Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 774
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 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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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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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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Monitoring of the construction site using an information model
Статья научная
BIM technologies are an integral part of the modern building process. In order to approach the complex implementation of BIM, it is necessary to use not only the 3D modeling process. The next step is to generate a 4D model based on the 3D model and work schedule. Russian construction companies implementing BIM are beginning to implement 4D models not only during the design phase but also during the construction phase. This article shows the principle of control of the construction site due to the information model. The most common software applications are identified. Their main characteristics are clarified and also in what situations the software applications can be used to organize the most effective work.
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Normative bases of labor costs influence on construction duration and crew forming
Статья научная
The paper considers the scheduling of construction of four objects using three different normative bases: Unified Norms and Prices (further - UN&P, Russia), KI “Rakennustöiden laatu RTL” (further - RATU, Finland), “Building Construction Costs with RSMeans Data” (further - RSMeans, United States of America, USA). An integrated approach to the calculation of amounts of works for each object, labour hours, the number of labours in the construction crew, allowed to reveal fundamental differences in terms of the building and its resource providing. The conducted research gives an opportunity to objectively assess the applicability of certain standards in today's construction market. According to the results of researches it was found that the smallest duration of construction is achieved by applying a normative base RSMeans (USA). The maximum duration of construction is obtained with the use of a domestic normative base. These conclusions indicate the necessity of modernization of the national normative base in building and possible integration of foreign one for the most effective scheduling of construction within the set terms and with necessary level of quality.
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Статья научная
This paper presents an investigation on the bending stiffness of sandwich panels at ambient and elevated temperatures. A finite element (FE) model is developed to verify simulations with experimental results, and then a parametric study at different temperatures is carried out. After that, an analytical study to determine the bending stiffness at room temperatures according to the current specification is conducted. Furthermore, the analytical solutions are developed to use at elevated temperatures. The objective of the current research is to compare the numerical and analytical results. It is observed that analytical solutions developed to evaluate the bending stiffness at elevated temperatures are conservative and reliable.
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Статья научная
The object of research is methods for determining reliability indicators, as well as methods for analyzing the propensity to develop progressive destruction in steel rod structures of increased responsibility that are many times statically indeterminate. The current state of the regulatory framework in the field of ensuring the reliability of building constructions is analyzed. The current regulatory framework in the field of preventing the development of progressive collapse of constructions is analyzed. Ambiguities in determining reliability indicators in difficult spatial constructions are noted. The question of a reasonable choice of a construction element, the destruction of which can cause the process of progressive collapse, is considered. The authors note the need to develop a clear methodology for determining the reliability characteristics of spatial many times statically indeterminate rod constructions of increased responsibility. Method. Based on the finite element method in a geometrically and structurally nonlinear formulation, an algorithm for determining the totality of key construction elements has been developed. The main purpose of the algorithm is the ability to analyze the propensity of the studied construction to progressive collapse based on the identification of stabilization states and subsequent calculation of its reliability indicators using a model of parallel connection of elements. Results. The article proposes a new method for the reasonable selection of a set of key most critical elements of spatial steel rod constructions. The use of this technique makes it possible to simplify and concretize the calculation of the construction for the tendency to progressive collapse. A method for determining the reliability indicators of spatial rod constructions of an increased degree of responsibility is proposed. The authors propose a methodology for determining the reliability indicators of spatial core constructions of an increased degree of responsibility. An algorithm for calculating reliability indicators of the constructions under consideration has been developed in the MATLAB programming language. The proposed methodologies have been tested on the example of a structural coating. The construction is square in plan and has a side length of 24 m. The cell of the core plate is made in the form of a pentahedron with a height of 3 m. A demonstration engineering calculation of the construction under consideration has been performed. According to the calculation results, the tendency to progressive destruction has been eliminated in the construction. The security characteristic increased from -1.54 to 2.67. This indicates an increase in the level of reliability of the core slab.
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One approach for extrapolation of rock mass parameters in tunneling
Статья научная
Designing of tunnels directly depends on the interactions of rock masses with engineering structures, which are examined in the paper. The essential issue is extrapolation of the parameter from the testing zone to the whole volume that is of interest for analyzing interactions in the system rock mass-structure. The paper exposes Empirical-Statical-Dynamical (ESD) methodology of extrapolation. That methodology is based on a combination of geotechnical and geophysical testing and rock mass classification, connected with definition of adequate regressive models.
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Optimal shape of arch concrete block bridge
Статья научная
The object of research is arched bridges made of concrete blocks backfilled with soil. The aim of the study was to develop a technique for determining the arch bridge's optimal shape in order to ensure the required size of the compressed cross-sectional zone at any automobile load position. The calculation takes into account the horizontal and vertical pressure of the backfill soil and the arch dead weight. The concrete blocks can have variable heights. Method. To solve the problem in a physically nonlinear formulation, the stepwise loading method and the possible stress states principle in increments were used. The solution was constructed by the finite element method based on piecewise constant approximations of the moments and forces. The nodes equilibrium equations obtained using the possible displacements principle are added to the additional energy functional written in increments form. The nodes vertical and horizontal displacements are accepted as possible displacements. When determining the required dimensions of the arch, the automobile load all possible positions are considered. Results. The optimum geometric parameters have been determined for an arch bridge with a span of 12 meters. The destructive automobile load value is determined. For the design load, the obtained internal moments and forces are compared with the ones calculated by the program based on the finite element method in displacements.
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Oscillation suppression of pedestrian overpasses
Статья научная
The objects of research are pedestrian overpasses. The purpose of this work is to analyze the issues of suppression of such overpasses from oscillation caused by movement of trains and crowds. There are many ways to suppress oscillation, including increasing the longitudinal stiffness, introducing an additional connection, and using elastic or viscoelastic dampers. Problems arise when determining the need for measures to suppress oscillation in particular cases. Method. The need for suppression is determined for a pedestrian overpass with a span of 44.6 m, which is tested to determine the natural vibration frequency and the logarithmic decrement of attenuation. A comparative analysis of different solutions for oscillation suppression is carried out. A computational model of a pedestrian overpass based on the finite element method is developed. The dynamic impact from the crowd is set as a time - force function, based on the condition that 12.5% of pedestrians move synchronously. The possibility of simplifying the design scheme by replacing the base and supports with boundary conditions is determined. The dynamic influence of a train on a pedestrian overpass is studied. The load from the train is set by the time-force function and the displacement equation. Three different cases of loading from the train are studied, varying on weight and the number of wheels. Results. A comparative analysis of oscillation damping measures shows that the most effective solution is to introduce a viscoelastic damper. This way, it is possible to reduce the mean square acceleration of oscillations by 8.4 times to the required values, with the lowest material consumption.
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Precast block houses built in the 1950s and urban mining potential
Статья научная
The transformation of the urban environment in Moscow continues at a high pace with the new constructions, renovations, and demolitions. Identical mass housing blocks built in the 1950s and after, which are also prevalent over Europe, are of distinct importance in this transformation since they generate a precious resource of industrialized precast concrete components. A nine-story precast dwelling type of the specified period is the research material in this current study for the determination of present material stock and its usability. Original design booklets and guidelines published by the planning committees in the 1960s and 70s provided architectural design-related data -i.e., materials, dimensions, and assembly details. Moreover, the visual investigation of facade components on ten randomly selected buildings revealed their current state. Design data invariably showed that constructors typically gathered these precast components using steel anchors and cement, which naturally evokes the critical question for their possible separation and reuse. Additionally, the visual survey sufficiently illustrated that the surface quality of these components was high, which is a valuable hint for their further utilization. According to our simple calculations, the selected building type comprises 915 precast facade components, which results in 778 thousand for the entire series in Moscow. In brief, the possible recovery of this tremendous amount from the landfill or downcycling is crucial in terms of environmental welfare, as the components of other identical buildings in the city and the country. Owing to the presence of similar structures all over Europe, this verdict is also valid and useful for different contexts. Consequently, the precast components used during the 1950s over many countries are still re-usable and their separation from the demolition waste creates a significant environmental impact reduction.
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Статья научная
The paper studies the temperature dependence of the surface of the asphalt concrete on the temperature of the environment of different Russian cities road-climatic zones with a view to determining the most effective method of calculating the temperature of the coating of the road. There are the materials of research, which shows that the fluctuation range of the surface temperature of asphalt pavement is roughly proportional to the range of air temperatures. Especially dangerous is winter and spring period, when the change in temperature occurs unevenly, as a result of which there is a decrease in strength and deterioration of transport performance indicators. Seasonal and diurnal variations of the temperature of pavement can be levelled by applying a special composition, which allows to maintain approximately the same temperature of the coating during the entire period of exploitation.
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Protective coatings of reinforced cooling towers
Статья научная
The technologies of anticorrosive protection used in modern construction of reinforced concrete cooling towers are considered. The analysis of technical and technological characteristics of protective systems of companies Sika, MC-Bauchemie, BASF and Hempel is performed. The calculation of the consumption of materials based on consumption rates from manufacturers and from the method of VGB-R 612 Ue (Germany) was carried out for the constructions of reinforced concrete cooling towers H = 150 m. The choice of recommended options for protective coatings of reinforced concrete cooling towers is made on the basis of an analysis of their technical characteristics, total consumption of materials and cost indicators of the anticorrosion system.
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Protective properties of anticorrosive coatings of steel thin-walled profiles for walling
Статья научная
Light steel thin-walled structures (LSTS), in particular with thermoprofiles, are widely used in construction of buildings and structures of various applications. These structures possess high heat-saving parameters, at the same time, durability of these structures may be limited by low corrosion resistance of steel. According to the latest amendments in the documentary standards, zinc coated thermoprofiles without additional paint coating may be used as load-bearing structures only in non-aggressive conditions. In this investigation we have established that the use of zinc coated steel with additional paint coating is much more effective measure of protection of steel articles against corrosion than separate zinc and paint coating. As a result of methods for corrosion testing, it was established, that the most effective measure of protection of steel articles against corrosion in aggressive conditions is the use of zinc coated steel with additional paint coating. These samples have been just slightly corroded during the test period (230 days)
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Quadrilateral finite element for thin and thick plates
Статья научная
The object of research is quadrilateral finite element based on linear approximations of moments for calculations thin and thick plates. Method. The additional energy functional, the virtual displacements principle and the moments approximations allows us to get analytically all necessary expressions of matrices elements. Using the virtual displacements principle, it is constructed the equilibrium equations, which are added to the additional energy functional. Results. The proposed method gives satisfactory results converging towards the reference solution as for the thin as thick plates. The locking effect for the thin plates is absent. It had been demonstrated the proposed finite element isn’t sensitive to the form distortions. The proposed method allows to calculate stiffness matrix of the finite element and to use it in the finite element method softs based on displacements approximations.
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