75504 2712-8172 Magazine of Civil Engineering 3 111 2022 1-174
RAR RUS 11101-11101 56035058900 0000-0002-1794-867X National Research Moscow State Civil Engineering University Stupishin Leonid lusgsh@yandex.ru
Moscow, Russia
 56189158100 0000-0001-8749-2252 Southwest State University Moshkevich Mariya mmoshkewich@yandex.ru
Kursk, Russia
 Limit states design theory based on critical energy levels criterion in force method form The article deals with the development of the theory of limit states of structures. There are various approaches to the formulation of limiting states of structures. They are related to issues of strength, structural stability (ULS) or safe operational requirements (SLS). All known theories are oriented to a certain hypothesis of the limiting state and exist separately from each other. Therefore, there is an opinion that there is no systematic view of the limit state theory. The article suggests a general approach to creating the theory of limit states based on the criterion of critical levels of internal energy proposed by one of the authors. The problem of determination of the structure limit state is formulated as finding critical energy levels by varying system stresses. The change of energy level is accompanied by removal of linkages in the structure. Self-stressing states of the system make it possible to find out the most loaded elements. Mathematical model of general approach is the eigenvalue problem. It is formulated in the force method form and the resolving equations are derived. The physical meaning of the obtained relations and the links between the variables are explained. The proposed technique allows making a forecast that shows the element and the load from which destruction of the system will begin and trace the progressive failure of structural elements. Depending on the hypothesis of the ultimate limit state of the structure or serviceability limit state, we can analyze the behavior of the structure under load and predict violation of the conditions LSD. The problem solving method of finding the limit states is shown in the example of the pin-jointed structure. 10.34910/MCE.111.1 624.046 structural analysis limit states design force method critical levels of energy pin-jointed structures https://engstroy.spbstu.ru/article/2022.111.1/
UNK RUS 11102-11102 Semnan University Asadollahi Nezhad Amir
Semnan, Iran
 0000-0002-3305-1782 Semnan University Arshadi Hamed hamed.arshadi@semnan.ac.ir
Semnan, Iran
 0000-0001-7802-2013 Semnan University Kheyroddin Ali kheyroddin@semnan.ac.ir
Semnan, Iran
 High-strength steel effects on the behavior of special shear walls In this research, the effects of applying high-strength steel (HSS) bars as horizontal and vertical bars of the web, and as the flexural and shear bars of the boundary elements on the behavior (load-displacement and maximum moment) of shear walls, were analytically investigated in 45 specimens by finite element analysis (FEA). In addition, the influence of concrete strength along with using HSS bars in the shear walls was studied. The results showed that HSS application as flexural bars of boundary elements improved the performance of shear walls more than other cases of bar locations. However, their shear reinforcement application did not affect their performance significantly. Moreover, HSS usage as the horizontal and vertical bars of the web of the shear walls improved the performance of the specimens. Finally, using higher-strength steel was more effective on the shear performance of shear walls than their moment performance. 10.34910/MCE.111.2 624.04 high-strength steel (HSS) reinforced-concrete (RC) structures shear wall finite element analysis (FEA) nonlinear behavior https://engstroy.spbstu.ru/article/2022.111.2/
RAR RUS 11103-11103 University of Science and Technology Beijing He Xiaonan 651600363@qq.com
Beijing, China
 University of Science and Technology Beijing Xu Yan 475546253@qq.com
Beijing, China
 China Coal Handan Special Drilling Well Co. Zhang Ligang 116124556@qq.com
Handan City, Hebei Province, China
 0000-0003-0736-8046 University of Science and Technology Beijing Wu w616000360@126.com
Beijing, China
 University of Science and Technology Beijing Zhou Xiaomin
Beijing, China
 Detection and prediction of weak points of a frozen wall based on grey theory The purpose of this article is to use theoretical analysis to determine the cause of an artificial frozen wall not closing. Due to the influence of the energy difference received by each freezing apparatus, groundwater flow, freezing hole spacing and other factors, their heat transfer with the surrounding soil layer has limited efficiency. Theoretical calculations and engineering examples are compared to verify the validity of the theoretical model. According to the longitudinal temperature measurement of the temperature measuring hole and the freezing apparatus, the whole field monitoring theory based on grey correlation method is proposed. Through the calculation of the hole-to-hole correlation degree to evaluate and predict the working effect of each freezing apparatus, it is determined that the freezing pipes No. 7~9 and No. 18~22 are the weak parts of the freezing wall. Therefore, the grey correlation analysis was compared and analyzed in the case of the "window" accident of the frozen wall of the shaft, which verified the practicability of the theory. 10.34910/MCE.111.3 624 frozen soils longitudinal temperature monitoring whole field monitoring theory grey system theory prediction https://engstroy.spbstu.ru/article/2022.111.3/
RAR RUS 11104-11104 University of Warith Al-Anbiyaa Kadhim Yasir yasirneamah@gmail.com
Karbala, Iraq
 University of Warith Al-Anbiyaa Abdulhadi Ahmed ahmedmouse@uowa.edu.iq
Karbala, Iraq
 0000-0003-4745-7916 University of Warith Al-Anbiyaa Mussa Mohamed dr.mhmussa@uowa.edu.iq
Karbala, Iraq
 The clay rocks properties for the production of the ceramic bricks This paper aimed to study the properties of clay rocks in terms of chemical, mineralogical, and granulometric compositions during the pre- and post-firing processes as compared to regulatory documents. Moreover, the electrochemical interactions between the clay rocks elements have been evaluated due to the electrophoresis of its core. The results revealed that the properties of the investigated clay rocks agreed well with the requirements of regulatory documents and it is suitable to produce the ceramic bricks by plastic and dry methods. However, the calculated energy charges of clay oxides prove that the chemical composition of clay rocks will provide an unstable and irritable brick system due to the negative charges being 1.6 times greater than the positive charges. To modify the composition, it is suggested to insert feedstock or additives containing 2.3 times more positive charge selected on the basis of the structure of s-, p- and d-electrons. Further studies are recommended to take into account the thermodynamic characteristics of the feedstock to monitor the firing process, reduce energy costs and improve the quality of bricks. 10.34910/MCE.111.4 691.4 clay rocks properties electrochemical interactions technology ceramic brick https://engstroy.spbstu.ru/article/2022.111.4/
RAR RUS 11105-11105 0000-0002-4854-0247 Beirut Arab University Baalbaki Ossama obaalbaki@bau.edu.lb
Beirut, Lebanon
 57197763819 Beirut Arab University Wehbi Nour n.wehbi@bau.edu.lb
Beirut, Lebanon
 Beirut Arab University Masri Adnan amasri@bau.edu.lb
Beirut, Lebanon
 Flexural behavior of partially composite concrete-encased steel tubular beams Composite steel-concrete construction has been widely implemented in high-rise buildings and bridges having long spans due to its favorable characteristics inherited from both materials acting as one unit. The main objective of this research is to propose a new beam system having a high strength-weight ratio, and to replace the shear studs used in composite beams by steel mesh wraps around the steel tube without any flexural or shear reinforcements. This new structural beam can be part of a lightweight-precast floor system with fast and easy ducting through its hollow tubular part. Four simply supported T-shaped beams of 3 m length are investigated experimentally to study and compare their flexural behavior. All beams are tested under two points quasi-static point loading. A comparison was initially performed between a control T-shaped reinforced concrete (RC) beam and a fully encased steel tube in a T-shaped RC beam of the same section dimensions as the control beam and without any mesh wrapping. The effect of full and partial wrapping of the steel tube was also investigated in the other two beams where 100 % and 60 % of the encased steel tube length were wrapped by a 3 mm steel mesh. Discussions and interpretation of the load-deflection behaviors and the failure modes are presented in this paper. The obtained results showed that the composite beam with unwrapped encased steel tubular section provided an advantage over the control RC beam in terms of load/weight ratio and ductility by 28.5 % and 22.4 % respectively. Besides, the use of steel mesh wraps in different length percentages revealed a much better partial composite action between the steel tube and the surrounding concrete. The attained strength ranged between 18.2 % and 33 %, whereas the ductility was enhanced by 63.8 % and up to 66.7 %. 10.34910/MCE.111.5 69.04 flexural behavior composite beams concrete-encased steel tubular beams polypropylene fiber joists https://engstroy.spbstu.ru/article/2022.111.5/
RAR RUS 11106-11106 0000-0002-3017-1834 Jordan University of Science and Technology Alkhatatbeh Huthaifa haalkhatatbeh16@eng.just.edu.jo
Irbid, Jordan
 0000-0003-1106-5195 Jordan University of Science and Technology Barham Wasim wsbarham@just.edu.jo
Irbid, Jordan
 0000-0002-0533-366X Jordan University of Science and Technology Obaidat Yasmeen ytobeidat@just.edu.jo
Irbid, Jordan
 Behavior of heat damaged reinforced recycled aggregate concrete beams repaired with NSM-CFRP strips The behavior of heat damaged Recycled Aggregate Concrete (RAC) beams repaired with NSM-CFRP strips is the subject of this experimental study. The effect of heat damage on the RAC beams and the post-heating residual strength of beams were studied and compared with natural beams. Different volumetric percentages (0 %, 25 % and 50 %) of coarse Recycled Concrete Aggregates (RCA) were used in three concrete mixes (N, R25 and R50), producing a total of 16 reinforced beams having the same cross-section (100 mm×150 mm×1150 mm). Specimens were exposed to two levels of heat, 25 °C at ambient air and 400 °C for a three-hour period. The post-heating residual strength of RAC beams was studied and compared with natural ones. The flexural test conducted indicated a reduction in the load carrying capacities and stiffness due to mechanical deterioration in concrete properties and bond strength. The reduction in stiffness increased as RCA content increased due to a large amount of weak decomposed cement mortar in the RAC. The NSM-CFRP strips technique was used with epoxy adhesive for strengthening/recovering the flexural capacities of intact/ heat-damaged RAC beams. Four groups of simply supported beams were tested in a four-point bending test; the enhancement/reduction in strength and the mechanical properties were recorded. Results indicated that strengthened beams showed comparable behavior with those made with conventional concrete at room temperature. On the other hand, the behavior of repaired beams after being exposed to 400 °C showed different failure modes depending on the RCA percentage and the repairing configurations. RAC with higher RCA replacement ratio has a lower bond strength and therefore, a larger slippage was reported. The weak bond between the epoxy adhesive and the surrounding concrete caused the reduction in stiffness. Finally, using NSM CFRP with two strips at the sides (one strip at each side) for strengthening and repairing of intact/heat-damaged RAC beams resulted in slight improvement of the load carrying capacities. It reduced the induced strain in the CFRP strips to about 40 % of its value when a single concentrated strip at the bottom is used, and minimizing the slippage due to lower stresses and strains in the CFRP strips. 10.34910/MCE.111.6 69.04 reinforced concrete fiber reinforced plastics recycling heating flexural strength near-surface mounted strips heat damage experimental https://engstroy.spbstu.ru/article/2022.111.6/
RAR RUS 11107-11107 57194440024 0000-0002-3792-7198 Don State Technical University Butko Denis den_111@mail.ru
Rostov-on-Don, Russia
 57197823322 0000-0002-3853-2796 Don State Technical University Volodina Marina mclavender1984@gmail.com
Rostov-on-Don, Russia
 Regularities of rapid filter backwash water clarification in reagent-free mode Discharge of rinsing water from fast filters into surface water bodies as a way of their disposal is unacceptable for environmental reasons, and in some countries it is prohibited by law. Research by Russian and foreign scientists is aimed at studying the schemes for returning wash water to the main stream using reagent methods of clarification, ultrafiltration or filtration on ceramic filters. In this paper, the processes of removing suspended solids from rinsing waters by means of reagent-free clarification under static conditions of sedimentation facilities are considered. In this case, the treated water was exposed to mixing with Camp’s criterion obtained as a result of the analysis of the modes of movement in pipelines from the fast filter to the settling facility for the treatment of rinse water, as well as under conditions of additional mixing inside the treatment facilities either by stirrers or by aeroflocculation. Based on the analysis of the results of water clarification under the conditions of reagent-free sedimentation with stirring, mathematical dependences of the clarification effect on the Camp’s criterion, water temperature, initial content of suspended solids and clarification time were obtained. 10.34910/MCE.111.7 628.168 spent filter backwash water precipitation mixing treated water water recycling coagulation https://engstroy.spbstu.ru/article/2022.111.7/
RAR RUS 11108-11108 0000-0002-0414-9051 Northeast Forestry University Zhang Hetong 2586762756@qq.com
Harbin, Heilongjiang, China
 0000-0002-5953-8919 Harbin Dongan Automobile Engine Manufacturing Co. Wang Jianwu nihaone@163.com
Harbin, Heilongjiang, China
 55516020800 Northeast Forestry University Zhao Qianqian 492954791@qq.com
Harbin Heilongjiang, China
 Northeast Agricultural University Fu Qiang fuqiang0629@126.com
Harbin Heilongjiang, China
 Performance improvement model of cement pavement in seasonal-frost regions The paper evaluates the performance improvement of cement pavement in seasonal frost regions. The typical diseases of cement concrete pavements in seasonal frost regions are proposed through the analysis of measured data, and the influence factors of pavement performance mutation value in those regions is determined. The application conditions of the model are obtained by the response surface test method; the road performance improvement model is established by the regression analysis method. The goodness-of-fit and significance state of the model were tested, while the validity of the model was verified by comparing it with the evaluation results of the existing model. The results identified the typical diseases of cement concrete pavement in seasonal frost regions: broken slabs, staggered platforms, cracks, exposed aggregates, broken corners and potholes. The mutation value of pavement performance is most sensitive to the impact of road damage index, running quality index and anti-skid performance index before pre-maintenance, that is under pre-curing conditions. The evaluation effect of the model for improving the performance of cement concrete pavement in seasonal frost regions is good, and the interpretable part of the improvement by the model is 99.2 %; the fit of the improved evaluation value and the measured value is 0.991, and the model is high fitting. The evaluation effect of the proposed model is better than the existing model, and the determination of the model is of great significance to the pre-maintenance of cement concrete pavement. 10.34910/MCE.111.8 625 concrete pavement management numerical model regression analysis maintenance strategy https://engstroy.spbstu.ru/article/2022.111.8/
RAR RUS 11109-11109 Russian Scientific Research Institute of Land Improvement Problems Silchenko Victoria vika-silchenko@mail.ru
Novocherkassk, Russia
 Russian Scientific Research Institute of Land Improvement Problems Baev Oleg Oleg-Baev1@yandex.ru Russian Scientific Research Institute of Land Improvement Problems Kosichenko Yuri kosichenko-11@mail.ru Effect of subsoil moisture on filtration through a screen defect The aim of the scientific work is to study the features of filtration under a defect of a polymer screen made of a geomembrane, where the movement of the filtration flow occurs with incomplete saturation of the soil with water. According to the results of experimental studies, local filtration is formed on the filtration tray under the screen defect with incomplete saturation of the soil with water, caused by the action of capillary forces and the presence of trapped air. The article presents the results of studies of a model of a polymer screen with a defect in the form of a slit with a relative width of 0.005 to 0.5. On the basis of studies in a soil flume and experimental pits with film screens, the average moisture content for sandy and loamy soil was established directly under the screen defect. According to the results of the calculations performed, the piezometric pressure along the screen slit significantly decreases with an increase in the permeability of the screen base and reaches negative values at relatively large values ​​of the slit width. The filtration flow through the slit increases with an increase in the permeability of the base soil, and the width of the spreading zone of the filtration flow under the screen decreases. The urgency of solving this problem is due to insufficient study of the influence of moisture saturation of the base soil on filtration through a screen defect. 10.34910/MCE.111.9 626.823.91 polymer geocomposite material filtration hydration numerical model coating https://engstroy.spbstu.ru/article/2022.111.9/
RAR RUS 11110-11110 0000-0002-1383-1271 Samara State Technical University Panfilova Olga samoliasgsy@yandex.ru
Samara, Russia
 57191170562 0000-0002-9139-680X Samara State Technical University Stepanov Sergey stepanovsv3@yandex.ru
Samara, Russia
 56966432300 0000-0002-0419-4231 Samara State Technical University Strelkov Alexander a19400209@yandex.ru
Samara, Russia
 Removal of heavy metals from wastewater with natural and modified sorbents The paper presents research results of heavy metal ions sorption from a model solution and wastewater of an electroplating enterprise under static conditions. The purpose of this work is to develop a technology of tertiary treatment of electroplating production wastewater from heavy metals to achieve MPC levels for fresh fishery water bodies using local powder sorption materials. The authors examined such sorbents as modified clay (MC) obtained by thermal modification of its natural components (montmorillonite, kaolinite, peat, dolomite), as well as certain primary components and their mixtures without thermal modification. The studies were conducted at low initial concentrations of heavy metals (from 0.002 to 2.8 mg/l) characteristic of wastewater subjected to tertiary treatment. The concentration of heavy metals in wastewater was determined by inductively coupled plasma optical emission spectrometry on Avio™ 200. The research demonstrated that the contact time required to achieve the equilibrium of the treated wastewater and the modified clay sorbent varied from 60 to 120 minutes for the investigated heavy metals. Taking into account the time required to reach the MPCs of heavy metals for fresh fishery water bodies, the estimated contact duration of 90 minutes was recommended. The calculated dose of the modified clay sorbent, sufficient for tertiary treatment of acid-base wastewater of electroplating production to the MPC, was 1 g/l. Experiments with unmodified materials conducted on a multicomponent model solution showed that montmorillonite had the best sorption properties, ensuring the achievement of MPC for all metals, except aluminum, at doses from 0.1 to 0.9 g/l. Peat was the most effective in extracting nickel to MPC with its estimated dose being 0.1 g/l. Dolomite turned out to be the only material that provided the removal of aluminum to MPC at a dose of 1 g/l. The obtained results suggest that it is possible to increase the efficiency of heavy metals removal by selecting sorbent mixture without thermal modification and with mixed sorbent dose of 1–1.6 g/l. The authors recommend a technology of tertiary treatment of acid-base wastewater of electroplating production. This technology is to carry out the sorption process under static conditions using powder sorbents based on local natural materials, followed by separation of the spent sorbent with a precoat cartridge filter. 10.34910/MCE.111.10 628.316 water adsorption heavy metals wastewater modified clay montmorillonite dolomite kaolinite peat https://engstroy.spbstu.ru/article/2022.111.10/
RAR RUS 11111-11111 Riga Technical University Ratnika Lasma lasma.ratnika@rtu.lv
Riga, Latvia
 55359846700 0000-0002-7292-0821 Riga Technical University Gaile Liga liga.gaile_1@rtu.lv
Riga, Latvia
 H-5843-2013 57205122537 0000-0002-8367-7927 Riga Technical University Pakrastins Leonids leonids.pakrastins@rtu.lv Structural health monitoring by merging dynamic response data The process of Structural Health Monitoring aims to detect changes in material and/or geometric properties, boundary conditions or member connectivity of a structural system in time. However, the transfer of research results into engineering practice poses several challenges, especially for stiff structures with very diverse geometry that could not be well dynamically exited like low and medium-rise structures under ambient vibration conditions. Noise in modal parameters from output-only modal analysis due to variable environmental and operational conditions is considered one of the most problematic aspects of detecting structural damage using a vibration-based method. This research proposes a new way to reduce environmental noise in vibration data and dynamic parameters by merging dynamic response data from two similar shear wall buildings. The object of the study is a three-story reinforced concrete building. First, the damage features as natural frequencies and zero-order temporal moment of the vibration response are studied. Further, those feature changes are explored by means of modelling wall removal/opening introduction into the finite element models. It is established that the variation in the base excitation spectrum has more impact on dynamic response than introduced structural changes. Therefore, a time-domain feature like a zero-order temporal moment of the vibration response is not applicable for the proposed method. The appropriate damage sensitive feature vector for this approach is the difference of natural frequencies from two monitored buildings. The proposed method for fusion of vibration information from several buildings that share the same environmental and operational conditions filter out environmental noise effectively and give a clear advantage in reducing false alarm possibility during continuous and automated structural health monitoring process. 10.34910/MCE.111.11 69.059.4 structural health monitoring modal analysis damage detection finite element method dynamic response natural frequencies structural analysis temperature vibration analysis structural dynamics buildings https://engstroy.spbstu.ru/article/2022.111.11/
RAR RUS 11112-11112 57210564892 0000-0001-5292-7295 Peter the Great St. Petersburg Polytechnic University Shonina Ekaterina shonina_ev@spbstu.ru
St. Petersburg, Russia
 6507403952 Peter the Great St. Petersburg Polytechnic University Bolshev Аleksandr bolshev_as@spbstu.ru
29 Politechnicheskaya St., St. Petersburg, 195251, Russia
 7102906681 0000-0002-1811-7712 Peter the Great St. Petersburg Polytechnic University Frolov Sergey frolov_sa@spbstu.ru
St. Petersburg, Russia
 Mooring system optimization for marine floating hydrotechnical structures Existing offshore areas require development and mining using floating structures. The article presents design issues and settings of anchor mooring systems for marine floating structures. Improving and optimization methods for mooring systems, presented in publications of Russian and foreign authors, are discussed. The parameters influencing the safety of floating marine structures operation are identified. The parameters that are advisable to take as criteria are discussed. The restrictions imposed on non-criteria parameters are considered. The optimization criterion of the marine floating structures mooring systems in extreme operating modes is formulated. An optimization method for mooring systems is suggested in accordance with the proposed criterion. The study gives an example of mooring system optimization in the storm mode for a platform operated in ice-free seas. A similar methodology can be used for mobile ice-resistant platforms, conceptual variants of which are being developed for operation in Arctic conditions.  Research results were obtained by the method of mathematical modeling. 10.34910/MCE.111.12 629.563.2:004.942:626/627 offshore structure mooring system multi-objective optimization penalty function method optimization semi-submersible platform mooring tension force method of golden section https://engstroy.spbstu.ru/article/2022.111.12/
RAR RUS 11113-11113 Irkutsk National Research Technical University Kuz'mina Marina kuzmina.my@yandex.ru Irkutsk National Research Technical University Kuz'mina Alina zhuravlyova-alina@yandex.ru 0000-0003-0685-0420 Shenzhen University Ran Jia Q ranjiaqi26@gmail.com
Shenzhen, China
 Irkutsk State Technical University Burdonov Aleksandr slimbul@rambler.ru 57056173700 0000-0003-4414-0307 Irkutsk State Transport University Zenkov Evgeniy jovanny1@yandex.ru
Irkutsk, Russia
 Irkutsk National Research Technical University Kuz'min Mikhail Mike12008@yandex.ru Irkutsk National Research Technical University Larionov Leonid larionov59@rambler.ru Production of Portland cement using fluorine gypsum – hydrofluoric acid waste Introduction. The purpose of the research was to explore the possibility of making PC400–D20 Portland cement, as the gypsum stone was replaced with fluorogypsum during the milling process. The study deals with physical and mechanical properties of Portland cement obtained by mixing milled Portland cement clinker, fly ash (consisting of nanosized particles of SiO2 and Al2O3) and sulphate additives (gypsum stone or fluorogypsum). Methods. In accordance with the quality indicators set by Russian State Standard GOST 4913–82 (EN 13279–2), Angarsk Electrolysis Chemical Plant (JSC AECP) fluorogypsum is significantly superior to the gypsum stone mined in the Nukutsky Gypsum Quarry (Irkutsk Region). The use of high-quality fluorite concentrate in the production of the hydrofluoric acid can be accounted for exceptional characteristics of fluorogypsum found at the sludge fields of JSC AECP. Results and Discussion. The composition of sludge fields of Angarsk Electrolysis Chemical Plant has been investigated. The quality of its main component, fluorogypsum, has been determined with accredited classification. The studies of chemical composition and physical properties of fluorogypsum deposited at the sludge fields of JSC AECP proved that it can serve as a first-grade raw material in accordance with Russian State Standard GOST4913–82 for the production of high-grade gypsum. Laboratory tests confirmed the practicability of using fluorogypsum as a substitute for natural gypsum stone in cement production process (when grinding cement clinker). A technology and parameters for the production of high-grade gypsum production from the fluorogypsum have been developed. Conclusions. Laboratory tests confirmed the possibility of using fluorogypsum as a setting regulator in cement production when grinding cement clinker. The exact quantity of fluorogypsum when grinding cement clinker was determined, which ensures the production of high-quality cement in compliance with Russian State Standard GOST 10187–85. The prospects of using fluorogypsum as a raw material for the production of high-quality gypsum as well as a wide range of building mixtures based on it has been identified. 10.34910/MCE.111.13 691.3, 628.51, 661.25 gypsum fluorogypsum concrete by product waste management gypsum stone Portland cement clinker microstructure https://engstroy.spbstu.ru/article/2022.111.13/
RAR RUS 11114-11114 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University "Moscow Power Engineering Institute" Kirsanov Mikhail mpei2004@yandex.ru
14, Krasnokazarmennaya, 111250 Moscow, Russia
 0000-0002-3780-2838 Voronezh State Technical University, Voronezh, Russia Safronov Vladimir vss22@mail.ru
Voronezh, Russia
 Analytical estimation of the first natural frequency and analysis of a planar regular truss oscillation spectrum A statically determinate truss of a beam type with a triple lattice with short descending and long ascending braces is considered. The mass of a truss is modeled by concentrated loads at its nodes. For the first natural frequency, the Dunkerley’s method derives a formula for the dependence of its lower boundary on the number of panels. The calculation of the efforts in the truss required to obtain the stiffness value according to the Maxwell-Mohr formula is performed in the Maple computer mathematics system by cutting out the nodes. It is shown that for a certain number of panels the proposed scheme of the truss has the property of kinematic variability. For admissible numbers of panels, by induction, the sequence of solutions for trusses with different numbers of panels is generalized to an arbitrary case. The coefficients of the required dependence are obtained as solutions of linear homogeneous recurrent equations. To obtain and solve recurrent equations, the operators of the Maple system are used. The found solution is compared with the minimum frequency of the spectrum obtained numerically. It is shown that the accuracy of the analytical assessment monotonically increases with the increase in the number of panels. Multiple frequencies and the independence of several higher frequencies from the number of panels were found in the frequency spectrum. 10.34910/MCE.111.14 624.04:531.391.3 truss natural vibrations lower frequency estimate vibration spectrum kinematic variability Dunkerley’s method https://engstroy.spbstu.ru/article/2022.111.14/
RAR RUS 11115-11115 57195684636 0000-0001-8800-2657 Voronezh State Technical University Slavcheva Galina gslavcheva@yandex.ru 57197819710 0000-0002-0462-4991 Voronezh State Technical University Britvina Ekaterina
Voronezh, Russia
 3D-printable artificial marble This paper presents the rheological and hardened properties of novel 3D-printable materials imitating structures of marble. The effects of mixed proportion on rheological behavior, kind of texture, setting time, density, compressive strength, water absorption, drying shrinkage, frost resistance are presented together. Two kinds of squeezing tests were used to evaluate the extrusion ability and shape stability of the fresh mixture. A high compression speed test using constant plate speed of 5 mm/s was implemented to simulate the behavior of the system in the process of extrusion. The squeezing test was conducted with a constant strain rate of 0.5 N/s as to model the behavior of the system in the process of multi-layer casting. Properties of the 3D-printable artificial marble were determined by Russian standards. The fresh mixtures of 3D-printable artificial marbles had plastic yield value of 1.2–3.5 kPa, structural strength of 1.2–3.3 kPa, the value of plastic deformations was 0.05–0.06 mm/mm. This defined the ability of these mixtures to plastically deform without structure destruction and hold their form, resist the deformation under compressions load during multi-layer casting. The received specimens of artificial marble resemble six kinds of textures of white and color marble. The 3D-printable artificial marble had high compressive strength (36–48 MPa and 55–68 MPa at 1 day and 28 days after production respectively), low water absorption (0.75 %), drying shrinkage (1.3–1.9 mm/m), high frost resistance and short setting time that determine the effectiveness of 3D-printed structures life cycle. 10.34910/MCE.111.15 666.9.03 additive manufacturing 3d-printable material rheological behavior compressive strength setting time https://engstroy.spbstu.ru/article/2022.111.15/