As part of the work, finite element modeling and numerical studies of single-layer cylindrical rod roofs were carried out. Horizontal faces are introduced and the influence of the side elements on the stress-strain state of the structure is determined. The degree of change in the forces and movement of the nodes has been determined. The features of the work of roof are analyzed and dangerous areas with maximum parameters are identified. The analysis of the introduction of horizontal faces is performed by comparing the obtained patterns. A positive redistribution of forces on the surface has been achieved and a reduction in the movements of characteristic nodes has been ensured. There is a space for wiring engineering communications.

Keywords: cylindrical rod roofs, horizontal faces, side elements, forces, displacements

The article examines the criteria for the mechanical strength of pipelines made of steel and polyethylene pipes when the pressure category is increased as part of the reconstruction of gas distribution networks. The minimum values of the pipe wall thickness are determined, taking into account the maximum allowable values of the temporary resistance and yield strength of the pipe material. It is determined that the conditions for the optimal pipe wall thickness are met for the entire range of steel pipes used. For polyethylene pipes, the required mechanical strength depends on the standard size coefficient. 

Keywords: polyethylene gas pipelines, dynamic load, stability of the circular cross-section, external pressure

The article examines the features of adaptive design in construction as a fundamental component for ensuring life safety in the zone of a special military operation. The modern world is changing at an incredible pace: climate anomalies are becoming more frequent, technological paradigms are being replaced within years, and social and economic conditions are undergoing constant transformations. Nowhere are these challenges manifested as acutely and concentratedly as in the zone of a special military operation (SMO). It is precisely here that the traditional approach to construction, focused on creating static, "frozen" objects, proves not only ineffective but also dangerous. It is being replaced by adaptive design – a philosophy and methodology that views a building or infrastructure object not as a final product, but as a living, evolving organism capable of evolving in response to direct threats and changing operational conditions. Adaptive design is a strategy for creating architectural objects and urban planning systems that can be easily modified, transformed, or repurposed in response to changes in external or internal conditions. In peacetime, this is a response to changing markets and technologies. In the zone of a special military operation, it is a matter of ensuring life safety. This is not simply post-factum repair or reconstruction, but the inherent ability of an object to instantly change its function and protective properties without radical rebuilding. The experience of the special military operation zone has openly proven that adaptive design is not an abstract idea from construction textbooks, but a critically important discipline upon which people's lives and the success of the assigned task depend. The principles of flexibility, modularity, and multifunctionality that are being tested today in extreme conditions will tomorrow become the new standard for the entire construction complex of the Russian Federation. They will form the basis for the restoration of cities, the creation of sustainable civil infrastructure, and the formation of new, anti-crisis architecture capable of withstanding the challenges of both wartime and peacetime. In the zone of a special military operation, architectural heritage is being tested and created, which will remain functional, in demand, and sustainable tomorrow. The future of construction belongs to those who design not for years, but for possibilities.

Keywords: adaptive construction, modern trends, modern design technologies, construction industry, construction processes, special military operation

The results of a study of the shrinkage, mechanical properties, and durability of slag-lime concrete modified with machine and vegetable oils are presented. To determine the effect of the oils, the physical and mechanical properties (setting time, compressive strength, and autogenous shrinkage) were tested. The experimental results show that using oil as a structure modifier for slag-lime concrete can significantly reduce its autogenous shrinkage by reducing surface tension and creating a denser internal structure. It was found that emulsified oils provide superior physical and mechanical properties to concrete compared to non-emulsified oils. The setting time is also longer than in compositions without an organic modifier. The use of emulsified oils reduces the negative properties of slag-lime concrete, such as shrinkage, cracking, and reduced setting time.

Keywords: metallurgical waste, granulated slag, hardening activator, binder, superplasticizer, setting time, spray, strength

In reinforced concrete design standards, the values of concrete strain are taken as average values, whereas the strength characteristics are adopted with a high level of reliability. In the ultimate force method for calculating reinforced concrete structures, the strains of concrete and reinforcement are not directly used in the governing equations. In calculations based on the nonlinear deformation model, the strain values are directly used in the analysis. Using average values of the ultimate strains of concrete reduces the reliability of the obtained results. This study examines the influence of the variability of deformation characteristics of concrete and reinforcement on the load-bearing capacity of eccentrically compressed reinforced concrete elements. It was found that the variability of the deformation characteristics of concrete and reinforcement significantly affects the load-bearing capacity of eccentrically compressed reinforced concrete elements. This influence increases with the reinforcement ratio and depends on the eccentricity of the applied axial force. The reliability and safety of eccentrically compressed reinforced concrete elements decrease significantly when average values of the deformation characteristics of concrete and reinforcement are used in calculations.

Keywords: eccentric compression, reinforced concrete, variability of deformation characteristics, concrete, load-bearing capacity, reinforcement, nonlinear deformation model

The article discusses the issues of stability of single-layer cylindrical rod roofs and establishes the suitability of the theory of thin solid shells for similar-shaped core structures. An analysis of the factors was carried out to determine the magnitude of the critical load and the need to take into account the parameter characterizing the change in the geometry of the structure along the arc of the circle was proved. The values and ratio of flexural and membrane stiffness are obtained depending on the possible number of half-waves of the shape of the loss of stability, and a pattern for determining the critical load is established.

Keywords: cylindrical rod roofs, stability, critical load, stiffness, number of half-waves

The article examines the aspects of using bionics as a basis for adaptive architecture and construction in the conditions of the North Caucasus. Modern architecture is undergoing a shift from static and resource-intensive models to dynamic, intelligent and environmentally oriented systems. This approach is particularly relevant for regions with difficult climatic and landscape conditions, such as the North Caucasus, where traditional construction is often unable to effectively withstand the challenges of sudden temperature fluctuations, seismic activity, strong winds and high insolation. This article substantiates the thesis that the integration of bionics principles into adaptive construction offers not just innovative solutions, but a holistic design philosophy based on centuries of experience in the evolution of natural systems. It is proved that bionics is not an alien concept for the region, but, on the contrary, finds deep parallels in traditional mountain architecture, such as in tower complexes demonstrating organic integration into the landscape and effective thermoregulation, similar to natural prototypes. The paper discusses specific areas of application of bionic principles, including the development of adaptive facades inspired by plant and animal thermoregulation systems, as well as the creation of earthquake-resistant structures similar to the flexible structures of bamboo stems or trees. Special attention is paid to the design methodology that combines the analysis of local conditions, biomimicry methods and the integration of modern digital technologies such as computer modeling and 3D printing to create unique, energy-efficient facilities. The need for synergy between traditional architectural knowledge and innovative technologies is emphasized, which makes it possible to create buildings that not only adapt to the environment, but also reflect the unique cultural identity of the North Caucasus. In conclusion, it is argued that bionics is a logical and promising direction for the architectural development of the region, ensuring the creation of a sustainable, safe and comfortable living environment through harmonization with the natural context.

Keywords: construction, bionics, modern trends, modern design technologies, construction industry, biomimicry, adaptive architecture, North Caucasus

The paper analyzes the influence of damage to the protective layer of concrete of the zone of maximum bending moments of single-span beams on the load-bearing capacity of the structure and the possibility of restoring the initial load-bearing capacity. The study is based on laboratory research and numerical experiment, as well as on the analysis of earlier tests and accumulated experience in the restoration of structures. As a result, conclusions are drawn about the effect of concrete protective layer failure on the load-bearing capacity of bending structures, and recommendations are given for further research into the calculation and design of these systems.

Keywords: damage of concrete protective layer, corrosion of reinforcement, restoration, reinforcement

Axial tests demonstrate that strengthening reinforced concrete columns with carbon fiber reinforced plastic (CFRP) significantly improves their performance through lateral restraint. The circular winding creates a triaxial compression effect, increasing concrete strength and load-bearing capacity. The slows of carbon fiber brittle fracture, increases ductility, suppresses microcracks, and improves seismic resistance. This technology is lightweight, corrosion-resistant, and has low operating costs.
The effectiveness of the reinforcement depends on the number of layers and the winding pitch. Cylindrical columns respond better to reinforcement; square columns require rounded corners (radius ≥20 mm) to prevent stress concentration. Two to three layers of CFRP are recommended. This method is particularly effective for columns with insufficient load-bearing capacity, low ductility, or in seismic conditions.

Keywords: carbon fiber, reinforcement for reinforced concrete columns, compressive load bearing capacity

This paper provides an overview of modern stochastic and analytical models describing the effect of reinforcement corrosion on the system reliability and residual load-bearing capacity of reinforced concrete beams. Special attention is given to pitting corrosion as the dominant mechanism of strength degradation. Methods for estimating initiation time and progression of corrosion are summarized; criteria for the transition from ductile to brittle failure mechanisms and the assessment of moment redistribution losses are analyzed. Practical recommendations are provided for adjusting safety factors during the design and operation of such structures under high variability conditions.

Keywords: reinforced concrete, rebar, corrosion, pitting, system reliability, degradation, Gumbel distribution, reliability index, moment redistribution

This paper presents a comprehensive experimental study of an innovative reinforcement technique for reinforced concrete columns based on the combined use of steel and carbon fiber. The rationale for the relevance of the study is presented by analyzing existing technologies for reinforcing reinforced concrete elements subject to compression, with an emphasis on their limitations taken into account when developing a new approach. To assess the impact of the large–scale factor of the innovative reinforcement method based on steel and composite, two groups of samples of reinforced concrete columns (46 in total) of varying flexibility were designed and tested for axial and off-center compression before destruction. The key parameters of the study were the flexibility of the columns, the magnitude of the load eccentricity, the presence of internal and external steel reinforcement, as well as the pitch and cross-sectional area of the composite reinforcement. The effect of these factors on the nature of fracture, ultimate strength, maximum stress and deformation characteristics of columns reinforced with carbon fiber reinforced polymer (CFRP) reinforced carbon fiber is studied. The results demonstrated that reinforced concrete columns reinforced with CFRP, with identical dimensions and the same loading conditions, have a different increase in ultimate strength compared to their non-reinforced counterparts. The peak stress increases with an increase in the cross-sectional area of the steel reinforcement and decreases with an increase in the pitch of the composite clamps. The maximum axial deformations of reinforced samples increase with a decrease in the interval between composite clamps. The difference in the cross-sectional area of composite reinforcement has no significant effect on the bearing capacity and ultimate deformations of reinforced concrete structures.

Keywords: reinforced concrete, column, metal, testing, composite material, Carbon Fiber Reinforced Polymer, strengthening

The article presents the results of an analysis of the stress-strain state and the failure mode of a frame joint connecting a monolithic reinforced concrete crossbar with a column in a frame structural system. The distinctive feature of the considered joint is that part or all of the tensioned (top) reinforcement of the crossbar, bending with a certain radius R, continues into the column.
The research was conducted through a computational experiment. The modeling was performed in the LIRA-SAPR software package. The issue of calculating the normal sections of the joint from the standpoint of SP 63.13330 (Russian Building Code) using the formulas for eccentric compression is considered. An analysis of the joint failure modes during a physical experiment is performed. The dependence of the radial pressure exerted by the curved reinforcement on the concrete on the stress in the reinforcement and its bend radius is determined. The bisectoral section of the joint, represented as a rectangular plate of unit thickness cut by two planes perpendicular to the mid-surface of the joint, was adopted as the calculation object. The calculations were performed using a nonlinear formulation. Recommendations are made for limiting stresses in the reinforcement when calculating the joint according to SP 63.13330. A model for calculating joint failure due to spalling of the side faces from the radial pressure of the curved bars is proposed.

Keywords: reinforced concrete frame joint; curved reinforcement; stress-strain state; joint failure; finite element analysis; LIRA-SAPR; concrete spalling; bisectoral section; normal section; bend radius

Polyurethane foams (PUFs) constitute a major class of polymeric materials, widely appreciated for their excellent mechanical strength, chemical resistance, and physical versatility. They are used in a wide variety of applications, such as insulation, cushioning, coatings, and structural parts. Traditionally, PUFs are prepared through polyaddition reactions involving polyols, diisocyanates, and water, where the in-situ generated CO₂ in the reaction mixture serves as the blowing agent. However, there are significant concerns with the use of isocyanates as they are toxic, classified respiratory sensitizers, and contribute to environmental pollution. These issues have directed both researchers and industry experts to search for safer and more sustainable alternative feedstocks.
The polyaddition reaction between cyclic carbonates (CCs) and polyfunctional amines has been one promising alternative. The reaction leads to the formation of non-isocyanate polyurethanes (NIPUs), specifically polyhydroxyurethane foams (PHUFs). Foaming is achieved by using external chemical blowing agents or through self-blowing reactions, where gases are generated directly in the system. The generated   foam cells – the structures that give foams their unique properties – depends largely on the gas-forming reactions.
This review focuses on the different blowing agents used in NIPUF synthesis, such as poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons. It also looks at recent advances in self-blowing techniques, which eliminate the need for external agents and make the process more sustainable. Special emphasis is placed on NIPUFs derived from renewable feedstocks, as these align with global trend towards green chemistry and circular materials. The review provides an overview of both externally blown and self-blown biobased NIPUFs, detailing their synthesis, performance, and potential industrial applications.

Keywords: biobased polyurethane, blowing agent, non-isocyanate polyurethane, polymeric foams, polyurethane foams, self-blowing

The paper presents the results of the study of the condition of wooden structures of the attic floor of the St. Petersburg Theological Academy of the Russian Orthodox Church. The main defects and damages of the rafter system elements are indicated. Conclusions are given on the physical and mechanical characteristics of a beam over 200 years old. Conclusions are made on measures to maintain the operability of the structures.

Keywords: load-bearing capacity of wooden structures, biodestructors, strength reduction, rafter system

Reinforced concrete structures (RCS) operating under the natural conditions of the Far North are subjected to alternating freezing and thawing. The impact of freezing–thawing cycles (FTC) leads to the degradation not only of the strength but also of the deformation properties (DP) of concrete. In the current design standards for RCS, the DP of concrete and reinforcement are specified as average statistical values. This study investigates the influence of the variability of concrete’s deformation properties on the reliability of the load-bearing capacity of flexural reinforced concrete elements before and after exposure to FTC. It was shown that considering the variability of concrete’s deformation characteristics at reinforcement ratios up to 1% under alternating temperature conditions has practically no effect on the load-bearing capacity, while at reinforcement ratios close to the limiting values it leads to its reduction. In addition, recommendations were provided for the design of flexural reinforced concrete elements under alternating temperature conditions.

Keywords: freeze-thaw cycle, statistical regularities of resistance, flexure, reinforced concrete, ultimate deformation of concrete, assurance

In the current regulatory documents on the design of reinforced concrete structures, a number of conditional assumptions and limitations are adopted, taking into account the specific nature of the resistance of structural elements and simplifying the calculation. One of these assumptions is the assignment of the deformation properties of concrete as average statistical values, which, along with strength characteristics, determine the stress–strain diagrams of the material.
The influence of concrete freezing–thawing cycles (FTC) leads to the degradation of its deformation and strength properties. The failure mode of a flexural reinforced concrete element (plastic or brittle) depends on the strength and deformation characteristics of the concrete and reinforcement, as well as on the reinforcement ratio.
This study examines the statistical patterns of the ultimate reinforcement ratio and the limiting relative height of the compressed concrete zone under alternating freezing–thawing conditions. The analysis of the statistical regularities of the parameters used and their functional relationships confirms their significant variability and, as a consequence, the possible fluctuations (reduction) of the design reliability level of flexural reinforced concrete structures.
Modeling the variability of the strength of flexural reinforced concrete elements under FTC using statistically representative data on the kinetics of the physical and structural parameters of concrete confirms a sharp decrease in reliability and indicates the need for additional targeted research in this field.

Keywords: freezing–thawing cycles, statistical patterns of resistance, reinforced concrete, ultimate concrete strains, reliability of the limiting relative height of the compressed concrete zone, reliability of the ultimate reinforcement ratio

Fiber concrete is one of the most promising building materials. However, it is most commonly used in finishing materials, small architectural forms, industrial floors, and decorative facade details, and is less commonly used in load-bearing structures. Meanwhile, the use of fiber concrete, including fiber reinforced concrete, in load-bearing structures is limited due to a lack of information about the material's behavior under load, and additional experimental data is needed for theoretical understanding. The article discusses experimental studies of concrete reinforced with polypropylene fiber for compression and central tension. Qualitatively different patterns of destruction of concrete and fiber concrete samples were identified. The analysis of the results showed that the highest peak load values were observed in samples with a 1% polypropylene fiber content. Compared to the control series, the load-bearing capacity increased by up to 45%. 

Keywords: fiber concrete, fiber, polypropylene fiber, compression tests

Concretes based on ground blast-furnace granulated slag activated with alkaline solutions exhibit excellent mechanical properties. However, they have significant drawbacks, such as rapid setting and poor workability during concreting. The effect of various superplasticizers on the properties of pastes prepared from ground blast-furnace granulated slag activated with alkaline solutions was studied. An aqueous solution of sodium silicate and sodium hydroxide was used as an alkaline slag hardening activator. The effect of superplasticizer dosage on the setting time, flowability, and changes in compressive strength of slag-alkali solutions was studied. It was found that properties of the freshly prepared paste, such as the initial and final setting times, increase with increasing the solution-to-slag ratio and with the addition of a superplasticizer. Superplasticizers based on naphthalene sulfonic acid and polycarboxylate ether were found to effectively influence both the setting time, workability, and strength of slag-alkali binder-based compositions. It was established that a slag-alkali composition with a mortar-to-slag ratio of 0.4 exhibits low workability and is not technologically feasible for on-site concreting, while its optimal value is 0.5. A superplasticizer dosage of 2% of the slag mass ensures not only the technological requirements for concreting (the initial and final setting time and concrete mix mobility), but also the strength properties of the formed concrete based on ground blast-furnace granulated slag.

Keywords: metallurgical waste, granulated slag, hardening activator, binder, superplasticizer, setting time, spray, strength

The article analyzes a number of factors influencing and shaping modern trends in the development of green construction, assesses the reasons accelerating and inhibiting the current growth of "green" construction in Russia and the world, and lists the main advantages of green construction projects in comparison with traditional construction.

Keywords: green building, ecology, energy efficiency, "green" building materials, natural and climatic conditions, green houses

This article explores the architectural and engineering significance of surfaces of the second order, with a particular focus on the one-sheet hyperboloid of revolution. The study begins with a historical overview of architectural forms, highlighting the evolution from primitive shelters to complex spatial structures. Mathematical foundations are introduced through quadratic equations, illustrating the formation of second-order surfaces such as the elliptic paraboloid and hyperboloid. Special attention is given to the structural properties of the one-sheet hyperboloid, a doubly ruled surface that enables construction using straight beams, despite its curved geometry. Its advantages—strength, wind resistance, and material efficiency—are discussed, along with typical assembly methods such as segment welding and overlapping connections. The article further examines the iconic Shukhov Tower in Moscow, a pioneering example of hyperboloid design. It outlines the construction methodology, including the telescopic assembly process and challenges such as structural fatigue and support failure. The analysis demonstrates how Vladimir Shukhov’s innovations contributed to global architectural and engineering practices. Finally, the article emphasizes the hyperboloid’s relevance in modern construction and research, illustrating its blend of geometric rationality, aesthetic expressiveness, and structural efficiency. This synthesis of art and science continues to inspire both professionals and the public, highlighting the enduring value of advanced geometric principles in architecture.

Keywords: hyperboloid, quadratic surface, hyperboloid of revolution, engineering structure, architectural form, Shukhov Tower, steel structure, spatial lattice, structural technology, lattice shell

This paper presents a comparative analysis of test results for reinforced concrete columns strengthened with steel and carbon fiber–reinforced polymer (CFRP)-based composite materials. Particular emphasis is placed on deformability and stiffness characteristics. The experimental program included 21 columns fabricated from normal-weight concrete with a target compressive strength class of B25–B30. All specimens had a rectangular cross-section of 250 × 125 mm (width × height) and two different lengths—1200 mm and 2400 mm—corresponding to slenderness ratios (λₕ) of 10 and 20, respectively.
The columns were subjected to axial loading with three eccentricity values: e₀ = 0; e₀ = 2.0 cm (0.16h); and e₀ = 4.0 cm (0.32h). Additional test variables included internal and external steel reinforcement configurations, as well as the spacing and cross-sectional area of the composite strengthening layers.
The study investigates the effects of the aforementioned parameters on the performance of columns strengthened with CFRP composites and steel elements. The results demonstrate that strengthened reinforced concrete columns—despite having identical geometry and being tested under the same load eccentricities—exhibit significantly different structural responses.
The primary objective of this research was to determine the influence of strengthening element stiffness on the deformability of slender strengthened columns, and the effect of load eccentricity on the required stiffness of strengthening components.

Keywords: reinforced concrete, column, steel, testing, composite material, CFRP, strengthening

The article examines architectural approaches to the design of temporary museums and exhibition pavilions. Particular attention is paid to the concept of modularity as a tool for spatial adaptation and rapid installation, as well as mobility as a strategy for expanding cultural presence beyond stationary institutions. Historical and contemporary examples are analyzed, including so-called pop-up museums, container galleries, and disassemblable exhibition modules. The role of innovative materials, digital design, and transport logistics in the formation of a flexible architectural environment is emphasized.
The article reveals the potential of temporary exhibition structures as a tool for social inclusion, urban renewal and cultural decentralization. Special attention is paid to Russian and international experience. The modular museum is presented as a type of architecture sensitive to time, place and cultural context.

Keywords: museum, exhibition complex, architecture, modularity, mobility, flexibility, adaptability, design, construction

This article introduces a new method for creating architectural objects that can effectively withstand technological threats. The innovation of the design schemes is based on a unique conceptual duality: the system can be analyzed both in the traditional three-dimensional paradigm of force transmission and using a fundamentally new four-dimensional resource model of stress redistribution. How does this model enable active resource management and adaptation of the structure to changing conditions? This is the focus of this article.

Keywords: transformation, four-dimensional architecture, spatial rod structures, technogenic threats, transmetric monoparametricism, twisted spatial beam, pentachoron, four-dimensional simplex

The article presents the results of an experimental study of the effect of loading speed on the deformation and strength characteristics of concrete of class B45 under central compression. 15 prisms measuring 100×100×400 mm, divided into three series according to the loading speed, were tested. Regression dependences are constructed, correlation coefficients (up to 0.9975) and determination coefficients (up to 0.9950) are determined, confirming the high degree of consistency of the models with experimental data. It is established that an increase in the loading rate contributes to an increase in strength and a decrease in the magnitude of the marginal relative deformation of concrete. The obtained dependences can be used as an experimental basis for constructing a nonlinear deformation method for calculating bent and non-centrally compressed reinforced concrete structures made of concrete of the class under consideration (B45), subject to static and high-speed impacts.

Keywords: experiment, concrete samples, high-speed loading, central compression, statistical processing of results, least squares method, regression curve

When constructing reinforced concrete floors on profiled steel sheeting, it is possible to significantly reduce the construction time and provide simple and convenient support units. The article discusses the standard methods for calculating composite reinforced concrete floor slabs with profiled sheeting according to SP 266.1325800.2016. A series of calculations were performed using ultimate forces and a nonlinear deformation model (NDM), and a comparison was made with experimental data. The data obtained indicate a significant overestimation of the bearing capacity for a number of samples calculated using the NDM method. This indicates the need to change the approach to NDM calculations and the need to make adjustments to the σ-ε calculation diagram for profiled steel sheeting, reflecting the actual operating conditions of the element.

Keywords: steel profiled sheeting, floor, deformation model, stress-strain diagram, static load