Ductility Assessment of Hybrid FRP–Steel RC Beams Using Analytical Modeling

Year 2025, Volume: 17 Issue: 3, 537 - 553, 30.11.2025

Saruhan Kartal , Yasin Çağlar

https://doi.org/10.29137/ijerad.1756063

Abstract

This study aims to identify the most appropriate ductility definition for hybrid reinforced concrete (RC) beams combining fiber-reinforced polymer (FRP) and steel reinforcement. Although FRP bars are increasingly used due to their high corrosion resistance and tensile strength, their brittle failure mechanism limits ductility, which is critical for structural safety, especially under seismic or overload conditions. Hybrid reinforcement (FRP+steel), integrating the ductility of steel with the durability of FRP, has been proposed to mitigate this limitation. However, the literature lacks consensus on a standardized ductility definition suitable for such hybrid systems. An extensive experimental dataset of hybrid, FRP-only, and steel-only RC beams was analyzed using multiple ductility definitions from the literatüre to address this gap. Among these, the energy-based definition provided the most consistent and realistic representation of ductile behavior, capturing the elastic-brittle nature of FRP and the yielding response of steel. The selected definition was then extended to additional hybrid RC beams reported in the literature to assess its broader applicability. The analysis confirmed that the ratio of steel reinforcement to total tensile reinforcement (As/Atot) significantly influences ductility. A higher As/Atot ratio and co-location of FRP and steel in the same tensile layer consistently yielded more favorable ductile responses.

Keywords

Ductility , hybrid beams , reinforced concrete , fiber reinforced polymer

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