Vol 15, No 5 (2019)

Angular retaining walls are widespread in hydraulic engineering. They are characterized by large dimensions, small percentages of reinforcement, block cutting along the height of the structure. The bulk of the existing retaining walls were built in the 1960s-1980s. The regulatory documents that were in force during this period had certain shortcomings that caused the non-design behavior of a number of retaining walls. Improvement of calculation methods for reinforced concrete structures of retaining walls is required, within the framework of which a more complete account of the characteristic features of their behavior is needed. The aim of the work is to improve methods for calculating reinforced concrete retaining walls of a corner type. Methods of research carried out to improve the calculation of reinforced concrete retaining walls of the corner type included, among others, the classical methods of resistance of materials, the theory of elasticity, and structural mechanics. To determine the actual stress-strain state of the natural structures of retaining walls, visual and instrumental methods for examining retaining walls were used, including the method of unloading reinforcement. Results. To determine the stress state in the elements of the reinforced concrete structure of the retaining wall (in concrete and in reinforcement), a methodology was developed for calculating the stress state of retaining walls, which allows to determine the components of the stress state (stress in concrete in the compressed zone, as well as stress in stretched and compressed reinforcement) in horizontal sections of the vertical cantilever part of the retaining walls.

The aim of work. The paper analyzes the process of sheet drawing and develops a method for determining the minimum curvature of the torus fillet in the formation of a cylindrical product (glass), taking into account the plastic thinning of the deformable material by the end edge of the pressing punch. Methods. The existing scheme of forming with the use of permissible coefficients of drawing and tensile strength of the material, representing the basis of deformation-force calculation, which often ignores the factor of deformation thinning and its impact on the strength of the material, which together can lead to excess of the allowable stress in the material, causing its rupture, is analyzed. A mathematical model of the volume stress state of the metal is developed, which allows to estimate the value of the thinning in the formation of the torus surface of different curvature, followed by the approximation of the values found by a polynomial function. Considering the criterion of limit loads the level of radial stresses during folding and stretching of the sheet material, taking into account its thinning, the minimum curvature of the torus surface of the glass is established. Results. The results obtained will allow to simulate the stress-strain state of the metal in the development of sheet drawing technology: to establish the value of thinning and to estimate the level of radial stresses in the formation of the torus surface rounding to prevent the destruction of the elongated glass (separation of the bottom), which guarantees quality products.

The aim of the work. The static analysis and comparison of the results for translational shells under equally distributed load of dead weight are provided. The shells of the similar general dimensions in plan and rise of four different types: translation of catenary along catenary, circle along circle, ellipse along ellipse and sinusoid along sinusoid are investigated. Methods. The finite element method was applied for the analysis. The research was conducted for the shells of material of

reinforced concrete characteristics. Results. The comparison has shown that shells of catenary and circle translation surface demonstrate the most advantageous behavior under loading; the worst results for reinforced concrete were got for ellipse along ellipse translation shell. The peculiarities of each type behavior were revealed, that is of interest for their prospective reduction to practice of structural design.

Relevance. Thin-walled structures of shells constitute a large class in architecture, in civil and industrial construction, mechanical engineering and instrument making, aircraft, rocket and shipbuilding, etc. Each surface has certain ad-vantages over the other. So the torso surface can be deployed on the plane of all its points without folds and breaks, with the length of the curves and the angles between any curves belonging to the surface, do not change. The investigation of the stressstrain state of the equal slope shell with a director ellipse at the base is presented to date in a small volume. The aim of the work. Obtaining data for comparative analysis of the results of the stress-strain state of equal slope shells by the finite element method and the variational-difference method. Methods. To assess the stressstrain state of the equal slope shell, the SCAD Office computer complex based on the finite element method and the “PLATEVRM” program, written on the basis of the variational-difference method, are used. Results. The numerical results of the stress-strain state of the equal slope shell are obtained and analyzed, the pros and cons of the results of calculations by the finite element method and the variational-difference method are revealed.

Relevance. The nuclear power plant contains a large number of equipment and pipelines subject to flow acceleration corrosion. As a result of a combination of various parameters - sizes (diameters, wall thickness), operational parameters (internal pressure, temperature), steels and elements types - the number of design cases is tens of thousands, without counting the possible forms of thinning. The process of maintenance and repair at the stations are doing an assessment of the accordance of actual and allowable values of wall thicknesses. The ensuring safe operations of equipment and pipelines have been introduced correction functions for regulatory functions, taking into account the forms of thinning, to determine the permissible thinning. The aim of the work. The task is to determine the influence of the forms and types of thinning on the stress-strain state and to determine the most critical thinning for straight sections of pipelines subject to flow acceleration corrosion taking into account emergency conditions. Methods. The allowable values of stress concentration factors (deformations) of pipelines subject without flow acceleration corrosion was determined taking into account allowable values, the requirements of the federal norms and rules for emergency operating conditions. For researches of the stress concentration coefficients were used the finite element method and analytical methods for various shapes, sizes and depths of thinning. Results. A method has been developed, that allows getting the maximum allowable values of stress concentration factors (deformations) for emergency operation, which afford to determine the maximum allowable depth of thinning in emergency conditions - an above criterion. The researches have been carried out definition of the stress concentration factors for local thinning with various types of these thinning. The functions of concentration coefficients depending on the geometric parameters of local thinning wall thickness were determined for a straight section of the pipeline. As a result of the research, the dependences of the sizes of thinning on the concentration coefficients for straight pipelines were created and a master-curve was obtained. The researches were carried out take into account the load from internal pressure and bending moment.

The aim of the work. The work is devoted to experimental research of internal friction parameters of the material. Methods. The research of internal friction is carried out by consideration of damped oscillations of the experimental system that consist of rigid plates and a specimen in a state of pure bending. We propose to locate bearings in the fixed points to minimize energy losses in support fastenings. Fixed points are determined by using a finite element complex with consideration of free oscillations of the loose model. Results. Damping curves were determined, which demonstrate a very small logarithmic decrement of oscillations and frequency independence of inertial friction. The main result of the work is the tested improvements of the experimental technique, among which the main one is the use of fixed points for determining the places of fastening of the laboratory installation