A new approach to the optimization of ribbed reinforced concrete slabs of variable height with prestressing reinforcement is proposed. The approach is based on the design situation, due to the requirements of the strength of normal and inclined sections with full compliance with the design and design requirements, taking into account the strength and cost indicators of the materials used. The paper studies the optimization of elements that operate in the range without the need to install the calculated compression reinforcement. The study was carried out on the basis of taking into account the regularities of the resistance of reinforced concrete and the main provisions of the regulatory documents governing design and development activities in the Russian Federation, as well as relevant works of domestic and foreign scientists relevant to research in this area. The research method used is a structural-analytical analysis using the correlation dependences of the studied factors. Analytical dependences and graphic materials are presented that establish the optimal parameters of the element at the minimum cost of materials in order to use them in design practice. Recommendations for design are given, providing a structure of minimal cost and meeting the requirements of strength and durability. The results of the work indicate that measures to reduce the cost of the slab should be aimed primarily at reducing the cost of prestressing reinforcement. The conducted studies provide an opportunity at the design stage to determine the directions for reducing the cost of the product and justify the choice by rationally assigning the height of the slab, as well as the variable use of concrete and reinforcement of various classes.

Keywords: reinforcement, normal section, inclined section, optimization, prestressing, strength, ribbed plate, cost

The issues of optimization of ribbed reinforced concrete slabs with prestressing of reinforcement, taking into account geometric, strength and cost indicators, are considered. The study was car-ried out on the basis of an analysis of the sales market for building materials, the basics of rein-forced concrete resistance and the provisions of regulatory documents, design activities in the Russian Federation, as well as the works of domestic and foreign scientists. The research method is structural-analytical analysis taking into account the relationships of the factors under study. Analytical and graphic materials are presented, revealing the regularities between the geometric dimensions and the cost of components. The proposed method for determining the efficiency of a structure, taking into account the cost indicators of materials, indicates the feasibility of its ap-plication in design practice. Recommendations for design are given to ensure that structures of the minimum cost are obtained and that meet the requirements of strength and durability.

Keywords: reinforced concrete, strength, structure, reinforcement, diameter, price, cost, efficiency, dimen-sions, analysis, element

A theoretical study of the influence of geometric tolerances of reinforcement on the correspondence between delivery by weight and total length in meters of wire or rods is presented. The issues of efficiency and strength of bent reinforced concrete elements are considered, taking into account the influence of geometric deviations from the nominal values established by the norms for reinforcement of various classes. The documents of the regulatory framework regulating the design and construction and construction activities in the Russian Federation, as well as the works of domestic and foreign scientists, corresponding to the research in this area, were used. Used research methods such as structural and analytical analysis. The types of supplies of reinforcing steels, regulated by the current legislative framework and widely used in the practice of design and construction, are analyzed. Specific proposals have been developed for determining the need for reinforcement in weight and linear measurements, as well as for calculating the strength of reinforced concrete elements. It was revealed that the normalized deviation of the cross-sectional area significantly affects the length of the bar in unit of weight. Boundary values for the length of the rods have been determined for various diameters and classes of reinforcement.

Keywords: reinforcement, reinforcing bars, diameter, tolerance, reinforced concrete, reinforcement delivery, strength, cross-section, technical and economic indicators

The article presents the results of a study of the deflections of a monolithic flat floor with a different grid of columns with prestressed reinforcement without adhesion to concrete. To analyze the deflections, numerical studies of slabs with different rectangular columns and thicknesses were performed. The studies were performed using the LIRA CAD software package. The aspect ratio of rectangular cells of monolithic flat floors is determined, for which the application of prestressing is ineffective on the short side of the cell or most effective on the long side. It was revealed that the use of high-strength reinforcement of the "monostrand" type is most effective for a grid of columns 5x9m from the volume of the studied cell sides. It was found that the application of post-tension on the short side of the slab cell practically does not affect the total deflection of the cell - with the aspect ratio a / b> 1.2. The conclusion is drawn about the increase in the efficiency of using contour reinforcement with an increase in the deflections that affect the amount of rope repulsion. The results can be used in the design of slabs using prestressed reinforcement without adhesion to concrete of the "monostrand" type.

Keywords: rope, high-strength reinforcement, finite element, monostrand, repulse, prestressing, post-stressing, deflection

The article discusses the impact of high-strength reinforcement without adhesion to concrete on the strength of reinforced concrete floors. It was revealed that the rebound created by the prestressing force is distributed along the length of the element in accordance with the trajectory of the reinforcement laying. An analytical dependence has been obtained that allows one to quantify the decrease in positive moments depending on the magnitude of the load and relative deflections. The graphs of the dependence of the reduction of positive moments due to the resistance of the cables to the load and relative deflections are constructed. It is established that the influence of relative deflections on the decrease in moments does not depend on the magnitude of the external load. The main factors for reducing the positive aspects are the initial eccentricity and the deflection acquired during operation. The results can be used in the design of plates and beams using prestressed reinforcement without adhesion to concrete.

Keywords: high-strength reinforcement, reinforced concrete, bending moment, bending element, normative deflection, repulse, strength

The article discusses the features of the work of a monolithic flooring on a professional flooring, based on steel I-beams. An engineering method for determining the optimal cross-sections of I-beam steel beams is described, based on the compatibility of deformations of floor elements. Simple design formulas are proposed for preliminary determination of the optimal geometric dimensions, beams of their spans and loads. Strength calculations are performed, and the results of a numerical experiment are compared and analyzed. A table is presented in which the destructive linear load for some beams and spans is calculated, according to the results of the table, graphical dependences of the stresses in the beams are constructed as a function of the spans and relative deflections, as well as the stresses corresponding to the destruction of the beam. The optimal utilization rates of materials obtained in accordance with the requirements of strength and deformability of floors are established. The results can be used in the design of combined beams of various sections and spans.

Keywords: I-beam, combined beam, material utilization rate, standard deflection, profiled sheet, strength, profiled flooring, steel-reinforced concrete flooring

In the article features of work of monolithic overlap on the profiled flooring, leaning against steel I-beams, reinforced by pre-stressed bar reinforcement are considered. Often, when changing the functional purpose of a building or redevelopment, strengthening the structure of the floor is required to ensure strength. In addition, at spans of more than 7 meters, deflections exceeding the limit values may develop, which lead to a decrease in reliability and durability, and a deterioration in the appearance of the overlappings. The purpose of this study is to find the optimum reinforcement of the floor beams. To strengthen the proposed installation of prestressed reinforcement in the lower girdle of the beam, which increases the strength and reduces the deflections of the beams. In such ceilings, the bending moment from external loads is distributed between the structural elements: the beam and the reinforced concrete overlap, in accordance with the ratio of the stiffnesses of these components. As a result of the study, the optimal diameters of prestressed reinforcement for steel beams by spans from 6 to 9 m were determined and for the calculated linear load from 5 to 30 kN/m. The proposed reinforcement option allows to increase bearing capacity, reduce deflections, reduce labor costs for building reconstruction, and also increase the reliability and durability of the structure.

Keywords: reinforced concrete floor, gain, prestressed reinforcement, I-beams, overlap on profiled flooring

The optimum coefficients for the use of materials for combined beams in a wide range of loads are obtained in the article. The principles of designing and calculating the strength of Steel Reinforced Concrete slabs are outlined in accordance with SR 266.1325800.2016 ""Steel Reinforced Concrete Structures. Design rules"". Strength calculations are performed, the results of a numerical experiment are compared and analyzed. The optimal utilization factor of materials obtained in accordance with the specified regulatory document was established. The results obtained can be used in the design of combined beams of different cross-sections and spans. The purpose of this study is to find the optimum reinforcement of the floor beams. To strengthen the proposed installation of prestressed reinforcement in the lower girdle of the beam, which increases the strength and reduces the deflections of the beams. In such ceilings, the bending moment from external loads is distributed between the structural elements: the beam and the reinforced concrete overlap, in accordance with the ratio of the stiffnesses of these components. As a result of the study, the optimal diameters of prestressed reinforcement for steel beams by spans from 6 to 9 m were determined and for the calculated linear load from 5 to 30 kN/m. The proposed reinforcement option allows to increase bearing capacity, reduce deflections, reduce labor costs for building reconstruction, and also increase the reliability and durability of the structure.

Keywords: Steel reinforced concrete, floors, combined beams, profiled sheet, coefficient of use of materials