Строительство уникальных зданий и сооружений @unistroy
Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 849
Technical problems in churches in different climatic conditions
Статья научная
In buildings of cultural heritage, such as churches, it is quite difficult to ensure and to maintain the constant values of the indoor climate. Keeping a comfortable indoor environment throughout the year is a challenge due to special requirements for the preservation of the integrity of the interior decoration (frescoes, icons, stucco molding), strict canons to the exterior appearance, the presence of sharp peaks in the increase of hygrothermal parameters due to a peculiarly different number of visitors during church holidays compared to the rest of the year. Three churches described in this paper are situated in Russia and Latvia and despite different geographical position have similar problems: violation of the thermal insulation layer, problems with the provision of heat and humidity mode of condensation. The paper suggests possible ways of monitoring the state of the indoor climate of churches and possible solutions for its maintenance.
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Tekla Structures – инновация для создания конструкций
Статья научная
В статье рассказывается о программном комплексе Tekla Structures, предоставляющем большие возможности для проектирования любых видов зданий и сооружений.Он позволяет создавать детальные BIM модели, помогая инженерам принимать более обоснованные решения о конструкции и интегрировать процессы с раннего этапа разработки концепции и дизайна, до изготовления и монтажа.
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Tensile strength prediction method through compressive concrete cube test
Статья научная
The tensile strength of concrete is a crucial factor in civil engineering design of buildings and structures. Engineers are trying to find a new way to calculate tensile strength by using different characteristics in terms of the mechanical properties of concrete. This work aims to find the tensile strength through the apparent failure of cubic compression samples. In this way, the fracture angle, the diameter of the cubic sample, and the compressive strength were the factors most important in the tensile strength.
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The categorization of a country house
Статья научная
There are currently no methods of justification categories of suburban housing from an investment attractiveness of land in the Leningrad region. In addition, there is no classification of cottage settlements in Russia. This article provides an explanation of the link between the category of suburban housing and investment attractiveness of the land. The objectives of the study are the analysis of factors influencing investment attractiveness of land plots in Leningrad region; analysis of the factors influencing the category of suburban housing; justification competent relationships between these data. The article suggests recommendations for choosing the category of suburban housing, depending on the investment attractiveness of the land. People choose their house in a cottage settlement in accordance with their status and needs. The status of the cottage settlement directly depends on the investment attractiveness of the land on which it is built. The original characteristics of the land cannot radically change in the process of operation, and the house in this area can be significantly upgraded and modernized, the plot is largely a determining factor in the classification of suburban housing.
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Статья научная
The object of research is the thermal regime of a high-rise building (the Lakhta Center) equipped with modular double-skin facade structures with buffer zones. Method. A comprehensive approach was used, which included the development of a numerical model of the buffer zone and conducting field observations with the use of an actinometric station for accurate measurement of solar radiation parameters. Results. It was shown that solar radiation has a substantial impact on the building's thermal regime in the summer. The maximum recorded temperature in the buffer zone reached +54°C. The obtained results confirm the significant contribution of solar radiation to the heat and mass transfer processes within the buffer zone of a skyscraper with a transparent facade.
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The effective reinforcement ratio of expanded clay concrete by polypropylene fiber
Статья научная
The object of research is the dispersed reinforcement with polypropylene fiber of expanded clay concrete produced by using local raw materials. The purpose of this study is to select the optimal reinforcement ratio of expanded clay concrete containing polypropylene fiber. It is also proposed to investigate which variation of adding fiber is most effective (as an admixture with a constant content of the binding material or instead of cement mass). Method. Polymer fiber reinforcement should be added to the dry mix, thoroughly mix all the components and only then add water to the mix. In case of non-observance of this condition, it is impossible to achieve a homogeneous distribution of fiber in the hardened concrete, and therefore, the effect of disperse reinforcement will be reduced to zero. Results. As a result of investigations, special attention must be paid to the correct preparation technology at the time of concrete mixture preparation. Otherwise, the polymer fiber introduction will have a negative effect. In this case, the coarse aggregate use is a significant condition. The secant modulus of elasticity will decrease by more than two times if the diameter of expanded clay grains increases. It is recommended to use expanded clay gravel with smaller fractions in accordance with investigations. The maximum and minimum allowable content of polypropylene fiber are 0.5-1.5 %. The compressive cube strength increase of expanded clay concrete by polypropylene fiber is achieved by this allowable content in comparison with unreinforced expanded clay concrete with a similar concrete mixture. The most effective is reinforcement ratio of 1.5 %, and the maximum compressive strength increase by 14 %. The polypropylene fiber should be added in a percentage ratio depending on the cement mass with constant cement content in accordance with investigations. The fiber introduction instead of cement by mass negatively affects the strength characteristics.
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Статья научная
The object of the research is a planar, statically determinate girder of the beam type with a triple diagonal lattice.The truss mass is modeled by equal masses distributed over the nodes of the lower chord. By the Dunkerley method, under the assumption of vertical vibrations of loads, a lower analytical estimate of the first natural vibration frequency is obtained. Method. The forces in the members are calculated by cutting out nodes from the solution of a system of linear algebraic equations. Generalization of individual solutions to the case of an arbitrary number of panels is carried out by the induction method with the involvement of operators of the Maple computer mathematics system. Results. Comparison with the numerical solution found from the solution on the spectrum of natural vibrations of a multi-mass system shows that the estimation accuracy depends on the number of panels and varies from 16% for trusses with two panels to 4% for trusses with more than 11 panels. With a decrease in the ratio of the panel height to its length, the accuracy slightly increases. Based on the analysis of the derived formula, it is shown that the dependence of the first frequency on the height of the truss has a maximum. An algorithm for generalizing the solution to the case of members of different stiffness is proposed.
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The influence of the temperature and the structure of snow on the roof covering
Статья научная
Analysis of the highest snow load is important in the process of designing of a roof structure. It is also necessary to take into account a coefficient of snow friction in addition to the main stages of calculation. This parameter may depend on the structure and temperature of the snow and the coating material. The dependence of the friction coefficient of these parameters were determined using techniques developed by research and testing laboratory “Polytech-SKiM-Test” with using of tribometer. Various snow conditions and two types of roof coverings - PVC-tent and Pural were considered in the research. The results of experiments are the dependencies of the coefficient of friction on various materials and slipping speeds. Moreover, values of frictional forces of the snow on the coating at different temperatures were defined.
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The method and computation of air change required for attic rooms
Статья научная
The article deals with the recommendations how to eliminate ice dam formation on pitched roofs of the buildings with cold attics during heating period. The case of how to calculate required air change in cold attic rooms, where building structures which separate attics from rooms or utilities with high temperature (heat supply sources) are not insulated, is given in details. It is proved that natural ventilation system can ensure this condition only within short terms. It is necessary to both carry out works to ensure air change and insulate building envelopes, which separate cold attics from rooms with higher air temperature in order to satisfy all the requirements to eliminate reasons of ice dam formation on roofs
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The most effective crushing equipment and testing of recycled concrete aggregates
Статья обзорная
The goal of this research is to study the international experience in managing the construction and demolition waste, to study the methods of testing recycled aggregates for concrete and reinforced concrete in comparison with the Russian practice, and to identify the most effective equipment for concrete waste recycling. Recycling of concrete waste could be the optimum solution for such problems as the lack of space for construction, the exhaustion of natural resources etc. The comparative analysis of the results of different researches showed, that up to 50% of recycled concrete aggregates of total amount of aggregate in concrete mixture has a little effect on the properties of concrete. The recycled aggregates are in demand, because they cost much lower than that the natural aggregates. The analysis of technical and economical qualities of different types of crushers showed, that swing-jaw crushers with their crossfunctionality and power are best for reutilization of concrete and reinforced concrete. Requirements for the type of the crusher depend on the utilization project of the particular building or construction, because each case is unique.
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The pressure loss and the filtration coefficients in pipelines with grids
Статья научная
A variety of grids and lattices that occur in different spheres of practical activity requires detailed study. The presence of these devices leads to additional resistance and energy losses during their flow. The paper discusses a flat plastic perforated mesh with different degree of permeability at the outlet of the pipeline. The coefficients of grid resistance were determined experimentally. The effect of grids on the total head loss were established through the presence of resistance coefficients volume method at fixed pressure: we determined the flow at the exit of the horizontal pipe of constant cross section, the end of which was mounted the investigated grid. To precise definition, the obtained values along with the experiments on the measurement of costs used a method of determination using piezometers: according to the length of the flow part were installed piezometers and the values of the coefficients of resistance were established on the basis of differential pressure. The identity of the two methods of determining the resistance coefficients is shown, in terms of flow rate and pressure drop on the grids. The effect of grids on the capacity of the pressure pipeline has been established: the replacement of the flow part does not affect to the numerical values of resistance coefficients of the grids. The dependence of the relative flow rate in the pipe on the surface porosity of the grids is obtained; this dependence gives a qualitative estimate of the reduction in the capacity of the pipe in the installation of meshes. The experimental data for constructing this dependence agree with the calculations for the approximating dependence established earlier. The transition from resistance coefficients to filtration coefficients and permeability of the pipeline with grids is suggested, because it is more convenient in practical calculations by characteristics. Graphs of the permeability coefficients dependence, related to the pipe cross-section area, and the filtration coefficients on the surface porosity of the grids are given. The proposed dependencies are linear functions of the surface porosity.
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The stress-strain state of a rectangular covering spatial truss
Статья научная
The object of research is a model of a statically definable roof truss with supports on the sides of the structure. Spherical and cylindrical supports are located at two corner points of the covering, in other corners and on the sides of the structure at an equal distance from each other - stands. A multi-dome surface shape is set. For the case of loading the truss by the force in the middle of the span by the induction method according to the number of panels, the formula for the deflection is derived. Analytical dependencies of the reactions of supports on the number of panels under the action of a load uniformly distributed over the nodes of the coating surface are found. Method. The calculation of the forces in the rods and the reactions of the supports of an externally statically indeterminate truss is performed in symbolic form using the method of cutting nodes. To compose a system of equilibrium equations and obtain a solution, the operators of the Maple computer mathematics system are used. The deflection is determined by the Maxwell-Mohr's formula. Based on the data on the solution of a series of trusses with a sequentially increasing number of panels by the induction method, formulas for the dependence of the deflection on the load, the size and number of panels of the structure are derived. Operators of the genfunc software package from the Maple computer mathematics system are used to compose and solve homogeneous linear recurrent equations, which are satisfied by the sequences of the coefficients of the sought dependencies. Results. Dependences of deflection and forces on the number of panels have a form polynomial in the number of panels. It is shown that the vertical reactions of the corner supports can have negative signs, which makes it necessary to use retaining supports here. The curves illustrating the solution have a clearly pronounced jump-like shape. The quadratic asymptotics of the solution is found both in terms of the number of panels and linear in height. The dependence of the deflection on the height has a theoretically permissible minimum. The considered scheme of a spatial statically definable roof truss allows an analytical solution to the deflection problem. The obtained dependences can be used to estimate the accuracy of numerical solutions and in problems of optimization of the structure in terms of rigidity and solutions.
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Статья научная
The thermal performance property of a building envelope is straightly based on the character of the materials used in the construction. The materials used must be resistant to mechanical stresses and the effects of water on the walls to confirm the safety of the residents but ought also to have assured insulating effects to provide for the thermal performance of the building envelope. The object of research is the thermal performance and water erosion resistance of compressed stabilized earth bricks (CSEBs) using sheep wool as a fiber (SWF) and cement as a stabilizer agent. The study was conducted on bricks produced using local raw materials in Kabul, Afghanistan. Method. In this study, 0%, 0.05%, 0.1%, 0.2%, 0.3%, and 0.4% SWF and 0%, 5%, and 10% ordinary Portland cement were used. ISOMET 2104 instrument was used for the study of thermal performance. The effect of different amounts of SWF in the bricks, different amounts of cement, and the bulk density of the bricks on thermal conductivity, volumetric heat capacity, and thermal diffusivity was investigated. To determine the resistance of compressed stabilized earth bricks (CSEBs) to surface-contact water pressure, a study was conducted on bricks containing a low amount of cement (5%), both with and without 0.1% SWF, in accordance with the NZS 4298 (1998) standard. Result. The study found that the thermal conductivity is affected first by bulk density, then by cement, which causes a decrease in voids in the bricks, and then by an SWF. The volumetric heat capacity is affected first by SWF, then by bulk density, and then by cement. The thermal diffusivity is affected first by bulk density, then by SWF. As a result of a one-hour continuous test on the bricks using the water spray method with a water pressure of 50 kPa in the pipe according to the standard, no erosion occurred in either type of bricks. Overall, the findings demonstrate that the CSEBs exhibit adequate thermal and water erosion resistance properties, making them suitable for use in construction as a sustainable construction building material, particularly in regions with moderate climates and where resistance to water erosion is required.
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Thermo-mechanical evaluation of hybrid basalt fiber aerodrome concrete pavement under dynamic impact
Статья научная
The object of research is the thermo-mechanical behaviour of hybrid basalt fibre-reinforced concrete used in aerodrome pavements. The subject of the research is the effect of hybrid fibre composition on impact resistance and thermal durability under dynamic loading. The purpose of the research was to develop and assess a hybrid basalt fibre mix capable of enhancing the mechanical and thermal stability of airfield pavements. Method. Three concrete mixes were selected: a control mix (K, 0% fibre), a micro-fibre mix (2A, 2% micro-fibre), and a macro-fibre mix (2B, 2% macro-fibre). The mechanical properties, specifically the Modulus of Elasticity, were modelled as a function of temperature and using reduction factors based on existing building standards (Eurocode 2: EN 1992−1-2). A linear static analysis was performed for 12 cases (3 mixes, 4 temperatures) using Autodesk Robot Structural Analysis software. The pavement was modelled as a slab with elastic soil supports (Winkler foundation). Two cumulative load cases were applied: a static uniform pressure of over an area and a uniform temperature increase. The primary output parameters were Total Displacement and Maximum Bending Moment. Results. The results indicate that high temperature is the most governing factor in the slab's structural behaviour, causing a varied reduction in material stiffness. This thermal degradation led to a gradual and dramatic increase in maximum vertical displacement, which rose from a baseline of at (Mix K) to at across all three mixes. Crucially, at high temperatures, the reinforcing action of both micro- and macro-basalt fibres was rendered insignificant because the failure mode was completely governed by the thermal degradation of the cement matrix itself. The maximum bending moment exhibited a non-linear relationship with temperature, initially decreasing due to stiffness loss, but then increasing sharply at (to for Mix K) due to significant thermal stresses and warping effects, indicating a state of critical distress.
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Translucent elements as structural part of facade systems
Статья научная
The objects of research are translucent elements in curtain wall systems, which are common modern architectural and structural solutions. Method. To determine the stress-strain state of a translucent element as part of curtain wall systems, different calculation methods are applied to calculate insulating glass units under full wind load. These methods are based on recommendations from regulatory documents, Navier Solution and numerical experiments in Mepla ISO program and ANSYS software package. In calculations, insulating glass units have different values of linear dimensions, glass thickness and air gaps. The deformation characteristics of a two-component sealant are determined by testing the material in an experimental setup. Results. Based on the results of the work, the convergence of the methods with each other is considered, and the glass unit with the smallest deformation values in the outer glass from the action of wind loads is determined.
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Trihedral rod pyramid: deformations and natural vibration frequencies
Статья научная
The object of research is a new truss scheme of a statically determinate dome structure. The purpose of the study is to derive formulas for the dependences of the deflection under the action of a uniform load and the first frequency of natural vibrations on the number of panels, sizes, and masses concentrated in the truss nodes. Method. The forces in the truss rods are found from the equilibrium equations of the nodes. The system of equations also includes the reactions of vertical supports located along the contour of the structure. It is shown that the distribution of forces over the structure rods does not depend on the number of panels. The deflection values and stiffness of the truss structure are calculated using the Maxwell - Mohr formula. The lower analytical estimate of the first frequency is obtained by the Dunkerley method, the upper one by the Rayleigh energy method. As a form of truss deflection in the Rayleigh method, the deflection from the action of a uniformly distributed load is taken. Only vertical oscillations of the weights are assumed. Results. The dependence of the solution on the number of panels is obtained by generalizing a series of solutions for trusses with a successively increasing number of panels. The solution uses operators of the Maple computer mathematics system. Graphs of the dependence of the deflection on the number of panels for different truss heights are plotted. The horizontal asymptote of the solution of the deflection problem is found. The value for the first natural frequency is compared with the numerical solution obtained from the analysis of the entire spectrum of natural frequencies of the vertical oscillations of the mass system located in the truss nodes. The frequency equation is compiled and solved using the eigenvalue search operators in the Maple system. It is shown that the lower analytical estimate based on the calculation of partial frequencies differs from the numerical solution by no more than 37%, while the upper estimate has an error of 7%. In this case, the formula for the lower Dunkerley frequency estimate turns out to be more compact. The natural frequency spectrum of the truss is analyzed. Isolines were found in the set of frequencies for a series of regular trusses.
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Unconventional cases of the stone vaults
Статья научная
The evaluation of the technical condition of vaulted structures is the principal issue in the survey of historical buildings. It is also important to understand how any thrust system works, and what functions it performs. However, apart from visual inspection it is necessary to make apertures in vaulted ceilings and determine the methods of support. It is also very important to determine the strength characteristics of masonry. Unconventional cases should always be taken into account during the inspection of masonry vaulted structures. It needs to carefully conduct their inspection with the mandatory breaking opening and strength analysis based on numerical simulation before starting of all the reconstruction, restoration and repair. The use of modern program complexes in the simulation, such as Ansys, Abaqus, allows improving the quality of performed work
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Vibration characteristics of 3D curved cellular bridges via panel element method
Статья научная
The object of research is the development of a novel approach for the free vibration analysis of 3D curved cellular bridges using the Panel Element Method (PEM). The free vibration analysis of 3D curved cellular bridges was performed by the proposed Panel Element Method (PEM). The objective of this research is to examine the relationship between natural frequencies, mode shapes, and computational efficiency and the geometric configuration of curved bridge decks. Method. The PEM simulates curved cellular decks as assemblies of planar and non-planar panel modules based on a wide column analogy where two rigid arms joined by a flexible member mimic coupling between bending and torsion. Intrinsic dynamic properties are determined analytically using strain energy minimum principles, implemented in MATLAB for parametric analysis. Comparison with the Finite Element Method (FEM) assesses mode of vibration discrepancies and computational cost. Validation is done externally by solving the equations of equilibrium for bridge geometries with different curvature radius, support types, and cell shapes. Results. The PEM is verified against FEM by a variety of case studies for various bridge profiles and supports. It is found that the natural frequencies and mode shapes could be predicted accurately by the PEM with variation of less than 7% in fundamental modes compared to FEM. A high degree of computational efficiency by PEM is proved with over 90% savings in computational efforts without any accuracy loss. The paper concludes that the PEM is a good method for free vibration analysis that can achieve a compromise between accuracy and computational efficiency and is a possible substitute for the analysis of the dynamic behavior of curved bridge decks with various configurations.
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Water surface and drainage area measuring with satellite navigators
Статья научная
There are several geodesic methods of area measurement. The following article provides description of a non-conventional method which involves the usage of satellite navigation devices. Based on a practical research, the accuracy of the method is being estimated. The analysis of different measuring conditions and factors, regarding their effect on accuracy, is made. The suitable areas, where the method could be used, are mentioned. In particular, the possibility of water surface and drainage area measuring is examined with the usage of previous theoretical base. In addition, the results of a recent field check covering such type of areas are presented in the article.
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Wood-composite structures with non–linear behavior of semi-rigid shear ties
Статья научная
The object of research is composite structures with semi-rigidity ties, such as ribbed steel-concrete and wood-concrete floors, and structures based on structural wood and wood-composite materials, which are widely used in industrial and civil building. As a rule, various types of mechanical ties are used as shear ties in composite structures. In calculations of such structures according to the classical method, the behaviour of shear ties is generally assumed to be linear-elastic. It does not make it possible to consider the real character of the deformation of the ties during shear force action. Method. The presented calculation algorithm is based on the solution of A.R. Rzhanitsyn for the differential equation for the two-layer composite rod. Separating the element into sections and set the boundary conditions at the borders of the sections, a system of linear equations can be obtained from which the values of the shear forces T and integral constants can be determined. This approach makes it possible to determine forces in the shear ties and normal stresses in the layers in any cross-section of the composite element. As an example, a two-layer composite beam is considered, the layers of which are connected by cylindrical nails, the deformation of which occurs according to non-linear behaviour. Results. it was concluded that the calculation according to the classical method, taking into account linear behaviour of ties, gives an error of up to 25% while the shear force in the ties determining and up to 111% when normal stresses in the layers of the composite beam were determining. Such errors do not make it possible to get a reliable estimation of the strength of materials and shear ties of the composite structure
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