ARCHITECTURE AND CIVIL ENGINEERING
BUILDING STRUCTURES, BUILDINGS AND CONSTRUCTIONS
The article presents a new technical solution, which relates to the fi eld of construction, in particular, to the testing of bending reinforced concrete elements – building beams for strength, deformation and fi re resistance on a scale model. The new method of solution implies an increase in the information content, visual clarity and depth of experimental studies of reinforced concrete beams as a result of using the cost-eff ective way of designing geometric and forceful similarity to the scale model of reinforced concrete beams for strength, deformation and fi re resistance. The proposed method allows us to estimate the limiting states of a reinforced concrete beam by strength, deformation and fi re resistance; develop an analytical model for calculating the actual fi re resistance; save on labor costs in the manufacture of large-scale model of full-scale design for its testing.
The article presents experimentally obtained information about the features of the work of compressed models that simulate the rods of steel trusses of the coating. 9 rods of T-section, made up of paired angles, were tested. The rods were divided into 3 series: 1, 2 and 3. Series 1 – straight (reference); series 2 – curves with a common bend on the edge in the plane of connecting gaskets; series 3 – curves similar to rods of series 2, but amplifi ed under load by increasing the cross section. Elements of reinforcement – rods from the corners, similar to the caliber of corners of the main rods, deformed in order to obtain a reverse bend. The purpose of amplifi cation is to bring the reinforced rod to a state close to central compression. The att achment of the reinforcement corners was carried out by hand welding by welding over welds of minimum dimensions in 4 sections. The load during amplifi cation was close to critical for rods of series 2. The rods of all series were loaded until loss of stability.
ARCHITECTURE AND CIVIL ENGINEERING
HEAT SUPPLY, VENTILATION, AIR CONDITIONING, GAS SUPPLY AND LIGHTING
As part of the implementation of programs for the resett lement of dilapidated housing and rural construction, special att ention is paid to the construction of low-rise energy-efficient buildings. Analysis of various technologies for the construction of low-rise buildings revealed the feasibility of using expanded clay concrete as a structural and insulating material in three-layer exterior walls and well laying. The presented heat engineering calculation of the original construction of the well masonry showed rather high values of the reduced heat transfer resistance and the coeffi cient of heat engineering uniformity. Rather high accuracy of the presented engineering technique of thermal engineering calculation is confi rmed by comparison of the received data on resistance to heat transfer of an external wall by the approximate analytical method with data of computer simulation of temperature fields by a finite element method.
Using the exact analytical solution of the stationary thermal conductivity problem for a two-layer fl at wall under inhomogeneous boundary conditions of the fi rst and third kind, an analytical method for thickness determination of the sediment layer on the inner surface of the pipeline wall by the temperature known from the experiment on its outer surface is developed. The thickness of the deposits is found from the solution of the inverse problem by substituting the experimental value of the temperature of the outer surface of the wall into the formula of an accurate analytical solution. According to the results of theoretical studies, the thickness of the deposits was equal to 1.3 cm. Due to the large diameter of the pipeline (0.6 m) and the insignificant thickness of the two-layer wall (0.016 m), it was assumed to be flat. The thickness of the deposits according to experimental studies was equal to 1.1 cm. Therefore, the discrepancy between the results of theoretical and experimental studies is 15.3%. The sequence of obtaining a solution to a similar problem for a cylindrical wall is also presented.
A comparative metrological analysis of the instrument fleet of commercial accounting of heat energy and coolant was carried out based on the results of periodic calibration of measuring instruments in 2004-2005 and 2016-2017. Methods reviewed for assessing the suitability of coolants and their components (flow, temperature, pressure transducers) and measuring sets based on them. From the metrological point of view, the obtained results of the analysis make it more reasonable to form a list of recommended metering devices, and they will also be useful in predicting the costs of metrological and routine maintenance of existing heat metering systems.
Analysis of numerically simulated convective heat transfer for a variety of heater installations is presented. A critical review of the existing method of energy effi ciency assessment, which is based on empirical coefficients, is given. Numerically verifi ed nondimensional heat transfer coeffi cients for eight installations of the heater are presented. The results were validated with the adopted experimental data. Sensitivity analysis of heat transfer intensity towards heat carrier temperature for a variety of heater installations is presented.
ARCHITECTURE AND CIVIL ENGINEERING
WATER SUPPLY, SEWAGE, CONSTRUCTION SYSTEMS FOR PROTECTION OF WATER RESOURCES
The dependence of ZP on the magnitude of the redox potential and the ionic composition of water has been established. The physico-chemical composition of the studied water was determined, the analysis of the obtained results was made. During the studies, indicators such as pH, temperature, turbidity and alkalinity were additionally determined to obtain a complete picture of water quality. All studied water indicators meet the standards of SanPiN 18.104.22.1684-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control: Sanitary rules and regulations. Mathematical dependences between the ζ-potential, rigidity, and the content of anions and cations in the water under study with an accuracy of approximation R2 not lower than 0.83 are given.
Advances in fuel cells in recent years have made it possible to apply them with high efficiency in various engineering fi elds. In this paper, a scheme of functioning of an electrofloter was proposed in conjunction with a solid oxide fuel cell. Experimental studies of a hydrogen fuel cell were carried out to obtain a current-voltage characteristic and a curve for the dependence of the fuel cell efficiency on the specific power and current was obtained. The surface efficiency of the electroflater-fuel cell system was built and conclusions were drawn about energy savings and optimal areas of the active surface of the fuel cell under investigation when working with electroflotters with a capacity of up to 3 m3 / h.
The main physical and chemical parameters of a new sorbent developed on the basis of the minerals of the Samara region: clays, peat and dolomite are considered. The particle size of the clay after grinding at the stage of preliminary preparation was less than 1 nm, which relates them to highly dispersed materials. A chemical analysis of the composition of the components showed a high content of silicon and aluminum oxides, which possess ion-exchange properties, and also made it possible to assign clays to montmorillonite rocks. The modification of the sorbent was carried out by thermal method. The density of the finished sample was 1.8 g / cm3. The method of scanning electron microscopy showed that the structure of the finished sample belongs to spongy bodies. The method of IR spectrometry confirmed the presence of functional groups in the crystal lattice of the sorbent, which cause not only the physical, but also the ion-exchange and chemical nature of sorption.
The issues related to the problem of reducing unproductive water losses in the systems of cold and hot water supply of apartment buildings are considered in the article. The insufficient efficiency of application of known water-saving devices, reducing overhead costs, the cause of which is the contradiction between the requirements of rationality and ensuring the maximum demand for a public water supply service, is shown. The recommendations for improving the design of the piston apartment pressure regulator “after itself”, ensuring a reduction in non-productive costs are developed. The results of an experimental study of a pressure regulator with an improved water-saving characteristic are presented.
A topological model of the structure of the technical system of sewage settlement, which is displayed using graphs, is proposed. The functional description of the settlement technical system is verbally executed and reflects a multi-level hierarchy of sewer system functions. The proposed topological model of a technical system and its functional description allow the analysis of the real sewerage system of a settlement and modeling to solve its modernization problems and determine the direction of its prospective development, taking into account the many internal and external factors and relations with the surrounding knowledge space and technology complexes. The factors influencing the improvement of all complexes of the settlement sewerage system, as well as the choice of technological solutions at the stage of architectural and construction design of these technical systems are described in detail.
ARCHITECTURE AND CIVIL ENGINEERING
BUILDING MATERIALS AND PRODUCTS
Using the example of unmodified and modified cement composites, the effect of temperature and humidity operating factors on the strength characteristics of fine-grained concretes was studied. It was revealed that for unmodified concrete, varying the test temperature leads to a significant change in the strength characteristics of cement composites, increasing (taking into account their moisture content) during bending and compression tests in the region of negative temperatures. The greatest increase in the elastic strength characteristics is observed in moisture-saturated samples. For samples in the dry state, the change in the strength characteristics under compression with a decrease in temperature from + 40 to -40 ° C is 17 %, and 22 % for bending stretching. According to the research results, it has been established that for modified highstrength and dispersion-reinforced concrete there is a significant increase in tensile strength in bending throughout the entire range of temperatures studied for water-saturated samples compared to samples in a dry and equilibrium-moisture state. These differences in the nature of the influence of the test temperature and the moisture content of the samples on the change in the physicomechanical characteristics of the modified and unmodified concretes are explained by the difference in the structure and the type of moisture contained in them. In particular, the structure of modified composites is dominated by adsorption and crystallization-related water, characterized by high binding energy, and in the structure of “traditional” concrete there is a large amount of capillary-saturated and free water, which is weakly associated with the solid phase of unmodified composites.
ARCHITECTURE AND CIVIL ENGINEERING
TECHNOLOGY AND ORGANIZATION OF CONSTRUCTION
The results of the study of the effect of humidity on the surface energy of concrete are considered. It is shown that the value of the latter largely depends on the moisture content of the material and varies widely, sometimes several times, depending on the stage of destruction. Two groups of indicators aff ecting the process of destruction are identified: physicomechanical and kinetic. It is shown that the surface energy referred to the first group is one of the parameters determining the strength and performance characteristics of concrete. It is concluded that taking into account the moisture content of the material allows us to explain the behavior of concrete when it is soaked.
ARCHITECTURE AND CIVIL ENGINEERING
URBAN PLANNING, PLANNING OF RURAL SETTLEMENTS
The hypothesis of phenotypological causes of city formation is considered. It is proposed to look at the “city” as the most convenient model for the survival of modern man. In parallel, the author explains the reason for the emergence of this model, perceiving man himself as a representative of one of the biological species of our planet. The topic of professional ethics in the work of modern architects and city planners regarding the historical and architectural environment of the city is raised. The author introduces a number of terms to describe the observed phenomena. The study topic is supported by illustrative material. The arguments set forth in the article formulate a general thesis about the need to integrate related disciplines of a wide range into the professional field of architects solving modern urban planning tasks.
The article explores one of the characteristic final elements of the roofs of historic residential and civil buildings – the tent. The variety of forms and their varieties that appeared in Samara in the late XIX – early XX century, in the heyday of interest in folk traditions and stylisations in the spirit of national neo-romanticism, is noted. For the first time, the author classifies the tent completion forms common in the city in the form of simple four-sided tents, hubcaps, tents, epanches on the roofs of houses, as well as with various dormer windows; tents on corner turrets, compositionally complex tents with ornaments in the form of keel-shaped zakomars, stamped inserts, with side obelisks, hip overlays and cross decorations, cubic, barrel-shaped and multi-tiered tents. The author emphasizes the special significance of the tent in town planning, the composition of buildings and the recognition of the appearance of the Volga historical city of Samara. The purpose of the article is to study the characteristic features of the identity of the city, its architecture, in particular the tent elements of historical buildings.
The article is devoted to the consideration in a generalized manner of the range of possible strategies for the spatial development of provincial cities in Russia, taking into account the current specifics of the formation of their management institutions and construction business enterprises. The main options for the development of cities in the near future with their pros and cons are considered. The problem developed in this article is extremely relevant for almost any city in modern Russia at the stage of changing the economic structure and the country›s transition from an industrial to a post-industrial type of economy. The authors of the article substantiate the advantages of choosing a polycentric model of the development of the city of Samara. Conclusions and recommendations are made on a specific urban planning material.
The causes of the typology of low-rise multi-family housing construction in the very first years after World War II are considered. On the example of one of the most successful series of residential buildings (series 201), the principles underlying its design are identified. The coincidence of these principles with the main ideas of constructivism is shown. The post-war history of the further construction of the Kolomna village named after I.V. Stalin ZiS, the layout of the village, the advantages and disadvantages of houses, as well as the history of the subsequent development of this area of Moscow are described.
ELECTRIC POWER STATIONS, NETWORKS, AND GRIDS
In order to reduce the energy consumption, increase the reliability of the hydraulic drive of construction machines and mechanisms, studies of the hydrodynamic parameters of the viscous fluid flow in a flat diffuser during the oscillation of one of the walls of the channel are carried out. Navier-Stokes equations together with the continuity equation are used to construct velocity and pressure fields. The problem is solved in polar coordinates with boundary conditions. The General solution of the problem, which corresponds to the self-similar boundary condition on the moving wall, is obtained. The radial velocity profile has sections of forward and reverse currents and is a standing wave along the angular coordinate. The forces acting on the movable and stationary walls of the diffuser are determined.
INDUSTRIAL THERMAL POWER
Casting in a cooled mold is the main way to produce aluminum semi-finished products – round ingots. Continuous casting leads to the formation of a heterogeneous structure. Its elimination occurs during heat treatment – homogenization annealing followed by cooling in the chamber. To study the heat exchange between aluminum ingots and cooling coolant in the chamber, a mathematical model was developed. She showed that the cooling time of ingots in the chamber depends on structural and operational factors. This paper is devoted to the optimization of the design factors of the mathematical model of heat transfer in the cooling chamber of aluminum ingots. The questions of optimization criteria are considered, the objective function with restrictions on the set of feasible solutions of the function is defined.