Vol 17, No 1 (2021)

Analysis and design of building structures

Geometrically nonlinear analysis of the stability of the stiffened plate taking into account the interaction of eigenforms of buckling

Manuylov G.A., Kositsyn S.B., Grudtsyna I.E.


The aims of this work are a detailed consideration in a geometrically nonlinear formulation of the stages of the equilibrium behavior of a compressed stiffened plate, taking into account the interaction of the general form of buckling and local forms of wave formation in the plate or in the reinforcing ribs, comparison of the results of the semi-analytical solution of the system of nonlinear equations with the results of the numerical solution on the Patran-Nastran FEM complex of the problem of subcritical and postcritical equilibrium of a compressed stiffened plate. Methods. Geometrically-nonlinear analysis of displacement fields, deformations and stresses, calculation of eigenforms of buckling and construction of bifurcation solutions and solutions for equilibrium curves with limit points depending on the initial imperfections. An original method is proposed for determining critical states and obtaining bilateral estimates of critical loads at limiting points. Results. An algorithm for studying the equilibrium states of a stiffened plate near critical points is described in detail and illustrated by examples, using the first nonlinear (cubic terms) terms of the potential energy expansion, the coordinates of bifurcation points and limit points, as well as the corresponding values of critical loads. The curves of the critical load sensitivity are plotted depending on the value of the initial imperfections of the total deflection. Equilibrium curves with characteristic bifurcation points of local wave formation are constructed using a numerical solution. For the case of action of two initial imperfections, an algorithm is proposed for obtaining two-sided estimates of critical loads at limiting points.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):3-18
pages 3-18 views

Calculated assessment of the impact of geometric deviations from the design on the parameters of mechanical safety of building metal structures within the framework of scientific and technical support for construction

Belostotsky A.M., Dmitriev D.S., Petryashev S.O., Nagibovich T.E.


An important part of scientific and technical support of civil engineering facilities at a construction stage - evaluation of influence of fluctuations from a designed geometry onto mechanical safety parameters of load-bearing metal structures - is considered. A multi-tier structure (industrial frame tower) is employed to demonstrate main features of such an assessment. Given is an approach to an analysis of as-built documentation and to a choice of most significant fluctuations of structural metal elements from a designed geometry. Effect of erection sequence being taken into consideration, the so-called genetic non-linearity, during computational estimation of a stress-strain state of metal structures mounted with deviations from their design positions is investigated. Results of static and dynamic analyses of designed and as-built (with geometry fluctuations taken into consideration) models of the multi-level industrial frame tower are obtained and compared with each other. Basing on these results, guidelines for computational assessment of effects of fluctuations from a designed geometry onto mechanical safety parameters of similar frame systems are formulated.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):19-29
pages 19-29 views

Seismic resistence

Seismic stability of vibration-insulated turbine foundations depending on the frequency composition of seismic impact

Babsky A.E., Lalin V.V., Oleinikov I.I., Tarasov V.A.


The seismic resistance of vibration-insulated turbine foundations is a complex and multifaceted problem that includes many aspects. The turbine foundation is a special building structure that unites parts of the turbine and generator unit into a single machine and it is used for static and dynamic loads accommodation. The number of designed and constructed power plants in high seismic level areas is large and steadily growing. In addition, engineers and designers deal with the issue of the frequency composition of the seismic impact influence on the seismic resistance of vibration-insulated turbine foundations. Dynamic calculations were performed in Nastran software using time history analysis and the finite element method. The main criteria for the seismic resistance of a vibration-insulated turbine foundation are the values of the maximum seismic accelerations in the axial direction at the level of the turbine installation and the values of vibration-insulated foundation maximum seismic displacements (deformations of vibration isolators). The results of the calculation experiments proved a significant effect of seismic action frequency composition on the behavior of the vibration-insulated turbine foundations. Calculations of foundations, taking into account earthquakes of the same intensity, but with different values of the prevailing frequencies of the impact, lead to the differing by several times values of the maximum seismic accelerations at the turbine level and seismic displacements.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):30-41
pages 30-41 views

Geometrical investigations of middle surfaces of shells

Modeling and visualizing of the formation of a snub dodecahedron in the AutoCAD system

Romanova V.A., Strashnov S.V.


The article is devoted to modeling and visualization of the formation of flat-nosed (snub-nosed) dodecahedron (snub dodecahedron). The purpose of the research is to model the snub dodecahedron (flat-nosed dodecahedron) and visualize the process of its formation. The formation of the faces of the flat-nosed dodecahedron consists in the truncation of the edges and vertices of the Platonic dodecahedron with the subsequent rotation of the new faces around their centers. The values of the truncation of the dodecahedron edges, the angle of rotation of the faces and the length of the edge of the flat-nosed dodecahedron are the parameters of three equations composed as the distances between the vertices of triangles located between the faces of the snub dodecahedron. The solution of these equations was carried out by the method of successive approximations. The results of the calculations were used to create an electronic model of the flat-nosed dodecahedron and visualize its formation. The task was generally achieved in the AutoCAD system using programs in the AutoLISP language. Software has been created for calculating the parameters of modeling a snub dodecahedron and visualizing its formation.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):42-50
pages 42-50 views

Analytical and numerical methods of analysis of structures

Stress state analysis of an equal slope shell under uniformly distributed tangential load by different methods

Aleshina O.O., Ivanov V.N., Cajamarca-Zuniga D.


Nowadays there are various calculation methods for solving a wide range of problems in construction, hydrodynamics, thermal conductivity, aerospace research and many other areas of industry. Analytical methods that make up one class for solving problems, and numerical calculation methods that make up another class, including those implemented in computing complexes, are used for the design and construction of various thin-walled structures such as shells. Due to the fact that thin-walled spatial structures in the form of various shells are widely used in many areas of human activity it is useful to understand and know the capabilities of different calculation methods. Research works on the study of the stress-strain state of the torse shell of equal slope with an ellipse at the base are not widely available at the moment. For the first time the derivation of the differential equations of equilibrium of momentless theory of shells to determine the normal force Nu from the action of uniformly distributed load tangentially directed along rectilinear generatrixes to the middle surface of the torse of equal slope with a directrix ellipse is presented in this article. The parameters of the stress state of the studied torse are also obtained by the finite element method and the variational-difference method. The SCAD software based on the finite element method and the program SHELLVRM written on the basis of the variational-difference method are used. The numerical results of the parameters of the stress state of the studied torse are analyzed, and the advantages and disadvantages of the analytical method and two numerical calculation methods are determined.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):51-62
pages 51-62 views

Common irregularities and its effects on reinforced concrete building response

Ghimire K., Chaulagain H.


In most of the countries, the irregular building construction is popular for fulfilling both aesthetic and functional requirements. However, the evidence of past earthquakes in Nepal and the globe demonstrated the higher level of seismic vulnerability of the buildings due to irregularities. Considering this fact, the present study highlighted the common irregularities and its effect on reinforced concrete building response. The effect of structural irregularities was studied through numerical analysis. The geometrical, mass and stiffness irregularities were created by removing bays in different floor levels and removing the columns at different sections respectively. In this study, the numerical models were created in finite element program SAP2000. The structural performance was studied using both non-linear static pushover and dynamic time history analysis. The results indicate that the level of irregularities significantly influenced the behavior of structures.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):63-73
pages 63-73 views

Experimental researches

Ductility and flexure of lightweight expanded clay basalt fiber reinforced concrete slab

Galishnikova V.V., Heidari A., Chiadighikaobi P.C., Muritala A.A., Emiri D.A.


Relevance. The load on a reinforced concrete slab with high strength lightweight aggregate concrete leads to increased brittleness and contributes to large deflection or flexure of slabs. The addition of fibers to the concrete mix can improve its mechanical properties including flexure, deformation, toughness, ductility, and cracks. The aims of this work are to investigate the flexure and ductility of lightweight expanded clay concrete slabs reinforced with basalt fiber polymers, and to check the effects of basalt fiber mesh on the ductility and flexure. Methods. The ductility and flexural/deflection tests were done on nine engineered cementitious composite (expanded clay concrete) slabs with dimensions length 1500 mm, width 500 mm, thickness 65 mm. These nine slabs are divided in three reinforcement methods types: three lightweight expanded clay concrete slab reinforced with basalt rebars ∅10 mm (first slab type); three lightweight expanded clay concrete slab reinforced with basalt rebars ∅10 mm plus dispersed chopped basalt fiber plus basalt fiber polymer (mesh) of cells 25×25 mm (second slab type); three lightweight expanded clay concrete slab reinforced with basalt rebars ∅10 mm plus dispersed basalt fiber of length 20 mm, diameter 15 µm (third slab type). The results obtained showed physical deflection of the three types of slab with cracks. The maximum flexural load for first slab type is 16.2 KN with 8,075 mm deflection, second slab type is 24.7 KN with 17,26 mm deflection and third slab type 3 is 32 KN with 15,29 mm deflection. The ductility of the concrete slab improved with the addition of dispersed chopped basalt fiber and basalt mesh.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):74-81
pages 74-81 views

Experimental-theoretical studies of hydrotechnical angular-type retaining walls

Pashchenko F.A.


Relevance. Retaining walls are common structures that are part of waterworks. They have the characteristic features of hydraulic structures, such as large dimensions, low percentages of reinforcement (up to 1.0%), horizontal interblock joints. The listed features determine the nature of the work and the stress-strain state of the retaining walls. The main loads on the rear faces of the retaining walls are loads from the action of the backfill soil. The incomplete consideration of the design features and the nature of the loads action in the design of a number of retaining walls that are in the stage of long-term operation has caused the need to strengthen them. One of the reinforcement methods was to install reinforcement rods in drilled inclined holes in the zones of horizontal interblock joints. It was necessary to conduct experimental studies of reinforced concrete retaining walls under the action of various loads, in particular conside- ring the reinforcement by inclined rods. The aim of the experimental research was to study the effect of variable load on the stress-strain state of these structures, among others with due regard to inclined reinforcement installed in the zones of horizontal interblock joints. When solving the set tasks, proven experimental methods of researching reinforced concrete structures of hydrotechnical structures were used. Results. Experimental data from the study of models of retaining walls, including those with reinforcement by inclined reinforcement, at different locations of the resultant load on rear faces of models were obtained. An experimental substantiation of the reinforcement of reinforced concrete structures of retaining walls with an inclined reinforcement crossing horizontal construction joints has been carried out.

Structural Mechanics of Engineering Constructions and Buildings. 2021;17(1):82-91
pages 82-91 views

Reviews, references

pages 92-93 views

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