TO THE QUESTION OF THE TECHNICAL CONDITION EVALUATION OF BENDING REINFORCED CONCRETE CONSTRUCTIONS

Abstract

It is indicated on the ambiguity of the categories definition characterizing the technical condition of building structures. The phrases "the impossibility of guaranteeing the integrity of the structure" and "the possibility of ensuring its integrity" in the existing wording of the categories in standards lead to an intuitive installation of them, which may lead to errors. For reinforced concrete structures, the specified wording of categories is given, in which the ambiguity of their interpretations is eliminated. On the basis of the results of two-level evaluation of the bearing capacity, a boundary between the unsuitable for normal operation and the emergency technical conditions is determined. It is offered to determine the state of structure as unsuitable for normal operation, when the bearing capacity of this structure is not provided by current standards, but it is provided by the normative method that it was preceded and operated for many years. To the emergency state should be attributed the structures, bearing capacity of which is not provided in both methods. The pointed out does not contradict the current standards, but it establishes a clear line between these states. Additional classification marks of technical condition are suggested. The prospect of using the theory of plasticity and extreme properties of concrete deformation parameters for the improvement of the method of calculating the bearing capacity of bending reinforced concrete elements are substantiated. To calculate the elements in the normal section according to the nonlinear deformation model, an important role is played by the determination of the values of the limit concrete strain in the most compressed fibers, in excess of which there is the restructuring of concrete. To determine the limit of the restructuring, it is proposed to apply the criterion for maximum deformation energy. To determine the value of the ultimate loading under the shear, a variational method in the theory of plasticity and an upper bound of the limit load value are used, which corresponds to the minimum of the power of plastic strain. The results of calculating the strength of concrete and reinforced concrete elements are confirmed experimentally. It should be noted that the localization of plastic deformation in thin layers on the surface of elements destruction is realized also in less plastic high-strength concretes.