At various stages of the life cycle - during manufacture, transportation, installation and operation, defects and damages may occur that affect the stress-strain state of structures. Some examples of survey the technical conditions of load-bearing structures of enterprises in the city of Ivanovo are given in the article. Defects and damages in operated bending structures are revealed. The results of experimental studies of reinforced concrete beams with initial cracks are presented. The tables show: the beam loading scheme, defect parameters, the location of initial cracks, the main characteristics of materials, as well as experimental data in the form of the relative moment Mult / Mtest, where Mult is the breaking moment of a beam with initial cracks, Mtest is the breaking moment of a similar beam without defects. The degree of influence of defects on the bearing capacity of beams is determined. Empirical coefficients are calculated that take into account the type and parameters of cracks, the cross-section reinforcement coefficient and concrete strength of the beams. A formula for determining stresses in concrete compression zones for beams with cracks is derived based on the theory of destruction mechanics and using experimental coefficients. A method for calculating of reinforced concrete bending structures bearing capacity with defects and damages is proposed. An analysis of experimental and theoretical studies confirming the correctness of this technique is made.

Keywords: reinforced concrete bending elements, beams with cracks, load-bearing capacity, calculation method