75504
2712-8172
Magazine of Civil Engineering
5
113
2022
1-169
RAR
RUS
11301-11301
57204526075
0000-0002-6875-754X
Levchenko
Artem
Voronezh State Technical University
Alevchenko@vgasu.vrn.ru
Voronezh, Russia
6505460291
0000-0001-7280-5746
Polikutin
Aleksei
Voronezh State Technical University
a.pl@mail.ru
Voronezh, Russia
Rubber concrete beams under the action of transverse bending
Bending elements made of rubber polymer concrete (rubcon), which was invented at the Department of Reinforced Concrete and Stone Constructions of the Voronezh Civil Engineering Institute, are a promising direction in the development of the construction industry for industrial buildings due to their high load-bearing capacity combined with universal resistance to aggressive environments. One of the primary building materials today is cement concrete, despite its disadvantages associated with the complexity of the maintenance of reinforced concrete structures in aggressive environments. The previous research on rubcon bending elements of the rectangular cross-section was carried out without implementing numerical studies that consider the nonlinear properties of the materials. Based on the conducted physical experiments, a deformation model of the resistance of the normal cross-sections to the action of transverse bending is developed, which allows estimating the strength of rubcon beams with the greatest deviation of 18%. The accepted prerequisites in the calculation model allow a more correct description of the deformation of polymer concrete in reinforced structures. The proposed analysis method is validated by numerical studies in the ANSYS® software. Due to the obtained excellent convergence with experimental values, physical studies can be replaced by numerical studies.
10.34910/MCE.113.1
624:691.34
concretes
polymers
rubber
strength
reinforced concrete
concrete construction
finite element method
rubcon
https://engstroy.spbstu.ru/article/2022.113.1/
RAR
RUS
11302-11302
0000-0002-6950-3138
Litvinova
Natalia
Military Space Academy named after A.F. Mozhaysky
skarlet27@list.ru
Saint Petersburg, Russia
0000-0001-5647-502X
Mirgorodskiy
Aleksandr
Military Space Academy named after A.F. Mozhaysky
a89112455906@yandex.ru
Saint Petersburg, Russia
Avsyukevich
Dmitriy
Military Space Academy named after A.F. Mozhaysky
avsdim@mail.ru
Saint Petersburg, Russia
0000-0002-1872-0861
Shishkin
Evgeniy
Military Space Academy named after A.F. Mozhaysky
shishkin78@ya.ru
Saint Petersburg, Russia
Thermoeconomic model of a building's thermal protection envelope and heating system
The article is devoted to the determination of the patterns of joint influence exerted by the heating system and heat-protective envelope of a building on its energy consumption, taking into account the composition of the enclosing structures and the peculiarities of the course of thermodynamic processes in the enclosing structures and engineering equipment. The paper presents an overview of the literature on energy saving in the field of construction. It is concluded that it is necessary to form a new approach to optimizing the thermal insulation of buildings based on the method of thermoeconomics, which allows increasing the energy efficiency of buildings. A schematic diagram of the object under study is presented, for which a thermoeconomic model has been developed in the form of several zones connected in series. All cost components affecting the energy efficiency of buildings have been investigated, and the division of costs into energy and non-energy costs is substantiated. Dependences of the reduced costs on the variables to be optimized are given. The dependence of the reduced costs on the cost of the chosen enclosing structures (heat-shielding shell) of the building and engineering equipment is revealed. The analysis of the results obtained is carried out. It is concluded that it is possible to decrease the reduced costs by an average of 20–25 % in comparison with traditional approaches, and the energy consumption of the building by 30–34 %.
10.34910/MCE.113.2
697.133
buildings
building component
heating system
energy efficiency
cost effectiveness
thermoeconomic model
civil engineering
https://engstroy.spbstu.ru/article/2022.113.2/
RAR
RUS
11303-11303
M-6585-2013
6508103761
0000-0002-1196-8004
Vatin
Nikolai
Peter the Great Saint Petersburg Polytechnic University
vatin@mail.ru
Polytechnicheskay, 29
56352359500
0000-0002-5156-7352
Sergey
Korniyenko
Volgograd State Technical University
svkorn2009@yandex.ru
28, Lenina Ave., Volgograd, Russia, 400005
Energy performance of buildings made of textile-reinforced concrete (TRC) sandwich panels
This research aimed to investigate the energy properties of buildings made of textile-reinforced concrete (TRC) sandwich panels in various humidity-climatic zones. Two configurations of sandwich panel are considered: conventional and advanced. The conventional sandwich panel consists of inner and outer 75 mm thick reinforced concrete layers with separated by a layer of insulation made of extruded 50 mm thick foam polystyrene (XPS) slabs. In the advanced design, due to the use of TRC, the thickness of interior and exterior structural layers is reduced to 40 mm (while maintaining strength), and the thickness of the heat-insulating layer increased to 120 mm. Glass plastic connectors of 10 mm diameter located in nodes of a square grid connect the structural layers. The authors applied an analytical method of research to buildings’ energy performance made of TRC sandwich panels based on the investigation of heat and moisture transfer processes in continuous heterogeneous media and analysis of energy indicators of buildings. For the purposes of this research, the element-by-element and complex assessment of building thermal protection was performed. Based on the results of this research, the main thermal advantages of these facade systems are identified. Building component thermal resistance is increased in multiple humidity-climatic zones, providing a high thermal protection level in winter compared to conventional facade systems. Building component heat absorption is increased by 34.4% (compared to conventional facade systems), excluding the risk of overheating of premises in summer. The risks of moisture condensation and deterioration of hydrothermal-protective properties of building components are minimized. The use of TRC sandwich panels allows reducing total heat loss through the building envelope by 26.5%. Simultaneously, the building’s specific thermal characteristic is decreased by 16.7%, and the energy-saving class increases to high levels. Construction with advanced facade systems, when the precast sandwich panels with structural layers from textile-reinforced concrete are used, extends the creative boundaries of architecture and allows you to solve the current problem of improving the architectural environment’s quality and conserve energy for future generations.
10.34910/MCE.113.3
699.86
building
façade system
sandwich panel
textile-reinforced concrete
building component
thermal conductivity
heat absorption
water vapour permeability
thermal resistance
thermal transmittance
energy saving
https://engstroy.spbstu.ru/article/2022.113.3/
RAR
RUS
11304-11304
57199423116
0000-0002-4942-0829
Bondar
Anastasia
South Ural State University
bondaraa@susu.ru
Chelyabinsk, Russia
7003469924
Pikus
Grigorii
South Ural State University
pikusga@susu.ru
Chelyabinsk, Russia
57199422173
0000-0003-1936-8238
Lebed
Anna
South Ural State University
lebedar@susu.ru
Chelyabinsk, Russia
Thermal stresses at the early stage of the hardening of steel-fiber reinforced concrete
The article studies the influence of steel fiber on the change in temperature stresses in concrete at an early hardening stage. When hardening concrete is exposed to heat treatment, its volume and, consequently, density change. Under certain circumstances, this can lead to its structural damage and, ultimately, to a decrease in its physical and mechanical properties at the design age. Such structural damage of concrete can appear even at the earliest hardening stage, before the formation of the elastic properties of the material. When testing concretes subjected to heating, we recorded the development of temperature deformations and assessed their plastic viscosity. To determine the temperature stresses, we proposed a method based on the Kelvin-Voigt rheological model. Studies have shown that the presence of steel fibers in concrete leads to a decrease in the deformations of concrete during heat treatment. To assess the thermal stresses arising at the early stage of hardening, we derived an analytical dependence, taking into account the viscosity of the hardening concrete. During the experiments, we obtained values for the viscosity of steel-fiber reinforced concrete depending on its fiber content. The results showed that, without changing its density, steel-fiber reinforced concrete can take significantly higher thermal stresses than unreinforced concrete at the early hardening stages. With an increase in the temperature, the change in the thermal stresses, depending on the fiber content, begins to have a more pronounced non-linear nature. We also showed that before a certain structural strength is reached, there are no thermal stresses in steel-fiber reinforced concrete due to the steel-fiber induced redistribution of temperature forces throughout the volume of concrete.
10.34910/MCE.113.4
693.557
steel fiber
thermal stresses
temperature control
thermal expansion
deformation
viscosity
fiber rein-forced concrete
https://engstroy.spbstu.ru/article/2022.113.4/
RAR
RUS
11305-11305
6603731053
0000-0002-3766-5079
Ranganath
Ramappa Venkataswamy
BMS College of Engineering
rvranganath.civ@bmsce.ac.in
Bangaluru, Karnataka, India
57219654804
0000-0001-9837-5449
Vidyadhara
Veerakyatharaya
BMS College of Engineering
vidyadharav@bmsce.ac.in
Bangaluru, Karnataka, India
Saurabh
Bhiman
KRIDL
saurabhbhiman@yahoo.com
Gulbarga, Karnataka, India
Impact of pond ash as fine aggregate on mechanical and microstructural properties of geopolymer concrete
In this research, geopolymer concrete (GPC) was produced using pond ash (PA) as a fine aggregate replacement to river sand (RS). The focus of the study is to investigate the effect of PA as fine aggregate on the mechanical and microstructural properties of GPC. The present study detailed characterization of PA which includes particle size distribution, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis, energy dispersive X-ray (EDAX) studies, and chemical analysis including reactive silica (R-SiO2). PA replaced RS at percentages of 0, 20, 40, 60, 80 and 100% in GPC. Properties like compressive strength, flexural strength, split tensile strength and water permeability of GPC were studied. It was found that compressive strength, flexural strength and split tensile strength of GPC with 80% PA as fine aggregate are, respectively, 26%, 29% and 31% greater compared to concrete with RS as aggregate. The inclusion of reactive sand-like PA increased the R-SiO2/Na2O ratio from 3.2 to 5.4 in GPC mixes with up to 80% replacement and contributed to higher compressive strength. SEM studies, R-SiO2, EDAX and Fourier-transform infrared spectroscopy (FTIR) analysis of GPC confirmed the participation of PA particles in polymerization thereby contributing to higher strength. Utilization of pond ash as fine aggregate provides a valuable addition to GPC in aspects of strength and economics as well as alleviates the environmental problems caused by coal ash ponding.
10.34910/MCE.113.5
624
concrete
geopolymer
pond ash
aggregate
microstructure
mechanical properties
https://engstroy.spbstu.ru/article/2022.113.5/
RAR
RUS
11306-11306
Naruts
Vitaliy
National Research Moscow State Civil Engineering University
insolent88@mail.ru
Moscow, Russia
Larsen
Oksana
National Research Moscow State Civil Engineering University
larsen.oksana@mail.ru
Moscow, Russia
Samchenko
Svetlana
Moscow State University of Civil Engineering
svet6783005@yandex.ru
Blended binder based on Portland cement and recycled concrete powder
The article investigates the properties of recycled concrete powder obtained by mechanochemical activation of recycled screening waste with organic plasticizer in vibrating mill. The waste concrete powder was considered as a part of blended binder based on Portland cement. The optimal powder ratio in blended binder was 30% by weight of cement with the maintenance of the strength properties. The laser diffraction method, X-ray analysis and IR spectroscopy, as well as standard methods were used to estimate the properties of activated powder. The activation of recycled screening waste in 150 min with 0.5% plasticizer allowed us to achieve the specific surface area of the powder at the range of 457.5 cm2/g with content of fine-grained particles in the size of 0–10 µm (26.6%) and 0–20 µm (31.2%). It was estimated that the increase of powder ratio in blended binder reduces the standard consistency of the paste and extends the setting time of the binder. The optimal content of the powder was 30% by weight of cement with standard consistency of 24.6%. The compressive strength at the age of 2, 7 and 28 days was 24.3, 37.4 and 50.5 MPa respectively. The structure change of recycled screening waste particles by mechanical destruction and surface amorphization of initial crystalline phases was confirmed by XRD method and IR spectroscopy.
10.34910/MCE.113.6
666.97
сonstruction and demolition waste
recycled concrete
recycled concrete powder
recycled screening waste
mechanochemical activation
blended binder
https://engstroy.spbstu.ru/article/2022.113.6/
RAR
RUS
11307-11307
57189074121
0000-0002-5945-3405
Kotov
Pavel
Lomonosov Moscow State University
kotovpi@mail.ru
Moscow, Russia
17344568900
0000-0002-9856-2604
Stanilovskaya
Julia
Total Energies
yulia.stanilovskay@totalenergies.com
Paris, France
Long-term strength of frozen saline soils
There are many experimental methods for determining the strength of frozen soils. However, the experimental period is always much shorter than the period of infrastructure facilities operation on permafrost. Hence, one of the main tasks of the frozen soils mechanics is the development of methods for prediction of long-term strength. The aim of the research is selection of equations for long-term strength prediction of frozen saline soils. The selection is carried out based on spherical template indenter test (STI) using artificial samples of two soil types (fine sand, loam) with different salinity (from 0.07% to 1.42%), water content and temperature (-2°C, -4°C,-6°C). There were 200 experimental tests. Two approaches with 10 empirical equations and time analogy method were used for long-term strength prediction. As a result, only four equations satisfied the selection criteria and can be used for the long-term strength calculations. Our studies have shown the possibility of using the time analogy method for saline frozen soils. Calculated values of equivalent cohesion for a saline-time analogy as well as for a temperature-time analogy were within confidence interval: 90% and 80% of values respectively.
10.34910/MCE.113.7
551.341
mechanical properties
strength
temperature
testing
forecasting
frozen saline soil
spherical template indenter test
time analogy method
equivalent cohesion
https://engstroy.spbstu.ru/article/2022.113.7/
RAR
RUS
11308-11308
57194148090
0000-0003-4887-0526
Nanayakkara
Anura
Department of Civil Engineering, University of Moratuwa
sman@civil.mrt.ac.lk
Moratuwa, Western Province, Sri Lanka
55320875600
Premasiri
Ranjith
Department of Earth Resources Engineering, University of Moratuwa
ranjith@uom.lk
Moratuwa, Western Province, Sri Lanka
57224625490
0000-0001-9058-6567
Arulmoly
Branavan
Department of Civil Engineering, University of Sri Jayewardenepura
branavanarulmoly@sjp.ac.lk
Ratmalana, Western Province, Sri Lanka
55514827300
Konthesingha
Chaminda
Department of Civil Engineering, University of Sri Jayewardenepura
konthesingha@sjp.ac.lk
Ratmalana, Western Province, Sri Lanka
Metamorphic rocks for manufactured sand and coarse aggregate for concrete and mortar
The present study determined the most applicable high-grade metamorphic rocks as the sources for manufactured sand and coarse aggregates production to apply in the construction industry. As the first stage of this study, representative samples of the most common ten types of metamorphic rock were collected and tested for mineralogical and chemical compositions to select the favorable rock types in concrete and mortar production. XRD diffraction patterns and quantitative analysis results of XRF were referred for identifying the mineral and chemical contents respectively. Secondly, among the favorable rock types, based on the geology, the area contribution by each rock was calculated and few abundantly available rocks were considered for further investigation. Finally, the compatibility of rocks was checked by analyzing the physical, mechanical, and durability characteristics. As the physical parameters, the specific gravity, water absorption, loose and packing density, and water content were checked. Mechanical properties of rocks were determined by investigating compressive and tensile strength, impact resistance, abrasion resistance, and crushing value. The durability of rocks against weather fluctuations was probed through the slake durability indexes. Results from the first stage revealed that Charnockite, Hornblende-Gneiss, Intrusive Charnockite, and Granitic-Gneiss were favorable rocks rich with concrete and mortar friendly minerals such as albite, k-feldspar, and quartz. Among the above four rocks, Charnockite contributed around 40% and Hornblende-Gneiss covered approximately 9.5% of the area, which were then considered for the next stage of the investigation. Charnockite and Hornblende-Gneiss showed similar porosities and water absorption in the range of 0.25–0.26%. Each mechanical property of both rocks complied with the requirements provided by the standards; moreover, they manifested excellent durability performance against cyclic wetting and drying as well.
10.34910/MCE.113.8
624.69-033
aggregates
concrete
mortar
construction industry
porosity
water absorption
compressive strength
tensile strength
mechanical properties
durability
https://engstroy.spbstu.ru/article/2022.113.8/
UNK
RUS
11309-11309
0000-0003-0044-1781
Marandi
Seyed Morteza
Shahid Bahonar University of Kerman
marandi@uk.ac.ir
Kerman, Iran
0000-0002-6438-132X
Lotfi Omran
Navid
Shahid Bahonar University of Kerman
navid.lotfii.omran@gmail.com
Kerman, Iran
0000-0001-6449-874X
Rajaee
Komeil
Graduate University of Advanced Technology
rajaee.geotech@gmail.com
Kerman, Iran
Effect of temperature on permanent deformation of polymer-modified asphalt mixture
This study aims to evaluate the permanent deformation of unmodified and styrene-butadiene-rubber (SBR) modified asphalt mixtures using dynamic creep test. The purpose was to assess the effect of SBR as one of the most plentiful and low-cost polymers in Iran on rutting resistance of asphalt mixtures in the regions with hot climate, such as the areas around the “Persian Gulf”, and the central deserts of the “Iran Plateau”. First, the critical gradation of aggregates with higher permanent deformation was determined. Then, the aggregates with critical gradation were mixed with the optimum amount of bitumen modified by different amounts of SBR, and tested to obtain an optimum SBR content with lower permanent deformation. Finally, the unmodified and SBR-modified asphalt mixtures with optimum SBR content (6%wt) were tested at 40 and 50 ˚C as the simulated ambient temperatures in order to evaluate the effect of SBR and rising temperature on rutting resistance of the asphalt mixtures. In addition, the flow number (FN) of asphalt mixtures is calculated according to Goh and You method. Results showed that with addition of 6% SBR, the permanent strains of asphalt mixtures decreased by 39 and 60%, and the creep modulus increased by 64 and 133% at 40 and 50 ˚C, respectively. Furthermore, with the temperature rising from 40 to 50 ˚C, the permanent strains of asphalt mixtures containing 0 and 6% SBR increased by 61 and 5%, and their creep modulus decreased by 34 and 6%, respectively. The FNs of unmodified samples were obtained 8416 and 9728 loading cycles at 40 and 50 ˚C, respectively. In contrast, up to the last loading cycle, the SBR-modified samples did not experience the tertiary flow at both ambient temperatures. These results let us conclude that the SBR-modified bitumen is able to significantly reduce the permanent deformations, and enhance the resilience and creep modulus of asphalt mixtures; moreover, it can minimize the negative effects of rising temperature on their engineering properties.
10.34910/MCE.113.9
625.85
asphalt mixtures
polymers
temperature
dynamic creep test
permanent deformation
https://engstroy.spbstu.ru/article/2022.113.9/
RAR
RUS
11310-11310
0000-0001-9032-8138
Rakov
Mikhail
Novosibirsk State University of Architecture and Civil Engineering (Sibstrin)
westcoast89@mail.ru
Novosibirsk, Russia
57076182100
0000-0002-8520-4453
Ilina
Lilia
Novosibirsk State University of Architecture and Civil Engineering (Sibstrin)
nsklika@mail.ru
Novosibirsk, Russia
Kudyakov
Aleksandr
Tomsk State University of Architecture and Building
kudyakow@mail.tomsknet.ru
Aerated dry mix concrete for remote northern territories
The study results on aerated concrete based on imported long-term storage clinker and mineral additives for northern remote construction sites are presented here. The relevance of the research is due to the need for cement composites of stable quality to install enclosing structures at remote northern construction sites. It is impossible to ensure stable quality and safety of construction objects using imported cement due to a significant decrease in its activity during transportation and long-term storage. This problem is shown to be solved by organizing the production of aerated concrete from imported Portland cement clinker using a mechano-chemical technological platform, including: scientific substantiation of the components’ choice, mechanical or mechano-chemical activation of clinker by joint grinding with additives and obtaining a dry mixture, preparing aerated concrete mixture and hardening aerated concrete in molded products. Modern physicochemical methods for studying cement compositions are used in this scientific work. Ensuring the required characteristics of aerated concrete on imported Portland cement clinker is provided by introducing activated mineral additives of wollastonite and diopside, which have a chemical affinity with cement minerals and hydrosilicates. It was found that the activity of the binder increased by 30 % and 59 %, respectively when 7 % wollastonite and diopside with a specific surface area of 309 and 323 m2/kg were added to cement from imported clinker for long-term storage. At the same time, the initial activity of cement (43 MPa) is restored even with the 2 % content of diopside of a specific surface area of 323 m2/kg. An increase in the activity of cement from imported clinker was explained by the formation of an additional amount of low-basic hydrosilicates and a decrease in stone porosity. Aerated concrete from cement, based on imported clinker, has a homogeneous structure of evenly distributed pores with an average diameter of 6.81 microns, which provides a 10–15 % increase in strength with a compression variability coefficient of 5.4. The obtained aerated concrete had the strength of B2 class, F75 grade frost resistance and thermal conductivity coefficient of 0.14–0.15 W/(m∙oC). The developed aerated concrete and the technology of its preparation from imported Portland cement clinker are intended for the construction of buildings in the remote northern territories.
10.34910/MCE.113.10
691.32 : 666.9.03
aerated concrete
dry raw mix
Portland cement
clinker
mineral additives
joint grinding
compressive strength
porosity
frost resistance
thermal conductivity
https://engstroy.spbstu.ru/article/2022.113.10/
RAR
RUS
11311-11311
0000-0003-0670-5143
Mitina
Anna
National Research Tomsk State University
mit1na4n@yandex.ru
Tomsk, Russia
55210135000
https://orcid.org/0000-0002-1032-6077
Mitina
Natalia
National Research Tomsk Polytechnic University
mitinana@tpu.ru
Tomsk, Russia
7801463567
0000-0003-4184-1554
Revva
Inna
National Research Tomsk Polytechnic University
revva@tpu.ru
Tomsk, Russia
Magnesia cement in the MgO-CO2-H2O system
A detailed study of the MgO-CO2-H2O system allows creating new inorganic binders. The present research is focused on the process of structure formation during hydration and curing of magnesia composition from active magnesium oxide and magnesium bicarbonate solution. Magnesium hydroxide and magnesium hydrocarbonates, basically hydromagnesite and dypingite are the products of MgO interaction with solution of magnesium bicarbonate Mg(НСО3)2. This was established by means of complex thermal analysis using thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectrometry (MS), and electron microscopy. These methods allowed us to define the influence of the curing environment of magnesia composition. Results show that processes of hydration and curing of composition of magnesium oxide with magnesium bicarbonate solution proceed most effectively in water conditions at the course of cyclic reactions of magnesium hydrocarbonate formation. The magnesia composition transforms magnesia cement into the state of hydraulic magnesia cement.
10.34910/MCE.113.11
666.962
magnesium oxide
water resistance
thermoanalysis
carbonation
microstructure
https://engstroy.spbstu.ru/article/2022.113.11/
RAR
RUS
11312-11312
B-6662-2019
57204916380
0000-0002-6877-8420
Kozinetc
Galina
Peter the Great Saint Petersburg Polytechnic University
galina4410@yandex.ru
St. Petersburg, Russia
Kozinetc
Pavel
Peter the Great St. Petersburg Polytechnic University
pavelkozinetc@yandex.ru
St. Petersburg, Russia
The calculation of the dynamic characteristics of the spillway of the dam
The object of the presented studies is a concrete spillway dam of a run-of-river hydroelectric power station. The modes of vibrations are determined on the basis of a solid model, which is necessary to take into account possible resonant phenomena in the structure. A review of publications on the method of calculating the dynamic responses of structures is made. Computational studies were carried out by the finite element method based on the calculated three-component accelerogram. When processing the results, the possibilities of modal temporal calculation were used. The response of structures excited by forces, time-varying or earthquake is calculated. Based on the calculation results, the natural frequencies and vibration modes of the concrete spillway dam were determined. The description of the oscillations of the dam is made. According to the obtained response spectrum, the maximum horizontal accelerations were achieved. Based on the response spectra, a calculated three-component accelerogram was synthesized at the equipment installation marks.
10.34910/MCE.113.12
626
concrete spillways
earthquake
natural frequencies
mode shapes
finite element method
deformation
https://engstroy.spbstu.ru/article/2022.113.12/
RAR
RUS
11313-11313
0000-0002-4109-5742
Belous
Olga
Donbas National Academy of Civil Engineering and Architecture (DNACEA)
o.e.belous@donnasa.ru
Makeevka, Donetsk People Republic
56437725200
0000-0002-6687-7249
Garanzha
Igor
Moscow State University of Civil Engineering (National Research University)
garigo@mail.ru
Moscow, Russia
0000-0003-4662-6650
Belous
Alexey
Donbas National Academy of Civil Engineering and Architecture (DNACEA)
a.n.belous@donnasa.ru
Makeevka, Donetsk People Republic
0000-0002-4534-7302
Kotov
German
Donbas National Academy of Civil Engineering and Architecture (DNACEA)
g.a.kotov@donnasa.ru
Makeevka, Donetsk People Republic
Calculation of heat resistance of external enclosing structures with heat-conducting inclusions
The paper is devoted to the development of a method for calculating the thermal stability of external enclosing structures with heat-conducting inclusions. Based on the analysis of existing methods and methodologies for solving the problem of heat resistance of enclosing structures with heat-conducting inclusions, the solution of the one-dimensional problem of heat resistance was established to be characteristic for all these works. One of the possible methods for determining the amplitude of temperature fluctuations on the inner surface of the enclosing structure with heat-conducting inclusions is the simulation of non-stationary temperature conditions in software systems. However, this solution causes great difficulties, since it transfers the indicated calculation from engineering to scientific and, therefore, cannot be recommended for direct practical application. The second solution to this problem is to use the convergence coefficient α, which can be obtained empirically. By choosing the value of the coefficient α, one can take into account the effect of a heat-conducting inclusion on the weighted average value of the surface temperature depending on the design of the fence. The paper presents values of the convergence coefficient α for six most common cases of heat-conducting inclusions in enclosing structures. When analyzing the design solutions of external enclosing structures, the features of the influence of heat-conducting inclusions on the averaged amplitude of oscillations on the inner surface were revealed. In the schemes with outer edge or through location of the heat-conducting inclusion, there is a slight influence of the amplitude of the oscillation of the heat-conducting inclusion on the averaged amplitude over the surface of the structure. The greatest degree of influence is exerted by the scheme with the through arrangement of heat-conducting inclusion. On the basis of the comparative analysis, it was found that when constructing harmonics of average temperature fluctuations on the inner surface, preference is given to the methodology with the convergence coefficient.
10.34910/MCE.113.13
699.866
heat exchangers
heat transfer coefficients
flow resistance
non-stationary mode
temperature field
https://engstroy.spbstu.ru/article/2022.113.13/
RAR
RUS
11314-11314
55235780600
0000-0001-9234-7287
Vakhnina
Olga
Volgograd State Agricultural University
ovahnina@bk.ru
Volgograd, Russia
57212340737
0000-0002-9167-075X
Sobolevskaya
Tatyana
Volgograd State Agricultural University
moonway13@rambler.ru
Volgograd, Russia
57215535887
Klochkov
Michael
Lomonosov Moscow State University
m.klo4koff@yandex.ru
Moscow, Russia
57170472500
0000-0002-1027-1811
Klochkov
Yury
Volgograd State Agricultural University
Klotchkov@bk.ru
Volgograd, Russia
7202396806
0000-0002-7098-5998
Nikolaev
Anatoliy
Volgograd State Agricultural University
anpetr40@yandex.ru
Volgograd, Russia
Physically nonlinear shell deformation based on three-dimensional finite elements
The aim of the study is to determine the stress-strain state of the shell under step loading beyond the elastic limit. At the loading step, relations between strain increments and stress increments are obtained without accepting the hypothesis of a straight normal. For the numerical implementation of the algorithm in the calculation of the shell without using a straight normal, a prismatic finite element has been developed. We consider the physically nonlinear deformation of the shell, an arbitrary point of which is represented by a radius vector defined by the curvilinear coordinates of the reference surface and the distance from the reference surface to the point under consideration. By differentiating the radius-vector function, the basis vectors of the point under consideration are determined, the scalar products of which are the components of its metric tensor. The increments of deformations at the loading step are defined as the differences of the corresponding components of the metric tensors. The defining equations at the loading step are obtained in two versions. In the first version, they are determined by differentiating the stress functions of the deformation theory of plasticity, which are obtained on the basis of dividing deformations into elastic and plastic parts using the hypothesis of material incompressibility during plastic deformation. In the second version, they are obtained without using the operation of dividing the strain increments into elastic and plastic parts on the basis of the proposed hypothesis that the components of the deviator of the stress increments are proportional to the components of the deviator of the increments of deformations. For the numerical implementation, a three-dimensional prismatic finite element with a triangular base was used for nodal unknowns in the form of displacements and their first derivatives with respect to curved coordinates. The correctness of the proposed variant of obtaining physically nonlinear defining equations at the loading step of the deformable shell is confirmed by a numerical example. On the example of calculating a cylindrical shell under the action of internal pressure, clamped at one end and free at the other, the values of normal stresses in the embedment turned out to be approximately 14% lower in the case of using the proposed variant of obtaining the constitutive equations at the loading step. The developed algorithm for determining the stress-strain state in the physically nonlinear deformation of elements of technospheric objects can be used in the practice of engineering calculations.
10.34910/MCE.113.14
539.3
physical nonlinearity
three-dimensional finite element
shell
stress increment deviator
strain increment deviator
https://engstroy.spbstu.ru/article/2022.113.14/