Concrete Corbels: A Narrative Review of Load Transfer Mechanisms, Failure Behaviour, Strut-and-Tie Models, and Design Approaches

Abstract

Corbels are short projecting cantilevers with concentrated reactions from precast beams and girders that are transferred to supporting columns or walls, which are typically reinforced concrete. They have a low shear span-to-depth (a/d) ratio and are not designed using plane-section beam theory, but rather shear-friction, truss, and strut-and-tie (STM) design. The paper is a narrative review of corbel literature based on three questions: How load is transmitted through a corbel, which failure modes occur and what parameters control them, and how various design methods compare to the experimental results. The review draws on classical shear-friction tests, work on high-strength, fibre-reinforced, FRP-reinforced and strengthened corbels, refined STM and numerical models, and code comparisons. Across the studies, a/d emerges as the dominant parameter, followed by concrete strength and the quantity of main tension and horizontal reinforcement. Softened and compatibility-based STM formulations estimate capacity more accurately than empirical code equations, whereas code STM provisions are conservative and scattered when applied to corbels. Steel fibres have a reliable effect on improving ductility and crack control, but some reports indicate that there is no consistent effect on ultimate load. The critical areas of concern are that there are no strut and node effectiveness factors available for corbels, there is very limited code guidance for fibre-reinforced and FRP-reinforced corbels, and there is no common, quality-controlled test database.