scholarly journals Criteria of strength of walls from large masonry blocks

2019 ◽  
Vol 15 (4) ◽  
pp. 271-277 ◽  
Author(s):  
Konstantin P. Pyatikrestovsky
Keyword(s):  
Shear Strength ◽  
Stress State ◽  
Experimental Studies ◽  
Strength Criterion ◽  
Plane Stress State ◽  
Complex Stress ◽  
Operating Conditions ◽  
Orthotropic Materials ◽  
Design Standards ◽  
Strength Criteria

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.

scholarly journals An Integrated Approach to the Optimization of Plates in Plane Stress State Operated at High Temperatures

2021 ◽  
Vol 24 (3) ◽  
pp. 52-60
Author(s):  
Мark M. Fridman ◽  
Keyword(s):  
Stress State ◽  
Optimal Design ◽  
High Temperatures ◽  
Plane Stress ◽  
Integrated Approach ◽  
Double Effect ◽  
Plane Stress State ◽  
Machine Building ◽  
Operating Conditions ◽  
Material Damage

Many critical elements of building and machine-building structures during their operation are in difficult operating conditions (high temperature, aggressive environment, etc.). In this case, they can be subject to a double effect: corrosion and material damage. Corrosion leads to a decrease in the cross-section of a structure, resulting in stress increase therein. In turn, damage to the material is accompanied by the appearance of microcracks and voids therein, due to inelastic deformation (creep), leading to a deterioration in its physical properties (for example, the elastic modulus) and a sharp decrease in the stress values at which the structure is destroyed. This article continues the study in the field of the optimal design of structures subject to the aforementioned double effect by the example of the optimization of plates with holes in the plane stress state, exposed to high temperatures (in previous works, the use of this approach was demonstrated in the optimization of the bending elements of rectangular and I-sections). Used as a corrosion equation is the modified Dolinsky mode, which takes into account the (additional) effect of the protective properties of an anticorrosive coating on the corrosion kinetics. Taken as a kinetic equation describing the change in material damage, is Yu. N. Rabotnov’s model, which enables to determine the duration of the incubation period of the beginning of the tangible process of material damage. To study the stress state of a plate, the finite element method is used. With a given contour of the plate, found is the optimal distribution of the thickness of the finite elements into which the given plate is divided. Acting as a constraint of the optimization problem is the parameter of damage to the plate material. The approach proposed in this work can be used to solve similar problems of the optimal design of structures operating under conditions of corrosion and material damage, using both analytical solutions and numerical methods.

scholarly journals OPTIMAL HEIGHT OF STEEL PLATE GIRDERS WITH CORRUGATED WEBS

2020 ◽  
pp. 76-86
Author(s):  
L.І. Lavrinenko ◽  
◽  
D.Y. Oleynik ◽  
Keyword(s):  
Shear Strength ◽  
Objective Function ◽  
Structural Model ◽  
Bending Strength ◽  
Classical Problem ◽  
Operating Conditions ◽  
Model Parameters ◽  
Design Standards ◽  
Beam Height ◽  
Plate Girder

Abstract. This work is carried out in order to study the classical problem of determining the optimal height of a plate girder with given moment of resistance in relation to the features of the real operation of a beam with a corrugated web. A bi-symmetric plate girder with a wavy web is considered. The structural model parameters of the girder correspond to the Zenam technology, which determines the structural limitations of the task. The physical model is the 1st class double-tee girder according to the stress-strain state (in accordance with the current design standards of Ukraine SCS (State Construction Standards of Ukraine) В.2.6-198). The mathematical model is considered as a task of minimizing the objective function (beam mass) taking into account design factors. The height is a project variable. The objective function is formulated as one-parameter taking into account the bending strength of the beam. The structural coefficients and their influence on the objective function are considered. Both the shear strength constrain and overall wall shape stability constrain are taken into account. Deflections are determined taking into account the shear deformations of the thin web. The minimum values of the beam height are considered when the permissible deflection is not exceeded. It is shown that the introduction of the conditions of shear strength and wall stability into the resolving equation indicates the lower limit of the calculated variable value. The constraint is inactive in the area of feasible solutions. Areas of rational decisions are shown. Numerical studies have been conducted for corrugated beam structures. Design requirements in accordance with design standards are used as method constraints. The optimal values of the beam height are obtained according to the minimum mass criterion in the range of applied spans and loads. The effective values of spans and loads for beams with corrugated walls in the range of optimal parameters and technological limitations have been determined. Further research is needed to explore constructive solutions that would minimize the values of constructive coefficients, taking into account specific effects such as local tensions and real-world operating conditions.

scholarly journals The theory of degradation for polymer concrete in complex stress state

2019 ◽  
Vol 135 ◽  
pp. 01054
Author(s):  
Yuliya Moreva ◽  
Andrey Varlamov ◽  
Yuliya Novoselova
Keyword(s):  
Stress State ◽  
Uniaxial Compression ◽  
Complex Structure ◽  
Experimental Studies ◽  
Complex Stress ◽  
Complex Stress State ◽  
Polymer Concrete ◽  
Steel Shell ◽  
Concrete Core ◽  
Energy Characteristics

The article discusses the features of the application of the theory of degradation to the work of an integrated structure operating in a complex stress state. The analysis of the work of an integrated structure consisting of a steel shell filled with concrete (core structure). Based on the analysis of the construction work, we obtained the relations connecting the deformations of the steel shell and the polymer concrete core of the complex structure. The obtained relations made it possible to apply the diagrams of concrete work for uniaxial compression to analyze the possibility of using concrete as a core of an integrated structure. Experimental studies of the polymer concrete core of the structure were conducted. In total, ten concrete compositions were made and investigated. The compositions of concrete differed in cementitious: cement and polyester resin. As a filler used sand, gravel, ground clay, marble flour, soda and fine mineral fibers. Samples were tested for central and eccentric compression. During the tests used the methods used in testing cement concrete. As a result of the tests, complete schedules of the work of materials for uniaxial compression were obtained. The analysis of the energy characteristics of concrete schedules based on the theory of degradation is carried out. As a result of the discussion of the results obtained, conclusions are drawn about the possibility of using polymer concrete as the supporting core of an integrated structure with an external steel shell.

Comparison of strength criteria of rock under complex stress state

2014 ◽  
pp. 715-720 ◽  
Author(s):  
H Li ◽  
H Liao ◽  
J Ren ◽  
G Xiong ◽  
G Zhao ◽  
...  
Keyword(s):  
Stress State ◽  
Complex Stress ◽  
Complex Stress State ◽  
Strength Criteria

Issues of further development and improvement of design standards for wood structures

2019 ◽  
pp. 35-41
Keyword(s):  
Complex Stress ◽  
Complex Stress State ◽  
Internal Stresses ◽  
Design Standards ◽  
Duration Of Action ◽  
Wood Structures ◽  
Strength Criteria ◽  
Current State ◽  
Wooden Structures ◽  
Further Development

The current state of design of wooden structures against the background of the historical development of design standards is analyzed, the tasks of their further development are formulated. The strength criteria ensuring progress in the design of unique and spatial wooden structures are considered. Examples of unique large-span coatings, principles of their design with providing a spatial scheme are presented. In addition, the methodology for the nonlinear analysis of such systems with due regard for the duration of action of the load and of redistribution of internal stresses, especially under unsymmetrical loads, including with due regard for the coverings between the ribs experiencing a complex stress state is proposed. The application of the calculation method considered provides material savings and at the same time increases the reliability and survivability of the structure. Some possible additions and proposals on the structure and content of the new version of the norms are proposed. Taking into account continuity and achievements of the technical progress the necessity of development of new standards on the basis of advanced technologies of production, design and calculation of designs on the computer is proved.

MODERN STRENGTH CRITERIA FOR CONCRETE UNDER TRIAXIAL STRESS STATES

2021 ◽  
Vol 97 (5) ◽  
pp. 16-30
Author(s):  
V.I. KORSUN ◽  
◽  
S.N. KARPENKO ◽  
S.Yu. MAKARENKO ◽  
A.V. NEDOREZOV ◽  
...  
Keyword(s):  
Experimental Data ◽  
Stress State ◽  
Concrete Strength ◽  
Plane Stress State ◽  
Triaxial Stress ◽  
Design Strength ◽  
Strength Criteria ◽  
Analysis And Design ◽  
Reliable Assessment ◽  
Stress States

Reliable assessment of the strength and deformations of concrete under multiaxial stress states is important for increasing the accuracy of analysis and design. Classical strength theories do not work for such materials as concrete due to the complex shear-pryout mechanism of its structural failure. Description of the key relations of strength criteria established by G.A. Geniev, G.A. Geniev – N.M. Alikova, E.S. Leites, A.V. Yashin, S.F. Klovanich – D.I. Bezushko, K.J. Willam – E.P. Warnke and N.I. Karpenko is given. Assessment of the compliance of the design strength with the experimental data under uni-, bi- and triaxial stress states is made. Strength criteria that most closely describe the experimental data in the specific areas of the stress state are determined. It has been found out that the most developed strength conditions are the ones developed by S.F. Klovanich – D.I. Bezushko, K.J. Willam – E.P. Warnke and N.I. Karpenko. The criteria introduced by E.S. Leites and A.V. Yashin describe the experimental data under conditions of the plane stress state with sufficient accuracy. The strength conditions established by G.A. Geniev and G.A. Geniev – N.M. Alikova require careful use, taking into account their deviations from the experimental data in certain areas of triaxial stress states. Loading programs in the process of experimental research of concrete strength aimed at identifying the forms of functions of meridional and deviatoric curves more accurately have been determined.

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