Load-bearing Structures Of Buildings Research Articles

IDENTIFICATION OF HIDDEN DAMAGE IN CONSTRUCTIVE ELEMENTS OF BUILDINGS AND STRUCTURES TO REDUCE THE RISKS OF THEIR DESTRUCTION

Problem statement. In emergency situations, which are activated by dynamic impacts from explosions, fires and earthquakes, it is necessary to monitor the stability of objects to assess their suitability for further operation. Purpose of the study. ensuring the safe operation of buildings and structures using methods, software and technical means for vibroacoustic monitoring of hidden damage in building structures. Methods. Analysis and generalization of data, computer modeling, experimental studies of the structures stability using the vibroacoustic method. Research results. Considered: loss of concrete stability, reinforced concrete, bricks and other elements of load-bearing structures; risk factors manifested in the gradual weakening of load-bearing building structures due to the accumulation of internal damage. Sudden loss of stability of structures occurs after the accumulation of a critical amount of damage in structural elements or the rapid growth of cracks, which are activated by the sudden unloading of extremely stressed structures as a result of any dynamic influences. By modeling the destruction process using the finite element method, it has been established that long before cracks on the surfaces of structures can be visually identified, zones of hidden damage can actively spread inside the wall structures of buildings. The main parameters for monitoring the condition of buildings and structures using visual and vibroacoustic methods have been determined. Due to the fact that the object of research is the partial destruction of buildings and structures (that is, not the root cause, but the consequences of the influence of a complex of negative main factors), two main groups of risk factors for assess the risks of stability loss have been proposed. The first group is associated with the detection of external structural damage identified by visual inspection methods. The second group is associated with the detection of hidden damage, the parameters of which are determined by the vibroacoustic method. The integral risk of stability loss is determined by comparing and selecting the maximum risk in the group. Scientific novelty. The methodology for identifying hidden damage in structural elements of buildings and structures has been further developed, which is distinguished by taking into account the parameters of vibroacoustic control of the destruction consequences and assessing the risks of the structures stability loss. Practical significance. The research results make it possible to improve the method for assessing changes in the structure of the medium as a result of the occurrence of observed and hidden systems of cracks using vibroacoustic monitoring.

Математичне моделювання динамічних впливів на будівельні конструкції

The solution of the problem of mathematical modeling of dynamic influences on building structures is considered in general and in connection with important scientific and practical tasks. In modern conditions, special attention should be paid to the problems of taking into account dynamic influences, parameters of load-bearing structures of buildings that affect their structural reliability and safety. For many years, information about catastrophic destruction of buildings and structures has been appearing more often, which are the result not only of errors that arose during the construction of facilities, but also due to dynamic influences that arose during their operation. A buildable technical system will be used in advance with the technical parameters set, which is responsible for the control of the process of the preparation of structures, the installation of the equipment, during the operation and operation. The development will be carried out and the sporud will be constantly used to promote the development of future technologies, the development and the establishment of the future, as well as the development of dynamic developments in the future. In particular, it is important to understand the development of the engineering and geological minds of the spores, as they have known the front deformation of the non-essential axis of the runt foundations. Various methods are used for structural dynamics, such as modal analysis, response spectrum analysis, time analysis, and finite element analysis. These methods include mathematical modeling, numerical simulation, and computational methods to predict the behavior and response of a structure under dynamic load conditions. Knowing the frequency and form of the structure, it is possible to estimate the dynamic reaction of the design to the application. For the purpose of including the transfer of the world, the destruction of internal forces in the real parts of the construction. Analyses of the response to the additional assessment of the characteristics of the construction, the identification of critical areas and the re-conversion, which the project is able to meet the criteria.

Stress-strain modelling for a composite reinforced concrete beam

The study is aimed at the features of modeling the stress-strain state of a concrete beam, reinforced with two types of fibrous composites. The necessity of strengthening existing reinforced concrete structures can be caused by the reconstruction or technical re-equipment, which often entails an increase in the load on the load-bearing structures of buildings and facilities, as well as during the elimination of the consequences of factors that led to a decrease in the bearing capacity or a failure of loadbearing structures. In order to study the applicability of the model, we analysed the results, obtained during bending and axial compression tests of T-section reinforced concrete beam specimens with welded frame reinforcement that were in operation and the results of a numerical study in a LIRA software suite. The stress-strain state of specimens was modelled in a nonlinear formulation using the finite element method. The conducted analysis and theoretical studies have shown the applicability of models, developed based on a limited test database, unclear, especially with regard to a wide range of compression coefficients, while the results of modeling the behavior of reinforced concrete beams have demonstrated sufficient accuracy for applying in the strengthening design using external composite reinforcement.

Comparison of ultrasonic and GPR methods for investigation of reinforced concrete columns

The presence of internal concreting defects such as pores, cavities, sinks, in load-bearing vertical structures can lead to serious consequences, up to accidents. In this regard, it is especially important to identify such defects is an important and relevant task during surveys of load-bearing structures of buildings and structures. At the same time, the search for internal defects is complicated by the fact that they may not be visible on the surface, but may be present in the body of structures. In order to control the quality of the erected monolithic structures, their instrumental examination is carried out with the identification of the possible presence of internal defects by the method of through ultrasonic sounding. The article discusses the comparison of ultrasonic and GPR methods for searching for internal defects in concreting reinforced concrete columns. The studies were carried out on real construction sites in which there were suspicions of internal defects in concreting of high columns. Conclusions are drawn about the possibilities and limitations of the methods. The resolution limits of the methods are presented. The results of the conducted studies show that, despite the relative modern popularity of ground-penetrating radar, ultrasonic methods can work equally well in this type of specific research scenario and have shown a high potential to overcome some inherent limitations of ground-penetrating radar when working with saturated reinforcement.

Применение системы мониторинга технического состояния конструкций покрытия опасных производственных объектов машиностроительной промышленности

The article presents data on the implementation of technical monitoring using the engineering structures monitoring system (SMIC) for the technical condition of the load-bearing building structures covering the Main Building of JSC "DMZ". The monitoring of the workshop coating elements was carried out after a complex of instrumental surveys with the strengthening of individual building structures, general geodetic monitoring with subsequent strengthening of crisis structures.

Studying the Efficiency of Composite Longitudinal and Transverse Reinforcement for Increasing the Strength and Rigidity of Flexible Eccentrically Compressed Reinforced Concrete Poles

Introduction. In recent years, the use of composite materials for improving the operational properties of the building constructions within the restoration process is gradually replacing the methods, developed for this purpose in the middle of the XXth century and implying the use of reinforced concrete and metal. However, the regulatory framework stipulating the process of strengthening the loadbearing structures of buildings and structures was developed based on the insufficient amount of experimental data. Due to this fact, the large number of structures, exceeding the normative limits, cannot be strengthened with the composite materials, or such strengthening incurs significant economic costs. Thus, nowadays, the experimental studies on strengthening the reinforced concrete structures with composite materials are considered to be forward-looking and relevant. The aim of this study is to analyse the results of a number of experiments conducted to investigate the use and efficiency of composite materials in construction. Materials and Methods. To determine the level of stress in composite carbon materials of the external reinforcement of the eccentrically compressed reinforced concrete poles, the tests were carried out with four specimens. All specimens were strengthened using different reinforcement schemes. The strain gauges with 2cm active measuring grid length were installed in the zones of the most evident work of the composite materials to measure the changes of relative deformation at each load level during testing of the specimens. From 10 to 16 strain gauges were installed at each structure, depending on the importance of the zones for determining the deformations.Results. The work presents the results of the study on determining the efficiency of composite longitudinal and transverse reinforcement for increasing the rigidity and strength of flexible eccentrically compressed reinforced concrete poles. The experimental data on the composite materials’ strength, deflections and relative deformations, obtained during testing of four reinforced concrete poles, is presented. The efficiency of composite reinforcement at ultimate strength and ultimate deflections is assessed. The relative deformations in composite materials are determined and the inclusion of the reinforcement system in the work of the strengthened reinforced concrete specimens is assessed.Discussion and Conclusion. Based on the obtained results, the analysis of the composite reinforcement efficiency has been carried out, and proposals have been developed on designing the reinforcement systems of the flexible eccentrically compressed reinforced concrete poles working with the large eccentricities of the load application.

The pavilion “Petite Maison” of the European Cultural Capital Esch'22: A case study of circular economy benefits in steel construction

Abstract“Petite Maison” is a collaborative architectural project on the theme of circularity in construction within the Esch2022, European Capital of Culture, in Luxembourg. Focusing on a similar concept, the RFCS project “REDUCE” has previously worked out the structural and environmental analysis of a modularized construction approach to evaluate and highlight the benefits of a reusable, circular steel structure. As a follow up to this project, CoCo Project (Carbon Counting and Projection) currently occupies with the determination of suitable routes to point out low‐carbon emission scenarios for the construction sector considering especially steel and steel composite solutions as well as prefabricated structural elements, which may be in concrete or timber. In other words, the project aims to demonstrate the impact of circular economy objectives in the load bearing building structures, considering majorly columns and flooring solutions containing concrete slabs, Laminated Veneer Lumber (LVL), and steel beams. In this article, the environmental performance of Petite Maison flooring system, as a case study, is investigated in detail. Different scenarios are defined for steel elements to quantify the environmental impacts and to emphasise the benefits of modular and reusable structural components.

ДВУТАВРОВЫЕ ГНУТОСВАРНЫЕ ПРОФИЛИ С ПЕРФОРИРОВАННЫМИ СТЕНКАМИ И РАСЧЕТ ИХ ОПТИМАЛЬНЫХ КОМПОНОВОК

A new technical solution of I-beam bent-welded profiles with perforated stacks and shelves with closed welds is presented. Each of the inclined faces of the shelves in cross-section has the shape of half a round halfring (a circle) with a radius equal to the height of the shelves. The maximum height of the cutouts is limited by the height of the single wall. The calculation of optimal parameters along the middle line of a thin-walled cross-section of an I-beam shape with a single wall and closed (tubular) shelves is given. As a double optimization criterion, the maximum of the moment of resistance of the section in the force plane of the supporting structure and the maximum height of the cutouts in the perforated wall. According to the results of solving the optimization problem, the moment of resistance and the height of the cutouts are maximal when this height reaches 0.84 of the entire height of the profile, and the ratio of the width and height dimensions is 1/6,4. The optimization calculation is supplemented by the calculation of the deflection of the punch using the reduced moment of inertia of the section, determined from the equality of the areas of the calculated and conditional plots. A comparative analysis of the design parameters of I-beam rolled and bent-welded profiles with perforated the main results of which revealed a noticeable increase in the mounting (lateral) rigidity of the new modification and confirmed the prospects of its use in load-bearing structures of buildings and structures.

Features of measuring deformations of load-bearing structures of buildings during their field and laboratory tests under the action of static and dynamic loads

The peculiarities of measuring the deformations of load-bearing structures of buildings during their field and laboratory tests using strain gauge-based sensors are considered. An overview of various problematic issues that arise in the process of conducting experimental tests and affect the measurement results is given. The most common, which affect the accuracy of measurements, are the effects of temperature, humidity, and vibration; the difficulty of calibrating and mounting strain gauges on different surfaces of elements; complexity of measurement data processing; combination of high-quality work of strain gauges, cable conductors, measuring equipment, data collection and processing system; the selection of the connection scheme of tensor resistors in the Wheatstone bridge. The peculiarities of the organization of the experiment for testing the load-bearing structures of the building, namely pile foundations, are considered, and the main problematic issues when using strain gauges as strain gauges of building elements are given. The use of strain gauges to measure deformations of load-bearing structures of buildings is one of the common methods, which has many advantages, which are discussed in detail in the work. Strain gauges can be used to measure deformations of elements that are mechanically connected to them. They have high measurement accuracy, sensitivity to element deformation, and a wide variable measurement range. The advantages of using the Wheatstone bridge to measure the change in electrical resistance are highlighted, as this method allows measuring very small values of the change in resistance. Methods of connecting tensor resistors according to the Wheatstone scheme are considered, the choice of which depends on the purpose of the study and the required accuracy. One of the easiest ways is to connect just one strain gauge to a current or voltage source and measure the change in resistance. But this method has low sensitivity and does not compensate for the effect of temperature. A more accurate way is to connect two or four tensor resistors in the Wheatstone bridge circuit, which allows you to measure the voltage change on the diagonal of the bridge. The bridge circuit has a high sensitivity and can compensate for the effect of temperature if the tensor resistors have the same coefficient of temperature dependence of the resistance. An algorithm for measuring the deformations of a metal pipe working under compression using strain gauges has been developed.

WAYS TO IMPROVE THE ENERGY EFFICIENCY OF PIPELINES AND STRUCTURES USING AEROGEL

Problem statement. The paper explores ways of energy saving in buildings, namely, the compliance of the regulatory framework with European standards, the possibilities of reducing heat losses during the transportation of energy carriers through pipelines on the example of heat supply systems and reducing heat losses during the operation of buildings and structures. The second part of the article presents the results of analytical studies of various heat-insulating materials that are most commonly used in Ukraine. Some of these materials cannot be used on structures and pipelines of complex configuration. The issue of energy efficiency, along with improving sound insulation properties, reducing fire hazard, and reducing loads on the load-bearing structures of buildings and structures, can be addressed by using aerogels as a thermal insulation material. The material is characterized by a low dependence of the thermal conductivity coefficient on changes in ambient temperature, which makes it the best option for use in harsh operating conditions. The purpose of the article is to consider ways to improve the energy efficiency of structures and pipelines using modern aerogel insulation material. Conclusions. Having conducted analytical studies of various thermal insulation materials, it was found that aerogels in roll form, in addition to a low heat transfer coefficient, are characterized by better performance properties, namely non-flammability of the material, environmental safety, low weight, which reduces the load on structures, ease of installation, the possibility of using for structures of complex configuration, and a high rate of sound insulation.

Comparison of efficiency for steel and combined frames

Recently, in the practice of design, customers of design works and investors of various projects have a dilemma regarding the choice of building material for load-bearing building structures. At the same time, the choice is usually limited to two types of materials – steel and reinforced concrete. Each of these materials has its advantages and disadvantages, which results in their different efficiency of application for various types of building structures. At the same time, the main attention is paid to the estimation side, because in modern complex and dynamic conditions, it turns out to be dominant in many cases. 
 The article presents the results of research of the completed master's thesis on the comparative analysis of the effectiveness of steel and combined frames (steel-reinforced concrete) on the example of the filter station building. The building has dimensions in plan of 54 × 36 m with a total height of about 22 m. Its supporting frame is a statically nondefined flat frame consisting of columns and crossbars in the form of trusses. In the longitudinal direction of the building, the frames are united into a spatial system by means of covering structures. The building is craneless and has three floors, each about 6.5 m high. 
 In the course of research, the considered variants of the transverse frame were analyzed using the finite element method on the basis of the LIRA-CAD multifunctional design complex. As a result, appropriate cross-sections for loads according to the climatic conditions of Ukraine were obtained. A comparison of variants showed that the first design variant is 9 % cheaper. Taking into account the additional technological advantages in its manufacture, the steel frame can be considered more effective for the given construction conditions and be recommended for practical implementation. Separately, it should be noted that such a frame also has an average of 5 times less total mass, which should be considered its additional advantage.

Evaluation of Effectiveness on Some Vibration Isolation Methods for Existing Buildings and Structures from Vibrodynamic Effects, Propagating in Soil Environment

The paper presents calculations of various design schemes for vibration isolation of a building with a reinforced concrete frame from a source of vibrodynamic exposure located outside it. It is noted that in most studies, the maximum value of the velocity of vertical vibrations of the foundation or soil in front of it is used as a criterion for the risk of damage to load-bearing building structures. The main factors that determine the risk of damage to structures are identified. These include the engineering and geological conditions of the soil at the base of the affected foundations, the degree of damage to the building, the type and design of the building or structure, the vibration frequency, the duration of the vibration, the distance to the vibration source, the type of vibration source, the material of the structure and the type of foundation. Based on the analysis of factors that determine the risk of damage to structures, the parameters of a building or structure that are least sensitive to vibrodynamic effects and have greater operational reliability are identified. It should be with a frame made of reinforced concrete or steel, not damaged, located on foundations of pile-racks in strong, low-moisture coarse sands or hard clays. The proposed design schemes for vibration isolation are mainly based on one of the vibration damping mechanisms in the soil medium – scattering on inhomogeneities. The finite element method has been used as the main tool for theoretical research. The ground medium has been considered as an elastic inertial array bounded by non-reflecting boundaries. The reliability of its application for calculating the development of dynamic processes in the system “oscillation source – propagation medium – oscillation receiver” has been confirmed by verification based on data from small-scale laboratory experiments. The use of the finite element method (FEM) makes it possible to take into account the spatial variability of soil conditions, the properties of materials, the design features of buildings and structures, the magnitude, direction and point of application of the dynamic load, as well as to model and optimize various vibration protection schemes. Seven variants of vibration isolation have been considered: the device of an inertial slab on the surface of the soil medium between the vibration source and the building, the installation of a vertical screen from gas-filled cylinders under pressure, a combination of these methods, the installation of a pile field in the soil medium, the reinforcement of the columnar slab foundations of the building with micropiles, the installation of a ribbed slab on the surface soil environment between the source and receiver of oscillations, the device of a reinforced concrete cage around the foundation-source of oscillations. The effectiveness of each method of vibration isolation has been evaluated by the damping coefficient K, a parameter showing how many times the speed of vertical oscillations of the building foundation decreases. Among the above methods of vibration isolation, two most effective options have been identified: in the form of a horizontal inertial slab of reinforced concrete on the surface of a soil mass (4.5-fold reduction in the rate of vertical vibrations), and a vertical barrier made of pressurized gas-filled cylinders (reduction in the rate of vertical vibrations by 3.32 times).

Датчик линейных перемещений для мониторинга инженерных конструкций зданий и сооружений

The article provides an analysis of techniques and devices used in monitoring and evaluating the parameters of the stress-strain state of load-bearing structures of buildings and structures. The prototype and the principle of operation of converters for measuring linear displacements under dynamic loads are described. The description of a new innovative linear sensor developed on the basis of an "electro-chemical converter" is given. At the end of the article, the tasks and directions of further research are given.

Оценка сходимости результатов экспериментальных исследований огнестойкости сжатых железобетонных элементов с повышенным процентом армирования с численными расчетами

Introduction. Evaluation of actual fire resistance of load-bearing building structures made of various materials and reinforced concrete, in particular, encompasses a rather complex and research-intensive case of analysis of integrated, mechanical and fire safety of buildings and structures. Current methods of analyzing the fire resistance of reinforced concrete structures do not take into account any thermal characteristics of reinforcement. Hence, values of the fire resistance limit of structures can only be consistent with experimental results only if the percentage of reinforcement in analyzed concrete structures and reinforced concrete structures is below 3.5 %. The purpose of the work. Is (1) the pilot testing of a hybrid experiment method and (2) evaluation of convergence between (a) results of experimental laboratory studies on fire resistance of compressed reinforced concrete elements with a higher percentage of reinforcement, (b) theoretical data and (c) numerical calculations. The following tasks were solved: in accordance with the developed method, analytical, experimental laboratory and numerical studies of fire resistance of compressed concrete and reinforced concrete elements (including those that have a higher percentage of reinforcement) were carried out; convergence between the obtained results was evaluated; conclusions were made about the issues under consideration. Research methods. Theoretical data, applied for comparison purposes, were obtained analytically (using formulas and nomograms of SP (Construction Regulations) 468.1325800.2019), experimental and calculated data were obtained in the course of concurrent experimental studies conducted at the fire testing laboratory of NRU MGSU, and numerical studies were obtained using the Abaqus PC software package. In the course of a laboratory experiment made using the loading equipment, the strength of reference concrete templates was identified, using the tensile machine to find the physical and mechanical characteristics of reinforcing steel. Next, reference concrete and reinforced concrete specimens with pre-set characteristics were made. Then temperature fields in concrete and cross sections of specimens, containing reinforced concrete, were identified using the thermocouple data. Centrally compressed concrete and reinforced concrete specimens were tested in a fire chamber at a standard fire temperature. The behaviour of concrete and reinforced concrete specimens was simulated using volumetric finite elements, having the size of up to 10 mm, and a built-in Heat Transfer Solver (Heat transfer). Temperature field distribution and fire resistance of reinforced concrete elements were analyzed at a standard fire temperature in concrete and reinforced concrete elements. Results and their discussion. The following knowledge was gained by means of this research project: convergence between temperature values at control points in concrete specimens (according to thermocouples), acceptable for practical purposes. These values were obtained in the course of experimental laboratory studies and calculations made according to current standards, which confirms the validity of the experiment; convergence between temperature values at control points in concrete specimens (according to thermocouples), acceptable for practical purposes. These values were obtained in the course of experimental laboratory studies and calculations made according to current standards, which confirms the validity of the proposed hybrid experi­ment method and the trustworthiness of the research; a great difference reaching 10 to 30 % (19.3 % on average for a group of specimens) between experimental and analytical values of fire resistance of reinforced concrete elements, which proves the hypothesis about a reduction in the heating temperature of concrete in a reinforced concrete section if the thermal influence of reinforcement is taken into account; convergence between fire resistance values (the difference is 7 to 10 %) in reinforced concrete specimens, which is acceptable for practical purposes. These values were obtained in the course of experimental laboratory studies and calculations, and their convergence proves the applicability of the proposed hybrid experi­ment method with account taken of the hypothesis about less intensive heating of concrete, if the thermal impact of reinforcement is taken into account. Conclusions. The hypothesis about a reduction in the heating temperature of concrete in the reinforced concrete section that has a high percentage of reinforcement (more than 3.5 %) was proven, taking into account the thermal influence of reinforcement. The consequence is the underestimated values of fire resistance of reinforced concrete elements, identified in accordance with a standardized approach. The applicability of the proposed hybrid experiment technique is also proven, taking into account the hypothesis about a reduction in concrete heating due to the thermal influence of reinforcement.

Analysis of damage to objects from the influence of subsidence soils

The article presents the classification of damage to objects located on subsiding soils, which was developed based on the results of the analysis of scientific research conducted using the complex method of geodetic observations of deformations of the earth's surface and supporting structures of 273 residential buildings, as well as buildings of the Kherson State Agrarian and Economic of the university, which are located on sites with the above-mentioned properties soils The analysis showed that the degree of damage depends not only on the discharge, dimensions, structural features, technical condition of the building or structure, the nature of the object's operation, but also on the location of the subsidence hopper under it. The use of the developed observation method makes it possible to fully determine the causes and negative factors of deformations on the earth's surface, as well as in the load-bearing structures of buildings and structures, and to develop a set of measures to preserve the normal operational quality of objects during the active stage of the process of soil subsidence and horizontal movements the earth's surface. To clarify the nature of deformations in buildings and structures located in different zones of subsidence, it is necessary to continue research in other regions of the country.

Production technology and properties of polystyrene concrete on recycled polystyrene

The article deals with the production of polystyrene concrete from recycled polystyrene crushed in a rotary crusher waste from the production of foam packaging. The resulting polystyrene concrete can be attributed to thermal insulation, used for insulation of load-bearing structures of buildings, as well as to structural and thermal insulation, used as a bearing layer of the outer walls of low-rise buildings. The dependence of the thermal conductivity of the sample on the density and strength of polystyrene concrete has been established, and the resistance to shock loads depends not only on the composition but also on the polystyrene concrete hardening accelerator used.

Dynamic load assessment of building structures

The questions of the theory and practice of testing structures with dynamic loads are presented. A concrete example of testing a structure on its physical model by dynamic load is clearly shown. Some information necessary for statistical processing of research results is given. Building structures are exposed to the intensive dynamic loads. The existing methods and regulatory requirements should consider the loss of strength subject to dynamic impacts. The dynamic load types will show what needs to be more focused on during the construction. Building structures should be designed to stay out of the resonance band during the use. Nowadays, the construction of new industrial complexes and modernization of factories is widely developing. Increased production, leads to increased loads, including load-bearing structures of buildings and structures, namely there are dynamic effects from a large number of machines and mechanisms. Dynamic loads are very varied in nature. They include impacts associated with natural phenomena, such as seismic shocks and wind gusts, as well as dynamic impacts of technological and accidental origin. The most important characteristic determine behavior of buildings and structures under the action of external dynamic load, and are frequency, and nature of vibration. All methods for calculating wind and seismic loads are based on determining these parameters. The purpose of this paper is to demonstrate the effects of dynamic loads on strength, durability, rigidity and crack resistance of building structures; to develop measures for mitigating oscillations; to verify the design performance of commercialized and exploited structures by the frequency and attenuation intensity of natural oscillations. The scientific novelty in this paper is that experiments were conducted to assess the dynamic stability and deficient dynamic stability using the “soil-to-building”.

Calculation for the progressive collapse of the steel frame based on the shutdown of an element of the structural scheme

Reliability of a building object - the ability of a building object perform the required functions during the estimated service life. In this case, the structure may experience a special limit state after exceeding the limit of the bearing capacity in the first and deformability in the second limit states, in which they do not fully comply with the functional requirements; further increase in loads and impacts leads to their destruction. The assumed initial local destruction implies the removal of a bearing structural element, simulating the loss of bearing capacity and stability, as well as leading to a change in the structural design of the structure. As a result of the damage received, a progressive avalanche collapse can occur in the form of the destruction of load-bearing building structures, leading to the collapse of the entire building or structure or its parts due to the initial local destruction.

FEATURES OF THE DESIGN OF STEEL EARTHQUAKE-RESISTANT STRUCTURES OF HIGH-RISE BUILDINGS

The design, construction and operation of buildings in Ukraine is associated with the need to take into account additional special loads and impacts, namely: seismic, in complex en-gineering and geological conditions, on weak soils, artificial territories and subsidence soils, and in the conditions of the war with Russia during missile and artillery shelling and bom-bardment of populated areas – effects from explosions, blast waves, spread of fires, etc. [3].
 The territory of Ukraine is located on the outskirts of the powerful Azores-Mediterranean-Alpine-Trans-Asian seismogenic belt of the planet. In general, Ukraine does not belong to particularly seismically dangerous regions of the planet. Low- and medium-magnitude (magnitude 3...6) earthquakes were recorded only within three of its regions: the Ukrainian Carpathians and the Crimean Moun-tains, the Azov region. But observations of the consequences of numerous earthquakes have shown that in different parts of the same seis-mic area they differ significantly in intensity. Thus, the intensity of the earthquake on the surface of the earth in areas with loose soils is 15 times greater than in areas with rocky ones. Therefore, during the design of buildings and structures, one should take into account the peculiarities of construction in the complex engineering and geological conditions of the territory of Ukraine, which are associated with research, design and arrangement of bases and foundations on weak water-saturated, clayey and peaty soils, peat and silt, subsidence, swell-ing, saline, swelling and unevenly compacted soils, loose sands and floating karst and forged territories, taking into account seismic and dy-namic action in compliance with the require-ments of DBN B.1.1-12:2014 "Construction in seismic regions of Ukraine" [5] and DBN V.1.1-45:2017 "Buildings and structures in difficult engineering and geological conditions. General Provisions" [6].
 The design of modern buildings in seismic areas is developing in two directions that corre-spond to the main principles of seismic protec-tion - traditional (passive) and special (active). Complex systems of seismic protection of buildings combine passive and active systems.
 With traditional seismic protection, the load-bearing capacity of the main load-bearing structures of buildings is increased (the dimen-sions of cross-sections, their reinforcement, strengthening of joints, etc.) to absorb addition-al forces caused by seismic influences. At the same time, the nature of the buildings does not change. Special (active) measures to improve the seismic resistance of buildings consist in reducing loads due to modifications of their dynamic work schemes. Active seismic protec-tion of buildings is a new direction, which con-sists in the implementation of additional con-structive measures to prevent dangerous reso-nant oscillations and thereby reduce seismic impacts. It is achieved by changing the dynam-ic stiffness or periods of natural oscillations of buildings during earthquakes as a result of the use of special structural devices: sliding belts, connections that can be turned on or off, instal-lation of dynamic vibration dampers, kinematic or pile foundations, which have dissipative characteristics of self-organization, frame-linking systems with complex stiffness dia-phragms, rubber-steel cylindrical supports, etc.The article analyzes the features of design-ing earthquake-resistant steel structures of high-rise buildings. The schemes of earthquake-resistant high-rise buildings with steel frames were studied. The feasibility of using steel en-ergy-absorbing elements is substantiated and schemes for their installation in earthquake-resistant buildings with steel frames are pre-sented.

Процесс технического обследования кукольного театра

The report of the inspection of the load-bearing building structures of the puppet theater building was analyzed. During the analysis, it was revealed that the operational reliability and durability of the building structures basically do not meet the requirements of the current regulatory documents. During the inspection of the technical condition, defects were identified that were acquired at the stage of building construction and during operation. Based on the instrumental examination of the building's load-bearing structures, a conclusion was made on the operational reliability and recommendations were given for further normal operation. Measures have been developed to improve the technical condition of the research object. Proposed: to ensure the normative technical condition of water-bearing communications; perform a waterproof coating of sidewalks; provide for maintaining the required temperature and humidity conditions in the premises, basements and technical undergrounds; transform the system for collecting wastewater from the ceiling of the open gallery; protect from atmospheric influences the joints of the steel beams of the gallery ceiling with columns; perform corrosion protection of steel structures; perform a set of works to protect the structures of the building and the outer walls of the technical underground from moisture; perform a set of works to protect against moisture the base of foundations, composed of subsidence soils; organize continuous monitoring of the state of the building with the maintenance of a log of observations.