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Adhesive bond integration into steel structures of emergency shelters

https://doi.org/10.58224/2618-7183-2025-8-6-4
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Аннотация
Natural hazards and resulting technological disasters are currently becoming regular. In these conditions, the creation of emergency shelters is a foremost task of the government to provide the harmed population with housing units in a short time. In the framework of the integration of advanced materials and technologies into steel structures to create safe emergency shelters, experimental research is conducted into adhesively bonded steel-to-steel connections based on epoxy resin laminate. Such connections are interesting for prefabricated modular construction of emergency shelters, as they allow avoiding sectional weakening and stress concentrators common to welding and screw connections. Young’s modulus and shear modulus determined for the epoxy adhesive, are crucial parameters for accurate design. The paper studies the strain distribution in epoxy bonded steel-to-steel connections, identifies strain stages and strain concentration zones, leading to a combined cohesive-adhesive fracture. The obtained results can be used to transfer form empirical building to theoretically substantiated strength analysis of safe and reliable assemblies of prefabricated adhesively bonded steel structures.
The paper presents integrated experimental research into epoxy bonded steel-to-steel connections based on FibArm Resin Laminate+. Tensile strain distribution is identified along the sample longitudinal axis. Four strain stages (elastic, yield plateau, plastic and pre-fracture) are determined together with the evolution of localized elastoplastic strain regions on the surface of the steel plate.
Identified are a nonuniform strain distribution with alternating compressive and tensile strain regions that correlates with transitions on strain-stress curves. The maximum primary relative strain in the epoxy adhesive reaches 3.38 % and concentrates along the adhesive–steel interface
In accordance with GOST 25717-83 requirements, the shear modulus of 236 MPa and Young’s modulus are determined for the epoxy adhesive by B method and the t distribution with the confidence level of 5%. These parameters are used for a transition from empirical building to theoretically substantiated finite element analysis of the stress-strain state of the steel-to-steel connection.
The obtained results help to optimize the design of epoxy bonded steel-to-steel connections in engineering, promoting more continuous load, reduced weight and defects as compared to conventional techniques (welding and screw connections). This work confirms the efficiency of sanding of the steel surface in gaining the best adhesion and resistance to environmental impacts, which is relevant for the iron, aerospace and construction industries.
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Numerical investigation of the dynamic impact of hybrid basalt fibre on the damage and split way resistance of reinforced concrete aerodrome pavement

https://doi.org/10.58224/2618-7183-2025-8-6-5
Аннотация
The study used Finite Element Analysis (FEA) to examine the influence of aircraft landing loads on the crack resistance of hybrid basalt fibre-reinforced aerodrome pavements. The study replicated a load from an Airbus A321neo on 25 distinct concrete mixtures, each incorporating different proportions of basalt micro and macro fibres. We measured the total deformation of each mix after 7, 14, and 28 days of curing. The results showed that all of the fibre-reinforced mixes had a significant and consistent decrease in deformation compared to the unreinforced control mix. Mix M11, which had 2% Basalt Microfibre and 1% Basalt Macro Fibre, was found to be the best mix. This particular hybrid combination consistently exhibited the lowest total deformation values throughout all three curing periods. For example, after 28 days, the control mix had a deformation of 0.0058265 mm, while Mix M11's deformation was only 0.0057363 mm. This numerical evidence shows that hybrid fibre reinforcement works together to make aerodrome concrete stronger and able to hold more weight. The results indicate that enhancing the hybrid basalt fibre content is an effective approach for creating pavements that are more resilient, long-lasting, and environmentally friendly, which is essential for enhancing safety and operational efficiency in the aviation sector.
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Heat and mass transfer in concrete mixtures during transportaion along the route «Manufacturer of liquid – phase solution – consumer of solid-phase concrete»

https://doi.org/10.58224/2618-7183-2025-8-6-6
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Аннотация
The durability of concrete is a critical operational parameter that directly determines the service life of concrete structures. Achieving a concrete mixture with specified rheological and strength properties is a vital technological stage, as the quality of the initial material governs the load-bearing capacity of the final reinforced concrete elements. In the technological process, the transformation of concrete mixture components into a liquid non-Newtonian system with distinct rheological characteristics, followed by solidification into a structured composition, depends significantly on the variability of physico-mechanical, thermophysical, and structural-mechanical properties of both individual components and the overall mixture.
Developing comprehensive mathematical models that describe the entire technological cycle—from production to placement—poses a multifactorial challenge aimed at ensuring the design durability of construction structures. Particular emphasis is placed on modeling heat and mass transfer processes within heterogeneous concrete systems, as these non-stationary external influences critically affect the operational characteristics of the final material. Transport and hardening parameters heavily influence structural transformations within the cement stone, ultimately impacting strength and deformation properties. Effective resolution of this problem necessitates modern numerical modeling techniques that incorporate the rheological behavior of concrete mixtures and hydration kinetics.
The proposed mathematical and algorithmic framework underpins efforts to minimize concrete structure degradation by simulating rheological parameters during transportation and placement. A principal achievement is the creation of heat and mass transfer analysis algorithms that integrate predictive models with real-time monitoring data, laying a methodological foundation for future technological process control systems. The solutions further include optimization of logistical parameters under varying temperature and humidity conditions and the establishment of criteria to assess the structural homogeneity of concrete mixtures.
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Kinetics of contact formation between dissimilar crystalline materials during the period of active strain of the first stage of a solid-phase topochemical reaction

https://doi.org/10.58224/2618-7183-2025-8-6-7
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Аннотация
One of the key processes that largely determines the quality of a permanent precision joint formed in the solid state under pressure and heat, which belongs to the class of solid-state topochemical reactions and proceeds in three main stages, is the formation of actual contact, which transitions to a state of physical contact (stage one) at a certain ratio of the level of thermal strain and the contact area. The latter is formed due to plastic strain and the shape change of microprotrusions on the surfaces being joined, which alters the mechanical properties of the resulting contact pads and the near-contact volume of the metal microprotrusions. To develop valid process parameters for producing a high-quality joint, it is important to establish the influence of temperature, pressure, and the height of microroughness of the contacting surfaces of the materials being joined on the kinetics of individual stages of the solid-state topochemical reaction under thermal strain. This paper presents the kinetic dependencies of contact formation during the period of active strain or active loading between dissimilar crystalline materials using the example of synthetic single-crystal corundum – MB copper (oxygen-free) and provides their physical and mathematical justification. Knowledge of the kinetic laws governing the formation of actual contact and the transition to physical contact at a certain ratio of the level of thermal strain action and stress state (the ratio of normal and tangential microstresses of the 2nd kind on the surface of contact pads and in the volume of microprotrusions) and the occurring mechano-physical-chemical processes on the surface of the forming contact pads and in the volume of microprotrusions, allows for a more rational consideration, construction and implementation of the technological process for obtaining a precision detachable (contact of the traction sheave with the cable) or permanent connection of materials in a wide variety of combinations, including those with different nature of chemical bonds and resistance to plastic strain, and will also allow for the consideration and assessment of the role of microstresses of the 2nd kind in the occurrence and propagation of microcracks in the grain of the metal and the provision of recommendations for the prevention of sudden brittle failure of welded building metal structures.
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Environmental safety management of city life cycle through low-carbon principles

https://doi.org/10.58224/2618-7183-2025-8-6-8
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Аннотация
The contemporary urban environment, being a complex system saturated with construction objects interconnected by engineering and social communications, contains numerous potential sources of hazardous technosphere situations. Preventing and mitigating their consequences becomes feasible only through timely automated monitoring of early warning signs and forecasting dynamics of development. At the same time, construction objects within the urban context consume significant material and energy resources, contributing to increased carbon emissions impacting the environment. Therefore, there is a pressing need for digital instruments capable of managing these processes across their entire lifecycle. In this regard, effective means of ensuring ecological safety in cities involves monitoring technical, organizational, and functional components of works conducted and planned for both construction and maintenance phases of urban infrastructure. Based on these measures, maintaining the carbon sustainability of urban immovable property and infrastructure funds becomes achievable when implemented within an adaptable City Information Model (CIM) tailored specifically for managerial tasks. The scientific novelty of the proposed research lies in developing scientific-methodological foundations for digital monitoring of current conditions and predicting the evolution of carbon state and resilience of constructed and operational urban objects and infrastructure integrated into a unified CIM. This approach serves as the basis for instrumentation aimed at managing ecological safety of construction objects. In the research, the technology of information modeling of city objects is constructed based on the author's factor space, incorporating monitoring and forecasting of conditions for realization and assessment of carbon sustainability of constructed and operated objects. This effort utilizes international databases regarding the carbon impact of construction materials and processes, along with analytical data derived from project estimates documentation of urban objects. Automated expert activity tools, including the integration of unmanned aviation systems, are utilized extensively. Algorithms for automated evaluation and forecasting of City carbon impact Indicator (CCII) are presented and to be used as a basepoint for unmanned city carbon analysis within city life cycle management. These algorithms aim to optimize recommended construction, restoration, or operational measures by leveraging results from drone surveillance, neural network detection, mapping, quantitative assessments, and dynamic parameter changes of objects. Ultimately, this allows for synthesizing optimal management decisions ensuring environmentally safe urban spaces towards the carbon homeostasis as an ultimate goal for modern city ecological management.
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Experimental analysis of a new high-tech method of strengthening reinforced concrete structures based on the use of metal and CFRP materials

https://doi.org/10.58224/2618-7183-2025-8-6-9
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Аннотация
This paper presents a large-scale experimental analysis of a new high-tech method for strengthening reinforced concrete columns using metal and CFRP materials. The research is justified by evaluating existing traditional and modern methods of strengthening reinforced concrete compressed elements, identifying their main drawbacks, and taking these into account, a new strengthening method was developed. To study the large-scale effect of the new high-tech metal and composite-based strengthening method, two groups of a total of 46 reinforced concrete column samples with different flexibilities were designed and tested for central and eccentric compression until failure. The main test parameters included column flexibility, load application eccentricity, internal and external metal reinforcement, spacing, and cross-sectional area of composite strengthening. The study investigated the influence of the above-mentioned variable factors on the failure pattern, ultimate strength, peak stress, and deformation characteristics of columns strengthened with carbon fiber composite materials (CFRP). The results showed that reinforced concrete columns strengthened with CFRP, having the same dimensions and tested under the same load application eccentricities, demonstrated different increases in ultimate strength compared to unstrengthened columns. Peak stress increased with an increase in the cross-sectional area of metal reinforcement and decreased with an increase in the distance between composite stirrups. Ultimate axial strains of strengthened samples increased with a decrease in the distance between composite stirrups. The difference in the cross-sectional area of composite strengthening did not have a significant impact on the load-bearing capacity and ultimate strains of reinforced concrete strengthened structures.
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Variatropic concrete compressive strength prediction under freeze-thaw conditions using machine learning methods

https://doi.org/10.58224/2618-7183-2025-8-6-10
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Аннотация
The introduction of intelligent models, in particular using machine learning methods, opens up prospects for the development of the construction industry. The construction of regression models for predicting the physical and mechanical properties of various types of building materials is a promising and relevant area. The use of such models makes it possible to take into account complex and multifactorial dependencies, while minimizing the influence of the human factor. In the present study, variatropic concrete B30, obtained by centrifugation, acts as the test material. The dataset (351 objects) was assembled during laboratory studies to study the effect of freeze-thaw cycles on the strength characteristics of the material. Using the computer vision method based on the convolutional neural network U-Net, the damage on each of the concrete layers was assessed on different cycles. 4 machine learning models for predicting compressive strength were trained and tested on the collected dataset: Ridge Regression (RR), Random Forest (RF), CatBoost (CB) and Multi-layer Perceptron (MLP). The hyperparameters of the models were optimized using Grid Search + 3-fold cross-validation. As a result of testing the algorithms on a test sample, the best quality metrics were demonstrated by tree architectures: MAE for RF and CB 0.09 and 0.17 MPa, respectively, R2 = 0.99. The results are supplemented by SHAP analysis. The results obtained are a useful tool for optimizing the composition of variatropic concretes used under aggressive conditions.
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Plasma electrolyte discharge in metal powder production processes

https://doi.org/10.58224/2618-7183-2025-8-6-11
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Аннотация
Zinc ultrafine powder has found applications in the medical, electronic, chemical, construction, and metallurgical industries. Existing methods of producing zinc powder have a number of drawbacks: some of them are highly energy-consuming, while others are characterized by low productivity and a coarse-grained structure of the powders. A solution to this problem can be found in the use of a gas discharge between an electrolytic anode and a metallic cathode immersed in an alkaline solution.The aim of this work was to study the combustion processes of a gas discharge between an electrolytic anode and a metallic cathode immersed in an aqueous solution of sodium hydroxide. The possibility of applying a gas discharge with a liquid electrolytic anode for the production of zinc powder from alkaline solutions has been established.The pulsed mode can be used at the voltages of the I-V characteristic curve only in the region where intensive hydrodynamic disturbances are observed and where a gradual increase occurs in the area of the metallic electrode surface covered by the gas discharge (U = 150–215 V for a 1% solution, U = 100–125 V for a 3% solution, and U = 70–110 V for a 5% aqueous solution of sodium hydroxide).
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Orientation-dependent mechanical properties of 3D-printed components fabricated by selective laser melting of metal powders

https://doi.org/10.58224/2618-7183-2025-8-6-12
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Аннотация
This study investigates the mechanical properties of aluminum alloys AlSi10Mg and AK9ch fabricated by selective laser melting (SLM), taking into account the build orientation (longitudinal, transverse, 45°) and applied heat treatment regimes (stress-relieving annealing, T6 treatment, prolonged aging). A comprehensive tensile test program was conducted to determine ultimate tensile strength, yield strength, elongation, and hardness. Results show that SLM-processed specimens significantly outperform conventionally cast AK9ch, especially after T6 treatment, achieving up to 285 MPa in strength with ~9% elongation. For the first time, it is demonstrated that the Russian casting alloy AK9ch is suitable for SLM technology, with post-treatment strength reaching 259 MPa and ductility ~5%, comparable to that of AlSi10Mg. The influence of build orientation was found to be negligible at high relative density (>99%). The findings confirm the potential of additive manufacturing to produce high-performance aluminum parts using domestic alloys, offering a promising path toward import-independent 3D production in Russia.
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Systemic-ecological symbiosis model: integrating secondary resources into construction materials to enhance the environmental safety of machine-building enterprises

https://doi.org/10.58224/2618-7183-2025-8-5-1
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Аннотация
The research addresses the integration of secondary resources from machine-building enterprises into construction composites as a pathway to reduce clinker consumption, lower the carbon footprint, and improve industrial sustainability. A symbiotic model was developed that links a machine-building plant as a donor of metallurgical, glass, and polymer by-products with construction material production as a recipient. The model operates on weekly “generation–utilization–storage” balances for production lots of 10 m³ and is optimized under three groups of constraints: economic (cost minimization), environmental (CO₂ intensity reduction), and technical (compressive strength, water absorption, and chloride permeability by RCPT). A multi-objective optimization scheme using ε-constraint methods was applied together with regression-based property models and stochastic simulations (Monte Carlo and bootstrap). The analysis demonstrates that partial clinker substitution with up to 50% ground granulated blast-furnace slag and up to 20% recycled glass achieves a 40–45% reduction in unit CO₂ emissions, while maintaining 28-day strength above 40 MPa and RCPT values within 2,000–3,000 C (Coulombs). The Pareto front highlights an equilibrium zone of 55–60% CO₂ and 84–87% relative cost as a rational compromise between environmental and economic performance. Statistical verification confirms the robustness of the solutions with failure probability Pf < 10%. Practical implications include the ability to design low-carbon mixtures with predictable durability, integrate secondary resource flows into construction supply chains with ≥95% utilization efficiency (and >97% for glass/ash streams), and reduce regulatory and environmental risks. The framework provides machine-building and construction industries with a reproducible methodology to scale decarbonization strategies while ensuring infrastructure reliability.
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