Relevance. When repairing hydraulic structures, it is often necessary to face the task of strengthening them. Among the methods of strengthening retaining structures, the most interesting are those that allow to immediately include reinforcement elements in joint work with the structure and carry out work without removing the backfill soil from the rear edge. When choosing repair materials, attention should be paid to corrosion-resistant composite materials, the use of which in hydraulic engineering is not yet standardized, but the scope of their application is expanding every year. The main aim of experimental research is to strengthen the reinforced concrete structures of hydraulic structures, including those with interblock construction joints and transverse cracks, using prestressed transverse reinforcement. Methods. The investigations were carried out on a reinforced concrete model of a beam type reinforced with prestressed transverse reinforcement in the zone of inclined cracks formation. The model was made taking into account the typical tasks encountered during the repair of long-term operating retaining hydraulic structures with open seams and cracks, insufficient transverse reinforcement, low reinforcement coefficient, and initial deflection. Results. The task of strengthening a special reinforced concrete model using prestressed transverse reinforcement was realized. Experimental data were obtained on the nature of deformation and destruction, the opening of interblock construction joints and cracks, and the stresses in the reinforcement. Recommendations are given for strengthening the operated low-reinforced concrete structures of hydraulic structures with interblock construction joints with prestressed reinforcement.