. Danraka, M. N., Mahir Mahmod, H., Oluwatosin, O. K. J., & Student, P. G. (2017). Strengthening of reinforced concrete beams using FRP technique: A review. International Journal of Engineering Science and Computing, 7(6), 13199–13213.

9. Dong, K., Hu, K. X., Gao, W. Y., & Yang, S. T. (2023). Fire endurance tests of CFRP-strengthened RC beams with different insulation schemes. Structures, 56, 104887. https://doi.org/10.1016/j.istruc.2023.104887
10. Gawil, B., Wu, H. C., & Elarbi, A. B. (2020). Modeling the behavior of CFRP-strengthened concrete beams and columns at different temperatures. Fibers, 8(2), 10. https://doi.org/10.3390/fib8020010
11. Green, M., Bisby, L. A., Khalifa, T., Benichou, N., Eedson, R., Bao, X., & Li, W. (2010). Performance in fire of fibre reinforced polymer strengthened concrete beams including embedded fibre optic sensors. In Proceedings of the Sixth International Conference (pp. 149–156). DEStech Publications, Inc.
12. Hawileh, R. A. (2012). Nonlinear finite element modeling of RC beams strengthened with NSM FRP rods. Construction and Building Materials, 27(1), 461–471. https://doi.org/10.1016/j.conbuildmat.2011.07.018
13. Hawileh, R. A., Naser, M., Zaidan, W., & Rasheed, H. A. (2009). Modeling of insulated CFRP-strengthened reinforced concrete T-beam exposed to fire. Engineering Structures, 31(12), 3072–3079. https://doi.org/10.1016/j.engstruct.2009.08.008
14. Jafarzadeh, H., & Nematzadeh, M. (2022). Flexural strengthening of fire-damaged GFRP-reinforced concrete beams using CFRP sheet: Experimental and analytical study. Composite Structures, 288, 115378. https://doi.org/10.1016/j.compstruct.2022.115378
15. Liang, X., Wang, W., Lili, H., & Feng, P. (2024). Experimental and numerical study on high-temperature performance of prestressed CFRP-reinforced steel columns. Engineering Structures, 301, 117347. https://doi.org/10.1016/j.engstruct.2023.117347
16. Mahmood, H., Gao, W. Y., & Hu, K. X. (2021, April). Fire Performance of Insulated RC Beams Shear-Strengthened with CFRP Sheets. In IOP Conference Series: Earth and Environmental Science (Vol. 719, No. 2, p. 022044). IOP Publishing. https://doi.org/10.1088/1755-1315/719/2/022044
17. Naser, M. Z. (2019). Properties and material models for modern construction materials at elevated temperatures. Computational Materials Science, 160, 16–29. https://doi.org/10.1016/j.commatsci.2018.12.055
18. Siddika, A., Mamun, M. A., Alyousef, R., & Amran, Y. H. M. (2019). Strengthening of reinforced concrete beams by using fiber-reinforced polymer composites: A review. Journal of Building Engineering, 25, 100798. https://doi.org/10.1016/j.jobe.2019.100798
19. Tafsirojjaman, T., Fawzia, S., Thambiratnam, D. P., & Zhao, X. L. (2020). Study on the cyclic bending behaviour of CFRP-strengthened full-scale CHS members. Structures, 28, 741–756. https://doi.org/10.1016/j.istruc.2020.09.015
20. Tekeli, H., Dilmaç, H., Demir, F., & Güler, K. (2020). Prediction of seismic performance of existing framed reinforced concrete buildings. Journal of Performance of Constructed Facilities, 34(3), 04020030. https://doi.org/10.1061/(ASCE)CF.1943-5509.0001422
21. Ustabaş, İ., Gürbüz, A., Kurt, Z., & Deşik, F. (2020). Betonda CFRP sargı uygulamasının deneysel ve analitik olarak karşılaştırılması. Mühendislik Bilimleri ve Tasarım Dergisi, 8(3), 921–930.
22. Williams, B., Bisby, L., Kodur, V., Green, M., & Chowdhury, E. (2006). Fire insulation schemes for FRP-strengthened concrete slabs. Composites Part A: Applied Science and Manufacturing, 37(8), 1151–1160. https://doi.org/10.1016/j.compositesa.2005.05.028
23. Yan, K., Yu, X., Ren, P., Zhang, R., Oh, E., Zhang, Y., & Zhang, X. (2025). Experimental research on fire resistance of the concrete beams strengthened with the CFRP sheets pasted by magnesium phosphate inorganic adhesive. Engineering Structures, 330, 119946. https://doi.org/10.1016/j.engstruct.2025.119946