Строительство уникальных зданий и сооружений @unistroy
Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 817
Energy-efficient construction in the climatic conditions of Latvia
Статья научная
The low energy building can be achieved by implementation of energy efficient building envelope as well as energy efficient heating and ventilation systems. In addition use of renewable energy sources allows reach nZEB and ZEB requirements. This paper provides calculation approach and conclusions on necessary insulation thickness for opaque elements. In addition optimal windows sizes, their orientation and thermal properties to achieve low energy buildings standards in Latvian climate is evaluated in this study. This has been done for single family house. Study takes into account specifics of low energy consumption buildings for five largest cities of Latvia located at places with maximally diverse climatic conditions. The paper presents economical and payback time calculations of low energy building constructions and HVAC systems in Latvia.
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Energy-efficient expanded clay concrete wall block
Статья научная
At the moment, the market of wall materials for low-rise cottage construction remains very conservative. People tend to erect the walls of cottages, using all the usual materials - wood (timber), brick, ceramic, gas concrete or aerated concrete blocks. At the same time, a relatively recently appeared technology of erecting walls of cottages with the help of a fixed formwork for concrete, which combines load-bearing, heat-insulating and enclosing elements at the same time. The aim of this work is to analyze the shortcomings of existing fixed formwork blocks and, taking them into account, create our own fixed formwork block, test its strength and heat transfer resistance, as well as analyze the above-mentioned characteristics and compare them with the most common energy-efficient wall materials for cottage construction presented on market of St. Petersburg. At the moment, the market of wall materials for low-rise cottage construction remains very conservative. People tend to erect the walls of cottages, using all the usual materials - wood (timber), brick, ceramic, gas concrete or aerated concrete blocks...
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Eurofacts: enhancing the Russian-Finnish dialogue
Статья научная
Eurofacts Oy is a family owned consultancy company with 20 years of working experience. Mainly based in Helsinki, Finland the company is also represented in St. Petersburg and Moscow. Eurofacts offers expertise across many areas of business and industry. The main focus of the company's activity is the communications and partnerships between Russian and Finish companies. The core of the assignments has been much focused on the big companies and corporations but nowadays the role of SME's is compelling. To establish the successful international business any company needs the proper network and knowledge - Eurofacts offers the decisive services to improve the dialogue.
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Статья научная
Shear wall is important and suitable part in high-rise building to carry (support) dead loads and resist lateral loads (wind and seismic), shear wall's position in the building influences on the all analysis and design's behavior of the building. This paper presents the different positions of shear walls in the building as well as effects of different position of shear wall on the building's behavior of analysis including; displacement, shear force and bending moment. Considering this case the results in different effect positions of shear wall for a building which represent G+17 storey separated into four different models. The analysis of different position of shear wall, which is using equivalent lateral load method in the building, have been performed by using ETABS 2016 Structural analysis software.
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Eye tracking в городской визуальной среде
Статья научная
Экология городской среды на сегодняшний день является областью внимания не только ученых, но и всего общества в целом. Однако, рассматриваются в основном проблемы химического, физического и иных видов загрязнений окружающей среды. Впервые В.А. Филин дает объяснение связи между визуальным загрязнением городской среды и ухудшением зрения, психическим здоровьем, и другими проблемами со здоровьем. Методы визуального определения загрязнения окружающей среды в настоящее время не разработаны, либо дают неточную оценку. В данной статье рассмотрена возможность применения метода айтрекинг к оценке визуальной городской среды. Для исследования были выбраны здания с элементами агрессивной или гомогенной сред, произведен их анализ и подобран оптимальный алгоритм для оценки здания с точки зрения визуальной загрязненности.
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FRP helical micro screw pile with cast iron pile cap: review
Статья научная
Calculation method of pipes’ FRP sections is proposed. Comparison of two options of piles’ bearing capacity calculations is made. Calculated bearing strength of the pipe’s sections for an axial load are compared to the results of site tests made earlier and soil’s bearing strength. Conclusions are made that existing calculation methods of soil’s bearing strength underneath helical piles are too conservative. Research provides results of bearing strength installed to weak clay helical fiberglass micropile. Pile was designed, produced and provided by Composite Group LLC. Pile is made with pultruded fibre reinforced polymer pipe and screw produced with cast iron. Screw is glued to the FRP pipe by epoxy. In addition rivets strengthen connection detail. This structure is stable for corrosion, ground electricity. FRP screw pile has small weight and high strength.
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Facade systems modal analysis in consideration its own dynamic characteristics of the frame
Статья научная
This article studies the degree of the wind load dynamic component influence on the bearing capacity of the hinged ventilated facade systems (HFS) of a high-rise building. The research model is a reinforced concrete building with a HFS with variable number of storeys and with constant dimensions and identical floor plans over the entire height. As a design of the HFS, a scheme based on the T-profile with a step of brackets of 600 mm vertically and a pitch of guide racks of 500 mm horizontally is adopted. The number of storeys is taken as a variable parameter of the research model. The following tasks were solved in the work: determination of the natural frequencies of the HFS as a multi-span beam; determination of natural vibration frequencies of the facade systems together with a reinforced concrete building, determination of dynamic factors, and comparison of the obtained values. As a result of the work, it was shown that when determining the bearing capacity of the HFS of a high rise building, it is impossible to consider the facade system as a separate structure from the building. A methodology for modal analysis is proposed, which allows determining refined values of the natural frequencies of a substructure vibration and dynamic factor.
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Fire resistance of statically indeterminate steel systems
Статья научная
The object of research is a single-span metal frame. Since the fire resistance of metal-bearing structures is insignificant, this is because at temperatures above 400 °C for steels and more than 200 °C for aluminium alloys, significant development of plastic deformations under constant load (creep) begins to manifest itself. The purpose of this work is to conduct research aimed at studying various emergency impacts, in particular, the impacts associated with heating during a fire and its effect on the stability of both individual elements and the entire structural system. To meet the new requirements of Federal Law "Technical Regulations on the safety of buildings and structures". To identify the influence of the heating temperature of the gas medium on the mechanical characteristics of steel structures by obtaining data from the accepted regularity and constructing a trend line and by the method of displacements, taking into account kinematic definiteness, to investigate the effect of temperature at uniform heating during a fire on the value of critical parameters of a single-span frame. By solving some problems that arose during the study, we can say about the necessity to improve steel structures to prevent irreversible consequences during an emergency. The research's main results are to identify the relationship between the temperature of the medium on the mechanical characteristics of steel structures.
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Fire resistance of thin-walled cold-formed steel structures
Статья обзорная
There is an increasing demand for cold-formed thin-walled steel structures on the building market nowadays. Owing to the assembly simplicity, materials’ cheapness, high ecological standard, recycling, reuse potential, and other numerous advantages of such structures are widely employed in both office and residential buildings. The temperature of thin-walled structures increases rapidly as a consequence of the high section factor (measurement of the fire-exposed area to the heated volume), which creates the demand for a durable fire safety system, one of the fundamental requirements of the building safety. Although, several sufficient researches have been undertaken, there is still no strict performance-based fire design for cold-formed steel systems due to the lack of data. This paper compiles the existing works on the cold-formed thin-walled structures’ fire performance, including numerical studies and experiments with mechanical and thermal properties of complete structures, purlins, joints (bolted, screwed, nailed, riveted etc.), plates, tubular structures, new calculation methods, new protective materials that are being used, such as intumescent coatings and etc.
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Статья научная
His article examines the flexural strength of reinforced and re-vibrated concrete beams using Saw Dust Ash (SDA) as a partial replacement for Ordinary Portland Cement (OPC). Chemical analysis of the SDA sample contains the major chemical oxides found in cement: SiO2 (27.23%), Al2O3 (29.05), Fe2O3 (9.32%). Seven beams of sizes 150mm x 150mm x 600mm reinforced with 12mm diameter steel bars (Y12) were cast for each 0%, 5%, 10%, 15% and 20% replacements of OPC with SDA. The beams were re-vibrated for 20 seconds at an interval of 10 minutes successions up to 1 hour after initial vibration. Another set of three beams of same size and reinforcement for each percentage replacements of OPC with SDA were also cast but were not revibrated. Fifty beams were cast in total: thirty-five revibrated and fifteen non-revibrated beams and were all cured for 28 days. Flexural strength test carried out on each beam shows maximum flexural strength at 0% followed by 5% replacement at twenty (20) minutes revibration time lag interval. The maximum flexural strength attained were 10N/mm2 at 0% then 9.5N/mm2 at 5% for the revibrated beams respectively, while for non-revibrated beams 8.87N/mm2 and 6.67N/mm2 for 0% and 5% replacements were attained. Revibration is thus seen to improve the flexural strength of reinforced concrete beams and thus SDA can be used up to 5% to replace cement.
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Formation of spatial structural coverings
Статья научная
The object of research is spatial structural coatings of buildings and methods of their formation. Areas of use of structural structures are premises of hall buildings and warehouses.
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Formula for natural frequency oscillation truss with an arbitrary number of panels
Статья научная
The object of research is the problem of the first frequency of free vibrations of a planar statically determinate regular beam truss with a mass uniformly distributed over the nodes.
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Formula for the lattice truss fundamental frequency vibration
Статья научная
The research object is a statically determinate planar lattice truss with an arbitrary number of panels. The design with two hinged supports allows kinematic variability for some numbers of panels regardless of the acting load. Method. As applied to a structure with an admissible number of panels, the analytical expression for the first frequency of free vibrations is derived using a simplified version of the approximate Dunkerley method. Comparison of the analytical solution with the numerical one shows its high accuracy, which increases with the number of panels. Analytical transformations were performed in the Maple computer mathematics system. Results. The formula for calculating the oscillation frequency has the form of a polynomial in the number of panels and can be used for simple evaluation of solutions obtained numerically. The algorithm for deriving the frequency formula can be used in similar problems of structural mechanics.
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Статья научная
The calculation of deformations of building structures is usually carried out by the finite element method in numerical form [1]-[3]. Analytical methods are used much less often in engineering calculations. For regular trusses with periodically repeating structures in the lattice, in [4]-[7], together with operators of computer mathematics systems, the method of induction is used, which makes it possible to derive calculation formulas for an arbitrary order of structure regularity. Problems of regular statically determinate rod systems were dealt with by Hutchinson, R.G. and Fleck, N.A. [8], [9]. Matrix methods and graph theory in the calculations of regular planar and spatial trusses in relation to their optimization were applied by Kaveh A. [10]-[12]. In the papers [13]-[18], by induction in the Maple system, solutions were obtained for the problems of deflection of various planar trusses with an arbitrary number of panels. An analytical estimate of the first natural frequency of oscillations of planar and spatial trusses was found in [19]-[21]. A two-sided estimate of the first frequency of a regular truss in an analytical form using the Maple system was obtained in [22]. The article [23] proposes a two-node method for predicting the effective elastic properties of a periodic cellular truss. The continuum representation for calculating a regular truss is used in [24]. In [25], in the problem of periodic truss networks based on the concepts of the quasi-continuum method, the decomposition of a regular truss lattice into simple Bravais lattices is used. To reduce computational costs while accurately taking into account the dominant deformation mechanisms, a homogenized continuum description of lattice trusses is introduced in [26], based on the application of the Cauchy-Born multilattice rule to a representative unit cell. The author's handbooks [27], [28] contain schemes of planar static determinate trusses and formulas for calculating their deflections and forces in characteristic rods. Analytical methods for calculating a regular truss in relation to the problem of optimization taking into account creep were also used in [29].
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Статья научная
Metal plate connectors (MPC) are used for attaching together different parts of wooden structures, especially truss joints. Plates have rectangular form, they usually are made out of steel and sometimes can be covered by protection layer, for example, by zinc. Teeth of the plate can have different shape, length and mutual position. In order to connect wooden bars, MPC are pressed symmetrically on both sides of the structure, that is why attached elements should have the same cross-sectional width. For better adjustment of the elements, their ends are usually polished. Compression is carried out with special equipment and can take place both at the plants and at the construction site. The simplest algorithm of strain calculation of the joints with MPC can described, as follows: the construction is computed by usual methods of structural mechanics (FEM, flexibility method, force method) assuming all the nodes connected with plates are absolutely rigid. Then, using obtained internal forces and reference data about loads, leading to destruction or pulling MPC out of wood (laboratory tests are made by the manufacturer), appropriate plates are chosen. One of the program complexes using this pattern is APM Wood, the part of computer-aided design software APM Civil Engineering. The disadvantage of this algorithm is that it does not consider uneven distribution of forces on the various teeth of a plate and deformations appearing in the plates themselves, which leads to considerable error in found internal forces and inaccurate selection of plates. The model proposed by Foschi [1] is free of these disadvantages and can be used to estimate deformations and forces in MPS’s teeth. The paper gives an analysis of algorithm of calculation the nodes attached with metal plate connector and comparison to the program complex APM Wood. As an example, the problem of wooden bar fixed on both sides by MPC and under the influence of a force applied along the longitudinal axis is solved. As a result, it is concluded that consideration of plate and teeth flexibility in finite-element scheme is very essential for calculation accuracy, uneven stress distribution between the dowels has big influence on strain computation of the whole construction.
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Fractal structure of cast iron and its strength characteristics
Статья научная
The object of research is the structure and hardness of cast iron rolls used in section rolling mills. The study focuses on the use of multifractal analysis to assess the microstructural features of cast iron and their correlation with hardness. Method. Quantitative metallography methods and a multifractal approach were employed to analyze the microstructure of cast iron. Statistical characteristics of the microstructure were calculated using Rényi's formula. Hardness measurements were conducted on rolls made from SPHN and SSHNF grades of cast iron at three equidistant points along the barrel. Correlation coefficients were computed to evaluate the relationship between hardness and both traditional structural characteristics (length, diameter, area) and multifractal parameters. Results. The analysis revealed the significant influence of statistical fractal dimensions and the morphology of carbides and graphite (lamellar and spheroidal) on the hardness of cast iron rolls. Correlation coefficients for hardness prediction based on traditional structural features ranged from , while prediction using multifractal characteristics showed higher coefficients: to for SPHN rolls and to for SSHNF rolls. These results demonstrate the effectiveness of multifractal analysis in assessing the quality of cast iron rolls. A novel approach for evaluating the hardness of SPHN and SSHNF rolls is proposed. It includes the calculation of the statistical dimension spectrum of cast iron structural elements, determination of sensitivity coefficients of hardness to the spectrum, and the development of a mathematical model for hardness prediction. This method offers an alternative framework for assessing the quality of cast irons by analyzing their structural characteristics.
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Frequency spectrum of natural oscillations of the spatial structure of the rod pyramid
Статья научная
The object of the study is a pyramid-type enclosure statically defined in space. The truss has support posts along the contour of the base. The corner buttons are fixed on the support sphere, cylinder, and bracket. Structure with axes of symmetry. The purpose of the study is to give formulas on the dependence of the deflection under the effect of uniform load and the first natural frequency of oscillation on the number of plates, size and mass concentrated at the nodes of truss. Method. By using equilibrium equations at the nodes it is possible to find the forces in the truss elements. The system of equations also includes the responses of the vertical supports located along the contour of the truss structure. From this, it can be concluded that the force distribution on the truss rods does not depend on the number of plates. The deflection and stiffness values of the truss structure are calculated according to the Maxwell-Mohr formula. The lower analytical estimate of the first frequency was obtained using the Dunkerley method. All mathematical transformations are performed in the Maple symbolic mathematics system. The dependence of the solution on the number of panels is obtained by generalizing a series of solutions for structures with a successively increasing number of panels. Results. The value of the first natural frequency is compared with the numerical solution obtained by analyzing the entire spectrum of natural frequencies of the vertical oscillations of the system of masses located in the truss nodes. The frequency equation is compiled and solved using the eigenvalue search operators in the Maple system. The natural frequency spectrum of the truss is analyzed.
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Fuzzy logic - based expert system for assessment of existing concrete structures
Статья научная
Fuzzy logic is a useful tool when assessing the existing reinforced concrete structures. The introduction of expert system in assessing the technical condition of the existing structures built on the fuzzy logic represents a transition to a new and higher-quality level for the survey of constructions sites. The paper presents the principle of development and implementation of expert system for assessment of the damages of the existing structures. The process is based on the algorithm in which the input data (crack width and propagation, residual strength of materials, amount and condition of the steel reinforcement, deflection, corrosion level et al.) and information collected at each phase are processed and interpreted in order to define the successive step of the procedure. As a result, it is seen that the assessment of the existing building with precast concrete elements with usage of the proposed fuzzy system is in compliance with the estimation of the qualified experts.
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GPR tomography as applied to delineation of voids
Статья научная
This work presents the evaluation effectiveness of the GPR tomography for characterization of square voids in engineering structures. One of the columns of the iconic main building of the Moscow State University was selected as a target object with known configuration. Given that the heterogeneity of the column complicates the interpretation of GPR data acquired in reflection mode, transmission tomographic ray coverage was employed. Mathematical modelling and tomographic inversion to locate real objects were carried out. The radar tomography and the common-offset GPR geometry techniques are compared with respect to the acquired information about location, shape and dimensions of the void inside the column. The tomography results are characterized by high precision and are more reliable compared to the results of single-fold GPR survey.
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Geotextile-reinforced soils in a modernized irrigation system
Статья научная
The use in irrigation construction of geotextile soils reinforced (strengthened) with fibrous materials, including cotton fibers waste of textile materials, requires strength assessment of these soils under tension and bending. Due to the low tensile and bending strength of soil, the load is born by the fibers reinforcing the soil. Direct methods to test tensile and bending geotextile soils are complex. It was proposed to evaluate the strength of geotextile materials through the strength characteristics of their components. Soils reinforced with textile waste cotton fibers are considered in the paper. To determine the strength of cotton fibers experimentally under the action of friction force only, a tensile test of cotton yarn consisting of cotton fibers was conducted. The diagrams of cotton yarn stretching obtained experimentally and the known diagrams of sandy soil compression are given in the paper. It was found that in the process of strain, both cotton yarn and soil change structurally. These changes are described by the change functions of their strain moduli, determined from considered experimental results in the form of graphs. Based on them, a method for assessing the strength of geotextile soils based on the general law of cotton yarn and soil strain is proposed. The possibility of using the formula obtained from this law for a particular case when determining and evaluating the strength of cotton yarns under tensile forces is shown. Therefore, it is recommended to use this formula in calculating the tensile strength of geotextile soils reinforced (strengthened) with waste textile materials used in innovative and modernized construction of irrigation reservoirs, canals, ditches, and reservoirs.
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