Строительство уникальных зданий и сооружений @unistroy
Статьи журнала - Строительство уникальных зданий и сооружений
Все статьи: 817
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
Protective oil molecular film on metal surfaces: Method for determining quality
Статья научная
A method for assessing the quality of a protective oil film by determining the contact angle and oil absorption capacity of the surface is presented. This method allows determining the efficiency of using the proposed surfactant based on an organofluorine compound. The use of this substance increases the contact angle and oil absorption capacity of the surface, which can affect the quality of friction pairs. Collection, processing and analysis of the results of laboratory experiments and determination of the main properties of the treated surface allow us to speak about the high efficiency of the proposed composition. The optimal concentration of the substance in the reference oil and the holding time for the formation of a stable protective oil film were experimentally determined. In the future, it is planned to develop a method and conduct laboratory tests on friction machines using the proposed composition.
Бесплатно
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)
Бесплатно
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.
Бесплатно
Radiant heating and cooling systems based on capillary micro tubes
Статья обзорная
Radiant heating and cooling systems based on capillary micro tubes have been gaining much popularity due to large operational area, space saving, small difference between temperatures of flowing water and air inside the room and consequently improved energy efficiency. The objective of this review is to find out fields of applying capillary micro tubes, to discover advantages and limitations and analysis of future development. Based on research results it can be concluded that heating system based on capillary mats is an effective and promising solution for residential and public buildings.
Бесплатно
Статья научная
Changes in the existing urban structures that result in obsolescence and abandonment of buildings open up the opportunities for an alternative use of the existing building fund that would be in line with the current needs and aspirations of today. Conversion of obsolete buildings to residential buildings might be an optimal solution for the social and demographic changes that continuously influence and intensify the demands for new housing. The paper points out the quality of this approach and explores the extent to which conversion of obsolete buildings for residential uses may be a valid tool in sustainable development strategy.
Бесплатно
Recreation of the historical site ornamental ponds “figurnye prudki”
Другой
The objective of this paper is reconstruction of a part of the Oranienbaum Palace-and-Park Ensemble, Saint-Petersburg, Russia, the conventional name of the part is ‘Figurnye Prudki’. At present Russian Federation have quite a few palace-and-park estates, landscape architecture monuments, which today are in a bad repair or breakdown state. The Figurnye Prudki site is one of such monuments, therefore recommendations containing in this article for the recreation of the property seem to be relevant.
Бесплатно
Reducing utility bills through the introduction of energy efficient systems
Статья научная
The object of the study is an improved system for the partial recovery of the condensation heat of refrigeration machines, its development, implementation and study of operational performance, which increases the share of waste heat in the air heating system in order to increase their energy efficiency and optimize operating costs. The purpose of this work is to analyze the costs of using heat to heat the coolant in the air heating system from the heat supply organization, with the costs in case of heating the coolant in the condensation heat recovery system. Method. To analyze the calculated and actual values, the development and implementation of a research stand based on an ultrasonic flow switch and a heat meter was carried out, which made it possible to evaluate the economic effect of the implementation of the proposed solutions. Results. With regard to the air heating system of buildings with artificial freezing of the ice surface, the economic effect in the form of a reduction in utility bills for heating is 2.46 million rubles per year, while reducing the thermal pollution of the environment by at least 1.4 GW.
Бесплатно
Renovation of apartment buildings in Russia
Статья научная
The existing housing stock of the Russian Federation makes 3.6 billion m2 (2016). The area of apartments is about 25 m2 per one person. About 50% of houses in Russia need renovation. The considerable part of housing stock was constructed during an era of industrial housing construction. Many buildings of the first mass series have high strength characteristics. However, thermal comfort of these buildings in most cases unsatisfactory. Taking into account that the heating season in Russia on average lasts from October until April, the specific heat consumption for heating and ventilation during the cold period is 150—200 kWh/m2 per year for non-modernized buildings. This paper demonstrates the results of the investigations based on the field study and calculations of the thermal performance indicators of the standard residential building made of many box units (HDD = 3925 K*day/year). According to calculations, after thermal modernization of buildings the level of specific heat consumption for heating and ventilation will decrease twice...
Бесплатно
Seismic shear design of twenty-story RC building with ductile wall system
Статья научная
This paper presents analysis of seismic shear design of twenty-story RC building designed in accordance with EN 1998-1. For this analysis, uncoupled ductile wall system is selected as structural system of building. Preliminary seismic analysis of structure is carried out using modal response spectrum analysis. The nonlinear time-history analysis is performed on the spatial model of the structure where the structure is exposed to seven real earthquake records selected in accordance with the rules defined in EN 1998-1. The subject of performed nonlinear time-history analysis is seismic shear design of DCH ductile walls in accordance with EN 1998-1. The analysis of determining design shear forces using magnification factor and analyses of diagonal compression and diagonal tension failure of the web due to shear for DCH ductile walls are performed. Based on the derived results, corrections for the magnification factor and for shear resistance of ductile walls are proposed. The analysis leads to conclusions regarding the design procedure for "large" ductile walls (L=6.0m), walls that accept the dominant part of seismic force, in relation to the "small" walls (L=3.0m), walls in which minimum reinforcement is relevant.
Бесплатно
Self-healing concrete using fly ash, macro synthetic fibres and recycled aggregates
Статья научная
The development of cracks in concrete can reduce its durability and service life, causing its steel rebar to be exposed to harmful substances from the external environment, eventually leading to strength loss of concrete and high repair costs. Self-healing technique can eradicate the crack spontaneously, likely replacing or decreasing maintenance and repair costs. Self-healing concrete using low calcium Fly Ash with recycled Aggregate (RCA) and macro synthetic fibers is a novel approach to increase durability and serviceability, decreasing repair and maintenance costs. This research intends to create self-healing concrete using different volumes of Fly Ash with partially replaced RCA and macro synthetic fibers and to study the autogenous behavior of Fly Ash. Various volumes of Fly Ash 35%,45%, and 60%, respectively, were used. In addition, the coarse Aggregate was partially replaced with RCA. The results show that replacing RCA with natural Aggregate and using Fly Ash significantly decreased the strength of concrete. Thus, to increase the mechanical properties of concrete macro synthetic fibers were used at two percentages 5% and 1%, respectively. After that, concrete samples were cracked after 28 days of curing, and after 5 weeks, they were cured for autogenous self-healing. The results showed that using Fly Ash from 45-50% gave the optimum healing to cracks in 5 weeks and the use of macro synthetic fibers at 0.5% caused the best improvement in mechanical properties of concrete with good workability.
Бесплатно
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.
Бесплатно
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.
Бесплатно
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.
Бесплатно
