Experience gained in design, erection and operation of span reinforced concrete structures has proved that practically all of them are subject to complex stress-strain state. At that, the researchers pay considerable greater attention to calculation of strength, deformation analysis and determination of crack resistance in normal cross-sections than to calculation of their support zones, including oblique sections, which results are generally taken into account for determining the section dimensions and the quantity of the cross reinforcement.

In the course of operation or armed hostilities the span r.c. structures are subject to substantial damage and considerable reduction of their bearing capacity, especially under low-cycle repeated loading. In this connection it becomes necessary to renew their operation capacity and/or improve their bearing capacity. However, the current design standards contain no recommendations as to determination of the residual bearing capacity of such structures and calculation of their reinforcement. There are methods of the operation capacity renewal and reinforcement of the structures by increasing their sections adding metal or reinforced concrete elements. Still, the calculation methods of such reinforcement are also imperfect. It is proposed to renew operation capacity of such structures by strengthening their tensioned parts with CFRP; the performed experimental research will provide the basis for calculating bearing capacity of said structures with the aid of the deformation method improved by the authors.