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Building and Reconstruction

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No 3 (2025)
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THEORY OF ENGINEERING STRUCTURES. BUILDING UNITS

7-21 24
Abstract

The methods of setting initial seismic effects in co-modern normative documents of different countries are described. The seismic impact is specified in the form of maximum spectra for rocky or rigid soils. To take into account local geological conditions, correction ground coefficients are used, which do not always correctly describe the amplification of vibrations. A methodology has been developed that makes it possible to take into account the influence of soft soil layers with consideration of nonlinear behavior on the parameters of the maximum response spectra. The nonlinear behavior of the ground is taken into account by means of an iterative nonlinear method equivalent to the nonlinear method. The method of solving problems of elasticity theory and structural mechanics based on the properties of Fourier spectra of finite functions is used in the construction of the method.

For a two-layer soil massif located on the bedrock, a system of equations for calculating the amplification coefficients of the spectra of maximum reactions by surface layers of soils is obtained, which allows to estimate local engineering geological conditions more accurately.

22-29 25
Abstract

The results of a study of the bearing capacity and deformability of non-centrally compressed reinforced concrete composite elements of low flexibility, made by concreting prefabricated elements to the design cross-section dimensions, are presented. The joint work in the composite section of concretes with various strength and deformation characteristics under short-term and long-term loading, the influence of loading history on the deformability of long-term loaded non-centrally compressed reinforced concrete elements, the mechanism of redistribution of internal forces between the components of the section during loading and over time, the nature of destruction of prototypes is established. It has been established that the joint work of concretes with various deformative characteristics significantly increases the ultimate compressibility of these concretes. With prolonged action of an off-center applied load on elements of low flexibility, the possibility of reaching the limiting state of the second group was revealed. 

30-44 26
Abstract

The article outlines the core principles of monitoring the thermal stress state during the concreting of massive concrete structures, using the foundation systems of high-rise buildings in a planned complex in Saint Petersburg as a case study. The study aims to develop methods for controlling the thermal stress state during concreting by establishing criteria for concrete crack resistance. To achieve this goal, calculations of temperature fields in the concrete structure during the hardening phase were performed, and crack resistance criteria were determined. The key findings of this research can be applied to the design and construction of massive foundation systems for unique buildings and structures. 

45-59 29
Abstract

The article is devoted to the urgent problem of protecting buildings and structures from dynamic influences of various nature and origin. An effective means of vibration suppression is being considered namely dynamic vibration dampers. A generalized model of a system of multi-mass dampers and a rational, engineering-oriented method for calculating their parameters at conditions of polyharmonic descriptions of complex dynamic excitations on construction objects are proposed, using the concepts and methods of the theory of regulating the stress-strain state of structures, where dampers play the role of regulators. Based on the decomposition approach, an analytical solution to the problem of determining the parameters of a complex of dampers according to pre-formulated requirements for the results of regulating the dynamic state of a deformable system (buildings, structures) is obtained. The test tasks were used to evaluate and analyze the accuracy of the results of calculations of model systems according to the developed methods, algorithms and formulas. 

60-72 30
Abstract

The article addresses the problem of identifying parameters for viscoelastic material models made from closed-cell polyurethane foam based on results obtained using a dynamic mechanical analyzer (DMA). DMA testing allows determining viscoelastic characteristics of materials — complex elastic modulus over a wide frequency range. For engineering applications, the most important practical application is within the frequency range of 1–1000 Hz to solve problems related to dynamics (vibration isolation and seismic insulation), as well as acoustics (protection against structural sound transmission). In engineering practice, various phenomenological material models are used, ranging from Kelvin-Voigt (KV) model and standard linear solid (SLS) model up to fractional derivative-based models such as fractional KV model, fractional SLS model including those with multiple fractional parameters. Using DMA test results—dependencies of real and imaginary parts of elastic modulus versus frequency, these models' parameters are adjusted by means of least squares method. The accuracy of approximation along with identified model parameters specific to the chosen type of material are evaluated.

BUILDING AND STRUCTURE SAFETY

73-85 29
Abstract

A model of static-dynamic deformation of compressed concrete in the ultimate state is proposed, as applied to the calculation scheme of a second-level reinforced concrete frame under a special impact. The main working hypotheses for determining the static-dynamic deformation of concrete are constructed and analytical dependencies are obtained for determining the ultimate deformations in concrete of the compressed zone during the transition of the n-times statically indeterminate system to the (n- 1) system. Concrete of the compressed zone is modeled by a representative volume in the form of a concrete prism of characteristic dimensions. For a reinforced concrete frame, a first-level calculation model with spatial sections simulating a complex stress state in a spatial crack of a complex-stressed beam is constructed. In the frame elements with the considered spatial sections, the distances between cracks and the ultimate deformations of concrete preceding destruction are taken into account.

86-98 24
Abstract

The paper considers an experimental method for assessing the degradation of physical and mechanical properties of steel elements subjected to accelerated corrosion. 

The study is based on tests of St3ps steel specimens with three samples by types of profile sections (round, rectangular, angle) The methodology includes two stages: electrochemical corrosion in 5% NaCl solution with fixation of mass loss and wall thickness of samples, as well as mechanical tensile tests of reference strips obtained in accordance with GOST 7564-73. To check the change of physical and mechanical properties of the metal from the action of corrosion and specifically its embrittlement, the dependence of corrosion resistance of steel elements on the shape of their cross-section and geometric parameters was experimentally tested.

99-110 27
Abstract

The production of building structures is accompanied by various violations of technological requirements, which may result in defects and damage to concrete, which lead to a decrease in its strength. Such defects may include surface cavities and cavities, cracks in various areas and voids in concrete. The most sensitive to such defects and damage are reinforced concrete bending structures, in particular, slabs. The influence of various positions of areas with defective concrete on the bearing capacity of hinged and clamped reinforced concrete bending slabs is considered. Graphs are constructed showing the change in the bearing capacity of reinforced concrete bending slabs depending on the strength value of the defective concrete and its location. It is established that for hinged supported slabs, the greatest danger is posed by zones with defective concrete in the span and in the corner support zones, and for clamped slabs in the middle of the support zone and in the span. 

111-119 30
Abstract

This article is the first in a series of articles devoted to the generalization and analysis of numerous published materials on the study of mechanical properties of concrete during heating. The need to study the effect of heating temperature on the mechanical characteristics of concrete is due to the need for their use in applied practical calculation methods for assessing the fire resistance of structures. An idea is given about the scope of the available research programs, their accessibility and differences. The results of numerous and diverse studies of the strength and deformation characteristics of concrete are described, confirmed by special methods of studying the effects of temperature. Studies of the mechanical properties of concrete during heating were carried out using various testing methods, different types and compositions of concrete, which led to a wide variety of data, which makes it difficult to establish any patterns. The relationship between stresses and deformations for concrete during heating cannot be obtained from experiments in direct form, and a methodology is needed to determine the required characteristics. The conclusion is made about the need for standardization of test conditions, scientific generalization, structuring and analysis of the revealed variety of results of studying the mechanical properties of concrete during heating, which can explain existing patterns and predict new ones. 

CONSTRUCTION MATERIALS AND TECHNOLOGIES

120-128 24
Abstract

The article is devoted to the study of the deformation and destruction characteristics of expanded clay concrete dispersively reinforced with fibers. The article presents the test results of expanded clay concrete samples reinforced with high-modulus basalt fiber, as well as low-modulus synthetic micro- and macrofiber. The article considers the experimental data on the strength and energy characteristics of crack resistance of fiber expanded clay concrete samples, obtained experimentally in accordance with the provisions of GOST 29167-2021 «Concrete. Methods for determining crack resistance characteristics (fracture toughness) under static loading». It was found that reinforcement with low-modulus synthetic macrofibers can lead to an increase in the strength of expanded clay concrete, and a more significant one even in comparison with reinforcement with high-modulus basalt fibers. However, achieving this strength will be accompanied by significant deflections. 

129-135 22
Abstract

Sealants are widely used in construction. They are used to seal detachable and permanent connections, structures, various joints and seams. The main volume of non-hardening sealants are sealants based on butyl rubber. These sealants, having a number of advantages, have a significant drawback - low weather resistance.

Weather-resistant sealants are of the greatest interest in construction. Such sealants can be obtained on the basis of ethylene-propylene rubber. It has high weather resistance, is resistant to ozone oxidation, but has low adhesion to various substrates.

The purpose of the research is to increase the adhesive strength of a non-hardening sealant based on ethylene-propylene rubber. To improve the adhesive strength, process additives are used. Bitumen was used as process additives. The article considers the effect of process additives on adhesive strength. It is shown that the use of process additives increased the adhesive strength by 1.5 - 2 times.



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ISSN 2073-7416 (Print)