Published: Građevinar 78 (2026) 7
Paper type: Scientific research paper
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Behaviour and bearing capacity of RC columns strengthened with UHPC jackets: the role of interfacial connectors and a predictive model

Ultra-high-performance concrete (UHPC) is increasingly used as a primary material for strengthening reinforced concrete (RC) columns owing to its ultra-high strength, excellent ductility, durability, and low permeability. However, two key issues remain unaddressed: (1) whether connectors are necessary at the UHPC-to-concrete interface to ensure monolithic behaviour, and (2) the development of a simplified yet accurate model for predicting the bearing capacity of strengthened columns. To address these questions, eight RC columns were tested in two stages. In the first stage, five columns were tested to analyse their failure modes. In the second stage, three specimens validated the numerical model for bearing capacity prediction. Results indicate sufficient steel connectors are required at the UHPC–concrete interface to prevent relative displacement between the UHPC layer and the original concrete, which could otherwise lead to premature structural failure. Moreover, the proposed model demonstrated high accuracy in estimating the bearing capacity of UHPC-strengthened RC columns.

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