Collection of scientific works «Modern structures of metal and wood»
Certificate of state registration: КВ 16172-4644Р from 02.12.2009 ​Founder and publisher: Odessa State Academy of Civil Engineering and Architecture. ​ Results of scientific and experimental-theoretical researches of building structures of metal and wood. It is assigned for scientific workers, specialists of design organizations and manufacturing enterprises of construction domain, postgraduates, masters of educational institutions. ​The collection of scientific works has been published since 1992. Periodicity: 1 times a year. ​The collection of scientific works is included in the list of scientific professional editions of Ukraine in which the results of the dissertation works can be published. Order of the Ministry of Education and Science of Ukraine № 409 from 17.03.2020.
Одеська державна академія будівництва та архітектури
THEORETICAL STUDY OF DEFLECTIONS OF COMBINED CROSS-LAMINATED TIMBER PANELS CONSIDERING CREEP
This study investigates the structural behavior of cross-laminated timber (CLT) panels incorporating secondary-origin wood-based composite materials (LVL and OSB) in their transverse layers. The research aims to evaluate how such modifications affect the panels' stress distribution and deformation characteristics compared to conventional solid-wood CLT panels. The methodology relies on Mindlin-Reissner plate theory, accounting for shear deformation effects in layered orthotropic materials through numerical finite element method modeling using RFEM 5 software. Three-layer and five-layer CLT panel configurations with spans of 3m, 4m, and 5m were analyzed under uniform loading conditions (100 kg/m²). The experimental models compared traditional all-solid-wood panels with innovative designs featuring OSB-3 (18mm) and LVL 36C (24mm) in non-load-bearing layers. Material properties were adjusted to consider long-term creep effects using deformation coefficients according to Eurocode standards for Service Class 1 conditions. Key findings reveal that engineered wood products in transverse layers cause no significant changes in internal stress distribution patterns while panel thickness remains the dominant factor affecting load-bearing capacity at equal spans. Creep deformation increases total deflection by 47-63% across all panel types, with the most pronounced effect (up to 61.1%) observed in LVL-modified panels. Three-layer composite panels show 10-25% higher deflections than conventional CLT, while five-layer configurations demonstrate better performance stability. The study confirms the technical feasibility of using secondary-origin wood composites in CLT production, potentially contributing to circular economy principles in construction, improved resource efficiency through utilization of low-grade timber and reduced environmental impact of building materials. However, the significant creep effects (1.5-1.6 deflection increase) necessitate careful consideration in design practices. The results provide a foundation for future research on hybrid CLT optimization and standardization of calculation methods for sustainable timber construction.
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INFLUENCE OF SINGLE AND SHORT-CYCLE LOADS ON THE MECHANICAL CHARACTERISTICS OF GLUE-LAIMED PINE WOOD MODIFIED WITH EPOXY RESIN
Wood is a natural unique material. It has its own exclusive physical and mechanical properties. Wood has many advantages compared to other materials. It is used in virtually all industries. The structure and unique physical and mechanical properties allow it to be used in the manufacture of a variety of products. The aim of the work is to conduct experimental studies of glued pine wood modified with epoxy resin under the influence of single short-term and low-cycle loads, construct deformation diagrams, and establish strength and deformation indicators. The method of experimental research of untreated and modified glued pine wood under the action of single short-term and low-cycle loads in axial compression along the fibers is presented. The method of wood modification with epoxy resin has been improved. Modified and unmodified prisms were tested under single and low-cycle loads on a STM-100 testing machine under axial compression along the fibers. Experimental studies of untreated and modified glued pine wood under the action of single short-term and low-cycle loads under axial compression along the fibers have been conducted. Averaged deformation diagrams of modified and unmodified glued pine wood under single short-term and low-cycle loads have been constructed. According to the results of experimental studies, the ultimate strength and corresponding deformability of untreated and modified glued pine wood were established, both under single short-term and low-cycle loads. Modification of glued pine wood with epoxy resin increases the ultimate strength by 1.27 times, while the deformability decreases by 1.05 times. The effect of low-cycle loads reduces the ultimate strength of untreated glued laminated timber by 1.06 times, while the deformability increases by 1.13 times. For modified wood, the same pattern is observed: the ultimate strength decreases by 1.07 times, while the deformability, in turn, increases by 1.08 times.
NUMERICAL MODELING OF THE BEHAVIOR OF A HYBRID-REINFORCED TIMBER BEAM USING PLANE FINITE ELEMENTS
The study is devoted to the numerical modeling of reinforced wooden beams using the LIRA-SAPR software package. One of the main disadvantages of wooden beams is their excessive flexibility, which leads to large deflections and displacements. Reinforcing wooden beams with stiffening elements is an effective method for increasing their rigidity and reducing internal stresses. However, in current engineering practice, there is a lack of design guidelines and examples for modeling such reinforced wooden structures using modern software tools. Therefore, the aim of this work is to investigate different methods for modeling reinforcement in wooden beams using finite element analysis. The paper presents an analysis of recent publications where different reinforcement types—such as basalt, carbon, and glass fiber—were used in wooden structures. Special attention is given to the challenge of numerically modeling such reinforcements, particularly when using planar finite elements instead of volumetric ones, as this approach significantly reduces computational complexity. Three reinforcement modeling methods are proposed and tested: 1) placing reinforcing bars between planar finite element nodes; 2) adjusting the modulus of elasticity of the elements to reflect the combined stiffness of wood and reinforcement; 3) modeling reinforcement as a separate layer with equivalent cross-sectional area. Each method was implemented and analyzed for accuracy and practicality. Experimental data from full-scale beam tests were used for comparison. Results indicate that all three methods provide acceptable accuracy, with deviations from experimental deflection values averaging around 11%, which is considered satisfactory for wood materials. Stress distributions obtained through numerical analysis showed good agreement across methods, though each has specific advantages. For instance, modeling reinforcement as individual bars allows precise evaluation of stresses in wood, whereas layer-based modeling offers direct assessment of stresses in reinforcement elements. The study demonstrates that numerical modeling of reinforced wooden beams using planar finite elements in LIRA-SAPR is a reliable and efficient alternative to volumetric modeling. Each proposed method can be effectively applied depending on the design goal, offering engineers flexibility in structural analysis and optimization.
NUMERICAL MODELING OF STRESS-STRAIN BEHAVIOR IN FRAME ROOFS OF VERTICAL STEEL TANKS
The article presents the results of numerical modeling and stress-strain state analysis of frame roofs of vertical cylindrical tanks with conical and spherical geometries. A comparative analysis of the efficiency of various structural solutions was carried out, considering both the presence and absence of the roof sheathing in finite element models. Analytical calculation methods are complex, labor-intensive, and not always suitable for practical application. On the contrary, quite often, in convenient numerical calculation tools, models are simplified, which leads to unreliable results: underestimation or overestimation of stresses and deformations in load-bearing elements of coatings. In view of this, there is a need to study the impact of such simplifications on the accuracy of calculations and to justify their feasibility. This study looked at roofing options without a central support. According to current design standards, when calculating the covering of a vertical cylindrical tank, it's important to consider how the frame elements and sheet flooring work together. It was found that simplification of calculation schemes without modeling the sheathing leads to a significant overestimation of internal forces and deformations in the frame elements. Critical factors were identified for the main load-bearing components depending on the tank diameter, which allows substantiating the choice of roof type and rational structural solutions to improve the reliability and efficiency of steel tanks. The obtained results can be used to improve engineering calculation methods and optimize structural schemes of frame roofs in the design of large-diameter tanks.
DETERMINING THE EFFECTIVE PARAMETERS OF FEM MODELS OF CYLINDRICAL TANKS SUBJECTED TO WIND-TYPE LOAD
The paper investigates the stability of steel vertical cylindrical tanks under wind load. Cylindrical tanks as thin-walled structures are vulnerable to compressive loads. The analysis of the behaviour of tanks under wind pressure, which can cause a loss of stability, is important. Analysis of publications. An overview of research works on the behaviour of thin-walled shells and tanks under external pressure is presented. It has been found that for the class of problems under consideration, critical loads do not always coincide with the limit loads. The difference in results depends on the nature of the load and the accuracy of determining the initial state of the shells. The ranges of relevance of the simplified calculation models were established. However, the geometric parameters of the studied shells do not correspond to the geometric parameters of the tanks. An analysis of the design standards methodology showed its shortcomings. This is an insufficient consideration of the geometric parameters of the tanks, the conditions of shell anchoring and the actual nature of the wind load distribution. This failure to take into account can lead to significant errors in the determination of critical loads. This can lead to a risk to the tanks safe operation. The aim of the study is to determine the effective parameters of FEM-models of cylindrical tanks for analysing their behaviour under wind load, taking into account the actual nature of its distribution. Main material and results. The calculations were carried out in the LIRA software package of the computer-aided design system. Different variants of boundary conditions were considered: free support and rigid clamping of the shell ends. The finite element mesh was gradually thickened to ensure convergence of the results. Refinement was stopped if the difference between two consecutive solutions did not exceed 5%. Conclusions. It is shown that the solution of the problem stabilises at some partitioning of the nynx shell into finite elements. For several adjacent partitions, the solution of the problem becomes constant. Such discretization was taken as the range of effective discretization of the shell into FEs. Recommendations for determining the effective parameters of FEM models of the tanks under the action of external pressure are given. It was found that the deviation of the numerical values of the critical uniform pressure for the analysed shells from the corresponding analytical values was 5-9%. This is a sufficient accuracy of the results obtained. The calculated numerical critical value of the wind pressure exceeds the critical uniform pressure for the considered shells. This excess is 19-40%.
INCREASING THE STABILITY OF CENTRALLY COMPRESSED METAL ELEMENTS BY EXTERNAL CFRP REINFORCEMENT
This work recognizes areas of rational use and the level of appropriate load increase for using external CFRP reinforcement to increase the stability of centrally compressed metal elements. An analysis of possible effective solutions for external CFRP reinforcement of compressed metal struts is presented and the principles of applied determination of general parameters of their stability are formulated. With symmetrical external reinforcement of compressed metal struts by FRP, their overall flexibility is reduced, which is ensured by the work of external reinforcement in the cross-sectional area that receives tension in the process of losing stability. Accordingly, the principles of practical determination of the overall stability of the considered structures are presented, taking into account the specific features of the combined operation of steel and FRP: significant heteromodulus of materials, additional temperature stresses that add to the load on the metal elements, the practical ability of FRP to effectively perceive only tensile forces, which changes the working position of the center of gravity of the cross-section upon loss of stability, as well as the inability of FRP systems that involve adhesive fastening, to be fully operational as part of a whole structure. Currently, there is a need for appropriate systematization and adaptation of existing global practices for reinforcing the elements in question with fiber plastics and for developing corresponding domestic standards. There is a need for appropriate development of applied methods for determining the overall stability of specified elements, based on the existing national regulatory framework for the calculation of metal structures and substantiated by the necessary experimental studies.
GENERALIZED MODEL OF THE ACTUAL WORK OF DECIDOUS AND CONIFEROUS WOOD UNDER AXIAL COMPRESSION ALONG THE FIBERS
Modern methods for determining the initial modulus of elasticity of solid wood are analyzed. The article presents the results of experimental and theoretical research on the selection of values of the initial modulus of elasticity of solid wood for determining the theoretical bearing capacity of bending unreinforced and reinforced elements made of glued laminated timber. The purpose of the work is to determine the features of determining the modulus of elasticity of wood and the reliability of determining the theoretical bearing capacity of bending elements made of wood using the deformation method. It is established that the closest results are the results of calculating the theoretical bearing capacity of bending elements made of glued laminated timber to the experimental ones using a deformation model, which uses the initial modulus of elasticity established on the basis of solid wood from which the structure is made. The deformation model for calculating bending elements made of glued laminated timber involves the use of determined normal stresses based on deformations that have arisen in the normal cross-section of the bending element under external loading. The stresses in the calculated normal cross-section are described by different functions in three different sections of the cross-section height. The first section is the tension section, starting from the bottom of the element to the neutral line and described by a linear function; the second section is the compression section, from the neutral line to the maximum value of the compressive stresses is described by a nonlinear function; the third section is also a compression section, from the end of second section to the top of the bending element is described by a nonlinear function taking into account the appearance of a fold.
STRENGTHENING OF REINFORCED CONCRETE SLAB WITH STEEL ELEMENTS
The need for inspection of building structures containing the fragment of the floor slab in the car park of a residential building arose due to appearance of damage. A fragment of the concrete floor slab was inspected, calculations for the slab were performed in accordance with the requirements of current regulatory documents, its technical condition was determined, and a conclusion was made concerning possibility for further operation. During the research, a regulatory procedure for assessing the technical condition and load- bearing capacity of operated structures was applied. The results of performed survey, calculation and technical condition assessment for building structures containing the slab fragment were presented. It was determined that according to the current regulatory documents containing requirements for technical condition the concrete slab fragment is unusable for operation. The cause for defects and damage in the slab structure was determined: violations of technology for execution of concrete structures in the winter. Based on the research, a design for strengthening the slab structure was developed. Manufacture, transportation and installation of steel reinforcing structures were carried out. Reinforcing the slab using the proposed method made it possible to complete the work in a short time without using wet processes. The load from the weight of the slab structures, according to the develo
fragment of concrete floor slab for car park
manufacture and installation of reinforcing structures
ANALYSIS OF DEVELOPMENT PATHS AND THE USE OF TIMBER AND GLUED LAMINATED TIMBER FOR FLOOR SYSTEMS
This paper explores the development and application of timber and glued laminated timber (GLT) in modern construction, particularly for floor systems. Timber has historically been one of the most widely used construction materials, and its utilization remains highly relevant due to its ecological advantages, architectural flexibility, and structural properties. The analysis focuses on the technological advancements that have led to the widespread implementation of GLT, enabling the construction of multi-story wooden buildings worldwide. The study examines scientific publications on the evolution of wooden structures, highlighting key aspects such as sustainability, carbon footprint reduction, sound insulation, vibration resistance, and fire safety. A particular emphasis is placed on the advantages of timber in mitigating environmental concerns associated with conventional construction materials like concrete and steel. Additionally, this paper presents computational models and experimental research addressing the mechanical behavior of cross-laminated timber floor systems. The structural integrity and design optimization of these systems are investigated, along with proposed improvements for connection nodes and innovative approaches for enhancing strength and durability. The findings demonstrate the growing importance of timber in contemporary engineering and urban development. Key directions for future research are outlined, including experimental validation of laminated timber connections, development of advanced fire-retardant treatments, and optimization of the material for large-scale construction applications. The study contributes to the understanding of timber’s role in sustainable architecture, offering recommendations for efficient integration in modern building practices.
FRAME MULTI-STOREY BUILDINGS WITH BEAMLESS PREFABRICATED FLOORS MADE OF GLUED WOOD
We propose the design of a transomless frame based on cross-beam slabs. Our proposal is to use an original steel connector, which allows us to make a slab from individual elements of small length. The invention belongs to the universal connections of frame elements that can form assemblies at different angles. A model of a 2 x 2 m cross-beam slab measuring 6 x 6 m with a corner support on column consoles was designed. Traditional beams of the beam floor are transformed into contour beams of the slab. When they are supported on the columns, we get a structure that is a slab supported at four corners on circular column consoles. Floors bear operational loads and ensure the rigidity and stability of the building in the horizontal plane by redistributing forces from wind and other horizontal loads. Ensuring spatial rigidity in the vertical plane is simplified by using a combined solution with steel columns and trusses.The peculiarity of the slab is the dome shape of its lower surface.The beamless slab of large-size slabs takes advantage of the spatial operation of the hollow core. The developed contour support beams of the slabs are well suited to accommodate bracing and overhang forces in the corners. To determine the feasibility of the proposed structural solution, two digital models of multi-storey buildings with the same space-planning solution were made. The first one has steel columns and wooden slabs - shells supported on column consoles, the second one has a conventional steel beam frame and monolithic reinforced concrete floors. The results of the calculations showed the efficiency of the beamless frame with cross-beam laminated wood slabs.
connector for wooden cross-beam elements
ARTIFICIAL INTELLIGENCE IN STRUCTURAL DESIGN, AN INTRODUCTION TO NEURAL NETWORKS
This article presents the potential application of artificial intelligence, particularly artificial neural networks (ANNs), in the design of engineering structures. The subject of the paper is the automatic recognition of the geometric shape of an arc as circular, elliptical or parabolic. Correct identification of the arc shape is fundamental to the creation of the static scheme and computational model of the structure, which is necessary for strength analysis of the structure. This paper analyzes two identification methods based on ANN: multilayer perceptron (MLP) and convolutional neural network (CNN). The MLP network classifies the type of arc based on the geometric features of selected points lying on the arc, while the CNN network makes recognition based on the graphical representation of the arc as a black and white image. The prospects for AI applications in civil engineering are also discussed, with a focus on generative models and their potential use in the design, simulation and automation of construction processes.
INFLUENCE OF DESIGN FACTORS ON THE STRENGTH OF BENDING 3D-PRINTED ELEMENTS
The main methods of mechanical testing of composite materials include: determination of the strength of the material in tension, bending, torsion, compression, impact loads, etc. This article presents the methodology and results of tests for the bending strength of structural elements made of ABS plastic manufactured using 3D printing. The shape of the cross-section of the test specimens-beams and the percentage of filling their internal cavity with the specified polymer material were selected as design factors that are predicted to have an impact on the output parameter. The most optimal configuration was established and the dependence of the strength on the change in the specified variable factors was determined.
WORKING FEATURES AND RELIABILITY OF METAL SPIRAL-FOLD SILOS
The article comprehensively discusses an innovative metal sheet structure - a spiral fold silo: its features, operation under load, and reliability. The stress-strain state of interfold zone of a spiral-fold silo is considered. The calculations of the stress-strain state of the silo were compared with the analytical calculations by the software package LIRA-SAPR. The work the midsection of the shell segment (zone between folded locks) of the spiral-fold silo was experimentally verified. Considering the results of the studies of the stress-strain state of this metal silos, a methodology for reliability analysis based on the analysis of the strength reserve was developed. The obtained results of calculations confirmed the high reliability of metal spiral-fold silos.
FIRE RESISTANCE OF COLD FORMED STEEL FRAMES OF 3D-VOLUMETRIC MODULES IN COMPARISON WITH ROLLED STEEL PROFILES
Compared to traditional building materials and techniques, the use of prefabricated modular structures has the potential to solve the problems of environmental impacts such as energy consumption and the associated carbon dioxide emissions. The use of materials with a high potential for recycling and reuse, such as steel in the form of rolled or cold formed profiles, is fully in line with the principles of the circular economy - a shift from a linear to a circular material use. Unlike rolled profiles with open and closed cross-sections made of structural steels, which use intumescent paints for fire protection, cold-formed steel profiles, due to their relatively small thickness, require the use of fireproof coatings of greater thickness (10-15 mm) based on gypsum or perlite. For galvanized profiles, the only fire protection method available is cladding using various types of fireboards. The investigation of steel volumetric modules design economic factors influenced by different methods of fire protection were conducted at the Department of Metal, Wooden and Plastic Structures. Further investigation of economical design related factors of fire resistance of cold formed structures of volumetric modular construction intended to fill the gap. The research is focused on the performance of cold formed steel bearing structures, as well as fire resistance of cold formed steel profiles and fire protection methods.
COMBINED CONTRIBUTION OF PU FOAM AND GYPSUM FIBRE SHEATHING ON THE BEHAVIOUR OF LIGHTWEIGHT STEEL C- PROFILE IN A COMPOSITE WALL PANEL
The research focuses on evaluating the mechanical contribution of the PU foam and sheathing to the load-bearing capacity, stiffness, and failure modes of the LSF system. Two groups of specimens were tested under axial compression: (1) bare LSF structures consisting solely of cold-formed C-profiles, and (2) composite panels consisting of the same LSF frame, a PU foam core injected under pressure, and external gypsum fibreboard sheathing. The experimental results demonstrate a substantial enhancement in structural performance due to composite action. Composite panels achieved an average load-bearing capacity of 316.7 kN, more than double that of the bare LSF structures, which averaged 133.4 kN. In addition, the composite panels exhibited significantly higher ductility, with average vertical displacements at peak load reaching 10.27 mm, compared to 5.43 mm for the LSF frames. The initial stiffness of the composite system was also markedly improved, reaching 45.76 kN/mm approximately 1.5 times greater than that of the LSF structure alone. The PU foam, injected in a controlled industrial process, ensures a uniform and firm bond with both the steel frame and the sheathing, enabling effective composite action and resistance to local and global buckling. Visual inspection and load-displacement analysis confirmed that while the bare LSF structures failed by local and out-of-plane buckling, the composite panels maintained stability and failed primarily through localized crushing, without global loss of structural integrity. These findings underscore the structural benefits of using composite panel systems and provide a foundation for the development of design models and future standardization of this type of construction element.
RESEARCH ON THE PERFORMANCE OF STEEL JOINT CONNECTORS IN CROSS-BEAM CONSTRUCTIONS MADE OF GLULA
Cross-beam systems involve the use of beams that are connected to each other at a certain angle, which allows for effective load bearing and increased structural rigidity. Connections using bolted joints with metal connectors are particularly relevant in cases where it is necessary to increase resistance to dynamic and static loads. The paper presents the results of a study of the stress-strain state of a joint with an original connector of a cross-beam slab made of glued wood under the influence of a static load. Two samples of the joint connection were manufactured for testing. The first is a prototype of a cross-beam slab joint, supported at the corners, with variable cross-sections of elements, and the second is a control sample with constant cross-sections of elements along their entire length. A distinctive feature of the connector for joining frame elements is the presence of a diagonal fastening element, the connecting ends are made at an angle of 45º to the longitudinal central axis of the connecting end of the corresponding frame element, and the two frame elements of the building structures are connected by the edges of their connecting ends, forming an angle of 90° between them. To analyse the stress-strain state of the element, a spatial computer model was developed in the LIRA-CAD software package. The stiffness characteristics of the volumetric finite elements were set taking into account the anisotropic properties of wood in accordance with regulatory requirements. The node was modelled using rod and plate elements. The results of the numerical experiment and testing showed that the node with the proposed connector had sufficient load-bearing capacity.
research of the connector of the cross-beam structure node
ROBUST DESIGN OF METAL STRUCTURES FOR MINIMIZING CORROSION RISKS
The article addresses the reduction of risks associated with the potential emergence of industrial hazards caused by decreased reliability of corrosion protection systems for structures, within the framework of robust structural design (RDCPS – Corrosion Protection System under Robust Structural Design Conditions). The proposed approach is based on the development of robust (resilient to disturbing external influences) methods for designing primary and secondary corrosion protection measures for metal structures. In order to improve structural operation at all stages of the life cycle, a diagnostic and maintenance technology is substantiated. Enhanced survivability and resistance to aggressive operational environments are achieved through effective robust design strategies for both primary and secondary protection of metal structures against corrosion. The proposed methodology contributes to the advancement of current standards (EN 1990) by incorporating principles of robust design. It is established that these requirements aim to ensure the quality of metal structures and are implemented through limit state calculations using partial safety factors (EN 1991). Structural load-bearing capacity and durability are ensured in accordance with the provisions of EN 1993. Characteristic values of metal structure quality indicators, protective coatings (EN ISO 12944, EN 1461), and materials (EN 1993-1-4) are applied. The methodology proposed herein is aimed at minimizing risks during the creation of metal structures and reducing the extent of damage due to corrosion loss, which remains a highly relevant objective in the construction industry.
DESIGN FEATURES OF PROTECTIVE ANTI-DRONE SHIELDS
The paper examines the structural and engineering aspects of designing steel protective screens to counter unmanned aerial vehicles (UAVs) at energy infrastructure facilities. The relevance of the topic is due to the targeted UAV attacks on transformer substations, which have prompted the implementation of passive protection in the form of steel anti-drone screens. The study includes an analysis of recent research and publications on UAV threats to power grids and existing protection methods. It explores structural solutions for protective screens and presents the results of their practical implementation in Ukraine. The paper summarizes design requirements, including material selection, ensuring appropriate screen height and distance, modularity, and maintainability of the structure.
INVESTIGATION OF THE CREEP EFFECT ON THE STRESS-STRAIN STATE ON TIMBER-REINFORCED CONCRETE MULTISTOREY BUILDINGS
In the conditions of military aggression against Ukraine, a special attention should be payed to the development of innovative solutions in various fields, which will allow effective rehabilitation of veterans and civilians. The building as an artificial environment is an integral part of how a person experiences trauma and has the potential to calm the body's response to perceived stressors by modulating and leveling the surrounding triggers. The development of project based on the concept of biopositive design involves taking into account the criteria of biophilic design, the use of "green" environmentally safe materials and resource-efficient structural solutions. The article presents the results of the experimental design of a biopositive rehabilitation building using the example of a prototype project of a residential block. The proposed structural solution of a biopositive building-prototype consisting of modular prefabricated elements: three-layer panels for walls and roof, consisting of two layers of cross-glued wood, connected with each other by flexible ties, and heat and sound insulation arranged between the layers made of an effective environmentally friendly material; ribbed floor panels consisting of glulam beams and cross-glued wood slabs, joined together with high-strength bio-based non-formaldehyde glue. To substantiate the proposed structural solution of the biopositive building, a study of the stress- strain state was carried out using the LIRA-CAD software complex. Theoretical provisions were formulated and an assessment of the degree of utilization of the load-bearing capacity of structural elements made of cross-laminated and glued laminated timber as well as an analysis of deflections and displacements was carried out. The degree of utilization of the load-bearing capacity of the floor panel in terms of normal stresses from the action of the bending moment is 45%, in terms of shear stresses is 18%. For wall and roof panels under the simultaneous action of compressive and bending stresses, the degree of utilization of the load-bearing capacity is 58%. The calculated floor deflection considering creep deformations and the maximum horizontal displacements from the wind load do not exceed the maximum allowable values.
TAILINGS DAM FAILURES: A STATISTICAL DATA ANALYSIS
Minerals processing produces two main products: a commercial product (concentrate, pellets) and tailings (waste from ore processing). The tailings are stored in a tailings storage facility (TSF), a special hydraulic structure for receiving and storing solid and liquid mineral processing waste. The focus is primarily on ensuring the reliability and safety of these facilities during their design, construction, and operation, as a failure of such structures can have catastrophic consequences. This paper computes the statistics of tailings dam failures using an up-to-date database on failures. The retrospective review covers the period from 1915 to 2024. During this time, about 373 cases of tailings dam failures were recorded. The historical trend regarding the number of failures has an average of 3.42 failures per year. The majority of failures occurred between 1960 and 2000 (230 failures), accounting for approximately 62% of the total number of accidents. In the 2000s, a decrease in the number of incidents compared to previous decades was observed, while after 2010, there is a tendency for an increase in the number of incidents (5.9 failures per year). The accidents in tailings dam breakages occur mostly in North America (41%). Statistical data analysis shows that the main causes of failures are overtopping (21%), slope instability (16%) and seismic instability (15%). The analyses of the distribution of the world’s tailings dam failures with regard to dam height show that 90% of the cases occurred in dams less than 50m in height and only 2% of incidents in dams higher than 100 m. The correlations between stored and released volumes have been verified using a database. Based on the relationship found from the regression analysis, as the tailings volume increases by 1%, the release volume increases by 0.25%. Statistical data analysis of tailings dam failures allowed for the identification of the most vulnerable and least reliable elements of the structures of TSF, which will allow them to be used in the probability analysis of accidents at these structures.
THE RELIABILITY ANALYSIS OF METAL SPIRAL-FOLD SILOS
The term «object reliability» is given in accordance with the current standards. The two main methods for determining the reliability of building structures are presented. Specific design features of spiral-fold silos and a brief history of their development are described. The results of experimental studies of spiral- fold silo structures are presented. The statistical characteristics of bulk materials are presented. A methodology for reliability analysis of metal spiral-fold silos based on the analysis of the strength reserve with consideration of the complex stress-strain state has been developed. This methodology was used to analyze the reliability of a silo with a capacity of 1020 m 3 . The silo structure was loaded with various bulk materials, the statistical characteristics of which were analyzed. The results of determining the main values of the parameters for the reliability analysis of the silo are presented in tabular form. In accordance with DBN B.1.2-14:2018, Table B.2, the recommended value of the safety characteristic (failure rate) β for the calculated silo (consequence class CC2, structural responsibility category A) should correspond to the value β=4,27, thus, the results of the calculations confirmed that the reliability of the considered silo is ensured. Based on the results, the plots of stress and safety characteristics depending on the variation of characteristics of wheat were constructed. The graphs showed that the stresses in the silo wall increase with an increase in the density and lateral pressure coefficient and decrease with an increase in the coefficient of friction against the walls. The graphs show a linear tendency to decrease the safety characteristic with increasing stresses in the silo wall. The general conclusion about the sufficient reliability of the structures of metal spiral-fold silos that were calculated according to current standards is proved.
EFFICIENT STEEL FRAME STRUCTURE OF MULTI-STOREY BUILDING
Currently, many buildings in Ukraine are affected by significant dynamic loads associated with military operations on the territory of the country. In practice, this can lead to the so-called progressive destruction, however, unlike static loads, shock-explosive loads require an assessment of not only the mechanical characteristics of the building, but also an assessment of its own dynamic characteristics. Such characteristics traditionally include the spectrum of natural frequencies and the forms of oscillations corresponding to them. However, the assessment of dynamic characteristics must be preceded by an assessment of the static performance of the building. Unfortunately, the specialized professional and reference literature lacks data on the dynamic operation of most types of buildings, including multi-story buildings with a steel frame. Therefore, such a task will be formulated and solved in the course of research. The obtained results of the static analysis confirmed the correctness of the accepted cross-sections of the main load-bearing elements of the steel frame of the building. The outermost columns of the frame were the most loaded, the cross-sections of which were recommended to be increased. As additional recommendations, it was proposed to replace rolled profiles with universal welded ones made of hot-rolled sheet steel. This will simplify the construction of nodal connections of the frame, which, in turn, will increase the level of its overall reliability. The dynamic analysis made it possible to reveal a rather dense spectrum of the lower natural frequencies of the frame, which lie in the range of up to 5 Hz. The corresponding lower forms of self-oscillations include the entire steel frame of the building in the work, which helps to reduce the amplitudes of its oscillations.
CREATING RELIABLE AND RESILIENT GRAIN STORAGE FACILITIES IN THE FACE OF WAR AND THE GLOBAL FOOD CRISIS
The article describes in detail the complete engineering methodology for the verification calculation of steel grain storage structures based on the pan-European Eurocode standardisation system in accordance with the provisions of DBN B.2.6-221:2021 and DSTU-N B EN 1991-4. The emphasis of the work is on determining the mechanisms for regulating the reliability of grain storage structures within the framework of the application of semi-probabilistic calculation in the form of the limit state method. To assess the stress-strain state of individual structural elements of the silo, two methods were used: the direct method of finite element analysis without taking into account the effects of geometric and physical nonlinearity and the theoretical method based on the membrane theory in a linear-elastic formulation assuming linear-elastic material characteristics and the linear theory of small deformations. The practical implementation of the methodology was tested on the example of real steel silo structures. It is established that the change in the level of reliability of steel grain storage structures within the framework of the limit state method is carried out through a system of partial coefficients that take into account the stochastic properties of external influences, variability of material characteristics, types of calculations, the degree of importance of structural elements in the structure and the degree of responsibility of the silo as part of the enterprise. The specified values of the partial reliability factors are governed exclusively by the regulatory requirements and guidelines of the national annex and cannot be adjusted by the design specification. The given values of the coefficients are limited to limit state checks on the bearing capacity and serviceability of structures under static load, including cases where the dynamic impact is assessed using equivalent quasi-static loads with appropriate amplification factors.
DEVELOPMENT OF LANTERN DESIGN FOR THE CLIMATE CONTROL SYSTEM OF THE BUILDING
Modern residential buildings are increasingly equipped with specialized climate control systems. Such systems are constantly becoming more complicated and nowadays allow to control and, if necessary, maintain at a given level a whole series of parameters in structures - temperature and humidity of air, its degree of purity and ionization, temperature and quality of water, level of illumination and irradiation, as well as technical design parameters. Placement of such climate control systems for low-rise residential buildings is assumed in the building itself, but for high-rise buildings such systems are placed on the roof. In this case, the practical task of protecting climate control systems from the dangerous action of aggressive external factors arises. The paper proposes the development of a special protective lantern capable of performing such a function. Structurally, the lantern consists of a steel frame made of bent-welded square profiles and translucent filling. Four architectural and constructive versions of the protective lantern are considered - arched, pyramidal-elongated, pyramidal and spherical. To select the most rational constructive option, numerical modeling was performed based on the finite element method using the domestic software product SCAD. Its results made it possible to choose the necessary cross- sections of the frame elements in accordance with the construction current standards in Ukraine. Based on the comparison of mass indicators and the market value of protective lantern materials, it was finally determined that the spherical lantern has the lowest indicators and is the most rational. However, for real buildings that have rectilinear load-bearing structural elements, this option may not be effective and may require reworking of the load-bearing structures. Therefore, for practical implementation an arched design version of the protective lantern was chosen. This option is recommended for practical implementation in the reconstruction project of a multi-story commercial-office-hotel complex in the city of Pavlograd.
TAKING INTO ACCOUNT THE JOINT OPERATION OF PRECAST CONCRETE COATING DISKS AS PART OF SPAN BENDING METAL STRUCTURES
Traditional methods of beam’s structures calculation for industrial buildings' coatings provide their consideration separately from the frame structures, in particular, reinforced concrete slabs, without taking into account their joint work, which leads to a significant safety margin of structures. Today, there is a significant number of industrial buildings and structures that require strengthening and reconstruction in Ukraine. In this regard, studies of the actual load- bearing capacity of single-storey industrial building frames are particular importance, both during reconstruction and new construction. Their results will significantly reduce costs and allow for more rational design of structures. At the same time, one of the most relevant areas is the study of the joint operation of metal load-bearing structures with precast concrete structures of hard discs coatings and slabs in their calculation. Moreover, in the Ukrainian national design standards, as well as in the educational and methodological literature, the calculation methods for taking into account the joint operation of such structures are not fully covered. The purpose of study is to assess the reduction of metal consumption for steel truss structure in its bending calculation, taking into account the joint operation with a rigid precast concrete slab disc. Method. As part of the study, It was calculated a flat roof truss from the paired corners of an one-storey industrial building according to the traditional design scheme – without taking into account the joint operation with the slab disc and taking into account the joint operation with the slabs by means of numerical modelling as part of a roof block using the finite element method. The modelling of the pavement fragment (block) was performed in LIRA FEM 2022 software. The main results. It is performed a comparative analysis of the internal forces in steel truss elements and the total mass of the truss based on the selected cross-sections of its elements by two design models. The practical significance of the obtained results is to determine the economic effect by reducing the material consumption and the degree of unloading of steel trusses as part of the roofing block of a one-storey industrial building, taking into account their joint operation with hard discs of precast concrete slabs.
METHOD OF IMPULSE IMPREGNATION OF TIMBER FOR BUILDING STRUCTURES
The article discusses the effectiveness of the impulse method of timber impregnation to improve its operational properties when used in building structures. A detailed analysis of modern timber impregnation methods is presented, in particular, the traditional static and the proposed impulse methods. The main advantages of impulse impregnation technology are defined, such as increasing the durability and fire resistance of wood, as well as improving its physical and mechanical properties, depending on the type of impregnation composition used. In the course of the study, an experimental comparison of both methods was carried out, the results of which confirm the high efficiency of the pulsed infiltration method. The materials and methods used for the experiments are described, including wood characterization and the pulsed impregnation process. A detailed description of the proposed technology of impulse impregnation of wood is given. The results of the research can be used to improve wood processing methods and increase its operational properties in building structures, which contributes to more efficient and widespread use of timber as a building material. The purpose of this study is to develop and optimize the method of impulse impregnation of wood to improve its properties when used in building structures. The research is aimed at identifying the effectiveness of the impulse method in comparison with the static method of timber impregnation. In the conducted research, a detailed description of an effective method of wood modification for building structures, which is implemented using the technology of impulse impregnation of wood with technological compositions, was proposed and performed. This technology allows you to intensify the wood processing process, increase the penetration depth of the impregnating liquid into the pores of the wood and ensure a more even distribution of the liquid in the wood structure. This is important for increasing the durability and operational properties of wooden structures depending on the type of impregnation composition (for example, fire resistance, biological resistance, strength, hydrophobicity). The obtained experimental data prove the positive effect of the impulse component of pressure on increasing the depth and achieving homogeneity of penetration of the impregnating liquid into the capillary-porous structure of wood. Keywords: wooden structures; building materials; fire protection; biological protection; impregnation; saturation; capillary-porous body.
LOCAD AND GLOBAL STRENGTHENING OF WOOD BEAMS DURING OPERATION
The work presents modern comprehensive methods for the rehabilitation and reinforcement of glued wooden beams or timbers that can be utilized during their service in buildings. The local or global reinforcement of wooden elements made of solid or glued wood, which are subjected to transverse bending, needs to be performed either with full or partial unloading of the structure. The reinforcement effect is greater with complete unloading of the structure compared to partial unloading. Local reinforcement of the structure, through altering the physical and mechanical properties of the material in problematic areas, often involves the injection of cracks with adhesives followed by the application of the chosen reinforcement system. Global reinforcement of wooden bending elements includes reinforcing both the compressed and tension zones of the element, as reinforcing only the tension zone provides minimal effect. The best effect in global reinforcement of beam structures is achieved through double reinforcement, either with high-grade steel reinforcement bars or by reinforcing the tension zone with polymer tapes while simultaneously installing steel reinforcement in the compressed zone. Often, global reinforcement of both the compressed and tension zones of wooden beams results in insufficient shear bearing capacity. Therefore, a comprehensive approach toreinforcing wooden beams as a whole necessitates reinforcing the element’s ability to handle increased shear forces at the edges. An effective method for increasing the shear force capacity of a wooden beam is reinforcing it by bonding one or more composite strips at a 45-degree angle. The bonding is performed using polymer adhesives at specific intervals on both sides of the beam in areas close to the supports. The issue of reinforcing wooden structures in service is quite complex and requires an individual approach in each case. The comprehensive development of methods for reinforcing wooden bending elements is currently hampered by the lack of regulatory framework in Ukraine to address this issue. At the time, there was no general work on reinforcement. Each engineer developed his own methods for reinforcing timber bending members.
RECONSTRUCTION OF FACTORY BUILDING WITH A STEEL FRAME
The reconstruction of the existing industrial building with a steel frame was carried out due to the need to convert the premises into a warehouse in order to increase the volume of the building for the storage of medical goods. The current state of the issue is summarized, research tasks are set, and the methodologyfor assessing the technical condition of the building's structures in use has been developed. The normative procedure for assessing the technical condition and load-bearing capacity of the operated structures during reconstruction and completion in order to increase the volume of the building and improve operational qualities has been adopted. A method of obtaining the determining parameters of the technical condition of structures has been developed. It is assumed that structures and elements during the entire life cycle as a result of aging, degradation and other actions and influences can consistently be in each of the four technical states according to the requirements of current regulatory documents. The results of the performed survey, computer modeling and assessment of the technical condition of the construction structures of the existing building are presented. On the basis of the calculations performed using the software complex of the finite element method, the forces in the elements of the computer model were determined, the necessary cross-sections of the elements of columns, trusses, spans, and connections were established. Manufacturing, transportation and installation of structures were also performed. The building after the reconstruction is a one-story frame structure consisting of column foundations rigidly connected to reinforced concrete structures, on which the covering structures rest. The connection of trusses with columns is hinged. The system of connections along the columns and covering ensures the spatial rigidity of the building. Strengthening of the foundations has been carried out. The thickness of the insulation of the enclosing structures is adopted in accordance with the requirements of current regulatory documents.
TECHNOLOGICAL RISKS IN THE DISMANTLING OF CRANE STEEL STRUCTURES
The article analyses unfavorable factors arising during dismantling and moving of crane structures, mechanical equipment in the conditions the urban transport network, access roads to the long-term storage warehouse. Paper is based on the analysis the causes accidents and emergencies and shows that many them are man-made (technical condition of buildings, structures, equipment and engineering networks, poor organization work technology).Article presents developments in the analysis process of dismantling a tower crane in the conditions limited space a construction site, urban development. Purpose of the research - identify factors affecting the safety dismantling process, analyses and systematize data e progress work in a cramped construction site and identify options dismantling cranes that are most beneficial enterprise. Proposed methodology is aimed at reducing the risks of the technological process dismantling crane structures, which is an urgent task in the field construction. Assessing principles the conditions limited space a construction site during construction depending on the technology work production are presented. Recommendations for dismantling metal structures tower-type cranes and determining technological safety are given. Methodology allows identifying and assessing risks when planning the decommissioning procedure for a tower crane. In this case, it is possible to optimize material costs economically to reduce the overall cost of construction. The efficiency of this method is increased when decommissioning several cranes involved in construction. Study of the state structures, considering the most unfavorable combination influences, was considered in accordance with the methodological approach to substantiate composition and structure parameters of structural durability for managing technological safety by reducing risks. The possibility ensuring service life structures through the combined use of analysis methods has been established, which is due to the rational design, development and use advanced means planning and ensuring the technology of construction processes.
PROJECT OF A REHABILITATION CENTRE FOR MILITARY PERSONNEL AND WAR VETERANS IN ZHYTOMYR, WHICH WON FIRST PLACE IN THE «STEEL FREEDOM» ARCHITECTURAL COMPETITION
The article is devoted to the study of the experience of using metal structures in the design of rehabilitation centres on the example of the project of the R-240 team ‘Rehabilitation Centre for Military Personnel and War Veterans in Zhytomyr’ for the Steel Freedom competition. Due to the Russian invasion of Ukraine, a large number of military personnel have suffered physical and mental injuries. As a result, the need for rehabilitation centres has increased. The engineering and architectural community is faced with the challenge of finding ways to meet these demands. Metal structures, due to their high reliability, industrial nature, the ability to provide architectural expression, the isotropic nature of the material itself and their invulnerability to various factors, are best suited for this purpose. When working on the project of a rehabilitation centre for military personnel and war veterans in Zhytomyr, a metal frame was used, and relevant calculations were carried out to prove its effectiveness. The structural scheme of the projected rehabilitation centre is a metal frame and ligature frame, in which columns and crossbars form the main flat supporting units of the frame system - transverse frames. As the building is quite large in plan (91.5×68.9 m in axes), has different heights of individual parts and is multifunctional, there is a possibility of significant deformation of the frame elements due to daily and annual temperature fluctuations and different temperature and humidity conditions of the premises. To avoid uncontrolled adverse movements and to differentiate between zones with different purposes, the building is divided into three blocks by expansion joints. Each block is an independent frame that is not connected to adjacent structures. A distinctive feature of the frame is the spatial cantilever structure with a 9 m overhang. The high ratio between the strength and density of steel and the permissible deflection values obtained in the calculation programme prove the feasibility of using steel structures and the reality of the plan. The study proves that the use of a metal frame is best suited for the construction of new buildings and structures, as well as the reconstruction of existing facilities during the post-war reconstruction of Ukraine.