Строительство уникальных зданий и сооружений @unistroy
Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 824
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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Ground improvement using stone column construction encased with geogrid
Статья научная
Using stone column to improve weak soil can be considered as an economic and technical viable for construction projects on the soft soil. According to the case history of the stone column it was provided that it is the best way of successful application for foundation of the structure such as, oil storage tanks, raft foundation, earth embankments. It should be noted that through the installation of the stone column inside the soil the lateral confinement offered by the soil around the stone may not be adequate to form the stone column; in this case encasing the stone column by the geogrid can induce the required lateral confinement. Experimental studies in the present work are carried out to investigate the behaviour of the stone column encased with Geogrid, Tests are carried out on a single installed stone column (ordinary and encased) in order to evaluate the effectiveness of the single column on bearing capacity and settlement. It was found that encasing the stone column with geogrid results in an increase in load carrying capacity and reduction in a settlement in comparison with the case without geogrid. By using geogrid, the ultimate bearing capacity increased by 60% compared to that without geogrid and load-bearing capacity increased by 20% for 10 mm settlement. Numerical analysis will be carried out by using PLAXIS 3D to validate the test and to make comparison between them
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Horeca Design - профессиональный update в Миланском политехнике
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При POLI.design - консорциуме Politecnico di Milano в январе этого года был запущен уникальный курс-интенсив на русском языке в формате воркшоп для архитекторов и дизайнеров, работающих в странах СНГ. Курс Horeca Design - Hotel Restaurant Cafe посвящен разработке, проектированию и дизайну интерьера инновационных заведений досуга.
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Hydraulic flow in the turning section of unpressurized water transmission structure
Статья научная
The object of research is the issue of studying the hydraulic process of fluid movement in open free-flow channels. As is well known in hydraulic engineering construction, open flume-type conduits are widely used, where the flow velocity sometimes exceeds the critical ones. Therefore, it is necessary to determine the main hydraulic parameters of the fluid flow in a turbulent regime. Of particular interest is the movement of the flow in the rotary part of the tray. Method. To determine the main hydraulic parameters of the flow in the turning part, we proceeded from the Euler equation for the polar coordinate system. Taking into account the Bernoulli equation and subsequent integration of the main formula, calculation formulas for the turning part of the flow were obtained. Result. Because of the study, we obtained the main expressions by which the turning radius can be determined and compared with the critical one. These parameters allow you to analyze the turbulence of the flow in the tray.
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Статья научная
Ice on the pitched roofs threatens pedestrians and vehicles parked near buildings. This article describes the scheme of ice formation on the roofs of buildings with a pitched roof and a cold attic. To determine the conditions for the ice formation in the building a mathematical model and an equation of the thermal balance of an unheated attic room are developed. A set of measures to normalize the temperature and humidity regime in an unheated attic is developed. The dependences of the air temperature in the attic on the outside air temperature before and after the implementation of the proposed set of measures to normalize the temperature and humidity regime are defined. The developed set of measures reduce the thermal energy consumption during the heating period due to an increase in the level of thermal insulation of enclosing structures separating the cold attic from heated rooms, as well as to improve the microclimate parameters on the upper floors of operated buildings. Unlike active protection methods (usually implemented in the form of heating cables, films, and mats), the proposed complex of passive engineering and technical solutions that do not require energy resources during operation can be defined as energy saving and sustainable. The results obtained will be applicable to buildings located in the cold climate zone (D - cold climate according to the international Köppen Climate Classification).
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Impact of flue gas recirculation on the efficiency of hot-water boilers
Статья научная
The topicality of the work is related to the fact that the combustion processes of various fuels, such as heat production, produce emissions that are harmful to the environment. The combustion of fossil fuels produces nitrogen oxides, which are about 10 times more dangerous than carbon monoxides. There are different methods to reduce nitrogen oxides emissions and one of effective methods is flue gas recirculation. Despite efficiency, flue gas recirculation has an impact on the efficiency of the boiler. The efficiency coefficient for the hot-water boiler was calculated with and without flue gas recirculation. The calculation with flue gas recirculation leads to a slight reduction in the efficiency factor, herewith flue gas recirculation reduced emissions of nitrogen oxides by 44,5%.
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Статья научная
The most commonly used building materials were reviewed concerning their impact on cooling load and architectural interventions. The continuing increase of energy consumption of air conditioning systems suggests a more profound examination of their tropical climatic environment and the impact on the building and an application of passive cooling systems. Furthermore, in this study, mathematical expressions were developed to support decision-makers to select their optimal envelope enhancement strategies for buildings under tropical climatic conditions. Moreover, an economic analysis was also carried out to help prospective users with their energy-saving ideas. Out of selected materials, glass was found to be the most influential material, followed by timber and wall. The results obtained in this study reveals that improvement of material and their impact on energy conservation, especially double glass window over the plain glass window per 100 m2 area, contributes to reducing the overall 22% monthly electricity bill and their AC capacity. Moreover, this study further reveals that improvement of the wall conserves a significant amount of energy; Improved wall over one layer brick wall per 100 m2 area contributes to reducing overall energy by 12 % of their AC capacity and monthly electricity bill. The primary object of this research is to study the impact of internal & external factors in building energy consumption under tropical climatic conditions. There are few specific objectives identified to fulfil the main objective. Firstly, the study tries to identify the impact of building cooling load for different building orientations with the most commonly used building materials and their optimisation. Then develop a mathematical equation and graphs for cooling load and their impact of most common use building materials under tropical climatic conditions. Furthermore, this research identifies the direct impact of the capacity of the air conditioning unit and their electricity consumption for RSCL. Finally, find out the payback period for different improvements of exterior walls through economic analysis.
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Impact response of steel fiber reinforced concrete beams with hooked fibers
Статья научная
The object of research is to investigate the impact response and structural behavior of steel fiber reinforced concrete (SFRC) at varying percentages of fibers by weight of concrete. The impact resistance of plain concrete is low, mainly due to low energy dissipating features and inadequate tensile strength. Steel fibers in concrete mix compensate for the weak tensile properties of conventional concrete.
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Influence of carbon nanotubes on the durability and permeability of foam concrete
Статья научная
The research object is foam concrete modified with carbon nanotubes (CNTs). The aim is to investigate how CNT incorporation and dispersion affect the material’s permeability and durability, addressing key limitations of conventional lightweight concrete. through adding a range of additives into the mixing process. Foam concrete is one of the types of light concrete that is prepared by mixing sand, cement, water and foam. In general, one of the ways to improve the mechanical properties of concrete is to add a variety of additives to the mixing plan. Method. The mechanical properties are considered for the investigation by adding carbon nanotubes and considering the latest advancements in the field of nanomaterials in the manufacturing of concrete additives and their compatibility with foam and cement types that are accessible in the market. It is hoped that conducting this research will be a start for the next steps in the field of optimizing the production of fiber concrete with high elastic properties. In this project, by using different percentages of carbon nanotubes in the design, favorable results can be obtained. Results. These results show that with the increase in the percentage of carbon nanotubes in foam concrete, the penetration of chlorine ions has decreased by 9.7% compared to the control sample, the depth of water penetration has decreased by 4.8% compared to the control sample, and the water absorption has decreased by 5.5% compared to the control sample.
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Influence of wind load on connection system of temporary towers
Статья научная
The objects of research are temporary demountable towers. When a wind load is applied to a structure at an angle, an uneven horizontal wind load occurs, which causes the structure to twist. For capital construction projects, due to the massiveness and greater rigidity of the nodes, this is not significant, but for light structures, accounting for this effect is very important. The purpose of the work is to study the connections of such towers and the influence of wind load unevenness on them. Method. Wind load studies are conducted, based on a model of a diving tower with the dimensions of the widest part 12 x 10 m and a height of 28 m. Different methods of calculation are taken into consideration, including the ones based on regulatory documentation and numerical modeling. Software packages allow calculating models with higher accuracy and less time, facilitating manual counting and reducing the probability of error. A gas-dynamic calculation is performed, as a result of which the aerodynamic coefficients are found. Results. A comparative analysis of two methods for calculating wind loads is carried out, after which measures are suggested to increase the load-bearing capacity of the structure.
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Injection mortars for road pavement subgrade fixing
Статья научная
The object of research is a range of injection mortars (IM) based on composite binders, crushed to Ssp = 500 m2/kg, obtained using CEM I 42.5 N, partially replaced by technogenic resources with the addition of superplasticizer Polyplast PFK-NLM. The purpose of this work is development and comprehensive research of injection mortars for road pavement bases. The tasks for achieving the set purpose are designing the composition of IMs, studying their fresh and physical-mechanical properties, as well as the performances of the fixed bases.
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Inspection of wooden building Villa Annala
Статья научная
The Renovation course 2012 subject in Helsinki is a brief survey of the Villa Annala, Hämeentie st., 154. The two-storey log and wooden-framed building is situated in a park area, and there forit has no plot or official registration number. For this reason, there have been no building permits or records of maintenance works in the building review office. The Parks department has served as the owner, and has organised together with the real estate department the upkeep of the building. The park itself is in excellent condition and the surrounding buildings are all in use. This main buildíng originally built by Konsul Wasenius in 1832 has been empty for over a year. The students have been asked to do a short survey of the building condition, offer alternatives for renovation, and finally give opinions concerning the future of the building. They are working in construction details and architecture team, ventilation and heating team and construction economics groups. The City of Helsinki is unable to give any information conerning the future of the building.The organizers are The Helsinki Metropolia University of Applied Sciences, The Tallinn University ofApplied Sciences with students also from St. Petersburg State Polytechnic University.
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Integrated efficiency assessment of road reconditioning
Статья научная
The paper dwells on the issues of improving traffic quality and safety; analyses domestic and foreign experience of road reconditioning by applying modern methods. It assessed the operating usefulness of modern repair methods (depending on the condition of road pavement before repair). The minimum warranty service life of pavements was established by analytic and experimental way after applying the relevant method of repair. The algorithm of operational and economic feasibility of repair work is designed and grounded on the basis of domestic and foreign methods of quality assessment of repairs. The proposed method considers not only condition of pavement before repair and cost of repairs but also effects of improving traffic quality and safety and prolonging road service life. The method also considers climatic conditions of regions that allows more reliably to predict operational efficiency of repair work. The main feature of this method is ability at a stage of substantiation of engineering and technical decisions to predict operational and economic benefits of using one or another option of roadwork and on the basis of economic-mathematical modelling to show which option will be more expedient and efficient.
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Interaction of a unique massive shell with a heterogeneous ground environment during immersion
Статья научная
The object of research. The research of interaction regularities of large-size reinforced concrete shells at the erection stages in heterogeneous soil mediums allowed to significantly expand the field of their rational use in underground construction for transport and engineering infrastructure facilities. For a defect-free erection of an underground structure of this type, it is necessary to solve the complex nonlinear design and geotechnical problems together. Method. Instability of interaction between a solid structure and ground environment, as well as the heterogeneity of the medium itself, generates a need to create an adaptive control stress-strain state of the system "gravitational large-size body - heterogeneous medium". The geotechnical and structural calculations are used to simulate the interaction of the shell with the ground environment and to predict the adaptive stress-strain control system parameters. The adaptive stress-strain control methods provide conditions for a defect-free lifecycle of the structure during its erection and operation in complex soil and man-made conditions. Results. In contrast to the traditional approach, the paper proposes the foundations of a new concept for evaluating the interaction of large size sinking structures in differently resistant soils, taking into account the non-stationarity of the immersion mode.
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Статья научная
The object of research is Acrylonitrile Butadiene Styrene (ABS) plastic waste, amalgamated with sand, as a viable alternative for constructing plastic-sand composite blocks. Method. The research employs a systematic approach to determine the optimal ratio of plastic to sand, ultimately establishing a 1:1 ratio that optimizes the compressive strength. Results. Experimental results revealed that the developed plastic-sand composite blocks achieved a maximum average compressive strength of 15 MPa, significantly surpassing the minimum requirement of 5 MPa outlined in the IS 2185-2005 (Part 1) code for solid concrete blocks. Comprehensive testing, including comparative analyses of compressive strength and water absorption, demonstrated the superior mechanical properties of the plastic-sand composite blocks compared to conventional concrete blocks. Additionally, thermal, hardness, soundness, and density assessments confirmed adherence to relevant standards. Microstructural examinations using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) tests revealed a compact microstructure with reduced porosity, indicating enhanced strength and durability. The XRD analysis further confirmed the presence of silica in the composite, supporting its structural integrity. These findings underscore the feasibility of utilizing plastic waste in environmentally friendly construction applications, promoting sustainable building practices.
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Mechanical properties of construction steel under rapid assessment
Статья научная
The object of research is the fractal modeling methodology applied to the structure and properties of materials, specifically metals. The study explores the relationship between the fractal (fractional) dimensions of structural elements and the physical and mechanical properties of materials, such as steel and cast iron. This work aims to analyze and refine the stages of fractal modeling to improve the prediction of material quality criteria. Method. The study employs a systematic fractal modeling approach, which includes the following steps: calculating the fractal dimension using Hausdorff’s formula, determining self-similarity and scale invariance, assessing sensitivity conditions, selecting a target function and variables, and formalizing results through appropriate modeling. The heterogeneity of fractal objects is evaluated using Rényi’s formula to detect multifractality, and the results are interpreted in the context of material structure-property relationships. Examples of algorithm implementation and its augmentation with fractal formalism for ranking quality criteria are provided. Results. The analysis demonstrates that the proposed algorithm improves the prediction of material properties based on structural and macrostructural analysis. It highlights the importance of correlating fractal dimensions with mechanical properties and emphasizes sensitivity assessments. The findings confirm that applying fractal modeling allows the ranking of quality criteria for materials, thereby establishing new structure-property relationships. Suggestions for algorithm enhancements include integrating advanced methods to evaluate sensitivity and quality metrics within specific operational ranges.
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Method for assessing the reliability of earth dams in irrigation systems
Статья научная
Irrigation systems for irrigated agriculture begin with reservoirs and basins. The latter are formed with earth dams and levees. The reliability and stability of earth dams under static and especially dynamic loading is of paramount importance. Destruction of dam structures, reservoirs, can lead to disastrous environmental and economic losses. The methods and ways to ensure the reliability of earth dams are different. Under static (own weight, water pressure) and dynamic (vibrations, explosions, earthquakes) loads, the strength and stability of earth dams are calculated at the stages of their design. In this case, it is necessary to determine the failure surfaces (surfaces of possible collapse) of the dam slopes. The circular cylindrical method for finding the failure surface (surfaces of collapse) of slopes of a homogeneous earth dam under static (own weight) loading is considered in the paper. It is shown that when the value of the total stability coefficient is greater than unity, there are local sections of the slip line where stability is violated. This circumstance creates the possibility for a fracture line development under seismic loads. It is proposed to take into account seismic stresses in the soil mass based on the solution of basic equations of continuum mechanics. The numerical solution of wave equations for the soil mass is presented by the finite difference method with known boundary conditions and zero initial conditions. The dynamic stress-strain state of earth dam is determined taking into account its moisture content and elastic, viscous, and plastic properties of soil. The ways of considering dynamic stress state when calculating the reliability and stability of earth dams are shown.
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Model of a spatial dome cover. Deformations and oscillation frequency
Статья научная
The object of research. A new scheme of a statically determinate spatial truss is considered. The design has a hexagonal dome resting on two belts. The belts are supported by vertical racks. Two corner supports have spherical and cylindrical hinges. The outer support contra consists of 6n horizontal rods, the inner one consists of 6(n-1) rods. The contours are connected by skews. Formulas are derived for the deflection of the vertex and the angular hinge depending on n. The upper and lower analytical estimates of the first frequency of natural oscillations of the structure are found. Method. Calculation of the forces in the rods is carried out by cutting out the nodes from the solution of the system of equilibrium equations for all nodes in the projection on the coordinate axes. To derive formulas for the dependence of breakdowns, forces, and the frequency of free oscillations, an inductive generalization of the sequence of solutions for structures with a different number of panels is used. The structural stiffness matrix and deflection are calculated using the Maxwell - Mohr formula in analytical form. To find estimates of the lowest frequency of vibrations of nodes endowed with masses, the Dunkerley and Rayleigh methods are used. Results. The vertical load distributed over the nodes and the concentrated load applied to the top are considered. Formulas for the forces in the characteristic bars of the structure are derived. A picture of the distribution of forces throughout the structure is presented. The resulting formulas for the deflection and frequency estimates have a compact form. The upper estimate of the first oscillation frequency of nodes under the assumption of vertical displacements of points has fairly high accuracy. The analytical solution is compared with the lowest oscillation frequency obtained numerically. All analytical transformations are performed in the Maple symbolic mathematics system. Some asymptotics of solutions is found.
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Статья научная
The object of research. Long-term operation of sewer tunnels in difficult engineering and geological conditions creates the danger of violating their structural safety. A long-term study of the changes’ dynamics in the technical state of the tunnels made it possible to establish the patterns of intense anthropogenic and dynamic influences on this process. Method. The developed discrete and continuous diagnostic models of the defects’ development in the tunnels’ structures make it possible to identify potentially hazardous areas subject to the manifestation of critical failures and methods of their localization. On the basis of numerical modeling, the boundaries of defect-free joint operation of the system “source of impact - geo-mass - sewer tunnel” have been determined. Results. With increasing external anthropogenic and dynamic impacts, modeling zones of urban areas with potentially dangerous sections of underground sewage facilities is the basis for the development of regulatory documents on monitoring methods and safe development geotechnical infrastructure.
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