## Vol 15, No 4 (2019)

**Year:**2019**Articles:**10**URL:**http://journals.rudn.ru/structural-mechanics/issue/view/1215**DOI:**https://doi.org/10.22363/1815-5235-2019-15-4

###### Abstract

Aims of research. The article is devoted to actual problems of computational analysis of stress-strain state, strength and stability of load-bearing structures with allowance for the main and special combinations of loads and impacts, comparison of the results of alternative structural analysis of unique cultural and business complex “Congress Hall” in Chelyabinsk. The natural conditions of the area of location of this object and main load-bearing structures of the object are described. Besides, characteristic and design loads, their combinations, formulation of objectives of computational research and methods of solution are presented. Methods. Space discretization and solution of the corresponding problems of mathematical (numerical) and computer modelling of the considering unique building were carried out with the use of finite element method. Detailed finite element models of the coupled system “combined foundation - loadbearing structures” and its fragments (subsystems) were developed and verified. They adequately reflect geometric-stiffness, inertial and load parameters of the object and the resulting stress-strain state. Progressive collapse analysis are under consideration as well. Licensed, certified and verified (by the Russian Academy of Architecture and Construction Sciences) finite element software package “ANSYS Mechanical” was used. Results. The resulting parameters of stress-strain state, strength and dynamics of load-bearing structures of the building with allowance for design (in accordance with design codes) combinations of vertical and wind loads are considered. Besides, information about results of progressive collapse analysis is presented. Thus, a reasonable conclusion is made about the reliability of the criterion parameters of strength, stability and dynamics of the load-bearing structures of the object.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):251-260

###### Abstract

Aim of research - to continue the development of methods for determining the stress-strain state of rods during torsion using materials resistance methods. Methods. A new approach for determining tangential torsional stresses for arbitrary cross sectional rods, based on simplified assumptions of material resistance, is proposed. The main feature of this approach is the approximation of rectangular or any complex cross section of reinforced concrete structures by describing a large circle around the cross section and splitting it into small squares with circles inscribed into them. Results. Three theorems have been formulated, the first of which relates the accumulation of tangential stresses (increments) from the edges of a rectangle to the middle of a rectangular section with the formula for determining tangent stresses for round sections. The second theorem allows to establish a connection between the tangential stresses calculated for each of the small squares-circles and the tangent stresses of the large circle through their increments. The third theorem makes it possible to find tangential stresses for each of the small square circles. The proposed approach allows to remove the need to use special tables for the calculation and not only in the elastic stage. It also makes it possible to separate the stress-strain state in the whole set of round cross-sections from the additional field caused by the deplanation of the rectangular cross-section. In addition, the proposed approach makes it possible to take into account the concentration of angular deformations in the incoming angles and other places with changing geometric parameters.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):261-270

###### Abstract

Aims of research. The task is to apply modern strength criteria of anisotropic materials for the calculation of multilayer walls made of cellular concrete and silicate large masonry materials, which differ in exact dimensions and allow for thin-seam masonry with adhesive seams. Proposals for the inclusion in the design standards of guidance that takes into account the work of wall materials in complex stress states will be presented in a series of publications. Methods. The strength criteria of G.A. Geniev in a rather simplified form are used. The volumetric stress state of walls made of orthotropic materials is considered. The basis for the construction of strength criteria are three possible different mechanisms of destruction - separation, compression and shear. For modern thin-walled masonry is characterized by a combination of compressive (vertical) and shear (horizontal) loads. Of particular interest is the work of the masonry shift, since the plane stress state is not sufficiently studied. The article is devoted to the construction of the criterion of masonry shear strength. The peculiarity of the proposed calculations is the comparative simplicity of the strength criteria due to the accepted hypotheses. Results. The final expression of the shear strength criterion and the sequence of the shear strength verification in the case of simple loading are presented. The article is preliminary for a series of calculations and results of experimental studies of the walls under different operating conditions and different loads.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):271-277

###### Abstract

Aims of research. To analyze the stress state of the metal structures of the ribbedring dome of a hemispherical shape during the assembly process of the dome frame in two fundamentally different ways - “top-down” and “bottom-up”. Since different design schemes arise at different stages of assembly of the dome frame, different assembly forces result in their structural elements. To demonstrate how assembly forces lead to the tension state of a ribbed-ring dome that is transformed during the construction process. To perform the analysis of the stress states of the considered assembly methods and to present their evaluation. Methods. A computer model of a metal ribbed-ring dome made of steel I -beams with rigid joints has been developed. Several additional assembly models of an incomplete frame have been created for studying the considered assembly at different stages. Computer calculations for the effect of its self-weight were made for each assembly model of the dome frame. As a result of the calculations, the stresses in the structural elements of the frames of the assembly schemes were determined, which were compared with similar stresses resulting from the self-weight in the frame of the design scheme. Results. Diagrams of changes in the stress state of structural elements of a metal ribbed-ring dome are presented. The efficiency of use of steel strength at different stages of installation is also shown in the diagrams. A comparative assessment is given for the stress conditions due to the assembly methods under consideration. The inevitability of installation stresses is noted and the most efficient assembly method of installation is chosen.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):278-290

###### Abstract

Aims of research. The research is aimed at determining the critical buckling load at which the shell interacting with the soil loses equilibrium stability, and finding the buckling mode of the shell in the linear and nonlinear formulations of the task. Methods. The task is solved by a numerical method using a finite element complex, which allows investigating the stress-strain state and assessing the equilibrium stability of beam models and two-dimensional models of the round cylindrical shell. Three design cases of the beam model and two design cases of the two-dimensional model interacting with the soil are compiled. There is a load summary acting on the shell. The calculations are carried out in linear and geometrically nonlinear formulations using a linear elastic model of the material. Contact elements of one-side and two-side action are used. Critical buckling load are determined relative to the actual load of its own weight. Results. Critical buckling load are determined and the buckling mode of the round cylindrical shell interacting with the soil are found. There is a comparative analysis of the results. An assessment of the stability margin of the shell relative to the actual load is given.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):291-298

###### Abstract

Aims of research. Due to the growing interest in the design, calculation and application of architectural structures and structures in the form of a variety of smooth and composite surfaces, it is interesting to illustrate the use of analytical surfaces, i.e. surfaces that can be defined by vector, parametric or explicit equations, in parametric architecture. Methods. Parametric design unlike other styles has a relationship with mathematics. This article continues the author’s series of works devoted to the application of analytical surfaces in architecture and engineering structures, the study of the influence of studies on the geometric of ruled surfaces on the creation of unique projects of large-span shell structures and buildings. The article provides a list of known analytical surfaces, and each surface is illustrated by a photo of only one real structure, outlined on this surface. Results. It turned out that only degenerate unfolding surfaces described in the scientific literature found application in the world. For those who are interested in the mathematical side of the design of analytical surfaces, their computer modeling, or more detailed information about the real structures in the form of the surfaces under consideration is a bibliography of 20 items.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):299-307

###### Abstract

Aims of research. The use, design and analysis of architectural and building structures in the form of smooth and composite surfaces have become relevant and in demand lately, which determined the purpose of this article - to analyze the use of analytical surfaces given vector, parametric or explicit equations in real structures. Methods. The relationship between studies on the geometry of surfaces of revolution and transport and the creation of new forms of thin-walled structures and buildings is determined. An example of a real structure is given on each surface. The article does not consider composite, multifaceted, fractal surfaces, as well as surfaces that are not defined analytically. Results. It turned out that only a small number of considered surfaces of these two classes have found application in the world. At the end of the article, a bibliography is presented, which sets out the mathematical side of the design of analytical surfaces, their computer modeling, more detailed information about real structures in the form of the surfaces under consideration.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):308-314

###### Abstract

Relevance. The problems of decline of resource-demanding of objects of building and engineer dictate the necessity of consideration of processes of deformation of constructions at the resiliently-plastic state. The widely in-use theory of account of practical properties of material is a deformation theory of plasticity. The aim of the research is development of variants of receipt of determining correlations on the step of ladening at deformation of material outside a resiliency. Methods. Algorithms over of receipt of determining correlations of theory of small resiliently-plastic deformations are brought on the step of ladening in two variants. In the first they turn out differentiation of expressions of tensions as functions of deformations on the basis of deformation theory of plasticity; in the second determining correlations turn out on the basis of hypothesis about the proportion of components of deviators increases of tensions to components of deviators increases of deformations. Results. On the test example of calculation of the jammed cylindrical shell realization of the got determining correlations is presented.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):315-322

###### Abstract

The aim of research is to compare two calculation methods using the example of solving the axisymmetric thermoelasticity problem. Methods. The calculation of a thick-walled cylindrical shell on the temperature effect was carried out by the numerical-analytical method and the finite element method, implemented in the LIRA-CAD software package. The shell consists of three layers: two layers of heat-resistant concrete and an outer steel layer. In the calculation, a piecewise linear inhomogeneity of the shell due to its three-layer structure and continuous inhomogeneity caused by the influence of a stationary temperature field is taken into account. The numerical-analytical method of calculation involves the derivation of a resolving differential equation, which is solved by the sweep method, it is possible to take into account the nonlinear nature of the deformation of the material using the method of successive approximations. To solve this problem by the finite element method, a similar computational model of the shell was constructed in the LIRA-CAD software package. The solution of the problem of thermoelasticity for an infinite cylinder (under conditions of a plane deformed state) and for a cylinder of finite length with free ends is given. Results . Comparison of the calculation results is carried out according to the obtained values of ring stresses σθ.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):323-326

###### Abstract

Relevance of the research is due to the fact that over the past 10 years severe accidents at large hydropower plants and dams occurred in Russia (SayanoShushenskaya HPP, 2009), USA (Oroville dam, 2018), Brazil (Brumadinho dike, 2019), Colombia (HPP Ituango, 2018) and other countries, the need has arisen to improve the safety programs of the HS and dams. The main method of this important work is to use methods of analysis and assessment of risk accidents of HS and dams. Methods of this important work are to develop modern methodology for analyzing and assessing the risk of accidents of HS and dams. The introduction of the method of analysis and risk assessment in the safety programs of hydraulic structures (dams) in countries that are advanced in the construction of HS (China, Brazil, Canada, USA, Russia, Colombia, Norway, Spain, etc.) shows that in applying risk assessment analysis accidents of HS and dams still a number of difficulties, but this approach is of great benefit in monitoring the safety of HS and dams. The aim of this article is to familiarize and train specialists and hydraulic engineers with modern methods for assessing the safety of HS and dams.

**Structural Mechanics of Engineering Constructions and Buildings**. 2019;15(4):327-336