Introduction. The I-beams are deemed to have the highest load-bearing capacity. However, in practice, due to wide spreading and affordability of pipe-rolling products, the tubular beams are being used quite often. The load-bearing capacity of these beams should be compared under the condition of their equal mass per running meter. An I-beam according to the GOST R 57837-2017 with the mass of running meter equal to 194 kg and a pipe according to the GOST 33228-2015 with the mass of 194 kg/m have been compared. The load-bearing capacity of an I-beam was almost twice as high as that of a tubular beam. The data about the concrete filled steel tubular (CFST) beams, including the ones with the prestressed concrete core at the bottom, is also provided. In such beams, a steel pipe works as an external reinforcement — exo-reinforcement. The load-bearing capacity of the CFST beams is quite considerable taking into account their low cost and good processability. The present research aims at increasing the load-bearing capacity of the tubular beams, which will expand the range of the construction products.

Materials and Methods. The geometric optimisation and mental experiment methods have been used. The idea of using the fluid filling material for a tubular beam is based on the well-known property of fluid — its almost complete incompressibility. The maximum volume of a geometric long body with the rectilinear generatrix of lateral surface (for a given lateral surface) is reached if its cross-section has the shape of a circle, which corresponds to a round pipe.

Results. A tubular beam with the fluid filling material (a hydraulic beam) is a round pipe blanked off at both ends, completely filled with fluid (without air pockets). When a hydraulic beam is loaded, its lateral surface tends to deform. Consequently, the internal volume of the pipe tends to decrease. However, since fluid is incompressible, its volume doesn’t decrease, which, in turn, prevents the pipe from deformation.

Discussion and Conclusion. In a hydraulic beam, due to fluid, the entire load is distributed relatively evenly over the whole internal surface of a beam. The load-bearing capacity of a hydraulic beam has been estimated, which is five times higher than that of an I-beam and ten times higher than that of a tubular beam.

Introduction. A historical (retrospective) overview of the evolution and application of the methods of concrete mixture compaction by vibration, as well as an overview of the breakthrough scientific+ advancements in the studied field have been presented. The use of the dry concrete mixes that reduce cement consumption, accelerate the strength gain of concrete, reduce the shrinkage strain and heat emission and increase the strength and durability of products has been proposed. The theoretical and practical issues of vibratory compaction of the concrete mixes, the research on the effect reached by the various vibration modes of the vibrating tables, the issues of choosing an efficient mode of vibration impact during compacting the concrete mixes and optimisation of their parameters have been studied. The vibrating table design, the installation layout of the vibrator’s eccentric weights to obtain a given value of the exciting force and the layout of a vibration module with the directed vibrations have been studied in detail. The criteria of duration of the concrete mixture compaction have been defined, changes of the impact parameters during compacting the concrete mixes have been characterised and technical specifications of the vibrating tables have been defined. In the article considerable attention has been paid to the main parameters of the vibrocompacting machines: frequency, amplitude and acceleration of the working member. Most often, the parameter of intensity is used to assess the efficiency of the vibration impact received by the mixture during the compaction process.

Materials and Methods. A mixture that turns into concrete after compaction, setting and hardening was selected for the research. The various methods and parameters of concrete mixture compaction to obtain the high-quality concrete were studied. The impact of the various vibration modes on the process of compaction of concrete mixes was investigated, the criteria for the efficient selection and optimisation of the vibration impact parameters were revealed. The paper presents the criteria for assessing duration of the concrete mixture compaction and describes the changes in the parameters during compaction of the concrete mixes. The technical specifications of the vibrating tables of different types and sizes were also presented. The choice of the vibration compaction mode for the concrete mixture is a complicated task, which includes many parameters.

Results. Upon the research, the data on the process of concrete mixture compaction under the impact of vibration forces has been obtained. The process results in the destruction of the structural bonds and weakening the bonds between the particles, which leads to the emergence of a variable stress-strain condition. It has also been found that under such settings, the mineral particles get transferred and a denser packing is formed.

Discussion and Conclusion. The resulting denser packing of the concrete mixture particles ensures the undoubted economic advantage due to reduced consumption of a binder without loss of the strength properties of concrete.

Introduction. The technical effect attained during construction of the monolithic reinforced concrete structures made of self-compacting concrete mixtures, which results in the increase of the actual strength of concrete, can be put to use to reduce the cross section of the structures and to cut down the consumption of the reinforcement. The paper aims to assess the technical and economic efficiency of the monolithic reinforced concrete structures made of high-strength self-compacting concrete, with the use of the construction waste, in meeting the goals of green construction.

Materials and Methods. To assess the efficiency of the monolithic structure concreting options, the vibratory-compacting concrete mixture БСТ В25 П4 and the self-compacting mixture БСТ В40 РК1 were prepared using the Portland cement CEM0 42.5N. The crushed stone of fraction 5–10 mm was used as a coarse aggregate and natural sand and crushed sand from construction waste (concrete scrap) were used as a fine aggregate. To ensure the high fluidity of the mixtures, the additive Polyplast PK— a universal ester-based polycarboxylate superplasticizer was used. The calculation of the parameters of the reinforced concrete structures depending on the compressive strength of concrete was performed in the LIRA software package. The estimated cost of the works on construction of the reinforced concrete structures was determined for two alternative options that differed in the type of concrete mixture used, the method of its delivery to the place of concreting and in the method of compaction.

Results. The calculation of the parameters of the reinforced concrete structures has been carried out, which showed that for the structures made of high-strength B40 class concrete, the cross-section thickness can be uniform along the entire height — 200 mm, whereas the amount of concrete can be 20% less than for B25 class concrete. The calculation of reinforcing parameters along the structures’ height in correlation to the strength of concrete showed that when using the self-compacting B40 class concrete, it is possible to reduce the design diameter and to cut down the consumption of the reinforcement. The expected economic effect of using the self-compacting high-strength concrete, calculated for concreting the structures of the volume of 433 m3 , can be 1639.5 rubbles.

Discussion and Conclusion. The technical and economic efficiency of using the high-strength self-compacting concrete for concreting the monolithic reinforced concrete structures has been substantiated. As a result of using the self-compacting mixture and concrete pumping technology, the estimated cost of constructing the structures is reduced, the manpower inputs and labour costs are decreased, and, due to the use of the construction waste and refusal from utilising the electrical equipment for the vibratory compaction, the ecological effect is achieved.

Introduction. The most important reasons justifying the relevance of the research on the practical methods of reducing the consumption of materials in construction industry have been distinguished. The priorities of the Russian Federation referring to the foam concrete technology have been outlined. The level of reliability of the Internet resources describing properties of the dispersedly reinforced foam concretes has been briefly evaluated. The aim of the study is to establish the relationships between the individual properties of fiber, its quantity to the mass of cement ratio, and the most important operational properties of foam concrete manufactured using a single-stage technology.

Materials and methods. The types and properties of raw materials used in the experimental research, the methods for controlling the properties of mixes and hardened foam concretes have been defined.

Results. The relationship between the speed of phase transition of the viscoplastic properties of the foam concrete mixes into the elastic ones and the possibility of getting a high-quality structure of the hardened foam concrete have been briefly theoretically justified. The physical reasons influencing the direction and speed of forming the raw material dispersed particle clusters in the structure of the interpore partitions of foam concrete mixes have been revealed, which are the important factors to be considered in practice to get the high-strength foam concretes. Depending on the fiber concentration in the concrete mixture composition, the specifics of the fiber physical nature influence on the speed of phase transition from viscoplastic to elastic state have been established. It has been proved that the synergetic effect of dispersed reinforcement is achieved when fiber concentration is enough to provide the significant acceleration of the phase transition. New experimental data on the influence of the individual properties of fiber on the rheological and physico-mechanical properties of D500 foam concrete has been obtained.

Discussion and Conclusion. The scientific explanation of the reasons for emergence of the electret effect on the surface of synthetic fiber has been given. It has been revealed that the discovered effect is induced by the specifics of the foam concrete mixture preparation using a single-stage technology. The most important practical conditions due to be met to get the high-strength foam concrete have been determined.

Introduction. The machine learning algorithms are highly promising for predicting the load-bearing capacity of the building structures. The paper aims at building the predictive models for calculating the strength of the concrete-filled steel tubular (CFST) columns to enable a highly accurate prediction of the ultimate loads for the entire possible range of parameters affecting the load-bearing capacity of the eccentrically compressed columns.

Materials and Methods. The article studies the eccentrically compressed short concrete-filled steel tubular (CFST) columns of circular cross-section. Model input parameters: column outer diameter, pipe wall thickness, yield strength of steel, compressive strength of concrete, relative eccentricity. Output parameters: the ultimate loads without taking into account and taking into account the random eccentricities. The models were trained on synthetic data generated based on the theoretical principles of the limit equilibrium method. Two machine learning models were built. When training the first model, the ultimate loads were determined at a given eccentricity of the longitudinal force without taking into account the additional random eccentricity. When training the second model, the additional random eccentricity was taken into account. The effect of the features on the model predictions was assessed using the Feature Importance function. The Optuna method was used to select the hyperparameters. The machine learning models were implemented in the Jupiter Notebook environment using the Gradient Boosting learning method. The total volume of the training sample was 179 025 samples.

Results. The importance of the features most affecting the predictive values of the model have been determined. For both models, the outer diameter of the column and the relative eccentricity have proved to be the most important features, which is consistent with the existing experience of designing and calculating such structures. Optimisation of the hyperparameters using the Grid Search method enabled getting the improved results. The high accuracy of prediction has been ascertained by the low values of the regression metrics: MSE = 9.024; MAE = 9.250; MAPE = 0.004 — for the model built without taking into account the additional random eccentricity; MSE = 8.673; MAE = 8.673; MAPE = 0.004 — for the model built taking into account the additional random eccentricity.

Discussion and Conclusion. The developed Gradient Boosting models for predicting the ultimate loads of the eccentrically compressed short concrete-filled steel tubular (CFST) columns of circular cross-section, both without taking into account and taking into account the additional random eccentricities, have demonstrated high accuracy and stability of prediction, they can be applied for assessing the strength of the columns during design and construction, which will reduce the time and resources involved in physical testing. In the future, it is planned to expand the data range by including other materials, different cross-section geometries of the columns and a slenderness parameter, which may improve the generalization ability of the model.

Introduction. In the context of the “green transition” and decarbonisation of the Russian Federation economy, for the sake of supporting this process, it is necessary to have a tool optimising the choice of the territory allocated for implementation of the alternative energy sources as an option of the hybrid decentralised energy supply. It should be borne in mind that the types of alternative energy sources should differ depending on the territory and its features, therefore, application of the systematic approach and adjustment of the methodology of comprehensive assessment of the territory for future planning the integration of the renewable energy sources into the energy complex of a subject of the Russian Federation have been substantiated.

Materials and Methods. The object of the study was the territorial–spatial system (a subject of the Russian Federation) with its subsystems. The research was based on the synergistic approach, comparative and empirical analyses, methods of processing the statistical data and, in the cases of integrating the source data, the linear interpolation and the criterion function methods. The main fields of scientific knowledge and disciplines of science covered by the research were the urban planning, climate, geography and the energy complex. The geographic information systems within the QGIS environment were used as the tools for spatial analysis and visualisation of the simulation model data.

Results. The main result of implementing a simulation model for assessing the impact of the renewable energy facilities on the ecological condition of a subject of the Russian Federation is obtaining the list of territories (region ranking) designated for allocation of the alternative energy sources (solar power, wind power and biofuels). A secondary result of the research is identification of the environmental problems and consequences caused by implementation of the alternative energy facilities, as well as selection of the measures to reduce the negative impact on the environment.

Discussion and Conclusion. The theoretical and practical significance of the simulation model developed by the authors lies in taking into account the diverse parameters and conditions of a subject of the Russian Federation in the frame of the long-term and strategic planning of the region, its energy and spatial infrastructure, as well as in optimising the managerial decision-making. The use of the geoinformation systems makes it possible not only to store and visualise the data about the condition of a subject of the Russian Federation, but also to simulate the parameters of this data.

Introduction. It has become a modern trend to improve the quality of the urban environment using a public-private partnership (PPP) mechanism. By finding a balance between the interests of business and the state on the issues of infrastructure renovation, it is possible to boost the investment processes. Therefore, the PPP as a catalyst for the regional, innovative and social development has been studied in the scientific literature since long ago. Although, many authors recognise the prospects of the PPP efficiency, they still note the need to regularly revise the state support methods and tools, i.e. the existing system of measures requires improvement over time. Special attention has been paid to the models of financing the PPP projects and the ways of investment return. However, the PPP development potential in creation (reconstruction) of the park infrastructure has not been duly revealed yet.

Materials and Methods. During the research on identification of the features of the park complex transformation projects reconstructed in the frame of a concession business model, the projects were grouped according to the similarity of features. Then, by comparative analysis method, the problems of full recovery of the investment costs were identified in the selected projects. A hypothesis about the need of using the government budget co-financing for the certain concession agreements targeted at solving the various environmental, educational and awareness-raising issues was put forward.

Results. The national practices of transformation of the public spaces, such as parks and park infrastructure, have shown that the most optimal form of the PPP is a concession. The investor uses his funds at the design and construction stages of the creation (reconstruction) of the park complexes. At the stage of facility operation, a private party recovers its costs by collecting fees directly from the consumers. It is important that the expected project profitability should be within 15–25%. Due to the changes in the monetary policy, such profitability at the current key rate is hardly ever possible if the park infrastructure includes a variety of capital-intensive buildings and structures designated not so much for commercial but for social purposes. There arise the risks of receiving less income than expected. Therefore, for such projects, it is necessary to develop the measures expanding the ways of investment return. If a park has a complex infrastructure, which includes the large stadiums, museums, cultural and educational centres, i.e. facilities that are difficult to predict as having a high demand and, thus, not expedient for setting the high fees, it is advisable to combine the direct payment for services with the government budget co-financing. Co-financing is implemented through payment of a capital or operational grants. The variants of a grant can be considered depending on the areas of the park activities (educational, cultural, sport). The operational grant is due to reimburse the operational costs on maintaining the special facilities: adjacent embankments, lighthouses, memorials, etc. For the parks that include the indoor pools, large stadiums, museums, concert halls, it is relevant to use the capital grants to return the investments made into these facilities.

Discussion and Conclusion. In the current conditions, the public-private partnership is considered as an alternative to government budget investment into the infrastructure facilities. The transformation of the urban public spaces is also involved in this trend, and there are already positive results achieved. A private party, through investing its own capital, gets the opportunity to operate the created object to recoup its investments. But some projects are difficult in this sense, therefore the interest of the business companies to participate in the improvement of the urban environment quality reduces. In the context of the tight monetary policy, the additional state budgetary measures are needed to stimulate private investments.

Introduction. In design of a life-saving multi-storey building, a seismic isolation system in the form of the kinematic supports is used to ensure the seismic resistance and reduce the seismic loads. The structural system, the computational dynamic model and the results of the intermediate in-situ tests of a life-saving multi-storey building with a kinematic seismic isolation system being built in Grozny have been analysed in the article.

Materials and Methods. The research included modeling and computation of the structural system of a building with a kinematic seismic isolation system. In-situ tests were carried out to confirm the working capacity of the seismic isolation system connections.

Results. A multi-storey life-saving building was designed according to a frame-core wall structure, where the vertical load-bearing elements were core walls, columns and connections between the columns in the form of the stiffening diaphragms. The high-rise part of a building was designed using a kinematic seismic isolation system consisting of the seismic isolating concrete-filled steel tubular supports. The results of the calculations of the main and specific load combinations and internal forces in the load-bearing structures have been presented.

Discussion and Conclusion. The research has shown that the use of the developed structural system of seismic isolation with kinematic supports makes it possible to reduce the seismic loads and the total weight of a building and at the same time to increase its mechanical reliability and safety. The conducted intermediate in-situ tests have confirmed the working capacity of the joints connecting the supports with the monolithic reinforced concrete structures of a building, which makes it possible to implement the kinematic seismic isolation supports into the construction industry practices.