The stability calculation of a П-shaped hinged frame is considered. The concept of r-like frames is introduced as frames with the same ratio r of the linear stiffnesses of the transom and the strut. It is shown that the parameter vcr , which determines the critical load on the frame, is the same for r-like frames. Approximate formulas allowing to determine the critical load parameter vcr and design lengths of compressed bars with an error not exceeding 2% are obtained.

Keywords: flat frame, stability, critical force, reduced length coefficient, r-like frames, approximation, least squares method

The article provides an analysis of the state of the rationing issue in terms of performing the calculation justification and design of reinforcement of reinforced concrete structures using external reinforcement systems based on carbon fibers. The normative documents of the Russian Federation and foreign ones are considered, the analysis of the use of external reinforcement based on composite materials for structures of various types of work is carried out, the disadvantages of existing calculation and design methods are highlighted. In conclusion, recommendations are given on the appropriate improvement of calculation and design methods.

Keywords: external reinforcement, carbon fiber, reinforcement, restoration

The use of a solid analog and the involvement of an appropriate theory of stability made it possible to perform mathematical modeling and determine the parameters of the critical state of cylindrical mesh shells depending on the geometric characteristics and the number of half-waves of the shape of the loss of stability. The values of the critical load of cylindrical mesh shells are determined taking into account geometric and force factors. According to the results of calculations, the patterns of changes in the number of half-waves of the form of loss of stability and obtaining the minimum value of the critical load under the condition of maximum approximation of flexural and membrane stiffness are revealed and analyzed. A numerical example is shown in which the values of critical load and stiffness are determined, taking into account possible forms of loss of stability. The patterns of changes in these indicators for a given number of half-waves are established and analyzed.

Keywords: cylindrical mesh shells, mathematical modeling, critical load, stability, stiffness, number of half-waves

In the construction sector, the reform of design and survey work allows us to take a fresh look at the state of engineering and geological research. The use of software systems provides an opportunity to automate this process during construction, reconstruction of buildings and structures in order to avoid the formation of landslide processes and reduce man-made risks. Limit equilibrium methods are used to determine the stability of a slope or an underground structure. Therefore, the purpose of the study in the article was to conduct engineering and geological surveys using various methods and then calculate the stability of landslide slopes. The sliding surfaces with the lowest coefficients of stability margin were selected by the optimization method for the calculated slopes.

Keywords: integration, reformation, method, construction, soil, landslide slope, man-made risk, surveys, automation

The article contains the methodology and results of theoretical and experimental studies of the stress-strain state of a conical radial-beam dome with triangular shell elements. The results obtained by various methods are analyzed and compared. The triangular membrane panel is part of the radial beam dome structure and consists of a support frame and a steel membrane in the shape of a triangle. The shape of the triangle forming the membrane panel can be different and depends on the number of ribs in the radial beam dome. The supporting contour is a compressed-bending element of the dome and is made, as a rule, from a rolled steel profile with a channel section. The membrane is made of thin steel sheet and attached to the upper flange of the channel with self-tapping screws or spot welding. To assess the strength and deformability of a steel membrane sheet, its operation under the action of a uniformly distributed snow load, an unevenly distributed snow load and a concentrated installation load was considered. Several options for nonlinear static calculations in various computer systems are shown.

Keywords: building structures, wooden structures, membrane panel, stress-strain state, radial beam dome, dome, membrane, design, experimental study

This article investigates the moment redistribution behavior in corroded reinforced concrete (RC) beams. previous studies by different authors are reviewed, which shed light on the behavior of corroded statically indeterminate RC elements. The corrosion effects on the ultimate strength, deflection, and moment redistribution ratios are examined. The application of axial loads and location and severity of corrosion allowed for a comprehensive discussion of the moment redistribution behavior. The results showed that continuous RC beams with corroded reinforcement behave differently than simply supported RC beams. The corrosion process also affected the moment redistribution, providing additional safety to the RC structures. Existing research in this area is limited, and further investigations are required to address this knowledge gap and improve the understanding of the mechanism of moment redistribution in continuous corroded RC beams.

Keywords: corroded RC beams, statically indeterminate RC beams, moment redistribution, corrosion, accelerated corrosion method, ultimate strength, deflection, structures durability

The article is devoted to the study of flange beam to column connections to analyze their nonlinear behavior. In the course of the study, a simplified analytical model was created using the method of variable elasticity parameters to determine the stress-strain state of these connections. The proposed mechanical model makes it possible to predict the strength, stiffness, ductility of joints, as well as possible types of fracture and deformation mechanisms of the bent elements of flange joints. This model can be useful for engineers and specialists in the field of design and analysis of civil structures. The proposed refined component model is an analogue of the Eurocode 3 model. The paper presents a numerical experiment on modeling the junction of a beam with a column by the finite element method. A comparative analysis of the results obtained with the results of tests of flange connections of steel building structures performed by the University of Sydney (USYD) is presented.

Keywords: flange connections, flange plate, stress-strain state, method of variable elasticity parameters, component method, refined component model, finite element method, elastic-plastic state, plastic hinge, modified stiffness, bending model of flange plate

This study is a pilot one. The purpose of the study is to identify the nature of the relationship between Poisson's ratio and cohesion, on the example of a soil mass. The main objective of the study is to identify the dependence of Poisson's ratio and cohesion coefficient to obtain the fracture limit of the material (in this study of soil massif) - plastic flows in the material. The study is conducted by methods of mathematical modeling. In order to achieve the objective, it is necessary to justify the possibility of performing this experiment by means of boundary value problem, and to perform the ranking of the number of numerical experiments by experiment planning method to obtain the extrema. Next, it is necessary to perform the numerical experiment itself to reveal the relationship between Poisson's ratio and cohesion. The obtained data will be used to compose the inverse problem when testing a new Russian software product in the field of geotechnical and geomechanical modeling.

Keywords: Poisson's ratio, cohesion, soil massif, numerical experiment, finite element method, mathematical modelling, plastic flow, deformation, stress

The influence of the location of reinforcing bonds on the general condition of cylindrical mesh shells is investigated. Cruciform core elements made of tubular profiles were used as reinforcing structures. The number of reinforcing elements is 8 (4 on each panel). Opposite nodes of adjacent faces are connected by cross-shaped elements in the direction of the arc. The expediency of placing reinforcement elements inside each of the two middle panels and at a distance of one panel from the middle of the length is checked. As a result of the conducted studies, the regularities of the stress-strain state and dangerous areas of the shell were determined. When using cruciform joints, a decrease in the forces in the elements and a decrease in the movements of the nodes were revealed. A redistribution of internal force factors and a decrease in the number of typical sizes of elements were recorded. A rational scheme of reinforcement of the structure is obtained.

Keywords: cylindrical mesh shell, reinforcement, cross-shaped elements, forces, displacements