Introduction. Until now, in the analysis of timber structures, wood has been considered practically as an elastic material. Only in the latest edition of SNiP II-25-80 was an attempt made to account for creep in second-order analysis and stability design by introducing a reduced modulus of elasticity, E = 300 R. However, this provision turned out to be unclaimed, because residual relative deformations do not correspond to elastic ones and depend on the stress level at individual intervals of the bending element. Thus, in linear analysis, the integral modulus of elasticity of an element should be abandoned in favor of interval values of moduli that vary with the stress level.

Aim. Improvement of the linear method for the analysis of bending and beam-column timber structures taking into account wood creep by using the long-term modulus of elasticity.

Materials and methods. For the first time in timber engineering practice, a methodology has been developed and pilot long-term bending tests have been carried out to obtain the long-term modulus of elasticity depending on the stress level. Specimens were made of spruce and were held until the deflections stabilized. The stress increment step was 1.0 MPa.

Results. The test duration at low stress levels was 1–1.5 months; at high levels, 10–12 months. A preliminary table of long-term moduli was compiled based on the deflection data. A comparison of structural analysis results using variable moduli showed a significant discrepancy with the results obtained by the standard method.

Conclusions. The LIRA-SAPR software system enables the implementation of a two-stage linear approach for the analysis of bending and beam-column elements accounting for wood creep, using tabulated values of the long-term modulus of elasticity depending on the stress level. Reliable data for the table can be obtained from long-term tests of bending elements in adapted premises.

Introduction. This article examines the implementation of the Strategy's key provisions in terms of developing modern approaches to the methodology for transitioning to parametric standardization for loads and impacts on buildings and structures in our country. It analyzes the key criteria for developing basic parameters of loads, impacts, and environmental influences to ensure the required reliability and safety, as well as the normal operation of structures and protection against potential emergency design situations, and proposes ways to further improve them.

Aim. This article explains the key approaches to implementing parametric standardization for loads and impacts in construction, as implemented in the SP project "Loads and impacts. Key provisions". It also analyzes the differences in existing and prospective approaches to its interpretation in domestic and international regulatory documents and develops an innovative strategy for the further development of the domestic regulatory framework.

Materials and Methods. This article examines the structure of Russian and international regulatory documents on loads and impacts and provides a comparative analysis. Basic approaches to parametric standardization of loads and impacts in the construction industry have been developed.

Results. The analysis allowed us to establish criteria for determining various types of loads, impacts, their design combinations, and environmental influences while guaranteeing the reliability and safety of technical solutions. Basic requirements for standardizing deflections and displacements of building structure elements have been established. It has been shown that the combined use of a semi-probabilistic approach based on standardization of partial reliability factors for loads and certain qualitative, probabilistic, and risk-based criteria for assessing reliability, loads, and impacts adopted in international regulatory frameworks, particularly ISO 2394:2015 and Eurocodes, will assist in selecting optimal design and technological solutions.

Conclusions. Implementation of the SP project "Loads and impacts." The integration of the "Basic provisions" into design practice, along with the development of new SP containing design rules and parameter values for individual types of loads and impacts, as well as the definition of maximum deflections and displacements, will facilitate the unification of load and impact requirements based on the development of common approaches to the methodology for the transition to parametric standardization in construction in the Russian Federation. This set of documents will contribute to a reduction in construction costs and timelines, as well as the development of new materials and technologies. This set of documents will create a common basis for standardizing loads and impacts and will optimize the design of buildings and structures, thereby increasing their economic efficiency.

Introduction. High-strength power-actuated pins can be used for fastening equipment, cold-formed metal buildings elements, and roof decking to metal structures as an alternative to self-drilling screws and welded joints. Modern pins allow fastening steel and aluminum components with thicknesses ranging from 0.5 to 4.0 mm and tensile strength from 330 to 550 N/mm² to steel and cast iron bases with thicknesses starting from 3 mm and tensile strength from 350 to 750 N/mm². When an anchor connection is subjected to tensile load, several failure mechanisms may occur, and their likelihood must be verified by calculation. Currently, Russia has two design codes for metal structures (SP 260.13330.2023 and SP 294.13330.2017) that include provisions for calculating anchor connections. These provisions have significant differences and need to be harmonized.

Materials and methods. To verify calculation results, data from 25 series of tensile tests on steel structure fastenings were used. Five types of pins with different configurations were tested. The thickness range of the attached elements was 0.5–3 mm, and the thickness range of the base materials was 3–6 mm.

Results. Two failure modes were identified in the tests: pull-out from the base and tearing of the attached sheet. Test data were compared with calculation results according to Russian standards, as well as with provisions of EN 1993-1-3 and AISI S100-24. Analysis of these standards revealed differences in application scope and calculation approaches.

Conclusions. It was established that the methodology of SP 294.13330.2017 provides the highest prediction accuracy of load-bearing capacity within its application scope and can be recommended for extended use when fastening thin-sheet elements (t₁ ≥ 0.8 mm).

Introduction. In European countries, the use of timber structures is growing, not only for low-rise construction but also for multi-story buildings. When constructing multi-story buildings using timber, one often encounters the challenge of creating products with unique geometric and structural characteristics that cannot be manufactured from standard lumber.

Aim. To study modern building structures using CLT and MHM panels in industrial and civil engineering for the construction of multi-story buildings and structures, to explore possible design solutions, and to examine the technical characteristics of the structures.

Materials and methods. The subject of this study is modern timber building structures based on CLT and MHM technologies used to produce unique load-bearing structures in building construction.

Results. The paper presents the technical characteristics of panels for the construction of timber structures. Examples of completed and future buildings and structures are considered.

Conclusions. The main differences in manufacturing solutions are outlined. The main prospects for the use of timber in multi-story construction are analyzed. The main advantages and disadvantages of CLT and MHM panels are outlined.

Introduction. Studies of a precast large-span reinforced concrete space frame roof assembled from separate flat frames have been carried out at the A.A. Gvozdev Research Institute for Concrete and Reinforced Concrete.

The aim was to develop the fundamentals of the regulatory framework for the design of reinforced concrete space frame roofs.

Materials and methods. Computational and theoretical studies of the structural solutions of a precast large-span reinforced concrete space frame roof made of flat frames of different sizes for various loading schemes by finite element method have been carried out.

Results. Based on the analysis of the results of computational and theoretical studies, recommendations have been developed for the design of elements and assemblies, and reinforcement of elements. Proposals have been developed to normalize the parameters of the structural elements of reinforced concrete space frame roofs. Design proposals for two variants of space frame roofs have been developed.

Conclusions. The developed recommendations and design proposals are aimed at increasing efficiency and expanding the scope of structural solutions for reinforced concrete spatial roof systems of large-span buildings.

Introduction. This article describes the use of field modeling of fire to justify measures to ensure fire safety of buildings and structures, taking into account the temporary fire load.

Aim. Development of measures to protect safety systems in case of fire in NPP premises using field fire modeling, which is very important for substantiation of sufficiency of NPP fire protection level.

Materials and methods. Based on the analysis of various methods of modeling the dynamics of the development and spread of fire hazards, the possibility of using various methods of modeling fire in the analysis of fire safety of buildings and structures, taking into account the temporary fire load, was shown. It is proposed to take into account in measures to ensure the safety of nuclear power plants from the effects of fire hazards measures aimed at reducing the likelihood of fire.

Results. An analysis of the purpose and scope of various methods for modeling the dynamics of the development and spread of relative permeability (fire hazards) was carried out. The application of the field method for modeling fire in buildings and structures taking into account the temporary fire load is considered. The analytical material presented in the article is confirmed by examples of fire simulation results in such NPP premises.

Conclusions. Using the field method allows you to calculate the temperature, speed, concentrations of mixture components at each point in the design area, as well as apply the field method to determine the requirements for fire resistance of load-bearing and enclosing structures of buildings and structures, including taking into account the temporary fire load.

Introduction. The possibilities of increasing the physical and mechanical characteristics of special-purpose concretes are considered: heat-resistant concretes for repairing the lining of expanded clay kilns and concretes for making wall panels.

The aim is to study the processes of structural modification of special concretes (heat-resistant and gypsum concretes) using lime as an additive to increase their strength and durability.

Materials and methods. When selecting the compositions of heat-resistant concretes, the following materials were used: aluminous cement; sand obtained by crushing ceramic bricks; slaked lime – Ca(OH)2; orthophosphoric acid with a concentration of 30 %. The samples were fired at a temperature of 8000C and tested for strength using a hydraulic press. When selecting the compositions of gypsum concrete, the following materials were used: high-strength gypsum; unslaked ground lime – CaO. Electron microscopic and differential thermal analyses were performed. The samples were tested for strength using a hydraulic press.

Results. Tests of heat-resistant concrete samples prepared on alumina cement with the addition of slaked lime – Ca(OH) 2 in an amount of 10 % and impregnated with orthophosphoric acid of 30 % concentration showed a compressive strength of 45 MPa. As a result of studies of samples made of gypsum concrete, it was found that when 10 % of quicklime powder was added, the compressive strength was 373 kgf/cm2.

Conclusions. Heat-resistant concretes on aluminous cement with an additive of lime-powder in the amount of 10 %, impregnated with orthophosphoric acid with a concentration of 30 %, have high physical and thermal characteristics, satisfactory for the operation of concrete at temperatures of 8000C. Adding ground quicklime to gypsum concrete at a rate of 10 % of the gypsum weight increases the material’s strength (R cr = 373 kgf/cm2), making it suitable for use in the production of gypsum concrete panels for industrial and civil buildings.

Introduction. The sand of many deposits, especially in the far east of our country, contains a large amount of chlorides, which makes it unsuitable for use in reinforced concrete. This is because chloride ions are the most aggressive corrosive agent for steelreinforcement. The Laboratory of Corrosion and Durability of Concrete and Reinforced Concrete Structures at the A.A. Gvozdev Research Institute of Concrete and Reinforced Concrete Structures conducted research on the corrosion of steel reinforcement in concrete and cement-sand mixtures that contained sand with a high chloride content.

Aim. To determine the possibility of using sand from the Kamchatka Territory deposits in concrete mixtures in terms of corrosion aggression to steel reinforcement.

Materials and methods. The studies were conducted on a model cement-sand mixture (CPM) and concrete with smooth rod reinforcement of 6 mm in diameter. The sand contained 0.08 % by mass (based on chlorine ion) of water-soluble chlorides and 0.55 % by mass (based on chlorine ion) of total chlorides in the sand. An electrochemical method was used to accelerate the determination of the corrosion effect of the environment on steel reinforcement. The method is based on obtaining the dependence of the electric current density on the electric potential of the steel reinforcement, which is known as the potential-dynamic method.

Results show that sand with a high content of water-insoluble chlorides does not cause corrosion of steel reinforcement when the samples are in a non-aggressive (neutral) environment. In the initial state and exposure in the humidification – drying mode for 3, 6 months, neither in the cement-sand mixture samples nor in the concrete samples, the current density at a potential of plus 300 mV did not exceed 10 μA/ cm2, as well as the potential after (60 ± 5) s after the current was turned off did not drop below + 5mV.

Conclusions. Sand with a high content of water-insoluble chlorides can be recommended for use in reinforced concrete structures that are guaranteed to be free from aggressive environments even during operation.

Introduction. The article is devoted to monitoring the condition of permafrost soils in the Arctic zone of the Russian Federation. Intensive development of the Arctic combined with climate change leads to permafrost degradation and reduced stability of structures in the region. High rates of temperature drop in the air and soil of the coastal zone and the water area of the Northern Sea Route are indicated.

Aim. Analysis of the state of the permafrost monitoring system and proposals for the creation of a system of geotechnical and environmental monitoring of the coastal zone and the water area of the Northern Sea Route.

Materials and methods. The article presents the main aspects of geotechnical monitoring: assessment, control and forecast of the thermal condition of permafrost soils and assessment of the bearing capacity of foundations of engineering structures.

Results. There is an unsystematic approach to monitoring frozen soils, despite the existing regulatory framework and technical support. The necessity of creating a comprehensive system of state monitoring is indicated.

Conclusions. The necessity of background monitoring of the ecological and climatic consequences of the degradation of terrestrial and underwater permafrost is substantiated. Recommendations are given on monitoring in key areas of ground permafrost, including the coastal Arctic zone and underwater permafrost in the coastal zone and in the waters of the Northern Sea route.

Introduction. Slurried piles are widely used in construction on permafrost soils according to Principle I. Modern projects increasingly employ cement-sand mortar (CSM), yet its thermal interaction with the soil and the pile, as well as the freeze-bond strength at the contact interface, remain insufficiently studied. This leads to an underestimation of the design bearing capacity and unjustified overconsumption of materials.

Aim. To develop a method for determining the bearing capacity of a slurried pile in permafrost using CSM, taking into account the heat release during cement hydration and partial hardening of the mortar prior to freezing.

Materials and methods. A series of thermotechnical calculations was performed using the Borey 3D software package for various pile types, borehole diameters, and permafrost temperatures. Tray experiments simulating a segment of a slurried pile were conducted. The freeze-bond strength of CSM with a concrete surface was determined according to GOST 12248.8 for each combination of temperature (from –1 to –6 °C) and curing time at positive temperatures (1 to 7 days). Approximation was performed using a two-stage least squares method with linearization and nonlinear refinement.

Results. A nomogram of mortar freezing time as a function of mortar volume and permafrost temperature was obtained. It was found that when CSM is cured for up to 7 days at positive temperatures, the freezebond strength increases by a factor of 1.5 compared to sand mortar. An empirical formula for determining the shear resistance of CSM along the freeze-bond interface with a concrete pile was derived.

Conclusions. A calculation method for the bearing capacity of a slurried pile with CSM is proposed. This method will allow optimization of pile foundation designs on permafrost and reduce excessive safety margins, leading to material savings without compromising foundation reliability.

Introduction. Complex geotechnical works such as the construction of high-rise buildings with deep excavations, construction of trench-type diaphragm wall enclosing structures and bored-secant pile walls, as well as the construction of large-diameter boreholes for deep foundations installation actively develop in the dense urban conglomerations, affecting the adjoining surroundings and often leading to the risk of emergency situations. Targeting at mitigating settlements of existing structures and those under construction and eliminating the risk of emergent situations, additional foundation strengthening measures should be undertaken.

Aim. Elimination of settlements and assurance of the reliable serviceability of a shopping Mall building.

Materials and methods. The paper considers a method of cement or other hardening solutions injection into the ground under high pressure creating fractures in the soil. The solution is pressurized through injectors vertically inserted into the soil. Moving under pressure along the created fractures over the prescribed distance, the solution mechanically affects the soil and changes its stress-strain-state, thus increasing soil strength properties. After hardening in fractures, solution additionally reinforces the soil.

Results. The settlement of foundation of the shopping Mall building terminated. Stress and strain properties of the soil under the foundation slabs increased. A trend toward leveling foundation slabs and raising individual sections has appeared. The relative differential settlement of the slab foundations has decreased.

Conclusions. The results presented show the efficiency of the applied method of the compensation grouting, which is used to reduce foundation settlements, lift buildings and correct their tilts caused by complex geological conditions or mistakes in design and construction.