This paper presents, developed by the authors of this scientific article, a method for calculating the strength of reinforced concrete out-of-center compressed racks according to the current regulatory methodology according to SP 63.13330.2018. The peculiarity of this technique is the condition that when calculating the strength, an external force is unknown, in turn, the normative methodology, on the contrary, is focused on calculating the cross-sectional area of metal reinforcement, provided that an external force is known in advance. The inverse problem is not provided for by the norms, since it is used mainly for scientific purposes. Consequently, the methodology developed by us is of great value for research work, where an important factor is the determination of the strength of samples for subsequent comparison with the strength of the corresponding reference samples and the development of new proposals for calculation methods. For the convenience of the reader, the developed calculation method is presented as an example of calculating the strength of one off-center compressed reinforced concrete sample, with explanations and references to the formulas of the normative literature. The calculated sample was actually manufactured and tested in the laboratory of the Department of Housing and Communal Services of DSTU and all its characteristics were found experimentally, therefore, the calculation method is based on comparison with the results of experimental studies.

Keywords: steel, heavy concrete, reinforced concrete, test, rack, eccentricity, strength, off-center compression

The results obtained during experimental studies of deflections of reinforced concrete struts of two flexibilities λh = 10 and 20 tested at three load application eccentricities e0=0; 2.0cm (0.16h) and 4.0cm (0.32h) are considered.Theoretical calculations of deflections were performed according to the current set of rules (SP 63.13330.2018). Based on experimental data and calculation results, it was found that the values of theoretical deflections differ significantly from experimental ones. The influence of the eccentricity of the load application and the flexibility of the samples on the convergence of the theoretical and experimental values of the deflections of the images was analyzed, possible causes of the discrepancy were considered and proposals for improving the calculation methodology were developed.

Keywords: "concrete, reinforced concrete, compressed elements, flexibility, eccentricity, the second group of limit states, deflection "

The results of the studies show that the manufacturer of composite materials for the consumption of reinforced concrete structures depends and produces materials for reinforcement, material properties and their quality. Such a thing requires the study of properties, fixing in the structure of materials. The article is devoted to the appeal. A program has been specially developed for influencing structures with unexplored, but the most popular composite materials in Russia, in particular, in the Rostov region. Certain parameters of reinforced structures that will be checked during the testing process. The program of the experiment was designed in such a way as to capture the most important reinforced concrete structures used in construction.

Keywords: concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements

The choice of options for strengthening reinforced concrete structures is based on a large number of factors based on technical capabilities and economic efficiency. Modern construction requires new reinforcement methods that allow reducing labor costs and work time, while maintaining the aesthetic appearance of a building under construction or being restored. The stumbling block is the issue price and the reliability of new amplification methods. For this purpose, known and used reinforcement methods based on materials such as reinforced concrete and metal were compared with a fairly new reinforcement method used materials based on carbon fabric. This article provides examples and results of calculations for the reinforcement of a column with a reinforced concrete, metal and composite cage. Based on the results of the calculations, a technical and economic comparison of the existing reinforcement options was carried out.

Keywords: "concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements

The use of composite materials for reinforcing reinforced concrete structures is very popular abroad, and in recent years they have gradually conquered the Russian building materials market. Insufficiently complete scope of research activities does not allow the full use of composite materials in the field of reinforcing reinforced concrete structures. In addition, there is no single product range in which composite materials from different manufacturers have the same properties. Given the difficult political situation in Russia, a number of composites manufacturing companies have stopped supplying their materials to the country. In this regard, there is a need to research new manufacturers and their reinforcement materials. Given the great responsibility placed on structural reinforcement projects, the behavior and properties of the reinforcement materials must be studied. This paper provides a comparison of materials and techniques for performing work to strengthen 2 different firms, the reliability and efficiency of one of them, BASF, was tested as a result of research and development, but this firm stopped working in Russia, another firm, Hydrozo - is the most common, but little studied. Also, the work presents all the positive and negative properties of the technologies for performing work, an analysis is made regarding the prospects for the use of reinforcement materials.

Keywords: concrete, reinforced concrete, reinforcement, carbon fiber reinforced plastic, composite material, reinforcement, carbon fiber

In recent decades, composite materials have been widely used in the reinforcement and fabrication of reinforced concrete structures. However, the volume of experimental and research work in Russia is not large enough to determine all the possibilities and real effectiveness of composite materials in this area. This paper presents proposals for improving the methodology for calculating the strength of reinforced concrete flexible eccentrically compressed struts reinforced with composite materials in the transverse direction. The developed proposals are based on the results of experimental studies. The proposals were developed in the field of determining the additional compressive strength of concrete from the action of composite materials located in the transverse direction. The paper describes the shortcomings of the normative calculation methodology and developed a coefficient that corrects the formula for determining the resistance of concrete reinforced with composite materials Rb3.

Keywords: concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements

The work is devoted to a review of the study of a composite material based on CFRP in the field of reinforcing reinforced concrete structures. The main work on the study of the effectiveness of carbon fiber reinforced plastic in the reinforcement of bending elements along normal and inclined sections and compressed flexible elements are considered. The main achievements and conclusions are established, as well as the disadvantages of calculation methods and amplification technology are considered. The purpose of this paper is to review the areas already studied and identify promising topics for further study of composite material.

Keywords: concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements

The article discusses possible design solutions to improve the seismic resistance of stone buildings. In particular, the installation of antiseismic belts at the floor level, the installation of dowels and nodes for connecting the floor slabs with the walls and among themselves, the reinforcement of the walls with steel clips, as well as the installation of transverse frames, if the maximum distances between the axes of the transverse walls are not observed.

Keywords: stone buildings, seismic resistance enhancement, reconstruction, design solutions

On the basis of experimental data, it was found that when calculating flexible reinforced concrete racks reinforced with composite materials in the transverse direction, the strength of the elements is underestimated by the norms. The influence of the composite reinforcement is not taken into account when calculating the stiffness D, the conditional critical force Ncrc and the slenderness coefficient η. Experimental data from the experiments carried out showed that the deflections of the reinforced struts were less than similar, not reinforced specimens, therefore, the influence takes place. Based on the analysis of the results of experiments, in the methodology of norms when calculating D, proposals were made that take into account the step of the transverse amplification at different eccentricities of the load application.

Keywords: Determination of the conditional critical force of flexible strengthened concrete struts reinforced with composite materials

The analysis of the results of large-scale experimental studies carried out at the Department of Reinforced Concrete and Stone Structures of DSTU is presented. It is aimed at determining the possibility of effective implementation of new composite materials in construction. This article deals with the issues of strength and stiffness of bending reinforced concrete elements with internal working reinforcement made of composite materials, or reinforced with external glass and carbon fiber reinforcement. The possibility of using coal and fiberglass working reinforcement for conventional bending elements in which the value of the maximum permissible deflections is not decisive has been established. The high efficiency of external reinforcement when reinforcing reinforced concrete structures with composite materials has also been proven.

Keywords: concrete, reinforced concrete, composite materials, reinforcement, concrete, strength, deformability

The article presents proposals for the calculation of three-layer reinforced concrete slab structures, the outer layers of which are made of heavy concrete, the middle layer is made of lightweight expanded clay concrete. Experimental elements were calculated according to the compiled program of iterative calculation, which takes into account the concrete deformation diagram in an explicit form. The calculation program reflects a technique that allows you to determine the actual distribution of deformations in sections with a crack and in the areas between them. The results of the calculation of the prototypes indicate a close convergence of the theoretical values ​​of the breaking moments, deflections, deformations of the extreme fibers, and cracking forces with those directly recorded in experimental studies.

Keywords: concrete, reinforced concrete, expanded clay concrete, reinforcement, three-layer slab, prestressing, calculation methods, deformations, stresses, deflections

The article provides data on the influence of external composite reinforcement of reinforced concrete compressed elements on their deformative properties. It was found that the deformations of reinforced samples, found according to the current standards, have significant discrepancies with the experimental values. Based on the analysis of the results of experiments, proposals were made to the methodology of norms for calculating the ultimate compressive deformations of concrete εb3, which take into account the type and percentage of composite reinforcement and ensure a good agreement between the experimental and theoretical values.

Keywords: concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements

The strength, deformability and width of the opening of normal cracks of prototypes 220, section 12.5x25 (h) cm, reinforced with composite canvases and laminates of different cross-sectional areas, made on the basis of glass and carbon plastics, are compared. The samples had working reinforcement, represented by 2Ø14А600, transverse - with double-section clamps Ø5В500, installed with a pitch of 100 mm. Samples were loaded with two concentrated forces applied in thirds of the span. With composite reinforcement, the appearance of the external composite reinforcement was varied, as well as the presence or absence of U-shaped anchoring clamps glued to the supporting sections of the beams. It has been established that the greatest reinforcing effect is provided by composite materials based on carbon fibers, in which the modulus of elasticity is comparable to the modulus of elasticity of steel.

Keywords: concrete, reinforced concrete, bending element, composite, fiberglass, carbon fiber, strength, deformability

In this article, the problem of the application of high-strength steel reinforcement in flexible compressed reinforced concrete elements is considered. Conditions are considered for establishing the minimum necessary proportion of prestressed reinforcement in flexible columns with pre-stretched reinforcement with mixed reinforcement.

Keywords: concrete, reinforced concrete, structures, technologies, installation, reinforced concrete structures, tension, prestress, beams, reinforcement, efficiency

This article deals with the field of application of fiber-reinforced concrete, reveals the advantage of using fiber-reinforced concrete in comparison with conventional concrete. The efficiency analysis of the use of fiber-reinforced concrete is analyzed.

Keywords: fiber concrete, concrete, reinforced concrete, structures, technologies, installation, fiberglass concrete, reinforced concrete structures, tension, prestress, basalt fiber concrete