Строительство уникальных зданий и сооружений @unistroy
Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 824
Статья научная
The object of research is a concrete plate subjected to high-velocity projectile impact. The finite element method (FEM) is commonly used to obtain the nonlinear dynamic response of concrete structures. However, extreme loads such as projectile impact cause large strains, damages, material fragmentations. The mesh-based FEM cannot solve this task accurately. Smoothed particle hydrodynamics (SPH) is the meshless method that allows us to solve perforation and fragmentation problems but is characterized by higher computational costs. Methods. In this paper, we use the coupled FEM-SPH method to simulate the high-velocity concrete plate perforation. This method derives from switching from FEM to SPH by specific triggering criterion.Shear strain is the triggering criterion for the concrete plate perforation problem. The elastoplastic-damage Continuous Cap Surface Model (CSCM) describes nonlinear stress-strain relationships with strain-rate dependency for concrete. Results. Validation of CSCM on quasi-static cube compression gives good agreement with Eurocode-2 data: difference does not exceed 7% in FEM and 3.8% in the SPH method, respectively. For concrete plate perforation, the best match with the experiment is for the numerical model with spacings between FE nodes, and between SPH particles are equal to 2 mm. In this case, the ratio between the projectile diameter and the spatial discretization of approximately 6:1. The triggering value of shear strain for switching from FEM to SPH seems not to influence modeling results and computing time, independently of spatial discretization.
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Статья научная
Purpose of the present article is to introduce an unused analyze methodology for excavation of surge tank enlargement of HEC MATKA1. Paper exposes the explanation of the way which combines the analyzing methods of non-continual and continual media. The information about existing geological and geotechnical properties presents for the numerical and analytical analyses as a basis. Several results from the stability analyses of structural controlled instabilities during the excavation of water tank are also given. The newly secondary stress- deformation state as a result from enlargement (excavation) is analyzed with program Z-SOIL. The analyze of newly secondary stress-deformation state, which is the result from enlargement (excavation), was performed with Z-SOIL program.
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Static shading devices in the architecture of buildings
Статья научная
The paper shows that the daylight is a tool of energy efficiency of the buildings, if it is intelligently controlled. In order to reduce electricity consumptions and organize more natural illumination architects make bigger glazing area in their projects. However, shading devices are required to prevent overheating of inner premises. In the case classification of shading devices is given, as well as the European standarts in the field of shading devices. Also, the article includes guidelines for their designing, implementation and possibilities in using of building repairing. In the case study, the building of Agency for Electronic Communications and Postal Services in Podgorica, Montenegro is analyzed with the help of software tools, which present impact on distribution of daily illumination analysis, also designing of exterior static shading devices is considered.
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Strategies for redevelopment of gray belt objects on the basis of neural networks
Статья научная
The article considers the approaches for objects redevelopment in the gray belt. Information was collected about 45 objects located in different administrative districts of the city. As the criteria for clustering objects, general factors (year of construction of the building, сost of building restoration in prices of 1969, actual сost of building in prices of 1969, height, volume, number of stores, total building area, fundamental group, function) and factors on physical deterioration (wear of roof, floors, walls, foundation, finishing, MEP, total wear) were chosen. As a result of the study, SOMs with different learning parameters were created. As a result of the research, it was established how to change and select the desired redevelopment strategy for the zones of the gray belt, depending on the leaning parameters of the SOM and the individual characteristics of objects entering the gray belt.
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Strategy for energy efficient reconstruction of residential low-rise buildings o
Статья научная
Significant percent of population live in low-rise residential buildings. Energy efficiency of new houses is embodied in national regulations; proves on adequate energy performance represent the prerequisite for construction permit obtaining. Achieving energy efficiency in existing low-rise residential building, on the other hand, is more complex and problematic. By reviewing existing legal framework and taking into account the state on field, this paper aims to propose new methodology for energy performance improvement in existing low-rise residential sector (on the example of Montenegro and Serbia). Proposed problem solution is oriented towards both the additional legal actions and deeper understanding of social and economic impacts as barriers to energy efficiency achievement.
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Strength and deformability of compressed-bent masonry structures during and after fire
Статья научная
Monitoring of structures in conditions of beyond design basis impacts, including fire and similar impacts associated with exposure to elevated temperatures, which is relevant for both civil and industrial buildings, is especially important. The least studied area is the behavior of compressed-bent masonry structures in such conditions. Based on experimental data, a numerical analysis of compressed-bent masonry structures was carried out. Elevated temperatures from 500 to 1200 degrees were taken. Moreover, we took into account the change in the deformation-strength properties of the masonry depending on temperature, as well as the uneven heating of the structures and the stage of their cooling. The analysis results showed that at the stage of heating and maintaining a high temperature, the behavior of structure changes slightly, with the exception of temperatures of 1000-1200 degrees, when the material becomes ultra-brittle. It was also revealed that the most dangerous stage of cooling at the initial temperature rise above 800 degrees. This circumstance can be taken into account when developing monitoring systems for industrial facilities.
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Strength and durability of concrete using quarry dust as a substitute for sand
Статья научная
The object of research is quarry dust as a sustainable alternative to natural sand in M40-grade concrete, addressing the environmental and resource challenges caused by sand depletion in Russia. The study examines the effects of replacing fine aggregate with quarry dust (10% to 40%) on concrete's compressive strength, split tensile strength, and durability Method. The concrete mixes were designed following IS 10 262−2019 guidelines, with materials hand-mixed and each component precisely weighed. The mix was placed in cubic molds, compacted, and cured in water for 28 days. A total of 45 specimens were prepared and tested for compressive strength and split tensile strength at 7, 14, and 28 days using a universal testing machine C040PN, adhering to IS 516−1959 standards. Results. Replacing up to 20% of fine aggregate with quarry dust enhances compressive strength, achieving a peak strength of 46.35 MPa at 28 days, slightly below the control mix's 47.23 MPa. And up to 20% enhances tensile strength of concrete achieving a peak strength of 3.95 MPa at 28 days. However, beyond this threshold, performance declines, with strengths dropping to 35.21 MPa at 30% replacement and 34.04 MPa at 40%. making 20% the recommended limit for quarry dust substitution in M40-grade concrete. This approach enables sustainable use of quarry dust without sacrificing the structural qualities essential for construction.
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Structural inhomogeneity of metallic materials and quality criteria
Статья научная
The object of research is the structural inhomogeneity of metallic materials and its relationship with established quality criteria. The study focuses on the impact of microstructural variations, such as grain size distribution, defect presence, and phase heterogeneity, on the mechanical and physical properties of metals. Method. A combination of advanced microscopy techniques, statistical analysis of microstructural features, and standardized mechanical testing is employed to quantify structural inhomogeneity. Correlations between structural characteristics and quality indicators, such as strength, ductility, and durability, are established using regression models and quality standards. Results. The findings reveal that increased structural inhomogeneity negatively affects key quality parameters, including mechanical stability and material performance. Specific thresholds of inhomogeneity are identified, beyond which materials fail to meet quality standards. The study provides a framework for predicting material performance based on microstructural assessment and suggests pathways for improving quality through optimized processing techniques.
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Subsoil stabilized by polyurethane resin injection: fem calculation
Статья научная
The soil injection technology using an expandable polyurethane resin is one of the most efficient modern techniques that have been actively used in recent years for soil stabilization and foundations lifting. There are many advantages of using this technology, such as the rapid and strictly controlled process of lifting foundations, ease of use, high mobility and the lightweight of injectable foaming resin in addition to the independence of the physical and mechanical properties of resin from groundwater level, which allow the application of the proposed technology in a variety of geotechnical conditions and projects of various specificities. As part of the study of this technology in the world, very few theoretical and practical studies have been conducted. Most of these studies are focused mainly on the process of raising the foundations and monitoring of this technology. Thus, various monitoring methods have been developed around the world to control the injection process and to provide adequate tracking and a sufficient degree of visualization of the foundations lifting process in various geotechnical situations. Nevertheless, the application of this technology in the field of the soil stabilization and foundation strengthening has so far had certain limitations due to the lack of sufficient scientific theoretical and experimental justifications for the combined behavior of the composite (soil-resin) and the absence of an advanced calculation method, that allows predicting the altered characteristics of the treated soil massive after its injection by the expandable resin. The article demonstrates the results of a developed calculation method for predicting the averaged characteristics of the strengthened massive of a soil base after its injection by an expandable resin, based on theoretical and practical evidence obtained as a result of field and laboratory experiments, utilizing different approaches of the finite element method. The obtained by the developed calculation method results have been compared to the results of in-situ plate load tests obtained from field experiments without the injection of the resin and after its inclusion into the massive of the investigated soil to verify its accuracy.
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Substantiation of efficient use of land plots situated in the historical center of Saint Petersburg
Статья научная
The aim of the article is to find and substantiate an efficient use of unoccupied land plots in the central districts of Saint Petersburg. Three sectors of the city center were investigated and the most appropriate type of functional building assignment was chosen for the land. For this purpose in the research there was an analysis of the location of the chosen sectors, the experience of using the land of demolished buildings, the real estate market of the districts on which the land plots are located, also there was an interview of citizens for evaluating the potential exploitation of the sectors on certain criteria. According to the results, an art-development center got maximum rating but because of the economic reason – little space payback, building of the center is beside the purpose. The second place was given to a sports center but as one is currently situated not far from the investigated territories building of this structure is unprofitable. The third rating was for an overground parking which is very essential in the center of the city. As the social and economic significance of the parking are very high this object is the most favorable for building on the unoccupied territory. Efficient use of the land plot by choosing this object to be built in the central part of Saint Petersburg is confirmed by analyzed factors and results of the interview.
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Sulphur content in engine oil: Method for determining the amount
Статья научная
The object of the study is engine oil for internal combustion engines of agricultural machinery, with a focus on determining the content of sulphur and its compounds, such as sulphoxides and sulphides, which have a significant impact on the performance of oils. The research method involves the use of high precision titration techniques using specialised reagents and instruments to accurately measure sulphur concentrations. The obtained results demonstrate that the increased content of sulphur-containing compounds in motor oils leads to accelerated engine wear and increased negative impact on the environment. Application of the proposed methodology allows effective control of sulphur content, which contributes to optimisation of engine operation and reduction of machinery downtime. Thus, maintaining the optimal quality of engine oil is a key factor for increasing the service life of internal combustion engines and improving their efficiency in the agro-industrial complex.
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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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