The article presents and analyzes the algorithm for calculating bending reinforced concrete structures by normal section based on a nonlinear deformation model recommended in the standards for the design of reinforced concrete structures SP 63.13330.2018. Calculation of reinforced concrete structures based on a nonlinear deformation model is a priority, since it expands the set of controlled parameters, which leads to a more accurate description of the operation of building structures. The features of performing the calculation using this algorithm, as well as other approaches to calculating bending reinforced concrete structures by a normal section based on deformation and other models, are considered. The sequence of calculations using computer technologies is shown using the example of calculations in the engineering nonlinearity1 system of the LIRA-SAPR software package. The results of calculating a rod element of the calculation scheme are given: changes of the bending moment, stiffness, and deformation modulus for finite elements along the rod length. In this case, the calculation in the engineering nonlinearity1 system is performed with subsequent adjustment of the stiffness characteristics of the finite elements, carried out during the iterative calculation, with clarification of the stress-strain state, deflection of the element and its reinforcement. Additional capabilities of performing calculations using the engineering nonlinearity2 system are described: expanded the possibilities of assigning various laws of material deformation, describing the loading of the calculation scheme, reinforcement of structures, and the possibility of using a step processor.

Keywords: bending reinforced concrete structures, nonlinear deformation model, calculation scheme, calculation algorithm, PC LIRA-SAPR, engineering nonlinearity, system

Ring-shaped reinforced concrete structures are widely used in construction. For example, in the form of underground pipelines. They experience a complex nonlinear deformed state (VAT), which is analytically described as a complex mathematical problem of mechanics. Therefore, numerical methods are often used to solve it. This article uses the finite element method (FEM) implemented in the Lira-CAD 2022 PC. The VAT of reinforced concrete pipelines is determined in a physically nonlinear formulation, taking into account 4 factors of influence: the inner diameter, the concrete class, the properties of the filling soil, and the properties of the foundation soil. A plan has been drawn up for a complete multifactorial numerical experiment, which includes 81 models. The values of internal force factors in all sections of the underground pipeline are obtained, taking into account the variation of each factor individually and taking into account their mutual influence. Combinations of factors giving extreme values of internal forces in the pipeline have been established. Based on this, recommendations for rational design have been developed.

Keywords: underground pipeline, reinforced concrete, computer modeling, longitudinal profile, cross section, PC "Lira-CAD"

The kinematic characteristics of rod systems are given in the order of kinematic analysis of the mechanism diagram, made taking into account the sizes and mutual arrangement of links and hinges; by analogy with the structural analysis of kinematic characteristics, they also include the degree of kinematic anomaly and the degree of kinematic irrationality. The first characteristic relates to the mutual arrangement of the axes of the links in the circuit chain and uses the dimensions of the links, the second relates to the mutual arrangement of the axes of the kinematic pairs (joints). It is shown that the mobility of kinematic chains depends on dimensional conditions - general and particular, and kinematic connections are imposed by dimensions. Based on the contour approach, a knowledge base has been formed for a highly formalized analysis of kinematic chains, allowing the identification of kinematic anomalies - both excess mobility due to a special position and kinematic redundant connections. It is shown that for flat kinematic chains the degree of irrationality of kinematics can be expressed through structural parameters.

Keywords: kinematics, characteristics, rod systems, analysis, diagrams, links, hinges, axes, anomaly, irrationality, connections, dimensional conditions

The article describes the features of using a two-layer membrane with the use of injection control fittings in the installation of underground waterproofing. The circumstances preventing the mass application of this technology have been identified, the main part of which is related to the increase in the cost of work at the initial stage. However, the use of the technology is justified because it allows you to localize the location and period of leakage, has increased maintainability and durability.

Keywords: waterproofing, modern waterproofing technologies, double-layer membrane, injection control fittings

The article discusses issues related to assessing the quality and safety of road traffic. An analysis of the accident rate on the roads of the southern part of the Far East has been performed. The main causes of traffic accidents are considered. An analysis of the quality of road marking has been performed and an assessment of its durability has been given, depending on the operating conditions. Recommendations for improving the durability of road markings are given.

Keywords: highway, pavement, horizontal markings, traffic safety

Within the framework of this article, experimental studies of concrete reinforced with polypropylene fiber of two geometric dimensions of 6 mm and 12 mm are presented. Studies were carried out on samples of cubes 10 × 10 × 10 cm and samples of prisms 10 × 10 × 40 cm. In total, more than 100 samples were tested. The objectives of the experimental study: testing fiber concrete samples for compression, analyzing the results obtained, identifying changes in strength and deformation characteristics as a result of fiber reinforcement. Tests of the samples showed an increase in strength of up to 20%, as well as the effect of the percentage of fiber reinforcement on strength properties. The limit percentage of fiber reinforcement was determined, when exceeding which a decrease in strength properties occurs

Keywords: polyarmoured fibre concrete, fibre concrete, low-modulus fibre, polypropylene, strength properties

This paper provides an analysis of the main problems encountered during the installation of bitumen-polymer roofing materials. Special attention is paid to typical defects and errors related to insufficient qualifications, as well as problems related to violations of installation technology.

Keywords: bitumen-polymer roofing, installation of a surfaced roof, waterproofing defect, quality management, recommendations for improvement

The article is devoted to the design of local treatment facilities in the city of Borovsk, Kaluga Region. Treatment facilities play an important role in the modern world. They are necessary for processing wastewater so that it becomes safe for the environment and can be discharged into water bodies or drainage networks. Since the discharge of untreated water can cause irreparable harm to the ecosystem, it is important to provide treatment facilities in the sewerage system of the settlement. The article considers the tasks and importance of treatment systems, their role in the life of modern cities, and also presents in detail the step-by-step organization of work on the device of local treatment systems and their subsequent commissioning

Keywords: wastewater treatment plants, ecosystem, water disposal, wastewater, modular structures

The paper presents an analysis of experimental data reflecting the influence of the loading rate on the strength and deformation characteristics of concrete of class B25 under conditions of central compression. 12 prismatic samples with dimensions of 100×100×400 mm, distributed in three series with different load application rates, were prepared and tested for the study. Statistical data processing, including analysis of variances and the construction of regression models, allowed not only to predict the behavior of concrete under various loading conditions, but also to confirm the theoretical prerequisites associated with the dynamic hardening of the material. The high values of the correlation coefficients (up to 0.9943) and determination (up to 0.9922), as well as the Fisher criterion, which significantly exceeds the tabular thresholds, characterize the high reliability of the results obtained, indicating an increase in concrete strength with an increase in loading speed and a simultaneous decrease in its deformability. The derived dependences can serve as an experimental basis for the development of a nonlinear deformation method for calculating bent and non-centrally compressed reinforced concrete structures made of concrete of this class (B25), subject to short-term impacts, including classical static loads, as well as dynamic loads of medium duration, characteristic of the operating conditions of structures under the influence of factors such as the movement of overhead cranes along crane beams or the passage of fire trucks along the overpass. The results obtained contribute to a more accurate consideration of dynamic effects in the design and calculation of reinforced concrete structures operated in such conditions.

Keywords: experiment, concrete samples, central compression, loading rate, strength, marginal relative deformations, dynamic hardening, correlation and regression analysis

The article presents an analytical solution for a specific case of a system with unilateral constraints: a beam freely resting on a tensionless Winkler foundation, loaded with identical vertical forces F at both ends. It is shown that beam separation from the foundation occurs when the reduced beam length αl exceeds π (αl > π); the size of the detachment region does not depend on the magnitude of the applied force. An increase in foundation stiffness (for a constant beam length) leads to an expansion of the detachment zone. The bending moment at the midpoint of the beam with detachment is maximal at the «detachment moment» and equals 0.4F⁄α. The deflection at the midpoint also depends on the foundation stiffness and is proportional to the applied force. As the foundation stiffness increases, the bending moment and deflection decrease, approaching zero for an infinitely stiff foundation. The article provides a calculation algorithm for the described beam and an example demonstrating changes in the stress-strain state parameters of the beam with increasing foundation stiffness. The obtained results, in the author's opinion, are interesting in themselves and can also contribute to the set of verification problems for structurally nonlinear systems.

Keywords: system with unilateral constraints, tensionless Winkler foundation, beam, contact region, detachment region, Krylov functions

The article examines the key climatic and operational factors that determine the duration of safe operation of ice winter shelters in the northern regions of Russia. Based on the analysis of the temperature regime, precipitation and dynamic loads from transport, patterns of changes in the strength and deformation of the ice cover have been identified. Practical recommendations on monitoring, ice reinforcement and load management have been developed to extend the service life of crossings and minimize risks.

Keywords: regime, dynamic loads, snow cover, hydrological factors, crossing safety, ice monitoring

The calculation of wind loads on curtain facades and their fastening elements for high-rise buildings and structures using engineering methods and various numerical techniques remains an important task to this day. The corner sections of the building, where the greatest negative wind pressure occurs, are of particular interest. Incorrect calculation of wind suction can lead to the separation of panels during strong winds. The article calculates the peak wind load using a numerical method for a rectangular building with an aspect ratio of 0.6. Numerical calculations of the two-dimensional flow around the building profile in the ANSYS Fluent program using the k-e Realizable turbulence model were used to obtain the coefficients of drag, lateral force, and the distribution of the pressure coefficient at maximum lateral force. The calculations showed that the wind suction at the edge of the building exceeds the standard value by approximately 30%. The results obtained in the article should be taken into account when designing the facade.

Keywords: peak wind load, wind suction, rectangular buildings, peak negative aerodynamic pressure coefficient

Adhesive joints of reinforcing rods and wood are the weakest point in reinforced wooden structures, since they have low shear resistance of the reinforcing rod and contribute to the development of plastic deformations of wooden elements. To achieve elastic operation and increase adhesion to the rods, a reinforced adhesive compound with the inclusion of quartz sand is used. This article examines the operation of a reinforced adhesive joint with various types of core fittings – steel periodic profile, smooth steel and fiberglass. The work of the adhesive joint in solid and glued wood was also recognized as an important factor for the operation of the reinforced adhesive composition. Experimental studies are confirmed by graphs and tables of numerical results, which allows us to establish the reliability of the results obtained and conclude that it is necessary to improve certain methods of manufacturing reinforced wooden structures.

Keywords: rebar, reinforcing bar, reinforced wooden structure, pulling out, wooden structure, wood, glue, adhesive joint, strength, epoxy resin

Fiberglass core reinforcement could find its application in wooden structures due to a number of specific practical advantages not inherent in steel rods or other types of reinforcement. However, due to the weak adhesive properties of the surface of fiberglass rods, their full-fledged joint work with wood as a single body is not observed. The study suggests some ways to increase the strength of the adhesive joint of fiberglass reinforcement and wood, such as applying quartz sand to the surface of the rods, grinding the surface of the rods, as well as adding sand-resin casting molds to the adhesive composition. Tests of each of these methods were carried out and the results obtained were compared with the initial model of the adhesive joint, as well as with the calculated model of the adhesive joint in order to determine the most effective method.

Keywords: adhesion, reinforcing rod, pulling out, wood, adhesive joint, adhesive composition, bearing capacity, strength, fiberglass rod, epoxy glue

The paper investigates the formation and propagation of flexural cracks in beams made of ultra-high performance steel fiber reinforced concrete (UHPFRC). A comprehensive series of laboratory tests was carried out on seventeen beams of rectangular and T-shaped cross-sections, varying in longitudinal reinforcement ratios, fiber volume contents, and fiber types (straight and wave-shaped). The results demonstrate that the inclusion of steel fibers significantly enhances the crack resistance of the beams, promotes a more uniform crack distribution, and improves their load-bearing capacity. In under-reinforced UHPFRC beams, failure typically occurs due to fiber pull-out localized within one or more dominant cracks. Prior to the onset of deformation localization in the tensile zone – which coincides with the yielding of the longitudinal reinforcement – the crack widths in fiber-reinforced specimens remain below 0.25 mm. This behavior ensures that even under service-level loads (65–70% of ultimate), the crack openings stay within the allowable design limits (0.3–0.4 mm). The experimental findings contribute to a better understanding of the cracking mechanisms in UHPFRC beams and provide a valuable foundation for refining numerical models and optimizing design approaches for flexural members made of advanced high-performance cementitious composites.

Keywords: ultra-high performance concrete, beams, bending moment, steel fibers, flexural cracks

The article highlights the problems associated with the accuracy of calculations and measurements of the thermal protection properties of multilayer building envelopes. The authors consider options aimed at improving the accuracy of calculations, such as using numerical modeling to calculate the temperature fields of structures, using hot-box testing equipment to determine the heat transfer coefficients of structural fragments, and improving the accuracy of measurements. The article provides a description of the hot-box setup and explains why the measurement accuracy is three times higher than in conventional climate chambers.

Keywords: measurement of the heat transfer coefficient, thermal protection of buildings, energy saving, measurement accuracy, calorimetric measurement method, hot box installation

The article presents the results of laboratory testing of a precast lintel made of D600 aerated concrete blocks fastened together using assembly adhesive for laying aerated concrete blocks and three reinforcing bars, two bars in the lower zone with a diameter of 20 mm A400 and one bar in the upper zone with a diameter of 16 mm A400. When testing the beam lintel, 3 loading schemes were assembled, each of which was a beam hinged on concrete supports. The obtained data were analyzed. Based on the test results, destructive loads, the nature of destruction were determined and the resulting deformations were assessed. The nature of destruction is similar to that of reinforced concrete beam structures with insufficient transverse reinforcement; destruction in all tested prototypes occurs in the support zone along inclined sections. The bearing capacity of aerated concrete lintels made of piece material is sufficient for use in construction practice.

Keywords: testing, bearing capacity, reliability, deformability, gas blocks, lintels, destruction

As a result of changes in regulatory documents on acceptance of residential premises, there is a need to develop illustrative methodological materials that would allow the future owner to independently, i.e. without the involvement of an external qualified specialist, to perform the acceptance of the apartment, pointing out to the representative of the developer involved in the acceptance of significant construction defects. The purpose of the study is to determine the structure of construction defects in residential premises and to identify the most common defects in this structure, which will allow the future owner to independently perform the acceptance of the apartment. In the article, based on the analysis of a significant number of claims from apartment owners to the builder and the results of the authors' research in the scope of forensic examinations and pre-trial construction-technical investigations, the structure of construction defects, which are massively identified in the process of acceptance of apartments, is defined and presented. The groups of defects that are most frequently encountered in practice are presented. To ensure the clarity of practical use of the obtained analytical materials, a list of mass construction defects identified in the process of acceptance of residential premises, indicating their category necessary for making a decision on the mandatory elimination of defects is defined.

Keywords: acceptance of apartments, construction defects, structure, defect groups, construction defect, substantial defect, non-substantial defect, building and technical expertise, translucent construction, engineering networks, finishing of premises

A brief list of problems in the operational reliability of multilayer energy-saving walls is given, and the thesis is formulated that single-layer or equal-permeability multilayer walls may have better operational properties. Information about the equipment and technology for producing foam concrete mixtures using a one-stage method is provided. It is shown that the introduction of a fibrous filler instead of some of the sand significantly accelerates the phase transition of the mixtures from a viscous state to an elastic state and has a positive effect on the operational properties of the hardened foam concrete. The list of the material's investigated performance properties includes experimentally obtained indicators of sorption properties, equilibrium moisture content, thermal conductivity, and frost resistance of thermal insulation and structural-thermal insulation foam concrete containing different amounts of fibers of different lengths.

Keywords: foam concrete mixture, foam concrete, plastic strength, fiber, sorption properties, equilibrium moisture content, thermal conductivity, frost resistance

This article examines several key aspects related to the impact of high-rise buildings on human health and psychological state. First of all, the impact of high-rise buildings on mental health is analyzed, paying special attention to problems such as depression, anxiety and stress that can arise as a result of living in multi-storey buildings. We explore the social aspects of living in such conditions and the impact of architectural design on the quality of life. In addition, we would like to draw attention to the health problems of residents of high-rise buildings, including physical illnesses that can occur as a result of lack of natural light, poor ventilation and other factors associated with high-rise buildings. An important part will also be the discussion of possible solutions to improve the quality of life in multi-storey buildings.

Keywords: megapolis, high-rise buildings, high-rise buildings, building density, architectural design, emotional state, health, comfortable environment, quality of life.

The article defines the prerequisites and criteria for constructing rational shapes of cylindrical mesh shells. The correlations of geometric parameters, taking into account the overall dimensions in the arc direction, are revealed. The required number of nodal connections is installed at the attachment points along the contour and in the middle zone. The main provisions on the creation of geometric schemes for the formation of structures are formed and possible options for assigning dimensions are considered. The expediency of using identical cells in the framework of constructing a regular mesh surface structure is substantiated. The sequence of calculation of the parameters determining the shape of the structure has been developed

Keywords: cylindrical shells, mesh structures, rotation surfaces, shaping, parameters, ratios

In the article, as part of the study of the stability of circular spatial structures, the parameters of the critical state of cylindrical mesh shells are determined. The features of using a solid analog are analyzed and a dependence is obtained to determine the magnitude of the critical load. The influence of geometric parameters on the degree of vulnerability and the danger of curvature of the mesh surface has been established. A rational span value is found for a fixed length and a given radius of curvature. A computer simulation using square cells was carried out and possible forms of loss of stability of the shells were determined. An acceptable similarity has been obtained between the calculation results of solid and mesh surfaces

Keywords: cylindrical mesh shells, structural shape, surfaces, parameters, ratios

The article presents the results of comparing numerical modeling of wooden structures with laboratory and full-scale tests. In the course of the work, numerical models of the material were created in the Ansys Workbench software package from volumetric finite elements with a variant set of physico-mechanical parameters simulating the behavior of real wood. The simulation parameters were based on the laboratory testing results of a solid wood beam. The simulation results were compared with the full-scale test results of a composite wood slab. Modeling of constructions was carried out in the form of linear, bilinear and multilinear models.

Keywords: solid wood beam, composite wood slab, bilinear finite element model, multilinear finite element model, stress-strain state

The article is devoted to the study of the influence of the choice of the calculation scheme on the accuracy of the engineering assessment of the behavior of monolithic reinforced concrete frame structures. Various types of models are considered: rod, plate and volumetric, taking into account both linear and physical nonlinearity. It is emphasized that the adequacy of accounting for the spatial interaction of elements, the reliability of the assessment of forces and stresses, as well as the possibility of optimizing design solutions, especially under seismic and wind loads, depend on the correctness of the adopted calculation scheme.
As part of the study, a single-span reinforced concrete frame was modeled, the load on which varied from 5 to 55 kN. A comparison of the calculated results with experimental data was carried out. It is shown that models that take into account physical nonlinearity and use more detailed modeling (for example, volumetric finite elements) provide the greatest accuracy in predicting deflections and stresses in the structure.
The obtained results confirm the necessity of a careful approach to the choice of the calculation scheme in design, especially in the design of high-rise buildings and structures in seismically dangerous areas. Recommendations are made on the rational use of models of different levels of detail in engineering practice.

Keywords: linear calculation, nonlinear calculation, frames, reinforced concrete, deflections, modeling

The main design features and elements of industrial shaft furnaces are described. It is indicated that one of the undesirable phenomena in a shaft furnace is a large temperature gradient along its height; in this regard, the processes of air mass transfer through various parts of the furnaces are considered. The relationships and limitations that determine such a negative effect as the possibility of external air diffusing into the furnace through its walls are formulated. The results can be used to increase the quality of shaft furnace designs and the applied heat treatment processes.

Keywords: electric furnaces, heat treatment, tightness, gas permeability