# Structural Mechanics of Engineering Constructions and Buildings

**Editor-in-Chief**: Marina Rynkovskaya, PhD, Docent

**ISSN: **1815-5235 (Print)** ISSN: **2587-8700 (Online)

**Founded in** 2005. ** Publication frequency**: bimonthly publishing

**Open Access**: Open Access. **APC**: no article processing charge

**Peer-Review**: double blind. **Publication language**: Russian, English

**PUBLISHER**: Peoples’ Friendship University of Russia (RUDN University)

Journal **History**

**Indexation: **Russian Index of Science Citation, RSCI, WJCI, Google Scholar, Ulrich's Periodicals Directory, DOAJ, WorldCat, Cyberleninka, Dimensions, ResearchBib, Research4Life, Lens, JournalTOCs

The review-and-analytical and scientific-and-technical Journal "**Structural Mechanics of Engineering Constructions and Buildings**" acquaints the readers with the recent achievements of scientists, researchers, and engineers of the Russia and other counties. “Analysis and design of building structures”, “Dynamics of structures and buildings”, “Analytical and numerical methods of analysis of structures”, “Shell theory”, “Problems of theory of elasticity”, “Buckling analysis”, “ Geometrical investigations of middle surfaces of shells”, “Experimental researches”, “Theory of plasticity” , “Mechanics of liquids”, and “Strength of flying apparatus” are the main parts of the Journal that define the modern standards of scientific researches on building, machine-building, and architecture of space large-span structures.

The Journal is ready to widen the scope if it will receive original and topical contents.

The Journal was registered by the Federal Service of Supervision for Observance of Law in the Sphere of Mass Communications and Protection of Cultural Heritage. The Registration Certificate of mass media PI №FS77-19706 was given in April 13, 2005. The subscription index of “Rospechat” catalog is 20479 (for half of the year) and is 80344 (for full year)

Since the first January, 2007, the Journal has been included into the “List of leading peer-reviewed scientific journals” released by the Highest Attestation Commission of the Ministry of Education and Science of Russia (HAK). The results of PhD and DSc dissertations and fundamental scientific researches must be published in the journals from this “List”.

The new “List of the Journals” approved by the Ministry of Education and Science of Russia at 12.01.2015 also contains the Journal «Structural Mechanics of Engineering Constructions and Buildings».

Every issue of the Journal is sent to Russian State Library, as well as to other leading libraries, universities, educational and research institutions of the Russian Federation.

## Current Issue

### Vol 18, No 6 (2022): Scientific Legacy of Academician Vitaly Mikhailovich Bondarenko

**Year:**2022**Articles:**11**URL:**https://journals.rudn.ru/structural-mechanics/issue/view/1625**DOI:**https://doi.org/10.22363/1815-5235-2022-18-6

#### Full Issue

#### Articles

##### Vitaly Mikhailovich Bondarenko - life in the name of the Fatherland

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):487-489

#### Analysis and design of building structures

##### Non-equilibrium and nonlinear processes in robustness potential evaluation of reinforced concrete structural systems in ultimate states

###### Abstract

The problems of non-equilibrium and nonlinear processes in the evaluation of reinforced concrete structural systems robustness potential in ultimate states are considered. The definition of concept of “robustness exposition” is given for a quantitative assessment of the robustness potential. A calculation model based on the generalization of the well-known classical relationship between the current relative deficit change rate of the reinforced concrete stress-strain state with respect to each fixed time value is proposed to describe in time non-equilibrium processes of structural materials force resistance depending on the mode and level of loading. On the basis of the linear creep theory, aging materials, an algorithm was developed to determine the measure of creep, corrosion-damaged concrete and reinforced concrete and to determine the parameter “robustness exposition” of a reinforced concrete statically indeterminate structural system, taking into account non-equilibrium and nonlinear processes of its deformation in time. An example of a single-span rigidly clamped reinforced concrete beam calculating the robustness potential from the position of a special limiting state criterion is considered.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):490-502

##### Investigation of the properties of high-strength steel fiber concrete with a minimum effective fiber content under loads of various durations

###### Abstract

The authors review the results of complex theoretical studies of the physico-mechanical and rheological properties of high-strength steel-fiber concrete in comparison with non-reinforced fine-grained high-strength concrete made of self-compacting mixtures under short-term and long-term load exposure. Based on the data of extensive experimental studies, methods of Mathematical description of concrete properties depending on the key factors of influence have been selected and developed. A steel fiber concrete with a minimum content of the selected type of fiber is studied, at which the positive effect of fiber reinforcement begins to manifest itself. The theoretical approach of V.M. Bondarenko to the description of creep measures of steel fiber concrete has been developed. The developed methods can be used to calculate structures made of high-strength steel-fiber concrete using the modern diagram method.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):503-514

##### Stability of shallow shells with local changes in strength characteristics

###### Abstract

The authors deal with the structures of buildings in the form of shallow shells with some damage. The derivation of equations is given taking into account the geometric nonlinearity of the work of a thin-walled structure. A technique for solving systems of equations using the Bubnov - Galyorkin method is given. The work of the structure with various ways of fixing the edges is simulated. Damage is specified by changing the modulus of elasticity in an arbitrary section of the structure. The influence of the shape and location of the defect on the value of the critical load is investigated. The results of the studies carried out are given in a dimensionless form and illustrated by graphs, which makes it convenient to use them in engineering calculations. Recommendations are given for correcting the shape and thickness of coating structures in the form of shallow shells in order to maintain their bearing capacity in the event of defects. The proposed method can be used to determine and investigate the stress-strain state of structures in the form of shallow shells, taking into account the geometric nonlinearity of work in the presence of defects in them. The constructed graphs of the dependence of the critical load on various parameters make it possible to evaluate the operation of structures, taking into account changes in various factors at various stages of the structure's operation. The use of varying characteristics of the reduction in the modulus of elasticity, which appears because of the occurrence of a defect, shows results that are close to real conditions.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):515-524

##### Numerical-analytical method in reinforced concrete mechanics

###### Abstract

A variant of the numerical-analytical method in the nonlinear mechanics of reinforced concrete is proposed. Calculation models make it possible to take into account a number of important factors, such as discrete cracks, the effect of concrete discontinuity, and reinforcement reactions in a crack. When solving the inverse problem of determining the width of the crack opening, the deformation effect is not set, but is modeled using the “joining” of the assigned minimum possible width, its opening under the appropriate loading. In the calculation scheme, pairs of finite elements are distinguished, adjacent to such a crack from opposite special sides, called a two-element cantilever model. Pairs are considered in two states: before their jointing of cracks and after their jointing, taking into account the deformation effect and the effect of concrete discontinuity. The calculation algorithm is based on combinations of an analytical model for calculating the stiffness of complexly stressed structures and the intelligence of the “LIRA-SAPR” software package.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):525-533

##### Relaxation of stress in elements of reinforced concrete structures

###### Abstract

The calculation and prediction of the long-term safety of building structures is associated with the dynamics of the stress state of their composite elements and leads to relaxation problems for assessing the redistribution of stresses between the components that make up the structural element. In this study, reinforced concrete elements and the redistribution of stress from concrete to reinforcement are considered. To solve the corresponding relaxation problem an approach based on the concept of the strength structure of materials is proposed, which considers them as a union of their fractions (layers, fibers) with statistically distributed strengths. The loss of the ability of force resistance caused by loading by part of the fractions of the element entails a redistribution of stresses to its entire fractions. As a result of this, a nonlinear dependence of deformations on the design stresses arises, calculated under the assumption of equal strength of all fractions. For a material isotropic in strength, the relaxation problem is reduced to solving a linear integral equation conjugated with its linear rheological equation. The linear integral equation relatively structural stresses is reduced. After solving it, the desired stress is determined as the root of the algebraic equation connecting the structural and design stresses. The proposed approach significantly simplifies the obtaining of necessary for the long-term safety prediction of structures stress estimates in the components of structural elements.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):534-543

##### Fluctuations of pipelines of gas-containing liquids under changing bearing conditions

###### Abstract

The authors deal with the vibration of the pipeline that occurs during the transportation of a gas-containing liquid due to the uneven distribution of gas accumulation along the length of the pipeline, which produces pulsating movements of the center of gravity of the moving liquid, when the conditions for supporting the middle part change. The solution is constructed using the calculation scheme of a beam lying on an elastic foundation described by the Winkler model. To assess the impact on the stress-strain state of the beam of the sudden exclusion of the elastic foundation under the middle part of the beam, the circular frequencies and forms of natural transverse vibrations of the beam that occur in the absence of disturbing forces are determined. The given solution of the problem of vibrations of a pipe, through which a gas-containing liquid is transported, with a change in the conditions of support of the middle part of the beam, can be used to predict the durability of the pipe.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):544-551

##### Numerical calculation of bent reinforced concrete elements of rectangular section in the Abaqus software

###### Abstract

The calculation of building structures to a large extent began to be performed using automated software systems based on the finite element method. An urgent issue of the widespread use of this type of calculation is the accuracy of the calculation results in comparison with experimental data. In this study, by numerical simulation using the Abaqus software package, the stress-strain state of a bent reinforced concrete element of a rectangular cross section is investigated. Numerical modeling of the element is performed by volumetric finite elements, taking into account the non-linear (actual) state diagram of concrete, described by the model of plastic fracture of concrete with damage (CDP). Reinforcement is specified by rod finite elements, with a combination of elastic properties and metal plasticity model. The loading of the beam element in the model is performed statically with the application of concentrated forces at the centers of the thirds of the design span. As a result of the finite element calculation, the distribution of stresses in concrete and reinforcement according to Mises, deformations of finite elements along the main axes, as well as a model of concrete damage with increasing load were obtained. The obtained results showed a high convergence with the experimental data of testing beams for bending along a normal section, which allows using this algorithm for automated finite element analysis in the design of bending reinforced concrete structures.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):552-563

##### Stability exposure of building structural systems under environmental damage

###### Abstract

Environmental impacts on reinforced concrete structures may cause a decrease of in resource of their robustness under design and unforeseen actions. The research in this field mainly focusses on investigation of the behavior of bending elements as eccentrically compressed and damaged by corrosion reinforced concrete elements such as columns require more intensive investigation. Thus, the study has the purpose to assess the influence of the depth of corrosion on the bearing capacity of eccentrically compressed reinforced concrete columns of building frames, as well as to evaluate the time for exhaustion of load capacity. The phenomenological model, which was proposed by V.M. Bon- darenko, has been adopted in order to account long-term processes of corrosion damage. The study established an increase in the depth of corrosion damage leads to a decrease in the bearing capacity of eccentrically compressed reinforced concrete columns since the effective cross-sectional depth decreases which makes column more flexible. The relative cross-sectional depth lost strength resistance resource due to corrosion varies depending on the current stress-strain state of the reinforced concrete column that is adaptation mechanism of the structure to long-term actions. The exposure of building structural systems under environmental damage depends significantly on the parameters of the action as well as the stress-strain state of the structural element. The paper established that it may differ by several times depending on avalanche or clogging damage scenario.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):564-572

##### Analytical model of deformation of reinforced concrete columns based on fracture mechanics

###### Abstract

When conducting seismic calculations of reinforced concrete buildings and structures, it is quite important to use nonlinear models of structural performance, including those taking into account the overcritical operation in the fracture stage. The application of such models is especially important if the structures have an initial damage from fire or corrosion, as well as mechanical damage caused by force factors. The purpose of this study is to develop an analytical model of the deformation of eccentrically compressed reinforced concrete columns considering the stage of failure, which includes such processes as spelling of the protective layer, loss of stability of compressed reinforcement, and softening of confined concrete after reaching the design resistance. The existing models describing hysteresis behavior of reinforced concrete structures under low-cycle loading have been reviewed. The models have been analyzed in terms of considering the defining monotone curves, which are the boundaries of cyclic deformation. The model proposed in the research is constructed by analyzing the stages of the stress-strain state of a reinforced concrete column. At each stage, formulas are found for determining moment and curvature by solving equations of equilibrium of internal forces. Calculations based on the obtained model for a particular reinforced concrete column are carried out, monotonous diagrams are obtained, and a conclusion about the significant influence of the level of axial load on the character of deformation is made. On the basis of the obtained model, the construction of hysteresis diagrams under low-cycle loading is expected in the future.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):573-583

##### Basic principles in the theory of force and thermal force resistance of concrete

###### Abstract

In the development of the ideas and approaches to the analysis of the force resistance of concrete of V.M. Bondarenko, the initial prerequisites for the model of the thermomechanical state of concrete under short-term sharp high-temperature exposure, characteristic of fire conditions, are formulated. The separation of force deformations into components is carried out on the basis of the connection with the accumulation of damage in the structure of the material, based on the principle of independence of the limiting structural stresses from temperature and the mode of force action, which makes it possible to establish basic thermomechanical relationships and determine the deformation parameters of concrete operating under conditions of unsteady heating in a loaded state. Based on the extension of the hypothesis of entropy damping of nonequilibrium processes to the area of action of an active destructive factor, the principle of normalization was formulated and a kinetic equation was proposed, from the solution of which exponential dependences having a single structure were obtained, which make it possible to describe the basic temperature parameters of concrete, the relationship of stresses with deformations, and other nonlinear characteristics. The application of the proposed principles creates a reliable theoretical basis for describing the mechanisms of thermal resistance of concrete and greatly simplifies the modeling of the effect of high temperature on the properties of concrete in the practical implementation of methods for the numerical calculation of reinforced concrete structures.

**Structural Mechanics of Engineering Constructions and Buildings**. 2022;18(6):584-596