PSI - Issue 83

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

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Experimental and review data from more recent studies have supported these results. According to a summary of more than a hundred investigations, (Sharifianjazi et al., 2022) verified that strength, stiffness, and modulus all significantly decline following fire. Rapid resin softening and breakdown, as well as bond loss, were found to be the main causes. Even at temperatures as low as 150°C, single-layer CFRP strengthening may lose almost half of its effectiveness. Under fire circumstances, multi-layer or insulated systems still saw notable reductions, despite their superior performance. According to their review, mechanical properties quickly deteriorate after the polymer matrix exceeds its glass transition point, hurting both load-bearing and ductility performance. Experimental and review data from more recent studies have supported these results. According to a summary of more than a hundred investigations (Sharifianjazi et al., 2022) verified that strength, stiffness, and modulus all significantly decline following fire (Figure 2) (Table 2). Rapid resin softening and breakdown, as well as bond loss, were found to be the main causes. Even at temperatures as low as 150°C, single-layer CFRP strengthening may lose almost half of its effectiveness.

Fig. 2. The FRP strength retention versus critical temperature: ( a ) FRP bars; ( b ) FRP laminates; ( c ) FRP laminates; and ( d ) pultruded FRP profiles (Sharifianjazi et al., 2022)

Tab. 2. The research plan and results summary of the reported structural responses of concrete members strengthened with FRP laminates (Sharifianjazi et al., 2022)

Tg (°C) of Resin

Study Type

FRP Type

Exposure Condition

Test Type

Ref

Sample

Results

Significant degradation occurred in the bearing capacity above 65 °C. Failure moment decreased from 72.5 to 55.4 kNm.

A laminate of a single layer

Externall y bonded concrete beams

Exper iment al

(Krzywo ń , 2017)

Bending test

N/A

20–80 °C