Introduction. The article presents the results of research into the possibility of using PENOPLEX extruded polystyrene foam in formwork systems during winter concreting by the warm curing method.

Aim. The study is aimed at the development of the formwork system applying the PENOPLEX extruded polystyrene foam for shortening the periods of concrete hardening to the necessary strength and reducing the electric power costs during the combination of the warm curing with electrical heating in the winter concreting.

Methods and materials. The analysis of the acting regulatory and methodical bases, concerning the studied issue, was carried out for solving the stated goals. A special program of experimental studies was developed and tests were carried out to determine the strength of the obtained samples of concrete made according to various schemes of thermal insulating the formwork system both with and without using the concrete electric heating under fixed energy consumption. The performed works promote for the conclusions about the effectiveness of the extruded polystyrene application in the universal formwork systems during the winter concreting by the warm curing method.

Results. In the comparison with the developed schemes, the continuous thermal insulation of the extruded polystyrene foam was revealed to have the greatest effectiveness during the winter concreting by the warm curing method. Depending on the concrete holding time, the continuous thermal insulation scheme under electric heating saves energy resources 3.5-5.5 times efficiently in contrast to the scheme without using the extruded polystyrene foam in terms of the insulation. Concrete strength tests demonstrated that the concrete compressive strength required for removing the formwork can be obtained on the second day already.

Conclusions. According to the results of the study, the use of the PENOPLEX extruded polystyrene foam plates in the formwork system with the continuous heat insulation during the winter concreting by the warm curing method reduces the periods of concrete hardening to the necessary strength and decreases power consumption for the electrical heating in the combination of winter concreting methods.

Introduction. At present, the connection of precast concrete pile sections using Leimet ABB+ 350 pile joints becomes very popular. The main advantages of this joint include low labor intensity (relative to the widely used welded joints) for connecting pile elements, high installation speed, as well as the absence of welding works, concreting, etc. The wide application of this joint is currently limited by the insufficient study of its parameters and, in particular, strength characteristics.

Aim. Experimental testing of the strength indices of the Leimet ABB+ 350 pile joint under the compression, tension, transverse shear, and bending.

Methods and materials. The studies were performed on the series of samples represented by two fragments of the 1.011.1-10 standard precast reinforced pile sections connected by the Leimet ABB+ 350 four-lock pin joint. Loading tests of the samples were carried out in accordance with the GOST 8829-2018.

Results. The quantitative and qualitative destruction parameters of the samples are obtained.

Conclusions. The Leimet ABB+ 350 pile joint was concluded to be of the uniform strength to the pile concrete bodies under considered impacts. The obtained results on the strength of the pile pin joint can be used in the design development and the solution of practical engineering problems.

Introduction. The behaviors, advantages, and disadvantages of various types of frame-cladding buildings having cold-formed galvanized steel constructions under loads simulating seismic effects are considered. The paper stresses the relevance and demonstrates the problem of the widespread use of light gauge steel framing structures (LGSFS) in earthquake-prone areas in the Russian Federation.

Materials and methods. Normative requirements in different countries for calculating and designing frame-cladding buildings having cold-formed galvanized steel constructions erected in earthquake-prone areas, as well as domestic and foreign literature, were analyzed, using structural, comparative, and matching analyzes, systematization, and theoretical generalization of obtained.

Results. A brief review and analysis of current domestic and foreign standard technical documents, as well as research findings in the field of the calculation and design of frame-cladding buildings having cold-formed galvanized steel constructions erected in earthquake-prone areas, are presented. The recent advances in studying load-bearing and non-load-bearing frame-cladding cold-formed galvanized steel structures and joint elements under simulated seismic loads were reviewed and summarized in order to demonstrate current progress, challenges, and prospects for future research. Differences in current standard technical documents used in the USA and Canada concerning seismic load reduction coefficients, as well as the weaknesses of the European and domestic normative documents in terms of regulating requirements for calculating and designing frame-cladding buildings having cold-formed galvanized steel constructions, erected in seismic areas, were addressed.

Conclusions. The presented data confirm the necessity of theoretical and experimental research and development and improvement of standard technical documents. These documents will allow the reliability and mechanical safety of frame-cladding buildings having cold-formed steel constructions to be improved and their distribution in earthquake-prone areas of Russia to be significantly extended.

Introduction. The strength and deformability of cross-laminated timber (CLT) panels ensure the strength and stiffness of load-bearing frames. However, despite numerous studies on CLT joints, data on plastic behavior, safety coefficient, and the failure behavior of used joints are lacking in European and North American design standards.

Aim. The work addresses the load-bearing capacity, coefficients of stiffness and ductility of CLT joints, following the design features of cross-laminated timber.

Materials and methods. A series of samples were produced based on conventional solutions for CLT panels (“overlap,” “gasket-sealed,” “strapped,” “butt,” and “halved corner”), having various layers and diameters of a screw, and subjected to subsequent testing. The research procedure was developed following GOST 33082-2014 and foreign practices. The research was carried out at the Laboratory of Timber Structures of TSNIISK named after V.A. Koucherenko.

Results. Based on the experimental data, the normative and design load-bearing capacity, coefficients of stiffness and ductility for five types of CLT joints were established, depending on the number and direction of the outer layers, as well as the screw diameter. A plastic behavior rating scale was proposed to assess the performance of joints beyond elastic behavior, namely, a joint can be brittle, with low, moderate, or high plasticity.

Conclusions. The design features of CLT, such as the number of layers and their thickness, as well as the orientation of the outer layers, significantly influence the strength and deformation characteristics of screwed nodal CLT joints. The research results are intended for updating Rules and Regulations 299.13258800.2017 “Timber structures with screwed nodal joints.”

Introduction. The application of the Leimet ABB+ 400 pile joint appears to be a promising and technologically effective method of the connecting the sections of precast reinforced concrete piles. Currently, the issues of corrosion protection measures and service life forecasting for this type of joints are understudied.

Aim. The aim of the research involves the determination of the qualitative and quantitative parameters of corrosion damage to the pin joint elements affected by the specified liquid corrosive under various methods of corrosion protection.

Methods and materials. The studied samples included fragments of the Leimet ABB+ 400 pile joint between the sections of precast reinforced concrete piles. Three series of samples differing by the methods of corrosion protection were considered, including completely unprotected, with the galvanization of locking dowels combined with lubrication of locking elements by lithium-based inhibited grease, as well as with the selective application of bituminous cold mastic. The program of accelerated corrosion tests according to the GOST R 9.905-2007 was developed and implemented. The following two testing modes were included in the program: permanent exposure of the samples to 5 % sodium chloride water solution for the entire testing period; 8- and 16-hour cycles of exposing samples to 5 % sodium chloride water solution and to the air, respectively.

Results. Based on the results of accelerated corrosion tests, the quantitative and qualitative evaluation of the corrosive damage to the elements of the Leimet ABB+ 400 pile joint was performed. The results of forecasting their service life according to the conditional criteria are provided. The pin joint elements susceptible to the corrosion in a liquid corrosive medium were identified.

Conclusions. In the framework of the study, the most effective way of anti-corrosion protection of the Leimet ABB+ 400 pile joint was identified as the galvanization of the locking dowels combined with lubrication of the locking elements by the inhibited lithium-based grease. At the end of accelerated corrosion tests, the samples protected according to this method demonstrated no signs of corrosion damage. This method is applicable for ensuring the conditional service life of the pin connection under the exposure to highly aggressive liquid medium during the period considerably exceeding 25 years. Nevertheless, further refining studies of this issue are required.

Introduction. Reactive powder concrete (RPC) characterized by high strength and density falls into the category of concretes having ultra-high physicomechanical properties. NIIZHB specialists developed an RPC production and application technology involving the use of pit-run aggregates, silica fume, and low water demand binders (LWDBs) obtained via intergrinding using a rationally selected raw mixture, which includes portland cement, mineral admixtures, and a chemical modifier. The technology for developing RPCs adopts a higher dispersion degree, with cement as the most finely ground component replaced by silica fume, while the roles of fine and coarse aggregates are played by binder and sand, respectively. This factor ensures a compressive strength of 160-200 MPa at 28 days and a bending tensile strength of 20-30 MPa and greater, depending on concrete composition, hardening conditions, the presence of a micro-reinforcing component, etc. A distinctive feature of RPCs consists in the increased cement binder content (800-1000 kg/m³), leading to a high material consumption of RPCs, as well as reducing economic efficiency.

Aim. To study the feasibility of obtaining RPCs while replacing a certain amount of the clinker component with various mineral admixtures intended to reduce the consumption of the cement component, which is the most energy-intensive and costly component.

Materials and methods. A composite LWDB and various active mineral admixtures (metakaolin; granulated blast-furnace slag) were used as a binder in the production of RPCs.

Results. The paper provides a comparative analysis of the technological properties of concrete mixtures (density and water demand) and the physicomechanical properties of RPCs varying in composition (compressive strength).

Conclusions. It was established that up to half of the cement component used in LWDBs can be replaced by blast furnace slag at a constant silica fume content in the binder (25 %) while maintaining or slightly reducing the concrete strength (up to 5-8 %). In this case, it is possible to save about 300-400 kg of cement per 1 m³ of RPC.

Introduction. To date, construction principles applied to stone runs have only been developed in theory, while the extent to which they are tested in practice is limited since the engineering development of sloping stone runs is still rather narrow in scope. This factor leads to the lack of a unified formalized approach to the development of measures intended to reduce the risk of stone run formation when designing structures in areas affected by this process.

Aim. To consider a problem associated with factoring in stone run formation in the design of structures on the example of overhead line towers for Udokan Copper, as well as covering adopted engineering solutions providing a means to localize this process using a specific example.

Materials and Methods. The paper considers a problem associated with factoring in stone run formation in the design of structures on the example of overhead line towers for the Udokan Mining and Metallurgical Plant. Engineering solutions adopted for this facility in order to protect structures by creating buffer zones between the stone run and the structure are presented. In addition, the basis was provided for developing recommendations on structure design for areas prone to hazardous frost action. In order to justify adopted solutions, mathematical modeling was performed using PLAXIS 2D software.

Results. The calculations yielded isofields showing soil base and foundation displacements for a given stone run displacement along the slope. The obtained results indicate that stone run displacements do not affect overhead line tower foundations when a buffer zone is created.

Conclusions. The issue associated with factoring in the impact of hazardous frost action involving stone run formation in the design of structures remains to be explored in practice, requiring further consideration in order to further formalize the methods of engineering protection against stone runs in regulatory documents.

Introduction. As a result of the global warming, the thawing of permafrost soils in the northern regions occurs and leads to naturally increasing wind and snow loads on the buildings, structures, and their foundations. Snow accumulations create a heat-insulating layer preventing the soil freezing in the cold period of the year and moisturize the soil in the warm period, which leads to the deformation of the support structures of buildings and civil engineering works.

Aim. The study aims at the advancement of the spatial reinforced concrete foundation platform of a residential building on the permafrost soil by providing the direct cooling of the lower reinforced concrete slab of the foundation platform using the system of automatic control, as well as at the development of the thermally controlled shell of reinforced concrete foundation platform with the possibility of the resistance to wind currents and prevention of the massive snow transfer into the ventilated underfloor space.

Methods and materials. The system of automatic control of the soil cooling process due to the direct cooling of the lower reinforced concrete slab of the foundation platform was studied using the Arduino Uno printed circuit board.

Results. Based on the used equipment, the block diagram of the experimental setup was developed for recording variations in the air and permafrost soil temperature. In order to study the feasibility of the system for automatic control of the soil cooling process due to the direct cooling of the lower reinforced concrete slab of the foundation platform, a model was created and implemented in the SimInTechs environment for the dynamic modeling of technical systems.

Conclusions. As a result, the authors proposed a new technical solution represented by the thermally controlled shell, made of laminated timber in the form of a highly industrialized module forming the enclosed space with the reinforced concrete slabs. In addition, all laminated timber panels, installed with the possibility of resisting to wind currents and preventing the snow transfer, contain the electrically driven adjustable louvered grilles. The spatial reinforced concrete foundation platform on permafrost soil is patented.

Introduction. The article considers the aspects of the effect caused by the concrete biological corrosion on the durability of concrete and reinforced concrete structures of transport infrastructure facilities. Examples of real objects with identified areas of the combined effect of bio- and other types of the concrete corrosion are considered.

Aim. The study aims at investigating the processes of biofouling on the surface of bridge supports and mechanisms of biomass formation on the concrete surface depending on the mode of the fluid movement in the river flow.

Methods and materials. The dependence of the Reynolds number on the temperature and the coefficient of the river water kinematic viscosity is considered. A physical and mathematical model of the biocorrosion mass transfer, occurring during the flowover of a two-row bridge support system by a liquid flow under small Reynolds numbers, was developed and calculated.

Results. Due to the developed physical and mathematical model, the service life of the reinforced concrete bridge supports can be calculated, the “residual” durability can be determined, as well as the possible time of cleaning the concrete surface from biodeposits can be obtained.

Conclusions. According to the results of the conducted research, the dependence of the concrete biocorrosion effect on the process of the surface biofouling of concrete/reinforced concrete supports is revealed. In addition, the article provides the calculation of economic efficiency of the measures for cleaning concrete from biofouling. According to the calculation, the annual economic effect amounted to 9% of the budgeted cost of the performed works. In the case of perfoming scheduled preventive measures for cleaning from biofouling at least once every 5 years, the period for carrying out inter-repair work for eliminating defects in concrete and reinforced concrete building structures can be increased by 1.5 times. On the basis of the performed calculation, the recommendations on the increase in the durability and the period of the effective operation of bridge structures are provided.

Introduction. Numerous researchers have examined issues associated with the analytical and computer-assisted design calculations for reinforced-concrete waffle slab systems. The obtained data indicate that forces in the beams can vary significantly depending on the created finite element model. Some models provide no means to correctly select beam reinforcement in the automatic mode of the selected analysis system.

Aim. To create a computer model of a waffle slab floor system, forces, reinforcement, and deflections in whose beams would be comparable to the data of analytical design calculations performed in accordance with regulatory requirements.

Materials and methods. According to the finite element method, the most accurate model comprises bar finite elements. The simplest analytical calculation can be performed for a square structure comprising square waffle slabs since it becomes easier to ascertain coefficients determining how the load is distributed on the beams. In this connection, the authors developed three bar finite-element models of a rectangular floor system measuring 9.0 х 9.0 m (square waffle slabs of 0.9 x 0.9 m) to be used in the procedure. The first model comprises bar finite elements having a T-section directly subjected to a load per unit length distributed from the coffers according to the triangle law. The second and third models differ from the first model in the way the load is applied to a flexible shell finite element having regular and chaotic partitions.

Results. The obtained results indicate that computer models accurately reflect the stress state of beams in the waffle slab floor system as compared to the analytical calculations. Bending moment deviations do not exceed +5 %.

Conclusions. The developed SCAD finite-element models enable reliable determination of forces, design calculations for the reinforced-concrete beams of the waffle slab floor system according to the ultimate and serviceability limit states, as well as comparison of the obtained data with analytical calculations performed in accordance with regulatory requirements. The proposed models can be used in verification calculations for floor system models comprising different types of finite elements (bar, plate, shell, and their combinations).

Introduction. The paper discusses the development of economically feasible and efficient overhaul methods for trunk pipelines using composite materials that can be carried out without shutdown.

Methods. Full-scale experiments were carried out to achieve this goal. To determine the optimal structural composition of the repair assembly from composite materials, the algorithm of the SOLIDWORKS software was applied. Experimental and modeling results were further compared.

Results. A comparative analysis of the results obtained in the experiments and modeling of overhaul repair process of trunk pipelines using SOLIDWORKS software showed their good agreement. Based on the modeling results, the dependence of the stress-strain state at the assembly on the number of composite material layers was established. The obtained dependence allowed such parameters of the trunk pipeline overhaul process, as geometric dimensions of defects, the type of composite material, and the quantitative composition of a composite assembly, to be modeled.

Conclusions. The obtained research results on the development of overhaul process of trunk pipelines using composite materials proved highly reliable, hence recommended for industrial application. The proposed method of modeling the overhaul process of trunk pipelines using SOLIDWORKS software significantly reduces the complexity and duration of determining the optimal quantitative composition of the composite assembly for repairing pipelines based on the operating parameters of structures and the geometric dimensions of defects.

This article argues that contemporary research and educational literature attributes the birth of science to Ancient Greece or the Renaissance period in Europe during the 15th—17th centuries. Such a Eurocentric approach, in the author's opinion, is insufficiently convincing. The article provides specific examples to demonstrate that sophisticated scientific knowledge first appeared in the Ancient East, while the natural philosophers and thinkers of Ancient Greece and the so-called Hellenic world either appropriated this knowledge or used it as a basis for their discoveries, often without mentioning the original source. As evidence, the article discloses the history behind the origin of primary scientific knowledge in a number of countries in the Ancient East, its content and impact on the development of ancient eastern civilizations and science as a whole. Particular attention is paid to the practical application of theoretical knowledge in several applied fields of economic activity, such as construction, architecture, road building, hydraulic engineering, and others. In conclusion, the article reveals reasons for the limitation and utilitarianism of this knowledge, since it provided only ready-made solutions lacking critical evaluation and rational justification. Moreover, the system of evidence was rarely considered important. All these factors ultimately prevented the formation of a system of fundamental science.

Aim. This study aims to use natural weather conditions of the environment, caused by forming the dominant characteristics of the geometric model associated with freezing profiles of the industrial soil foundation in the natural surroundings. These profiles were obtained during soil investigations, followed by a direct laboratory analysis of soil samples, depending on the sampling depth. The relevance of the research is determined by Arctic development and climate change.

Materials and methods. The work is based on the results obtained in fields of not only geological engineering and natural spatial measurements, but also the philosophy of science. The relationship between the characteristics of varying parameters of heat transfer in foundation subsoil waters was empirically determined to ensure an optimal selection of materials and technologies employed in construction.

Results. The conducted study and computer modeling determined the nature of motion, formation, and impact of near-surface water on industrial soil foundations. Based on the stabilization of soil and industrial foundation states and the stability of essential characteristics associated with their natural state, the key aspect for developing the concept of design and construction under the conditions of permafrost soil was identified.

Conclusions. It is established that the parameters of thermal stabilization of soil foundations are inapplicable in subzone I₁.