The structural integrity of many reinforced concrete structures can be broken due to corrosion of reinforcing steel. This phenomenon is quite pronounced in infrastructure where de-icing chemicals are widely used. The aim of this study is to examine the bond characteristics between reinforcing steel and surrounding concrete to evaluate its effect in corrosion. The strength of the bond was studied in terms of elongation load response, cracking behavior.It is shown that the friction between concrete and reinforcement along the edge of the rib prevents the concrete key from sliding relative to the rib. The force due to friction between the reinforcement and concrete at the rib is vectorially added to the cohesion component acting perpendicular to the rib. If friction between the concrete and reinforcement is lost, the only component of bond strength is the force acting perpendicular to the rib. In pullout failure, the friction between concrete and reinforcement is less important than in spalling failure.

Keywords: reinforcement, concrete, bond, slip, sliding, pullout, corrosion, concrete deformation.

One of the main causes of structural failure is fatigue, which is caused by failure under repeated cyclic load. The vibration strength of welded joints depends on the height of the weld catheter, equivalent Mises stresses and general movements of frame assemblies of building metal structures experiencing multi-cycle loading reliability of frame assemblies when they are reinforced.

Keywords: reinforcements, reliability, assemblies, metal structures, multi-cycle fatigue

Increasing the energy efficiency of the construction process involves the use of materials with the lowest material intensity, including thickness, as well as with a reduced content of Portland cement clinker while maintaining or improving the technical characteristics of the products. In this regard, the use of textile concrete products, including concrete sheets, is promising. The development of a composite binder containing components that reduce nega-tive pressure in hardening concrete, and consequently shrinkage deformations and cracking, made it possible to obtain products with the following waterproofness indicators: determined by the ""wet spot"" method: 1.2 MPa; with a filtration coefficient of 5-7×10-11 cm / s; the concrete waterproof grade W12

Keywords: textile-concrete, concrete web, water resistance, shrinkage during hardening, cracking, fine concrete

This article discusses the results of studies of the behavior of reinforced concrete slabs during punching. The parameters affecting the shear strength of the joints of columns and slabs are considered. Studies of the influence of the strength of concrete, the location of reinforcement, the reinforcement coefficient, the shape and size of the column are given. Various types of reinforcement of reinforced concrete slabs in the punching zone are presented.

Keywords: floor slab, column, punching, shear, bending, transverse reinforcement, dowel action

The article provides an overview of the characteristic defects that occur during winter concreting as a result of violations of the technology of concrete work. The relevance of this topic is justified by the large-scale increase in the volume of construction of monolithic buildings for various purposes: residential, public, as well as various types of structures made of monolithic reinforced concrete. A feature of the review of these defects is in this case their main causes, which are associated with violations of concreting technology due to the need in some cases to accelerate production work. The defects presented in this article were identified based on the analysis of accounting documentation when performing visual surveys in the process of scientific and technical support for the construction of buildings of increased responsibility. The violations described in the article were observed at various monolithic construction sites within modern megacities. The article describes the main causes of these defects. The ways of eliminating these defects based on engineering practice are proposed.

Keywords: inspection of building structures, defects of monolithic structures, scientific and technical support of construction, flaw detection of building structures, concreting in winter

In most countries of the world, the construction industry is one of the main sources of air pollution in urban areas and agglomerations. One of the most dangerous pollutants are fine dust particles PM2.5 and PM10, formed from the production of dusty construction processes. Due to the optimal location of administrative facilities on the construction site, it is possible to reduce the concentration of dust emissions of particles PM2.5 and PM10. In addition, the cost of the dust control method is of concern to contractors, as it leads to an increase in the cost of construction. Therefore, reducing overall transportation costs is another optimization goal. To solve several tasks at once, the study uses multi-purpose optimization using the particle swarm method (MRF) algorithm to find an optimized construction site layout that can simultaneously reduce both the level of pollution from dust emissions and transportation costs.

Keywords: environmental safety, environmental monitoring, atmospheric air protection, ecology in construction, dust suppression, feasibility study, dust collection systems, labor protection in construction

We have considered the improvement of analytical formulas for the determination of bending moments in a single-span beam with semi-rigid nodes. We have obtained analytical relationships for deflections, angles of rotation, bending moments and shear forces in a single-span beam with semi-rigid nodes. A convenient coefficient from 0 to 1 is used to specify the intermediate stiffness node. The coefficient characterizes the fraction of possible rotation of the support node. When we derived the formulas, we used the assumption of constant bending stiffness of the beam along its length and linear deformation of the beam material under load. We did not consider the cases of loading the beam with concentrated forces and concentrated bending moments in the span. We realize the complexity and necessity of calculating beams with semi-rigid nodes, so we have created a table for easy calculation. In the table you will find the values of the supporting moments depending on the degree of possible angle rotation. With the information about the bearing moments, you can load the hinged beam with them and construct a bending moment diagram. The upper left and lower left values from the table are used to determine the bending moments at the supports. The upper right and lower right values of the table are used to determine the bending moments in the beam span.

Keywords: semi-rigid nodes, multilayer structures, calculation methods, contact zone, wooden beams, reinforcement, wood, reinforcement, environmental friendliness

Ensuring the reliability and safety of load-bearing structures, buildings and structures is the most important task. The reliability or safety of a structural system is inextricably linked with the elements of this system that provide strength and spatial stability. The importance of each load-bearing element in the building system in ensuring overall mechanical safety is assessed differently. For multi-storey frame buildings, load-bearing elements, for example, columns of the lower floors, if they fail, can lead to a significantly greater volume of destruction compared to the structures of the upper floors. The article provides a methodology for determining criteria by which the level of responsibility of columns can be established depending on their location in the building plan, developed on the basis of numerical studies. As a result, a classification was compiled according to the level of responsibility of the columns of a monolithic multi-story frame building.

Keywords: limit state method, special limit state, emergency design situation, responsibility of load-bearing elements, reinforced concrete columns

The article discusses the key problems of resource and damageability of crane beams over a long period of operation. A classification of the most dangerous defects in crane beams is proposed, taking into account not only the location of the defect, but also the mechanism of its development, as well as possible causes of its occurrence. The focus is on the effect of periodic loading on the initiation and growth of fatigue cracks. The article analyzes international research in order to identify methods and methodologies used to ensure the safety and reliable operation of the objects under study. It is shown that special attention should be paid to periodic examination for the purpose of early detection of cracks of various etiologies and timely adoption of the necessary measures. It has been revealed that the most effective approach to ensuring reliable and safe operation of the object under study throughout its life cycle is the collaboration of modern calculation methods, including fracture mechanics, and experimental techniques during periodic inspections, which will allow the crane beam zones to be ranked according to the likelihood of a defect occurring and reduce risk of sudden brittle failure.

Keywords: crane beam, crack, brittle fracture, fracture mechanics, shear deformation, normal separation, finite element method, ranking by fracture risk, maintenance, stress-strain state

The article provides the results of the calculation of a steel span structure. Two options for the design scheme were considered. In scheme №. 1.1, the bending moment is perceived by the beam elements. In scheme №. 1.2, the bending moment is perceived jointly by the beam elements and cable structures. A comparison was made of the results of determining bending moments.

Keywords: main beam, secondary beam, column, boundary conditions, loads, bending moment, CAD

This article is devoted to the analysis of factors influencing the energy efficiency of high-rise buildings. Using the example of the Aquamarine residential complex in the city of Vladivostok, an analysis of high-rise buildings was carried out, calculations were performed, and the results were presented in the form of graphs that reflect the dynamics of the speed of wind flows and temperature changes in the outside air along the height of the building. Changes in these parameters increase the intensity of heat loss, which must be taken into account when developing a space-planning solution and thermal protection of the facades of high-rise buildings.

Keywords: energy efficiency, aerodynamics, air exchange, heat resistance, high-rise building, microclimate, urban development, energy consumption

The paper considers the problem of automatic detection of defects in the geometric parameters of steel ropes of elevator systems using computer vision methods. The features of flaw detection of moving steel ropes based on video sequences are analyzed, associated with the fragmentation of the image of some defects in adjacent frames and the variability of the geometric dimensions of the rope and the characteristics of the defect visible by the camera due to vibrations of the rope during movement. Taking into account the considered features, two algorithms have been proposed: to determine the defect of thickening/thinning of the rope diameter and the defect of undulation. The paper presents the results of experimental testing of algorithms on a special test bench and calculates the reliability indicators of defect detection by the proposed algorithms in the form of precision and recall of detection of each defect individually, as well as the average precision and recall of detection of both considered defects of geometric parameters of the rope as a whole.

Keywords: steel rope defects, instrumental control, non-contact flaw detection, computer vision

The problem of safety in the construction of buildings and structures has always been and remains very relevant. In our time of actively developing scientific and technological progress, new risk factors of a technogenic nature appear. Studying the survivability of buildings, and consequently the resistance of buildings to progressive collapses, is a very important task. This article examines the influence of the compliance of nodal connections of a metal frame on progressive collapse.

Keywords: progressive collapse, yielding of nodes, metal structures, survivability, special effects, calculation methods

The article discusses the areas of application of the deformation model and reviews studies related to its use for various design solutions and operating conditions. A method for calculating eccentrically compressed reinforced concrete elements that takes into account second-order effects is presented. This methodology takes into account the current provisions of regulatory documents. A selection of experimental data was made for flexible eccentrically compressed columns. Calculations of bearing capacity and deflections for selected samples were performed. Various forms of concrete deformation diagrams were used in the calculations. Based on comparison with experimental data, conclusions are drawn about the applicability of various types of diagrams for calculating bearing capacity and deflections.

Keywords: deformation model, stress-strain diagram, eccentrically compressed element, flexibility

This article is devoted to determining the main characteristics and properties of concretes made from different concrete mixtures based on Vietnamese materials. A total of 16 formulas of concrete mixtures were studied. Concrete samples were tested to determine deformations under prolonged loading. Based on the data obtained, the main creep characteristics were determined, these are the creep measure C0 and the creep coefficient ϕ, as well as additional characteristics including prismatic strength and the initial modulus of elasticity of concrete. The main purpose of this study was to determine the dependencies of the prismatic strength of concrete Rpr, as its main indicator, in relation to the creep coefficient of concrete ϕ. In conclusion, experimental data on the creep coefficients of concrete ϕ were compared with the normative values found according to SP 63.13330 and conclusions were drawn on the effect of concrete creep on its prismatic strength of concrete Rpr made from concrete.

Keywords: concrete, reinforced concrete, structures, materials, creep, deflections, deformations, prolonged loading

In connection with the revival of interest in wooden housing construction in Russia, the creation of specialized software systems for the calculation and design of buildings and structures made of wood is becoming relevant. One of the most popular systems in the world is light-frame housing construction. As one of the possible tools for automated design of light-frame wooden buildings, this article presents the FrameCAD program, developed at the Department of Metal, Wood and Plastic Structures of the Don State Technical University. Some of its capabilities are presented, allowing you to design wall fences of light-frame buildings, beamed wooden floors, perform calculations of individual frame elements taking into account the requirements of current regulatory documents and automatically generate albums of drawings of wooden structures in the domestic NormCAD program, as well as specifications for them factory made. FrameCAD has been tested in the design of a number of objects. The software product is developed by engineers who have many years of experience in the actual design and construction of light-frame buildings. It continues to be improved and supplemented, and in the future it may become a replacement for similar foreign complexes.

Keywords: wooden structures, software package, wall panels, beam overlap, automated calculation

The article deals with the peculiarities of the study objectives and test methodology for characterization of different contact zones organized in different ways and requiring different methodological approach for specimen fabrication and testing. The steel plate-concrete contact zone organized by stamping on the steel plate requires the use of steel molds to prohibit horizontal movement. The contact zone between the steel plate and the concrete, organized by the stamping on the steel plate requires the use of steel molds to prohibit horizontal movement. The contact zone of two wooden bars organized by epoxy glue with reinforcing fabric placed between the layers of glue is tested for shear without organizing the prohibition of horizontal movement. The contact zone formed at the connection of a steel plate and incompletely gained strength concrete, with the association of steel bars has features of fixing the actual strength of the concrete part of the specimen. The considered methods have both a number of common features and differences, which are taken into account in the proposed methods of fabrication and testing.

Keywords: contact zone, contact characteristics, test methodology, shear tests, stamping, composite construction

Improving calculation models of concrete based on experimental data, especially when studying the volumetric stress-strain state, is an urgent task. When calculating the containment shells of nuclear power plants under the influence of beyond design basis accidents, it is absolutely important to take into account the available safety margins of the materials used. Under volumetric loading, due to the work of concrete in cramped conditions, its strength and deformation characteristics improve, which is not sufficiently reflected in the regulatory documentation in force in the Russian Federation. Taking into account the analysis of existing test methods, based on the labor intensity and reliability of the results obtained, the optimal method of testing for volumetric loading was identified. The article contains the results of testing the selected test method, taking into account the improvement of the deformation measurement system. They confirmed the effectiveness of using the proposed methodology from the point of view of data reliability and relatively low labor intensity of work.

Keywords: concrete, volumetric loading test, volumetric strain sockets, deformation diagram

The purpose of the work is to develop a methodology for calculating the stress-strain state of three-layer structures made of composite material under the action of dynamic loads in robotic systems: semi-natural simulation stands, intended mainly for testing the flight characteristics. The stand consists of movable channels that ensure movement of the tested product in three degrees of freedom. The algorithm for creating a three-layer stand made of composite material is as follows. We assign the characteristics of the filler to the model of stand, create surfaces on the model and assign to the created surfaces the characteristics of a multilayer composite material with the orientation of the base of the layers along the lines of the trajectories of maximum stresses. Calculations of a three-layer stand with eight-layer load-bearing layers, with different orientations of the layers, were carried out to determine the structure of a multilayer composite material of maximum strength and rigidity based on theories of the destruction of multilayer materials stating that the destruction of one layer leads to the destruction of the multilayer material as a whole. The stress-strain state of a three-layer of the stand for semi-natural modeling of maximum rigidity and strength was obtained. The developed methodology is applicable to a wide class of problems of calculating the robotic systems made of three-layer composite material.

Keywords: material characteristics, multilayer composite material, modeling methods, three-layer structures, calculation, analysis

The use of closed methods for laying underground polyethylene gas pipelines using horizontal directional and directional drilling methods when crossing artificial and natural obstacles is considered. The results of calculating the geometric parameters of the working and receiving pits when laying polyethylene gas pipelines using a closed method using horizontal directional drilling are presented.

Keywords: polyethylene gas pipeline, closed installation method, horizontal directional drilling, directional drilling, dimensions of working and receiving pits

The loads on the power floors and column foundations of modern logistics centers can reach 6-9 t/m2 and 1000 t, respectively. At the same time, the step of the grid of exploration wells in the mined areas does not allow reflecting on the geological sections the exact geometry of the occurrence of weak, untreated soils of backfilling pits. The use of a method for strengthening man-made soils by pressing in prefabricated prismatic piles made it possible to compensate for the missing information from engineering and geological surveys by controlling the forces of indentation and thus determining the occurrence marks of more durable foundation soils.

Keywords: engineering and geological surveys, the territory being worked on, man-made soils, soil reinforcement with piles, geological section

The article analyzes the heat-shielding properties of typical curtain-type ventilated façade (hereinafter referred to as CVF) systems used on multi-storey residential buildings in Moscow. We conducted analytical and visual studies, evaluated the technical condition by external features, including photographing the detected defects, thermographic scanning of facades, and took selective measurements of external geometric parameters, distortions, and structural properties for 18 objects in the city of Moscow. The level of defects in the thermal insulation layer at Moscow facilities was at least 50%. A gap of 10 mm at the joint of insulation slabs reduces the heat-shielding properties of the CVF fragment of the outer wall by 14.5–15%. The conclusions were drawn on the basis of the results of calculations of the reduced heat transfer resistance of a total of 18 CVF options from two manufacturers of the Kaptekhnostroy (aluminum CVFS subsystem) and Alfa-Prof (galvanized CVF subsystem) systems. When comparing these solutions, it is obvious that they are all inferior in value reduced resistance to heat transfer of the composite facade thermal insulation system. If the foundation is made of monolithic reinforced concrete or brickwork, the choice of finishing material does not matter. Moreover, the indicators of the reduced heat transfer resistance do not differ significantly. In the case of a base made of expanded clay concrete blocks, the galvanized steel subsystem is 2.9% (ceramic granite), 4.3% (fiber cement) and 4.6% (composite) more efficient.

Keywords: curtain-type facade system, ventilated, facing slabs, fasteners, defects, inspection, heat transfer resistance

The results of the coefficients of iciness for the northern and southern walls, in the attachment points of the frame of the ventilated facade for wall fences made of three-layer reinforced concrete panels with an internal thermal insulation layer are presented. The durability of the anchor attachment of the hinged ventilated facade is determined, depending on the frost resistance of the outer layer of the three-layer wall panel and the orientation of the wall to the north or south.

Keywords: hinged ventilated facade, reinforced concrete three-layer panel, attachment point of the hinged facade, ice coefficients, durability

Ultra high-performance or ultra high-strength concrete is a new class of cement-based materials with increased strength and durability. The widespread use of this concrete in construction practice requires theoretical and experimental studies of the stress-strain state of structures made from them. The article presents and analyzes the shear strength of I-shaped beams made of ultra-high-performance concrete tested by the authors. In the experiments, we varied the fiber content, the shear span, the shear reinforcement ratio, and the width of the compressed flange.

Keywords: shear strength, shear force, ultra high-performance steel fiber-reinforced concrete, I-shaped beams

Modern domestic calculation methods and developed countries for determining the bearing capacity of monolithic reinforced concrete slabs for punching do not fully take into account all factors of design solutions and operating conditions. The available design provisions are made for the static operation of structures and there are no recommendations for taking into account the features of the dynamic impact on the overlap and the nature of the work of the node interfaces. The accepted empirical assumptions of the calculation, based on numerous experimental data, do not take into account the features of the stress-strain state of the coupling of the overlap with the column during destruction according to the punching scheme. This is due to the lack of computational models in which all the acting internal forces ensuring the resistance of the interface to penetration would be considered comprehensively. The complexity of the problem is due to the fact that the sections of the nodal interface are in an inhomogeneous stressed state. The stress-strain state of plates for punching under dynamic load is currently little studied. This article proposes a method for determining the bearing capacity of a symmetrical nodal coupling of a column with an overlap for punching under static and short-term dynamic loading. The proposed design model of the punching strength is based on the following prerequisites: the resistance to punching of a monolithic reinforced floor consists of the shear resistance along the surface of the reduced punching pyramid formed by the height of the compressed concrete zone; the strength of the concrete shear resistance increases due to volumetric compressive forces on the surface of the reduced punching pyramid; the angle of inclination of the faces of the punching pyramid depends on the loading speed. The obtained theoretical dependences are applicable under static and dynamic loading and are in satisfactory agreement with experimental data.problems in the field of video analytics. Numerous studies have shown that, despite the dynamism of processes in the field of information technology and the introduction of various tools and methods, the task of object maintenance still remains relevant and requires further improvement of previously developed algorithms in order to eliminate some inherent disadvantages of these algorithms, systematization of techniques and methods and the development of new systems and approaches. The presented article describes the process of step-by-step development of an algorithm for tracking human movements in a video stream based on the analysis of color groups. The key stages of this algorithm are: the selection of certain frames when dividing the video stream, the selection of the object under study, which is further subjected to a digital processing procedure, the basis of which is to obtain information about color groups, their average values and percentages of their occupancy relative to the object under study. This information is used for the procedure of searching, detecting and recognizing the selected object with an additional function of predicting the direction of movement on video frames, the result of which is the formation of the entire picture of the movement of the person under study. The materials presented in this paper may be of interest to specialists whose research focuses on issues related to the automated acquisition of certain data in the analysis of various images and videos.

Keywords: coupling of a monolithic floor with a column, static and dynamic load, punching pyramid, tangential stresses, concrete shear strength, punching strength