In one form or another, all currently used methods for calculating the bearing capacity of normal sections of bent reinforced concrete elements reinforced with external reinforcement take into account the deformation model of the structure. In this regard, it becomes important to correctly determine the bending stiffness of the reinforced structure and the deformation diagram of the normal section reinforced with external reinforcement. Various methods are known for determining the bending stiffness of reinforced concrete bendable structures, including those reinforced with external reinforcement. At the same time, they mostly have certain limits of applicability, within which they show adequate convergence with real constructions. At the same time, methods that take into account external reinforcement based on carbon fibers are usually adaptive, i.e. in fact they were developed for reinforced concrete sections and are applied through transferable coefficients In this article, an analysis of previously conducted experimental studies of full-scale samples of bent single-span reinforced concrete beams is carried out in terms of evaluating various methods for determining deformations of concrete, reinforcement and external reinforcement, and the issue of constructing a deformation diagram of a reinforced concrete section that is close to real is investigated. In conclusion, the generalized results of the analysis of various methods and experimental data are formulated, as well as the direction of further research. [ABSTRACT FROM AUTHOR]