PSI - Issue 83

Wijdane Kachach et al. / Procedia Structural Integrity 83 (2026) 154–161

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A rigorous examination by (Kodur et al., 2025) also revealed that though FRP-enhanced structures can be designed to resist short-term fires, the long-term mechanical properties are usually damaged by fires. Therefore, the recent work in the area has been directed at research related to fire safety measures. According to (Abdullah et al., 2024), the use of insulating materials, which could be in the form of intumescent coatings, ceramic fiber blankets, or calcium silicate boards, greatly increases the fire endurance time. The percentage loss in the flexural strength of the FRP-strengthened beams after exposure to the fire for two hours was only 20% in the case of the insulated components, while it was substantially higher in the other case. Despite these benefits, there remain some fundamental thermal hazards. According to (Van Doan & Van Cao, 2025) , the fire resistance values decrease when the load ratio increases for the beams, as well as when the proportion of the reinforcements composed of FRP increases. Although thicker concrete covers reduce thermal penetration and hence lengthen the time to critical heating, they are ultimately unable to stop degradation (Figure 3). Although hybrid reinforcement techniques, like combining steel and GFRP, demonstrated better fire resistance when cover and reinforcement ratios were increased, they still experienced notable strength and stiffness losses when exposed to fire for an extended period of time. 3. Conclusions  FRP concrete exhibits considerable post-fire degradation in strength, stiffness, and bond properties.  The glass transition temperature (100-180°C) is the primary factor for the sudden deterioration of the material properties.  The FRP properties degrade rapidly after the onset of the glass transition temperature and completely degrade at high temperatures (>400°C).  The degradation of bond properties between FRP and concrete is a major concern, where the degradation can be as high as 90%.  FRP properties degrade under fire conditions; however, CFRP exhibits relatively better properties.  Protective measures can only delay the onset of degradation; however, the FRP properties completely degrade under fire conditions.  Fire conditions cause immediate and long-term weakening of the FRP structures.  The load-carrying capacity can degrade by as much as 70% after fire exposure.  The FRP structures degrade under fire conditions; however, the environmental effects accelerate the degradation.  Improved fire-resistant design and materials are necessary for the safe use of FRP structures. References Abdullah, M., El-Mahdy, O. O., & Hamdy, G. A. (2024). Effectiveness of Insulation Layers for Fire Protection of FRP Reinforced Concrete Flexural Members. ENGINEERING RESEARCH JOURNAL (ERJ) , (53), 56–63. https://erjsh.journals.ekb.eg Ahmed, A., & Kodur, V. K. R. (2011). Effect of bond degradation on fire resistance of FRP-strengthened reinforced concrete beams. Composites Part B: Engineering , 42 (2), 226–237. https://doi.org/10.1016/J.COMPOSITESB.2010.11.004 Ashrafi, H., Bazli, M., Najafabadi, E. P., & Vatani Oskouei, A. (2017). The effect of mechanical and thermal properties of FRP bars on their tensile performance under elevated temperatures. Construction and Building Materials , 157 (1), 1001–1010. https://doi.org/10.1016/j.conbuildmat.2017.09.160 Bhatt, P. P., Kodur, V. K. R., Shakya, A. M., & Alkhrdaji, T. (2021). Performance of insulated FRP-strengthened concrete flexural members under fire conditions. Frontiers of Structural and Civil Engineering 2021 15:1 , 15 (1), 177–193. https://doi.org/10.1007/s11709-021-0714 z Dai, J.-G., Gao, ; W Y, Teng, J. G., & Asce, M. (2012). Bond-Slip Model for FRP Laminates Externally Bonded to Concrete at Elevated Temperature. Journal of Composites for Construction , 17 (2), 217–228. https://doi.org/10.1061/(asce)cc.1943-5614.0000337 Demir, U., Unal, G., Sert, A. F., Calis, R. O., & Ilki, A. (n.d.). Influence of FRP Repair on the Axial Behavior of Fire Damaged Concrete . Dong, K., & Hu, K. (2016). Development of bond strength model for CFRP-to-concrete joints at high temperatures. Composites Part B: Engineering , 95 (4), 264–271. https://doi.org/10.1016/j.compositesb.2016.03.088 Gamage, J. C. P. H., Al-Mahaidi, R., & Wong, M. B. (2006). Bond characteristics of CFRP plated concrete members under elevated temperatures. Composite Structures , 75 (1–4), 199–205. https://doi.org/10.1016/j.compstruct.2006.04.068 Jadooe, A., Al-Mahaidi, R., Asce, M., & Abdouka, K. (2017). Bond Behavior between NSM CFRP Strips and Concrete Exposed to Elevated Temperature Using Cement-Based and Epoxy Adhesives. Journal of Composites for Construction , 21 (5), 04017033. https://doi.org/10.1061/(asce)cc.1943-5614.0000812