The optimum coefficients for the use of materials for combined beams in a wide range of loads are obtained in the article. The principles of designing and calculating the strength of Steel Reinforced Concrete slabs are outlined in accordance with SR 266.1325800.2016 ""Steel Reinforced Concrete Structures. Design rules"". Strength calculations are performed, the results of a numerical experiment are compared and analyzed. The optimal utilization factor of materials obtained in accordance with the specified regulatory document was established. The results obtained can be used in the design of combined beams of different cross-sections and spans. The purpose of this study is to find the optimum reinforcement of the floor beams. To strengthen the proposed installation of prestressed reinforcement in the lower girdle of the beam, which increases the strength and reduces the deflections of the beams. In such ceilings, the bending moment from external loads is distributed between the structural elements: the beam and the reinforced concrete overlap, in accordance with the ratio of the stiffnesses of these components. As a result of the study, the optimal diameters of prestressed reinforcement for steel beams by spans from 6 to 9 m were determined and for the calculated linear load from 5 to 30 kN/m. The proposed reinforcement option allows to increase bearing capacity, reduce deflections, reduce labor costs for building reconstruction, and also increase the reliability and durability of the structure.

Keywords: Steel reinforced concrete, floors, combined beams, profiled sheet, coefficient of use of materials