The article proposes an analytical description of the deformation diagrams of concrete and pre-stressed high-strength reinforcing steel used for development of calculation methods of reinforced concrete elements with combined prestressing. In the developed method of calculation is the rectangular stress distribution in the compressed area of the flexible reinforced concrete element is adopted actual curved that in the case where the relative height of the compressed zone of the cross section close to the boundary ξ ξR, significantly clarifies the calculation. With this purpose, the curve σв – EV, obtained at a Central compression of the concrete prisms.

Keywords: stress-strain diagram of concrete, stress-strain diagram of steel