The article obtains the results of experimental studies of reinforced concrete structures under torsion with bending. The basic parameters of the stress-strain state of eight series of structures, including those on the deformable base and composite ones, have been determined. A test stand is developed for realization of the chosen loading schemes and getting of reliable experimental values of crack loading, deflections, angles of turn, crack opening width, distance between cracks and other parameters of the structures. Loading is carried out smoothly, in small steps with endurance at each stage. The value of crack opening width is fixed in the compressed and stretched working reinforcement, at the distance of two diameters from the reinforcement axis, in the middle of the height of an experimental reinforced concrete structure, and at characteristic points along the entire crack profile. Tests is conducted for structures on a deformable base and for composite structures of two layers of different concrete classes. The deflections are measured at six points, with simultaneous determination of the rotation angles. The research results show, that the values of relative deformations according to the readings of electrical resistors, deflections and angles of rotation in the center of the tested structure and in the places where the load is applied are obtained.