Modeling of influence of shell fragments on the protective structure state is difficult and not sufficiently studied. This is due to the presence of wide spectrum of structural decisions of the constructions and different types of ammunitions. Ammunitions have different physical and technical characteristics, such as: a diameter, length and mass of the shell; a type and mass of explosive in TNT equivalent; a type and mechanical characteristics of shell material; time of detonation; amount and mass of fragments with maximal flight length and velocity. The amount of fragments depends on a construction a shell, which is increased with the increase of shell caliber, power of explosive, coefficient of filling and diminishing of strength and viscosity of shell metal. Therefore, in connection with the probabilistic parameters of shell fragments, kind and dispersion area on the surface of protective construction, it is necessary to apply the methods of probability theory and experimental test data. In article the stress-deformed state of the protective shell structure upon impact of shell fragments was investigated. Characteristics of shell fragments and their distributing on the affected construction area according to empiric formulas and experimental test data were determined. Static and dynamic behavior of protective shell structure upon impact of shell fragments was investigated in the software of finite element analysis NASTRAN. The nonlinear static problem and static stability of shell structure taking into account elastic-plastic property of its material were solved by the Newton-Raphson method and the Lanczos method respectively. The dynamic calculation of protective shell structure contained determination of forms and frequencies of natural vibrations using the Lanczos method and investigation of forced vibrations by the Newmark method. Characteristics of the stress-deformed state of protective shell structure and realizations of its reactions on the action of shell fragments were received. The presented numeral method simplified the process of modeling of shell fragments action on the protective construction and allowed to research its stress-deformed state.
The improvement of existing methods for calculating new structures and their elements in accordance with current regulatory documents in the field of construction is much slower than the development of production technologies. This, in turn, limits the implementation of modern technical solutions and technologies, and also complicates the creation of optimal conditions for their effective use and calculation. For example, calculations of piles and pile foundations for bearing capacity and base deformations according to DBN V.2.1-10-2009. Amendment 1 does not provide a sufficient level of accuracy and reliability due to a number of factors: the use of averaged tabular values of soil resistance, failure to take into account the state of the soil along the length of the pile, its origin and compression pressure, the use of deformation characteristics of soils obtained from the results of field tests, etc. The paper presents the results of an analytical study of the spatial distribution of vertical stresses in the soil base in the zone located under the lower end of the driven hanging piles of square cross-section 30x30cm in size with their different location in the plan. The construction of stresses was based on mathematical modeling of the distribution of stresses in the soil base developed by the Department of Geotechnics of the KNUBA for a single pile, which allows obtaining satisfactory results in comparison with experimental data, as well as a pile bush of two piles with different positions of the pile in the plan. The construction of the nature of the stress distribution in the horizontal plane below the pile tip was carried out using theoretical solutions based on experimental field studies of deformations of the base of sandy and clayey soils in field and laboratory conditions. Special attention is paid to the influence of the pile placement configuration on the change in the shape, size and area of the zones of the stressed state in the soil environment from the transfer of load by the lateral surface and the lower end of the pile. A comparative analysis of the geometric characteristics of conditional foundations determined by different methods, in particular, based on classical theoretical provisions and modern analytical approaches, has been performed. The results obtained allow a deeper understanding of the mechanism of interaction of piles with the base, and can also serve as a basis for refining calculation models when designing pile foundations, taking into account the spatial effect and the influence of the pile bush configuration.
In this article, the authorsexamine the issues associated with traditional approaches to determining resistance to progressive collapse, as regulated by national and international standards, which are based on the principle of independence from the type of threat. This is achieved by modeling the sudden removal of a single column or other vertical load-bearing structure from the structural model. According to statistical studies of progressive collapse cases, this approach is plausible; however, it does not fully reflect real collapse scenarios, in particular, it does not account for the nature of the cause of the structural failure and its impact on adjacent elements. To improve the predictive accuracy and reliability of the analysis, it is proposed to expand the traditional modeling approach by considering more complex and realistic damage scenarios. Based on the results of a series of verification numerical calculations, an effective methodology for determining the resistance of buildings and structures to progressive collapse is proposed. The method is based on a dynamic approach (direct integration of the equations of motion over time) and consists of six sequential stages. To validate the methodology, the results of modeling the progressive collapse of a steel-framed building of consequence class CC3, which sustained local damage due to a real emergency impact (UAV strike), are presented. A comparative analysis was conducted of the calculation results obtained using the traditional standard method of sudden removal of a single element and the refined approach based on reproducing the actual damage pattern. The main focus was on investigating the effect of dynamic unloading of the structural system caused by the instantaneous destruction of lightweight enclosure elements and the roof by a blast wave. The obtained data confirm the high consistency of the refined model with the actual condition of the structure and allow for an objective assessment of the remaining service life of the damaged structures to inform decisions regarding their further restoration.
The field of optimal design for spatial thin-walled structures has been developing since the 1950s. In general, when studying optimal design, one must determine all optimized strength characteristics based on the second group of limit states. These strength characteristics include: strength, stability, deflections, and deformations in spatial thin-walled structures. The implementation of optimal design with these strength characteristics occurs simultaneously with the weight of the spatial thin-walled structure. Multi-criteria parametric optimization is achieved by incorporating two objective functions simultaneously into the mathematical framework and research methodology for spatial thin-walled structures. These include weight or volume, and strength characteristics. Such objective functions include: weight and strength, weight and stability, weight and deflections, and weight and forced or natural frequencies of vibration of a spatial thin-walled structure. The specificity of such studies lies in the fact that when investigating these objective functions, it is necessary to employ three different types of calculations. Optimal design problems can be formulated in both linear and nonlinear settings. Nonlinear formulations include geometric and physical ones. This scientific article examines the geometric nonlinear formulation, which allows for the consideration of actual displacements and stresses when determining the bifurcation point. The instability coefficient λ is, in fact, the bifurcation point of the minimal surface. The use of this algorithm leads to a new approach in the design of building structures. This type of optimal design offers significant economic benefits when creating future structures. This approach can be applied not only to shell structures but also to beam and plate structures. An important aspect is the material, which must be isotropic; this includes metals and composites. The analysis of the objective function is shown in Figure 1.14. We were able to reduce the weight of the minimal surface shell from 52,593 kg to 40,391 kg, which represents a 23.12% reduction. At the same time, we were able to redistribute the thickness of the minimal surface shell to the loaded zones, which made it possible to reduce the buckling coefficient λ from 2.58 to 1.06. This significant result was achieved through a geometrically nonlinear formulation of the problem. Automation, in the optimal design approach, makes it possible to determine the required thickness of the minimal surface shell.
The completed scientific research proposed the use of vector rational parametric curves of the second degree for modelling of momentless thin-walled shells of revolution with the determination of meridian and hoop forces under axisymmetric loading. This approach represents the dissemination of progressive experience in design of complex technical objects in the domestic aviation industry. The appropriate mathematical apparatus was presented and its application was demonstrated. The obtained results were compared with the corresponding ones available in the literature. The greater flexibility and productivity of vector parametric geometric modelling tools compared to conventional algebraic ones has been substantiated. The generalizing nature of the developed methodology was demonstrated in relation to the existing development of individual models for spherical, conical, ellipsoidal, paraboloidal, hyperboloidal, toric and other middle surfaces of thin-walled shells. This further emphasizes the effectiveness of the presented mathematical apparatus and its suitability for implementation in the environment of computer information technologies. In addition to theoretical achievements, the proposed method also has important practical significance, illustrated by the example of the domes of Orthodox temples and chapels. The highlighted issue is relevant for the current historical stage of Ukraine's development, associated with military actions on its territory. The latter determines the destruction of these facilities, the need for their restoration and the construction of new ones. These circumstances are also caused by the growing number of people turning to higher powers for help. The presented approach successfully implements the desired variety of shapes and sizes of the analyzed architectural structures in accordance with the requirements of ensuring the individuality of Christian sacred buildings. The presented tools are appropriate at the stage of preliminary design, when a significant number of dome variants are considered for the purposes of comprehensive optimization, and detailed processing of each of them requires significant costs or is impossible due to the lack of necessary information. The discussed topic deserves further development by extending it to more complex operation cases, in particular under the action of non-axisymmetric loads.
It has been established that one of the most effective additional reserves for improving the deformation capacity and fracture toughness of pipe steel under static and cyclic loading is cost-effective modification by microadditions containing rare-earth and alkaline-earth elements or their compounds. This approach is especially important when the potential for improving mechanical and viscoplastic properties by traditionally used alloying elements, such as nickel, molybdenum, titanium, vanadium, niobium, etc., has been fully exhausted. At the same time, alloying pipe steels with these elements often fails to ensure high and stable mechanical properties, particularly under operating conditions in aggressive corrosive environments of oil and gas fields in Ukraine. Under alternating loading conditions, the service life of industrial pipelines in such environments is significantly reduced. For example, the service life of pipelines used for wastewater injection into wells at several oil fields in Western Ukraine is only 2–3 years instead of the planned 10–15 years. Optimal concentrations of modifying additions have been determined, the introduction of which into low-alloy steel during the melting process leads to a significant increase in viscoplastic properties, brittle strength, and fracture toughness of the metal (in wt.%): cerium – 0.01–0.03; yttrium – 0.01–0.025; barium – 0.007–0.015; calcium – 0.001–0.0025; zirconium – 0.02–0.04. It has been established that the introduction of modifying additions within the specified concentration ranges promotes an increase in the fracture toughness of low-alloy steel over a wide temperature range from +20 to −60 °C. The controlling role of globular non-metallic inclusions (mainly oxides and oxysulfides) in the process of brittle fracture of cold-resistant steels economically alloyed with Ni, Mo, V, and Nb has been demonstrated. Such inclusions contribute to microstructural refinement, while rare-earth and alkaline-earth elements, as well as zirconium, additionally influence the formation of second-phase particles, namely non-metallic inclusions. Non-metallic inclusions are considered to be sources of submicrocrack initiation at grain boundaries, thereby limiting the increase in the metal’s toughness reserve. It has been established that the presence of the above-mentioned non-metallic inclusions prevents the full realization of the beneficial effect of nickel, molybdenum, and vanadium on the level of brittle strength, despite grain refinement and an increase in the viscoplastic characteristics of the metal (KCV, K1 C, δC).
The growth of military threats and increased risks for the civilian population make the problem of increasing the level of security of buildings and integrating protective functions into their spatial structure more urgent. Traditionally, the issue of population protection is considered mainly in the context of creating specialized protective structures or increasing the strength of individual structural elements. At the same time, the spatial and structural organization of a building as a factor in the formation of potentially protected zones has not been studied sufficiently. The purpose of the study is to develop a multi-level structural and spatial model of protected zones in the structure of residential and public buildings. The study uses methods of analyzing scientific sources, comparative analysis of international regulatory documents and generalizing the practice of organizing protective spaces in different countries. The results of studies of the impact of explosive loads on buildings, the principles of increasing the resistance of structures to dynamic impacts, as well as international experience in integrating protected spaces into the structure of buildings are analyzed. Particular attention is paid to regulatory requirements and practical solutions used in NATO countries, in particular in Israel, Singapore, Finland, Switzerland, Norway and the United Kingdom. As a result of the study, a concept of a multi-level structural-spatial model of protected zones in a building was formed, which is based on the differentiation of the internal space of the building depending on its location relative to the external shell and the structural core. The proposed model involves the allocation of several spatial levels of protection: the external shell of the building, transitional (buffer) zones, internal spaces and the structural core. The role of the structurally separated core of the building as the central element of the system of protected zones is substantiated, as well as the value of transitional spatial layers, which can perform the function of an additional structural barrier between the external environment and the internal zones of the building. For an analytical assessment of the potential level of protection of different parts of the building, a space protection index is proposed, which takes into account the spatial location of the room, the number of structural barriers, the characteristics of the enclosing structures and the proximity to the structural core of the building. The proposed model is universal in nature and can be used for the analysis of residential and public buildings, as well as used as a theoretical basis for further research into the architectural typology of protected spaces and the development of recommendations for improving the security of buildings in the face of modern military risks.
Due to the growing requirements for the quality of building materials, as well as the expansion of the scope of their use, the task of reducing energy costs for the processes of manufacturing building materials arises. The main areas of reducing energy costs are optimization or improvement of the designs of individual machines included in technological lines, technological lines themselves, the processes of extracting materials for construction and their delivery to the consumer. On the other hand, Ukraine is experiencing a sharp increase in the volume of construction waste, which is associated with large-scale destruction of infrastructure and housing stock, reconstruction and dismantling of dilapidated structures. Recycling construction waste allows you to reduce future construction costs and also solves environmental safety problems. A large number of current problems in the production and processing of building materials are solved by mobile crushing and sorting plants. Mobile crushing and sorting plants designed for crushing and separating rocks, construction waste or other bulk materials directly at the place of extraction or processing. Such complexes can function as independent units or as elements of entire plants, while ensuring flexible adaptation to production conditions. Mobile crushing plants combine high productivity, autonomy, mobility and economic feasibility, ensuring minimal loss of time and fuel while maintaining the quality of crushing and sorting. One of the most important advantages of mobile crushing plants compared to stationary machine designs is a significant reduction in logistics costs associated with transporting raw materials to the crushing site. In addition to direct savings in fuel and transport resources, reducing logistics provides a number of indirect benefits. First of all, the technological cycle time is reduced. This, in turn, increases the company's cash flow and reduces the need for intermediate warehouses. An important advantage is the reduction in infrastructure construction and maintenance costs. For stationary crushers, it is necessary to build concrete foundations, access roads, overpasses, loading hoppers, and also provide for the supply of communications. Another aspect that has a financial impact is the reduction of downtime related to weather conditions and road conditions. The paper performs a criterion-based assessment of mobile crushing and screening plants, builds models of technological schemes for single-stage crushing and two-stage crushing, which include the designed mobile crushing plant, and provides calculations of the parameters of the mechanical mode of the jaw crusher, the running gear, and the hydraulic system. Based on the load scheme of the structural elements of the jaw crusher, the stress-strain state of the eccentric shaft and the spacer plate was determined using the finite element method.
The paper considers the features of propagation of explosive and impulsive loads in soil media and their influence on the stress-strain state of building structures. It is shown that modern design approaches are often based on the quasi-static representation of explosive loads, which does not fully reflect their dynamic nature and may lead to reduced accuracy of calculations. The time characteristics of a blast wave, including the positive and negative phases, are analyzed, and analytical relationships for determining overpressure and load impulses are presented. The application of the Friedlander equation and simplified triangular approximations for engineering calculations is discussed. Special attention is paid to the propagation of wave processes in soil masses, including longitudinal, transverse, and surface waves, as well as to the influence of the physical and mechanical properties of soils on wave attenuation and transformation. It is established that the nature of energy transfer from an explosion largely depends on the interaction conditions between the explosive source and the soil medium, the depth of charge placement, and the structural heterogeneity of the soil. It is shown that in the case of buried explosions, a significant part of the energy is transferred into the soil, generating intense wave processes that may substantially affect structures. The nonlinear elastoplastic behavior of soils under dynamic loading is analyzed, which is accompanied by the development of plastic deformations, compaction, and decompaction processes. The necessity of considering these effects in modeling the dynamic response of the “soil–structure” system is emphasized. Taking into account the negative phase of the blast wave and the nonlinear properties of soils makes it possible to improve the reliability of computational models and to ensure a more accurate assessment of structural performance under extreme loading conditions.
Adoption of foreign and new domestic types of weapons and ammunition requires conducting a large amount of experimental research. However, the short-term nature of the processes that occur with ammunition on the trajectory complicates direct measurements of the quantities that characterize them, forcing the use of complex measuring and recording equipment. In this context, mathematical modeling of the processes of external ballistics and aerodynamics of ammunition movement comes to the fore. The mathematical modeling method allows to significantly reduce the time and reduce the total cost of ammunition for their testing. Modeling methods, based on mathematical calculations and formulas, allow you to determine the future trajectory of ammunition based on a minimum set of parameters and in a short time. This method makes it possible to accelerate the compilation of temporary firing tables for the use of ammunition and accelerates their arrival to units that directly perform tasks in the combat zone. Mathematical modeling methods allow us to obtain dependencies for determining the level of protection of military personnel when performing assigned tasks by units, taking into account the fact that the effectiveness of measures to ensure the protection of personnel depends on the type of protective barriers, effect of small arms bullets depends on their mass, shape, and bullet speed at the moment of encountering a protective obstacle. The development of a scientific and methodological apparatus for conducting research to determine the parameters of new weapons and increase the ballistic protection of personnel from small arms remains an urgent scientific task. The paper examines the process of interaction of a bullet with various types of protective environments. A method for determining the penetration ability of small arms bullets into protective equipment and models for determining the depth of bullet penetration into various types of obstacles are proposed. The results of calculations of the penetration depth of a bullet from an AK-74 assault rifle into various types of protective environments are presented. Further improvement of armor protection designs can be achieved by developing new technical solutions using the proposed method for determining the penetration ability of small arms bullets into protective equipment.
The design of critical steel structures faces a persistent dilemma between computational speed and physical fidelity. While classical 1D beam elements are computationally efficient, they often fail to capture complex spatial effects like non-uniform torsion and cross-sectional distortion, whereas detailed 3D solid finite element models (FEM) offer reference accuracy but come at a prohibitive computational cost, making them unsuitable for real-time generative design or multi-objective optimization. This study proposes a novel Physics-Informed Neural Network (PINN) architecture designed to function as a real-time “AI-Surrogate” capable of predicting the stress-strain state of spatial members with the accuracy of a high-fidelity 3D FEM model but at analytical speeds. The proposed approach utilizes a Kinematic Decomposition strategy, separating the displacement field into a macroscopic “spine” behavior and a field of local cross-sectional deformations. This effectively reduces the dimensionality of the problem and allows for training on a compact dataset of 10,000 samples. To address the “linearization trap” and the vanishing gradient problem associated with predicting higher-order derivatives (curvature and bi-moments), we introduce a Coordinate Scaling technique. This method normalizes the derivative space, ensuring numerical stability and physical consistency of the solution. Validated against nonlinear 3D solid FEM simulations (Ansys), the model demonstrates high precision, achieving a Mean Absolute Error (MAE) of 0.08 mm for deflections and 0.2 mrad for torsion angles. Furthermore, the specialized physics-informed loss function successfully minimizes the curvature error to 1.510–4 m–2, ensuring the accurate recovery of internal forces. The results confirm that the proposed PINN architecture effectively bridges the gap between the speed of beam theories and the accuracy of volumetric models. The introduced Coordinate Scaling method proves critical for learning differential relationships in mechanics, paving the way for the next generation of real-time structural analysis tools.
Cylindrical shells of circular and non-circular cross-section are used as structural elements in many industries, as well as computational models in the study of the properties of newly created materials that can increase the operational capabilities of these structural elements. This research investigates long non-thin cylindrical elliptical shells made of a continuously non-homogeneous material, the elastic properties of which vary along the thickness. The shells are under the action of internal pressure under conditions of hinged fastening of the ends. The subject of research is the stressed state of the shells and, as a result, the establishment of dependencies between its characteristics and the parameters of the law of change of the moduluselasticity of the material. The purpose of the work is to conduct a numerical analysis of the stressed state of shells of this class depending on the law of change of the elastic properties of the material. The problem is solved using a spatial model of the linear theory of elasticity based on the method of approximation of functions by discrete Fourier series. In this case, an analytical method of separation of variables in two coordinate directions is used, with parallel use of approximation of functions by discrete Fourier series and a stable numerical method of discrete orthogonalization. The stress state of the considered shells is analyzed depending on two parameters of the law of change of elastic properties of the material along the thickness.
The paper presents a methodology for solving three-dimensional problems of thermo-visco-elastoplasticity of prismatic bodies using the semi-analytical finite element method. An approach to modeling geometrically complex heterogeneous structures subjected to spatially and temporally varying mechanical and thermal loads is described. It is noted that accounting for nonlinear deformation processes, such as plasticity and creep, requires step-by-step iterative algorithms. The use of nonhomogeneous skew prismatic finite elements is proposed, in which the formulas account for the variability of the metric tensor. This makes it possible to significantly reduce the number of unknowns and improve the accuracy of approximating the stress–strain state. An algorithm for solving thermo-visco-elastoplastic problems has been developed, which includes two iterative cycles: an inner cycle for solving the system of linear equations and an outer cycle for the nonlinear problem. The approach is based on the Newton–Kantorovich iterative procedure. A distinctive feature of the method is the use of displacement extrapolation at the current step based on the results of the previous step, which ensures faster convergence. An example of modeling the deformation of a non-uniformly heated cube is presented. For this example, the semi-analytical finite element method results showed a discrepancy of less than 5% compared with known reference data, confirming the reliability of the method. The analysis shows that the maximum stresses are concentrated in the center of the cube, where a state close to hydrostatic compression is realized, while plastic deformations reduce the stress level by up to 35%. The application of the algorithm with displacement extrapolation made it possible to reduce the number of iterations by more than half and decrease computational costs by 1.5–3 times. The obtained results confirm the efficiency and accuracy of the proposed approach for three-dimensional thermo-visco-elastoplastic problems of complex prismatic bodies.
Traditional approaches to the design of building structures are considered, which are based on the full use of their resistance and rely on the search for conditions of equi-strength, equi-stability or equi-reliability of system components. Attention is drawn to the fact that the equi-strength of structural elements tacitly assumes their equal role in ensuring the reliability of the system as a whole, when the failure of at least one element is a critical event. That is, the structure is considered a system with sequentially (in the sense of reliability) connected elements, and this often does not correspond to reality. That is why the optimization conditions do not coincide with the principle of equi-strength. Examples of deliberate deviation from equal strength in order to increase the survivability of structures are given. The design of equi-stable structures is based on the independence of various forms of loss of stability, but such independence is violated when switching to nonlinear analysis. Then it turns out that structures designed according to the principle of equi-stability have a special tendency to the destabilizing effect of initial imperfections, and here there is a possibility of destruction of structures, which has an avalanche-like character. It is emphasized that it is quite logical to formulate the same requirements for the reliability of functioning (target reliability levels) for objects of approximately the same degree of responsibility, regardless of the material from which they will be designed and the type of structural scheme. The condition for the equi-probability of the occurrence of design loads is also valid, regardless of the number in the design combination. But the equal reliability of structural elements may not correspond to their functional purpose, which leads to a decrease in overall reliability. A simpler example is ensuring survivability by using key elements with increased reliability.
Actuality. Violation of operating rules and underestimation of real temperature regimes of fires in generator stations lead to an increase in fire hazard and the risk of loss of load-bearing capacity of building structures. Insufficient consideration of real temperature regimes of fires in diesel generator stations makes it difficult to ensure fire resistance and operational reliability of buildings and structures. In this regard, there is a need for scientifically substantiated research into the thermal effects of diesel generator fires to form effective and safe spatial planning and design solutions. Purpose. Study of the nature of the development of a diesel generator fire in a closed room by combining numerical modeling and full-scale fire tests to determine critical temperature regimes and thermal loads on building structures in order to substantiate the fire safety requirements of generator station premises. Main results. The work experimentally and numerically investigated the temperature regime of a diesel generator fire in a closed room, established critical thermal loads and dangerous zones that can lead to the loss of the bearing capacity of metal, reinforced concrete and brick structures. Comparison of the results of full-scale fire studies and computer modeling in the FDS environment showed their consistency with a deviation of 12-15%, which confirms the possibility of using numerical modeling to substantiate the fire resistance requirements of generator station premises. Established the spatial-temporal dependencies of the change in the temperature regime of a diesel generator fire in a closed room depending on the height and distance from the combustion center, and also determined critical temperature ranges for different zones of the room. Quantitative dependencies of thermal loads on enclosing and supporting structures on the diesel fuel combustion scenario were obtained, which allow predicting the loss of fire resistance of structures and justifying the requirements for their fire resistance class and fire zoning of generator station premises. Conclusions. As a result of the conducted numerical and full-scale fire studies, it was established that fires of diesel generator sets in closed rooms are characterized by rapid development and formation of critical temperature regimes, capable of leading to the loss of the bearing capacity of building structures in a short time. The obtained results confirm the feasibility of using computer modeling together with experimental studies for the scientific substantiation of fire safety requirements and fire resistance of generator station premises in buildings of various functional purposes.
The work develops precisely solvable models of pulse optics for dispersive, dissipative deformed media (bodies) and composite materials during their laser processing with short wave pulses. Unsteady thermoelastic fields excited by video pulses in these media (bodies) and materials are presented analytically thanks to exact periodic and unsteady solutions of thermoelasticity equations obtained directly in the time domain outside the limits of Fourier series by analogy with the well-known results of A.B. Schwarzburg. This study also obtained a hyperbolic heat conduction equation for a moving body and a solution to this equation in a cylindrical coordinate system using Green's functions. The solution obtained in this work corresponds to the hyperbolic theory of heat conduction, which takes into account the finiteness of the heat propagation velocity and allows for a more accurate assignment of strength standards for parts operating under thermodynamic stresses, and in technological processes, for example, in the problem of temperature field distribution in cylindrical samples during their processing with a grinding tool, to optimize the processing mode parameters.
Given the security situation in Ukraine, some underground structures and premises are used as simple shelters to protect the population from explosions and shrapnel. Certain requirements are imposed on the maintenance of such structures, namely: the structure must be protected from the effects of ground, surface and technical water by means of waterproofing. If the waterproofing is damaged or missing, the structures lose their operational properties and collapse. In addition, high humidity has a negative impact on the people inside. There are three common methods for repairing or installing waterproofing: excavating the structure and applying waterproofing from the outside, installing waterproofing from the inside, or installing external waterproofing using the injection method. To ensure sustainable development with the aim of reducing the impact on the environment and human health, the third method of waterproofing is the most acceptable. Given the wide choice of materials and their properties, it is advisable to study the effectiveness of the technology of waterproofing by injecting material outside the structure (externally). To this end, a series of experimental laboratory studies were carried out, which revealed the influence of soil moisture on the material's ability to increase in volume, spread and adhere to the structure. The waterproofing properties of the material were also tested. Based on the results obtained, practical recommendations were formulated for the use of improved technology for external waterproofing of underground structures. The optimal level of soil moisture for waterproofing was established. Further research directions were outlined for the installation of external horizontal waterproofing of reinforced concrete structures.
An applied mathematical apparatus has been developed for predicting the thermal and acoustic resistance of building elements and the effectiveness of electromagnetic radiation shielding. Thermal resistance calculations take into account the influence of solar radiation and convective heat exchange on the outer surface of buildings. This makes it possible to rationalise the thermal protection of buildings and their energy efficiency. To predict the acoustic resistance of building structural elements, a multifactorial model of sound transmission through a protective layer has been improved, which has reduced the calculation error compared to known solutions. An applied calculation tool has been developed to predict the effectiveness of shielding electromagnetic radiation with building and facing materials. It is based on the relationships of electrodynamics of continuous media and is most suitable for multicomponent materials compared to semi-empirical formulas. Verification of the results obtained indicates an acceptable convergence of theoretical and experimental data. Given the presence of certain assumptions and simplifications in the calculations, in practical activities, a certain margin of effectiveness must be included in the protective properties of the designed materials and structures.
raditional methods for foundation subgrade analysis are frequently based on linear-elastic models, which may lead to inaccurate estimations of the compressible thickness, particularly under high load intensities. This study aims to quantify the error of the analytical corner point method in comparison with advanced nonlinear constitutive soil models across diverse geotechnical conditions. To achieve this, a series of numerical experiments using the finite element method (FEM) was conducted for a reinforced concrete raft foundation with dimensions of 1.8×2.6 m. Two types of subgrades were analyzed: sandy soil (E=30 MPa) and clayey soil (E=15 MPa). Calculations were performed using various constitutive models, with a primary focus on the Hardening Soil Small Strain (HSsmall) model, which accounts for strain-dependent stiffness degradation. The research results verify the hypothesis of "vertical stress concentration" within nonlinear models. It was established that the geometry of the "stress bulb" undergoes significant transformation depending on the soil type: in clayey subgrades, a more intensive stress penetration depth is observed compared to the predictions of the elastic solution. Furthermore, a redistribution of contact pressures in the central and corner zones of the raft was recorded. It is proven that the error of the analytical method increases proportionally to the load magnitude and the decrease in the soil's deformation modulus. The simulation results demonstrate the necessity of implementing correction factors for the standard tabular stress distribution coefficients α. The application of the HSsmall model provides the most reliable representation of the stress-strain state (SSS), which is critical for avoiding the underestimation of stresses in the deeper layers of the foundation base.
Relevance. In the context of the full-scale war of russia against Ukraine, the issues of ensuring the reliability and survivability of buildings and structures under blast loading caused by aerial attack means, missile and artillery strikes, and other damaging factors are of particular relevance. Modern engineering practice provides the use of several principal methods for analyzing structures under blast wave effects, among which the most widely applied are the quasi-static method, the impulse (shock impulse) method, and the direct integration method of the equations of motion. Despite the availability of these methods, their practical application in the design of protective structures is complicated by the lack of generalized recommendations for selecting an appropriate calculation method depending on loading conditions, structural configuration, and the consequence class of the facility. The aim of this study is to systematize existing methods for analyzing building structures under the action of blast waves, to examine their advantages and limitations, and to improve approaches to modeling loads and the dynamic response of structures. Results. The work summarizes the main methods of calculating building structures for the effects of an blast-shock wave, the shock impulse method, and the method of direct integration of equations of motion, which allowed us to determine their areas of effective application. It was established that the quasi-static method is advisable to use at the initial stages of design to obtain engineering estimates, while the method of direct integration of equations of motion provides the most accurate results in a detailed analysis of the operation of structures under the action of a blast-shock wave. The results of the study can be used to improve the regulatory framework in the field of designing structures for special impacts.
