Том 14, № 1 (2024)

Introduction. Some results of implementation of the integrated approach to reliability assessment of design solutions of buildings and structures of increased level of responsibility (large-span rod and sheet metal structures, vertical cylindrical tanks of large volumes) with load-bearing metal structures are presented.Materials and methods. The initial stage of the developed approach to assess the reliability of buildings and structures of increased responsibility is the formation of refined finite element design schemes based on the detailing of nodal connections and geometric schemes of designed structures, which allows to identify the features of the stress-strain state (SSS) and perform a refined assessment of the stability of structural elements. Some general patterns obtained based on such detail are given for large-span structural coatings and structures of vertical cylindrical tanks. To realize the next stage of assessment of the propensity of the designed system to avalanche collapse, a special algorithm for calculating the SSS of the structure, implemented in a geometrically and structurally non-linear formulation, was developed and presented. At the same time, for the considered calculation situation, during the multi-stage calculation, a set of key elements is determined, the failure of which, on the one hand, initiates the beginning of avalanche-like destruction, on the other hand, allows using the established set of elements to determine the upper bound of the numerical value of the probability of failure (or the reliability index) of a repeatedly statically indeterminate system. At the final stage, if necessary, optimization of the obtained structural solution is performed using the Nelder – Mead method according to the specified failure probability indicators for key and minor elements.Results. The proposed approach allows to determine reliability indices of multiply statically indeterminable systems with acceptable practical accuracy. This is especially relevant for unique structures of increased responsibility. The mechanism of loss of stability of compressed rods of structural structures of the MARHI system was clarified, the methodology of correction of the µ coefficient determination taking into account the obtained results was proposed; the data of change of the aerodynamic coefficient of cylindrical tanks of large volumes V = 10,000–30,000 m3 were obtained. This allowed us to determine the following features for the constructions under consideration: with an increase in the volume of the reservoir, there is a change in wind pressure in the area of the ladder junction, compared with a reservoir without a ladder; the maximum discrepancy with the normative values (up to 20 %) was noted in the negative pressure zones (opening effect on the wall); in the active pressure zone, there is a decrease in the vacuum pressure, depending on the size, up to 6 %.Conclusions. A complex algorithm is proposed, which allows, on the basis of detailed design schemes and assessment of the propensity of the designed structures of high level of responsibility to avalanche-like destruction, to perform a refined assessment of their level of design reliability. On the basis of the algorithm, an optimization procedure of the initial design solution is proposed, based on the use of the Nelder – Mead method and currently implemented to minimize the target function in the form of the mass of the main structural elements (rods and connector nodes).

Introduction. In the current process of climate change, the phenomenon of unusual rainfall and flooding is causing widespread flooding and causing great loss of life and property. In addition, the most vulnerable structures are dams and reservoirs. A dam failure causes a disaster that can threaten human lives and entire socio-economic activities. There are many causes of dam failure, of which hydraulic fracturing is considered one of the most likely causes as it causes concentrated seepage leading to the risk of dam failure. Hydraulic fracturing is a process in which cracks form in soil or rock and then propagate under water pressure. Hydraulic fracturing is not a new topic, nor is it an old one, receiving a lot of attention from scientists, but it is still a controversial issue. Many opinions are given. This paper aims to summarize the mechanism of hydraulic fracturing based on previous studies and at the same time proposes some methods to prevent hydraulic fracturing in an earthen dam.Materials and methods. Literature analysis of sources related to the phenomenon of hydraulic fracturing.Results. Hydraulic fracturing is closely related to the phenomena of differential settlement of dam soils and building structures. In earth-fill dams, the phenomenon of differential settlement often occurs in the areas between the fill soil of the dam and the side masses of the dam site, fill soil and concrete structures such as culverts and spillways, foundation structural elements, the impermeable core of the dam and adjacent soil zones. Based on an analysis of the causes of hydraulic fracturing, a number of measures were proposed to reduce the risk of hydraulic fracturing.Conclusions. Hydraulic fracturing, that is, the formation of cracks and cavities in the soil mass, which contribute to the formation of concentrated seepage paths. The occurrence of hydraulic fracturing increases the likelihood of seepage instability in the dam, which affects the safety of the dam and can lead to serious damage. Implementing hydraulic fracturing prevention techniques is critical to ensuring safe dam operating conditions.

Introduction. Aluminium alloys are characterized by the absence of a cold fracture threshold, have high strength and ductility characteristics at low temperatures. However, the norms do not provide the design of aluminium structures that take cyclic force effects at low temperatures. In this regard, there is a need to study the properties and mechanisms of deformation and destruction of aluminium alloys to assess the possibility of their use in the Far North, as well as well as for the inner shells of isothermal reservoirs.Materials and methods. The mechanical properties of structural aluminium alloys 1915, 1565ch and 6082 (similar to AD35) were studied. The specimens were tested for uniaxial tensile strength, impact toughness and fatigue strength, and the characteristics of static crack resistance were determined. The tests were carried out using Instron 8802, Instron 1000HDX, LabTex machines and Instron 450 MPX pendulum coper according to the relevant GOST standards of Russia.Results. Experimental dependences of strength and elastic characteristics (tensile strength, offset yield strength, modulus of elasticity), as well as deformative ones (relative elongation and contraction of the cross-sectional area of specimens) of the studied alloys on the test temperature are obtained. The change of character of deformation of aluminium alloys with decrease in temperature is shown. The results of deformation and fracture resistance under conditions of impact bending and eccentric tension in the temperature range from –104...+20 °C are presented. Fracture toughness (crack resistance) was estimated according to the criteria of fracture mechanics when testing standard specimens with fatigue cracks. The paper also shows the limited limits of endurance based on 2 · 106, 107 cycles of the studied alloys at positive and negative temperatures.Conclusions. The obtained results make it possible to reasonably select materials, assign loads when designing structures made of aluminium alloys and evaluate their service life.

Introduction. The development of architectural and planning solutions of educational institutions of Yekaterinodar (now Krasnodar), built from the end of XIX to the beginning of XX century, is considered. Two objects — the Alexander Real School and the Mariinsky Women’s Institute — are studied. The development of the architectural and planning structure of these buildings is interconnected with the development of ideas about function — changes in the attitudes of pedagogical science and peculiarities of the use of premises in the conditions of the educational process. In each institution there was a constant increase in the number of students, however, the evolution of space-planning solutions developed in different ways. The school was completed and supplemented with new buildings located close to the main one. New, more perfect, purpose-designed buildings were regularly erected for the Mariinsky Women’s Institute.Materials and methods. Materials of the State Archive of the Krasnodar territory, scientific articles and monographs, historical photo-documents, periodicals were used. The authors used field survey of the current state of the described objects with photo fixation, methods of abstraction, typological, historical and comparative analysis, systematization and classification.Results. The study of educational institutions in Yekaterinodar integrated the study of their functional-typological, architectural-planning, volumetric-compositional and decorative-stylistic solutions. The presence, location and functional interrelations of groups of main and auxiliary premises, the reasons for changes in the structure and functional composition of groups of premises of educational institutions were determined; the stages and reasons for the emergence, operation, demolition or current form of use of objects were studied.Conclusions. The information from different sources about architectural and planning features of buildings of large educational institutions of Yekaterinodar in their interrelation with the history of the city development were systematized and combined. Changes in the planning structure, stages of architectural modernization and construction history of each individual building in connection with the political situation, social factors, the emergence of new research in the field of hygiene and pedagogy are reflected. The reasons that required the opening of auxiliary classes and schools in Yekaterinodar are identified.

Introduction. 3D printing is a promising technology to improve the efficiency of construction. At the present time, one of the main disadvantages of this technology remains the low functionality of printed products, in particular, traditional methods are used for thermal insulation and conditioning of printed buildings, which reduces the productivity of the technology. In this regard, the use of thermal accumulative materials (TAM) with phase transition function in building 3D printing to ensure a constant comfortable temperature in the building seems promising. A paraffin-based composite TAM has been investigated for the development of “smart” construction “ink” that will provide printed buildings operating in a temperate climate zone with a passive thermoregulation function.Materials and methods. Differential scanning calorimetry method was used to study the thermal effects of phase transitions of composite TAM consisting of paraffin, paraffin oil and petroleum jelly.Results. A decrease in the peak temperatures of TAM phase transitions was recorded from 53.8 to 32 °C during melting and from 47.6 to 32.6 °C during crystallization. For the two-component composition, the maximum enthalpy reduction was from 102.4 to 27.0 J/g during melting and from 47.7 to 8.5 J/g during crystallization; for the three-component composition, the enthalpy was 60.6 J/g during melting and 20.6 J/g during crystallization. The peak melting temperature for mixtures with 60 and 40 % paraffin is 39.4 and 39.9 °C, the peak crystallization temperature is 43.5 and 33.8 °C, respectively.Conclusions. The conducted studies have shown that the use of paraffin oil and petroleum jelly allows to shift the temperature boundaries of thermal effects of paraffin-based TAM towards lower values. At the same time, a decrease in the intensity of the corresponding peaks on thermograms is recorded, which indicates a decrease in the enthalpy of phase transition processes. Obtaining three-component TAM makes it possible to maintain a higher enthalpy by providing a sequential phase transformation of each of them.

Introduction. In modern society, different types of lighting fixtures with a variety of shapes, colours and brightness are widely used. However, not all of them effectively fulfil their functions and can negatively affect human health. Optimal lighting parameters are identified, taking into account safety and energy efficiency. Key aspects include the analysis of the spectra of incandescent, fluorescent and LED lamps using a spectrometer and assessing their impact on the vision and mental health of employees working in an office space through a written survey.Materials and methods. The illuminance, luminous flux and economy of workstations in office premises were analyzed.Results. The analysis of the obtained results allowed to determine the rationality of application of the investigated spectra of different types of lamps. The results of the research will be useful both for specialists and manufacturers in the field of lighting engineering, as well as end users.Conclusions. Recommendations for the use of LED lamps as the main source of lighting in office-type premises are given. These lamps provide an almost uniform spectrum, which creates optimal conditions for vision and reduces the negative impact on mental health. It is proposed to supplement the workspace lighting with individual light sources in the form of desk lamps of a yellowish shade at each employee's workplace. LED lamps are not only energy efficient, but also contribute to the formation of a comfortable and safe working environment.