Aging steel infrastructure is increasingly affected by corrosion-induced section loss, fatigue cracking, and impact-related damage, necessitating efficient and durable rehabilitation strategies. Fibre-reinforced polymer (FRP) composites have emerged as a promising alternative to conventional steel-based retrofits due to their high strength-to-weight ratio, corrosion resistance, and ease of installation. However, their performance is governed by interfacial mechanics, durability constraints, and loading conditions, which are not systematically synthesized in existing studies. This paper presents a mechanics-informed and consequence-oriented review of FRP-based repair strategies for deteriorated steel structures. The study integrates damage mechanisms, bondline behavior, and structural performance within a unified framework linking deterioration characteristics to repair effectiveness and reliability considerations. A quantitative synthesis of experimental and numerical studies indicates that carbon FRP (CFRP) strengthening can recover approximately 10–30% of load-carrying capacity, restore 15–25% of stiffness, and extend fatigue life by approximately 1.9–16 times, depending on stiffness compatibility, interfacial fracture properties, and loading conditions. The influence of environmental effects, including thermal mismatch and moisture-induced adhesive degradation, on long-term performance is examined. A comparison of international standards (ISO 24817, DNV-RP-C301, ABS, and BV NR613) with conventional design codes (e.g., Eurocode 3 and AISC 360) reveals a notable gap in the treatment of flexural members, welded joints, and cyclic loading. Emerging developments in hybrid FRP systems, nanomodified adhesives, and digital twin enabled monitoring support performance-based, reliability-informed lifecycle management. The proposed framework links damage mechanisms, repair design, and monitoring, enabling a shift from localized strengthening to system-level resilience.
Ghimire et al. (Tue,) studied this question.