The paper deals with the issues of bending moment redistribution in statically indeterminate corroded reinforced concrete beams. It is noted that the ability of a reinforced concrete beam to rotate is crucial for both operational and limit states, as it affects the deflection, moment redistribution and energy absorption. A mathematical model that predicts the moment redistribution factor is developed. The redistribution of moments allows the beam to adapt to the changing conditions caused by corrosion and ensures its structural stability. 

An approach to the assessment of the dynamic behaviour of the floor slab of a buried structure is proposed. The estimation of the limiting dynamic load at changing the stiffness of the slab support nodes is performed. The design of supports in the form of crumpled inserts made of electric-welded steel pipe is considered. When building the fibre concrete model, volumetric finite elements were used, coupling with reinforcement was taken into account by using interpolation elements, steel reinforcement was represented as an ideal elastoplastic body. The impulsive impact was represented as a multiplication of a constant and a series of time-varying unit functions. The effect of the presence of damping supports in the perception of dynamic impact with the direction of propagation across the span of the slab was analysed. The results of the research can be used in the design of coverings of buried buildings and structures.

A method is proposed for calculating a reinforced concrete flexible foundation on a soil base in an aggressive environment under rheological deformation conditions, taking into account corrosion damage, reflecting its real operation under the combined influence of force and non-force influences based on the modern phenomenological theory of deformation of an elastic creeping body. The possibility of considering the processes of long-term deformation of rein-forced concrete under a changing mode of action of an external load based on the method of integral estimates is shown. It is shown that environmental damage to reinforced concrete structures can affect the strength of the material, change the calculation schemes, redistribute efforts in the sections of the structure and also lead to other consequences that reduce the design life of buildings. An example of the calculation of a reinforced concrete flexible foundation of a residential building on a soil base is given, taking into account the friction forces along its sole at various periods of service life and the presence of corrosion damage.

A brief review of the development of a new section of solids mechanics — mechanics of reinforced concrete — is given. For rod reinforced concrete elements, the expediency of allocating a new subsection – mechanics of rod reinforced concrete elements with normal cracks — is substantiated. Classical prerequisites and assumptions for determining the distance between normal cracks in the state of pure bending are considered in detail, and the need for their complete revision based on the ultimate tensile strength of concrete and the development of a deformation criterion is substantiated.

When performing concreting works for structures in sub-zero temperatures, a situation often arises in which the technology of heating the concrete mix during its setting and hardening is violated. It is customary to specify in the project the minimum (critical) strength of concrete before its freezing to ensure the strength gain to the brand indicators. Low strength of concrete at the time of freezing is the basis for dismantling the structure or reinforcing it. As a result — a decrease in the profitability of construction and an increase in the terms of production works. The paper presents a technique for constructing a deformation diagram of concrete samples after early freezing of the concrete mix in order to use it to assess the stress-strain state of structures with low strength. To assess the effect of early freezing times on the final strength of concrete and to plot deformation curves, compression tests were carried out on cube samples with an edge of 100 mm with different periods of curing of concrete before its freezing. A technique is presented for taking into account the obtained deformation curves for assessing the stress-strain state of structures based on a nonlinear deformation model. Initial information has been prepared for developing a program for calculating the SSS using the obtained methodology. The results obtained allow for assessing the technical condition of structures after early freezing of the concrete mix, taking into account the changed deformation characteristics of concrete in areas with early freezing of the concrete mix.

When erecting a number of nuclear power plant structures, a precast-monolithic construction technology is used using reinforced formwork blocks consisting of a reinforcing frame and permanent formwork made of steel fiber concrete. The use of this technology allows to reduce the time of construction of the facility. At the same time, a number of problems arise related to the strength assessment and quality control of the laid concrete located behind the permanent formwork. The lack of direct access to the concrete surface does not allow the use of standardized non-destructive strength assessment methods. Defects of mono-lithic concrete in the form of caverns and voids become hidden and the use of specialized instrumental methods is required. To select the optimal method for assessing the strength of concrete and quality control of its laying, experimental studies of a fragment of a reinforced formwork block with laid monolithic concrete were carried out. It was established that the optimal method of quality control of laying is ultrasonic tomography, which allows to detect a defect be-hind permanent SFRC formwork, as well as to control reinforcement parameters. As a result of testing, it was proposed to use methods of predicting concrete strength based on temperature-time dependencies.