Pub Date : 2024-03-15DOI: 10.22363/1815-5235-2024-20-1-27-39
R. Kiseleva, Natalia A. Kirsanova, A. Nikolaev, Yu. V. Klochkov, Vitaliy V. Ryabukha
For describing elastoplastic deformation, three versions of constitutive equations are used. The first version employs the governing equations of the flow theory. In the second version, elastic strain increments are defined the same way as in the flow theory, and the plastic strain increments are expressed in terms of stress increments using the condition of their proportionality to the components of the incremental stress deviator tensor. In the third version, the constitutive equations for a load step were obtained without using the hypothesis of separating strains into the elastic and plastic parts. To obtain them, the condition of proportionality of the components of the incremental strain deviator tensor to the components of the incremental stress deviator tensor was applied. The equations are implemented using a hybrid prismatic finite element with a triangular base. A sample calculation shows the advantage of the third version of the constitutive equations.
{"title":"Mixed FEM for Shells of Revolution Based on Flow Theory and its Modifications","authors":"R. Kiseleva, Natalia A. Kirsanova, A. Nikolaev, Yu. V. Klochkov, Vitaliy V. Ryabukha","doi":"10.22363/1815-5235-2024-20-1-27-39","DOIUrl":"https://doi.org/10.22363/1815-5235-2024-20-1-27-39","url":null,"abstract":"For describing elastoplastic deformation, three versions of constitutive equations are used. The first version employs the governing equations of the flow theory. In the second version, elastic strain increments are defined the same way as in the flow theory, and the plastic strain increments are expressed in terms of stress increments using the condition of their proportionality to the components of the incremental stress deviator tensor. In the third version, the constitutive equations for a load step were obtained without using the hypothesis of separating strains into the elastic and plastic parts. To obtain them, the condition of proportionality of the components of the incremental strain deviator tensor to the components of the incremental stress deviator tensor was applied. The equations are implemented using a hybrid prismatic finite element with a triangular base. A sample calculation shows the advantage of the third version of the constitutive equations.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"11 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140240924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.22363/1815-5235-2024-20-1-40-56
S. Krivoshapko
The information about main results on geometry of developable surfaces with an edge of regression which have a directrix ellipse in the base is gathered. These surfaces constitute a group called “Ruled surfaces of conical type on elliptical base”. This group includes elliptical cones, torses with two ellipses defined in the parallel planes, equal slope surfaces, and ruled surfaces with the main frame of three superellipses that are ellipses in one coordinate plane and broken straight lines in the other two coordinate planes. The paper presents a method for developing torses onto a plane, approximation of torses by folded surfaces, and parabolic ending of a thin sheet from elastic material into a torse shell. A brief review of the methods of stress-strain and buckling analysis of the considered ruled shells is given, including the displacement-based finite element method and variational energy method. It is shown that analytical methods can be used only in the case of applying the momentless shell theory for ruled thin shells of conical type. The analytical formulae for determining the normal and tangent internal forces in any momentless conic shell with a superellipse in the base are derived. References to forty four scientific articles of other authors, working or having worked on the subject of the paper are given. These references confirm the conclusions of the author and the perspectives of investigations of the considered ruled surfaces and shells.
{"title":"Ruled Shells of Conical Type on Elliptical Base","authors":"S. Krivoshapko","doi":"10.22363/1815-5235-2024-20-1-40-56","DOIUrl":"https://doi.org/10.22363/1815-5235-2024-20-1-40-56","url":null,"abstract":"The information about main results on geometry of developable surfaces with an edge of regression which have a directrix ellipse in the base is gathered. These surfaces constitute a group called “Ruled surfaces of conical type on elliptical base”. This group includes elliptical cones, torses with two ellipses defined in the parallel planes, equal slope surfaces, and ruled surfaces with the main frame of three superellipses that are ellipses in one coordinate plane and broken straight lines in the other two coordinate planes. The paper presents a method for developing torses onto a plane, approximation of torses by folded surfaces, and parabolic ending of a thin sheet from elastic material into a torse shell. A brief review of the methods of stress-strain and buckling analysis of the considered ruled shells is given, including the displacement-based finite element method and variational energy method. It is shown that analytical methods can be used only in the case of applying the momentless shell theory for ruled thin shells of conical type. The analytical formulae for determining the normal and tangent internal forces in any momentless conic shell with a superellipse in the base are derived. References to forty four scientific articles of other authors, working or having worked on the subject of the paper are given. These references confirm the conclusions of the author and the perspectives of investigations of the considered ruled surfaces and shells.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"36 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140237427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.22363/1815-5235-2024-20-1-14-26
E. Lebed
Investigation of the stress state of the metal frame of a ribbed-ring dome, when the number of supporting columns under it is gradually reduced. With that, the same distances or steps between the columns are maintained along the entire contour of the support ring. The main elements of the dome frame and columns are made of steel I-beams. Frames, the domes of which are supported by a different number of cyclically symmetrical columns, were considered as subjects of research. All the domes are characterized by the same geometric structure and size, the same cross sections of the same type of frame elements and are exposed to the same loads. The research was carried out on computer models by calculating the combined effect of the load from the weight of load-bearing and enclosing structures and an asymmetric snow load. The models with a reduced number of columns are obtained by regularly removing them from the original computer model. During the analysis, the stresses in the elements of the frames of all models were determined, which were compared with each other. Deformation graphs and comparative diagrams of the stress state relationships of the frame elements of the original and transformed models are obtained. An assessment of the change in the stress state of the ribbed-ring dome frame with a decrease in the number of columns is given. Significant changes in the stress state of the support ring were noted.
{"title":"Behavior of Metal Frame of Ribbed-ring Dome with Decrease in Number of Supporting Columns","authors":"E. Lebed","doi":"10.22363/1815-5235-2024-20-1-14-26","DOIUrl":"https://doi.org/10.22363/1815-5235-2024-20-1-14-26","url":null,"abstract":"Investigation of the stress state of the metal frame of a ribbed-ring dome, when the number of supporting columns under it is gradually reduced. With that, the same distances or steps between the columns are maintained along the entire contour of the support ring. The main elements of the dome frame and columns are made of steel I-beams. Frames, the domes of which are supported by a different number of cyclically symmetrical columns, were considered as subjects of research. All the domes are characterized by the same geometric structure and size, the same cross sections of the same type of frame elements and are exposed to the same loads. The research was carried out on computer models by calculating the combined effect of the load from the weight of load-bearing and enclosing structures and an asymmetric snow load. The models with a reduced number of columns are obtained by regularly removing them from the original computer model. During the analysis, the stresses in the elements of the frames of all models were determined, which were compared with each other. Deformation graphs and comparative diagrams of the stress state relationships of the frame elements of the original and transformed models are obtained. An assessment of the change in the stress state of the ribbed-ring dome frame with a decrease in the number of columns is given. Significant changes in the stress state of the support ring were noted.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"71 S2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140238558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.22363/1815-5235-2024-20-1-3-13
Alexander D. Beglov, R. Sanjarovskiy, T. Ter-Emmanuilyan
The important features of the theory of creep of reinforced concrete, identified and published earlier, are explored. The creation and development of the theory of creep of reinforced concrete is based on non-scientific principles take from systems of classical mechanics that do not correspond to this theory. A detailed analysis of the theory used in many countries was performed, while five oversimplifications were identified that reject fundamental experiments, Eurocodes, rules of mathematics and mechanics: listed in the law of creep, oversimplifications that grossly distort the calculation results, not only the deformations themselves, but also subsequent methods for calculating reinforced concrete structures. These include: unnecessarily modified classical Hooke’s law; imposing a property missing from concrete - an algebraic measure of creep; erroneous superposition principle; use of viscoelastic deformations instead of instantaneous nonlinear plastic deformations; replacement of obvious - nonlinear and non-stationary properties of concrete with linear ones, distorting the qualitative side of phenomena inherent only in nonlinear systems. These errors are covered by unreasonable safety factors, which undermines the economic component of the problem, and of the enormous volumes of reinforced concrete used throughout the world, the analyzed unscientific theory of its calculation causes enormous economic damage in global construction.
{"title":"Modern Theory of Creep of Reinforced Concrete","authors":"Alexander D. Beglov, R. Sanjarovskiy, T. Ter-Emmanuilyan","doi":"10.22363/1815-5235-2024-20-1-3-13","DOIUrl":"https://doi.org/10.22363/1815-5235-2024-20-1-3-13","url":null,"abstract":"The important features of the theory of creep of reinforced concrete, identified and published earlier, are explored. The creation and development of the theory of creep of reinforced concrete is based on non-scientific principles take from systems of classical mechanics that do not correspond to this theory. A detailed analysis of the theory used in many countries was performed, while five oversimplifications were identified that reject fundamental experiments, Eurocodes, rules of mathematics and mechanics: listed in the law of creep, oversimplifications that grossly distort the calculation results, not only the deformations themselves, but also subsequent methods for calculating reinforced concrete structures. These include: unnecessarily modified classical Hooke’s law; imposing a property missing from concrete - an algebraic measure of creep; erroneous superposition principle; use of viscoelastic deformations instead of instantaneous nonlinear plastic deformations; replacement of obvious - nonlinear and non-stationary properties of concrete with linear ones, distorting the qualitative side of phenomena inherent only in nonlinear systems. These errors are covered by unreasonable safety factors, which undermines the economic component of the problem, and of the enormous volumes of reinforced concrete used throughout the world, the analyzed unscientific theory of its calculation causes enormous economic damage in global construction.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"1 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140241269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.22363/1815-5235-2024-20-1-57-72
Z. Abaev, Faiz Sulthan
The methodology for seismic performance evaluation of a residential building in Indonesia with the use of seismic isolation is considered. An 8-storey reinforced concrete frame residential building with shear wall structural system was selected as a case study. Nonlinear methods of seismic response analysis were used to calculate the response of the structure: nonlinear static (Pushover) and Nonlinear-Time History Analysis, NLTHA. The analysis is performed in STERA 3D freeware. The nonlinear time history analysis was performed for seven pairs of horizontal components of earthquake ground motions, selected according to the parameters of possible earthquakes for the considered site (Bandung city). The selected earthquake records were modified using the spectral matching procedure for design spectrum. Friction-pendulum bearings developed by Nippon Steel Corporation of Japan were used as seismic isolation. The results of nonlinear time history analysis show that shallow earthquakes result in greater damage compared to megathrust earthquakes, with both scenarios providing a life safety (LS) performance level. The use of seismic isolation can reduce seismic loads, as evidenced by the reduction in top-level accelerations and shear forces at the base.
本研究考虑了对印度尼西亚一栋采用隔震措施的住宅楼进行抗震性能评估的方法。案例研究选择了一栋采用剪力墙结构系统的 8 层钢筋混凝土框架住宅楼。采用非线性地震反应分析方法计算该结构的反应：非线性静力分析（Pushover）和非线性时间历史分析（NLTHA）。分析在 STERA 3D 免费软件中进行。非线性时间历史分析是针对地震地面运动的七对水平分量进行的，这些分量是根据考虑地点（万隆市）可能发生的地震参数选定的。所选地震记录使用设计频谱的频谱匹配程序进行了修改。日本新日铁公司开发的摩擦摆支座被用作隔震材料。非线性时间历程分析结果表明，浅源地震比大地壳地震造成的破坏更大，两种情况下都能达到生命安全（LS）性能水平。使用隔震措施可以减少地震荷载，这体现在顶部加速度和底部剪切力的减少上。
{"title":"Seismic Performance Evaluation of Multi-Storey Residential Building with Friction Pendulum Bearings: Indonesia case study","authors":"Z. Abaev, Faiz Sulthan","doi":"10.22363/1815-5235-2024-20-1-57-72","DOIUrl":"https://doi.org/10.22363/1815-5235-2024-20-1-57-72","url":null,"abstract":"The methodology for seismic performance evaluation of a residential building in Indonesia with the use of seismic isolation is considered. An 8-storey reinforced concrete frame residential building with shear wall structural system was selected as a case study. Nonlinear methods of seismic response analysis were used to calculate the response of the structure: nonlinear static (Pushover) and Nonlinear-Time History Analysis, NLTHA. The analysis is performed in STERA 3D freeware. The nonlinear time history analysis was performed for seven pairs of horizontal components of earthquake ground motions, selected according to the parameters of possible earthquakes for the considered site (Bandung city). The selected earthquake records were modified using the spectral matching procedure for design spectrum. Friction-pendulum bearings developed by Nippon Steel Corporation of Japan were used as seismic isolation. The results of nonlinear time history analysis show that shallow earthquakes result in greater damage compared to megathrust earthquakes, with both scenarios providing a life safety (LS) performance level. The use of seismic isolation can reduce seismic loads, as evidenced by the reduction in top-level accelerations and shear forces at the base.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140239756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.22363/1815-5235-2023-19-3-261-275
Vladimir I. Kolchunov
Based on a comprehensive analysis of the experimental studies from the standpoint of their convergence with the theoretical solutions, the computational models of resistance (CMR) of reinforced concrete are proposed. These models include CMR1 - modeling of normal cracks, CMR2 - modeling of inclined cracks, CMR3 - modeling of diagonal cracks, CMR4 - modeling of intersecting cracks in the wall, CMR4* - modeling of cracks in a flat slab, and CMR5 - modeling of spatial cracks in torsion with bending, CMR5* - modeling of spatial cracks in bending with transverse force. Also, a hierarchy of computational models of the second and third levels is proposed. The distribution of intensity of working reinforcement along the cross-section of the calculated element was obtained in an analytical form by creating closed equations of blocks, corresponding to the blocks of the reinforced concrete element under the condition of equality to zero of partial derivatives of the Lagrange function to determine the maximum crack opening width. It is considered the effect proposed by the author on the additional deformation impact of the reaction “concrete - reinforcement” from the discontinuity of concrete during the formation of the crack by means of a special model of the two-cantilever element of fracture mechanics. Hypotheses about the distribution of linear and angular deformations during cross-section with account of gradients of deformations caused by formation of cracks were formulated for a complex-stressed element subjected to torsion with bending. Crack opening is defined as mutual displacements of reinforcement and concrete, taking into account deformation. The consolidation of substructures in the building system is performed by the method of initial parameters.
{"title":"Method of computational models of resistance for reinforced concrete","authors":"Vladimir I. Kolchunov","doi":"10.22363/1815-5235-2023-19-3-261-275","DOIUrl":"https://doi.org/10.22363/1815-5235-2023-19-3-261-275","url":null,"abstract":"Based on a comprehensive analysis of the experimental studies from the standpoint of their convergence with the theoretical solutions, the computational models of resistance (CMR) of reinforced concrete are proposed. These models include CMR1 - modeling of normal cracks, CMR2 - modeling of inclined cracks, CMR3 - modeling of diagonal cracks, CMR4 - modeling of intersecting cracks in the wall, CMR4* - modeling of cracks in a flat slab, and CMR5 - modeling of spatial cracks in torsion with bending, CMR5* - modeling of spatial cracks in bending with transverse force. Also, a hierarchy of computational models of the second and third levels is proposed. The distribution of intensity of working reinforcement along the cross-section of the calculated element was obtained in an analytical form by creating closed equations of blocks, corresponding to the blocks of the reinforced concrete element under the condition of equality to zero of partial derivatives of the Lagrange function to determine the maximum crack opening width. It is considered the effect proposed by the author on the additional deformation impact of the reaction “concrete - reinforcement” from the discontinuity of concrete during the formation of the crack by means of a special model of the two-cantilever element of fracture mechanics. Hypotheses about the distribution of linear and angular deformations during cross-section with account of gradients of deformations caused by formation of cracks were formulated for a complex-stressed element subjected to torsion with bending. Crack opening is defined as mutual displacements of reinforcement and concrete, taking into account deformation. The consolidation of substructures in the building system is performed by the method of initial parameters.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"170 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135039361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.22363/1815-5235-2023-19-3-276-284
Leonid Yu. Stupishin, Konstantin E. Nikitin, Maria L. Moshkevich
Solving of calculation problems for building structures is currently based on the principle of minimum total energy of structures deformation. However, it is not possible to determine the remaining bearing capacity of the structure using this principle. In the study it is proposed to use the criterion of critical levels of deformation energy to solve this problem. As a result, the ultimate state conditions of a design are formulated on the basis of extreme values of generalized parameters of designing over the whole area of their admissible values, including the boundary. The task is solved as a problem of eigenvalues for the stiffness matrix of the system. The extreme values of design parameters that correspond to critical energy levels are found, which are used to find the maximum possible value of the energy of deformation for the considered structure. The residual bearing capacity is calculated by the value of residual potential energy, which, in turn, is equal to the difference between the maximum possible value of the deformation energy of the structure and the work of external forces. A gradual methodology for investigating the progressive ultimate limit state is proposed, which is based on the sequential exclusion of those elements where the onset of the ultimate limit state is expected firstly. An example of the practical use of the proposed methods is given on the example of calculating a simple but visual design - a statically indeterminate truss.
{"title":"Methodology for determining progressing ultimate states based on the displacement method","authors":"Leonid Yu. Stupishin, Konstantin E. Nikitin, Maria L. Moshkevich","doi":"10.22363/1815-5235-2023-19-3-276-284","DOIUrl":"https://doi.org/10.22363/1815-5235-2023-19-3-276-284","url":null,"abstract":"Solving of calculation problems for building structures is currently based on the principle of minimum total energy of structures deformation. However, it is not possible to determine the remaining bearing capacity of the structure using this principle. In the study it is proposed to use the criterion of critical levels of deformation energy to solve this problem. As a result, the ultimate state conditions of a design are formulated on the basis of extreme values of generalized parameters of designing over the whole area of their admissible values, including the boundary. The task is solved as a problem of eigenvalues for the stiffness matrix of the system. The extreme values of design parameters that correspond to critical energy levels are found, which are used to find the maximum possible value of the energy of deformation for the considered structure. The residual bearing capacity is calculated by the value of residual potential energy, which, in turn, is equal to the difference between the maximum possible value of the deformation energy of the structure and the work of external forces. A gradual methodology for investigating the progressive ultimate limit state is proposed, which is based on the sequential exclusion of those elements where the onset of the ultimate limit state is expected firstly. An example of the practical use of the proposed methods is given on the example of calculating a simple but visual design - a statically indeterminate truss.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135039364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.22363/1815-5235-2023-19-3-329-336
David Cajamarca-Zuniga, Oleg Vasil'evich Kabantsev, Daniel Campos
In Ecuador, about 95.9% of dwellings are built with masonry, however the local production of bricks does not meet technical standards and there is no scientific research on its geometric characterization and the technical state of their production. The geometric characterization of bricks is essential for the standardization of materials and constructions and allows the design of structures with a higher degree of accuracy. This research, conducted in 12 provinces of the 3 continental regions of the country, where 79% of the buildings are concentrated, studies for the first time the geometric characteristics of solid clay bricks in Ecuador. The results show that 67% of the brick production in Ecuador is artisanal and 98% of the factories do not comply with the technical standards for brick production. The authors present the characteristic dimensions of solid bricks produced in different regions of Ecuador. The results show a high variation in brick dimensions depending on the region, and even in a same province the dimensions depend on the factory, since its production does not comply with any standard. Ecuadorian standards regulating brick geometry need to be updated taking into account the real characteristics of the national brick production.
{"title":"Geometric characterization of solid ceramic bricks for construction in Ecuador","authors":"David Cajamarca-Zuniga, Oleg Vasil'evich Kabantsev, Daniel Campos","doi":"10.22363/1815-5235-2023-19-3-329-336","DOIUrl":"https://doi.org/10.22363/1815-5235-2023-19-3-329-336","url":null,"abstract":"In Ecuador, about 95.9% of dwellings are built with masonry, however the local production of bricks does not meet technical standards and there is no scientific research on its geometric characterization and the technical state of their production. The geometric characterization of bricks is essential for the standardization of materials and constructions and allows the design of structures with a higher degree of accuracy. This research, conducted in 12 provinces of the 3 continental regions of the country, where 79% of the buildings are concentrated, studies for the first time the geometric characteristics of solid clay bricks in Ecuador. The results show that 67% of the brick production in Ecuador is artisanal and 98% of the factories do not comply with the technical standards for brick production. The authors present the characteristic dimensions of solid bricks produced in different regions of Ecuador. The results show a high variation in brick dimensions depending on the region, and even in a same province the dimensions depend on the factory, since its production does not comply with any standard. Ecuadorian standards regulating brick geometry need to be updated taking into account the real characteristics of the national brick production.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135039363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.22363/1815-5235-2023-19-3-313-321
Lev M. Dobshits
The key factor of engineering structures made of concrete and reinforced concrete is insufficient frost resistance of concretes. It is important to identify the causes and prevent concrete damage caused by frost. The research provides the basic points of the developed physical and mathematical theory of cement concretes frost resistance. Under consideration are the processes occurring during cyclic freezing and thawing of concrete in a water-saturated state. The results of the performed theoretical and experimental studies are presented. The criterion of concrete frost resistance, which estimates the pore structure of concrete, was derived on the basis of the obtained results. The suggested criterion has a close correlative relation with the frost resistance of concrete. Using this interrelation, the method was proposed for accelerated determination of actual frost resistance of concrete, as well as the method of selection concretes' compositions for a specified design frost resistance of concretes. The methods of accelerated determination of concrete frost resistance, as well as ways to increase it, are described. The developed physical and mathematical model was used to carry out computational modeling for freezing of an extended concrete structure. This made it possible to determine the changes in humidity, temperature, and pressure in concrete during cyclic freezing and thawing at different distances from the surface of its freezing and also draw graphs of changes in these parameters. The recommendations on assignment of concrete design grades by frost resistance for various elements of concrete and reinforced concrete structures are given.
{"title":"Physical and mathematical modeling of frost resistance for cement concretes","authors":"Lev M. Dobshits","doi":"10.22363/1815-5235-2023-19-3-313-321","DOIUrl":"https://doi.org/10.22363/1815-5235-2023-19-3-313-321","url":null,"abstract":"The key factor of engineering structures made of concrete and reinforced concrete is insufficient frost resistance of concretes. It is important to identify the causes and prevent concrete damage caused by frost. The research provides the basic points of the developed physical and mathematical theory of cement concretes frost resistance. Under consideration are the processes occurring during cyclic freezing and thawing of concrete in a water-saturated state. The results of the performed theoretical and experimental studies are presented. The criterion of concrete frost resistance, which estimates the pore structure of concrete, was derived on the basis of the obtained results. The suggested criterion has a close correlative relation with the frost resistance of concrete. Using this interrelation, the method was proposed for accelerated determination of actual frost resistance of concrete, as well as the method of selection concretes' compositions for a specified design frost resistance of concretes. The methods of accelerated determination of concrete frost resistance, as well as ways to increase it, are described. The developed physical and mathematical model was used to carry out computational modeling for freezing of an extended concrete structure. This made it possible to determine the changes in humidity, temperature, and pressure in concrete during cyclic freezing and thawing at different distances from the surface of its freezing and also draw graphs of changes in these parameters. The recommendations on assignment of concrete design grades by frost resistance for various elements of concrete and reinforced concrete structures are given.","PeriodicalId":32610,"journal":{"name":"Structural Mechanics of Engineering Constructions and Buildings","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135039365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.22363/1815-5235-2023-19-3-285-301
Fedor A. Pashchenko, Nikita S. Kharkov, Alexander A. Sidorenko, Valery V. Garbuzov
The compaction of the snow base of the wintering complex under construction of the Russian Antarctic station “Vostok” is considered, which was required due to the unsuitability of the natural snow base for the perception of loads from the supports of the foundation of the wintering complex. Technical solutions were developed for snow base compaction on the basis of heating by solar radiation with the use of thermal mat and on the basis of snow vacuuming. The computational justification of the developed technical solutions was performed, which was carried out based on spatial finite element models using the computational software complex ANSYS. In this case, to substantiate the method of snow base compaction by solar radiation heating with the use of thermal mat, the calculated volume was analyzed, including the snow base zone, thermal mat and the space filled with air. When substantiating the method of snow base compaction by snow vacuuming, there was explored the calculation area for modeling the method of vacuuming for the hermetic volume of the excavation pit with immersed columns under the wintering complex foundation supports. The results of the of the calculated research have fully confirmed the assumptions laid down in the technical solutions for compaction of the wintering complex snow base by using of thermal mat and snow vacuuming.
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