Contribution of CFRP to the behavior of retrofitted reinforced concrete deep beams: Experimental study and analytical investigation
Construction and Building Materials, cilt.537, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 537
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.conbuildmat.2026.147160
- Dergi Adı: Construction and Building Materials
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
- Anahtar Kelimeler: Analytical modeling, FRP, RC deep beam, Repair mortar, Retrofit and strengthening, Shear strength
- Yıldız Teknik Üniversitesi Adresli: Evet
Özet
The behavior of reinforced concrete (RC) deep beams is controlled by shear forces rather than flexural moments, and due to load transfer mechanisms and arching effects, failure in these elements generally occurs suddenly as brittle shear fracture. Retrofitting and strengthening damaged structural elements in-situ instead of demolition and reconstruction stands out as a more attractive option in most cases. In this study, the effectiveness of shear strengthening of pre-damaged RC deep beams using carbon fiber reinforced polymer (CFRP) composites after repair with repair mortar and epoxy injection was investigated experimentally and analytically. During the experimental phase, failure mechanisms, load-deflection relationships, energy dissipation capacities, and strain behaviors showing the dynamic interaction between steel stirrups and FRP wrapping were analyzed in detail. Experimental results demonstrated that repair combined with CFRP strengthening significantly restored the lost stiffness and markedly increased the ultimate load-carrying and deflection capacities. In the analytical part, existing international design codes and literature equations were noted to be primarily based on the slender beam principle. Existing models exhibit high scatter and remain insufficient in predicting the FRP shear contribution in deep beams because they do not fully incorporate the shear span-to-effective depth ratio (a/d) into their formulations. Accordingly, a new analytical formulation was proposed to calculate the FRP contribution to shear strength more rationally and accurately. The performance of the proposed model was tested using a comprehensive dataset compiled from the literature, and the results provided statistically more reliable and successful predictions than existing literature and design code models. This study aims to expand the experimental body of knowledge regarding the repair and FRP strengthening of damaged RC deep beams and provide a scientifically based tool for design engineers to reliably calculate the FRP contribution to shear.