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

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