Kiyamova L.I.

Assistant Professor, Bauman Moscow State Technical University, Russia

Probabilistic analysis of the “multilayer soil – structure” system response to seismic load

https://doi.org/10.58224/2618-7183-2024-7-4-6
Аннотация
Based on the analytical model of a horizontal layered medium, applying the probabilistic formulation, the article presents the results of the investigation of joint work of a structure and multilayer soil bed subjected to seismic loading. The damping properties of soil were taken into account. The authors drew a comparison between the fundamental frequencies of the free vibrations of the “soil - structure” system obtained using the layered medium model and the platform model. By the example of a two-layer soil bed, the dependence of the resonant frequencies of the system on the thickness of the near-surface or buried weak layer was determined.
The results of the analysis of the “two-layer soil - structure” system for seismic loads at various locations of the weak layer were presented. The seismic acceleration of the soil bed was modeled as a stationary random process with a given spectral density. The investigation included an analysis of the amplitude-frequency characteristics, acceleration spectral densities and dynamic coefficients for both the entire system and the individual layers. It was demonstrated that the resonant frequencies of an individual layer being a part of the multilayer system can differ significantly from the resonant frequencies of a homogeneous soil bed with similar dynamic characteristics. A comparison between the dynamic responses of the two-layer soil bed system and a system with the reduced characteristics of the soil bed was drawn at various parameters of the spectral density of seismic load. The intervals of possible values of the resonant frequencies of the system were determined taking into account the random variability of the velocity of transverse waves within each layer.
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The effect of temperature difference on bending of external panel walls

https://doi.org/10.58224/2618-7183-2024-7-3-6
Аннотация
One of the most common structural systems of buildings intended for various purposes is a prefabricated panel system of factory-made elements assembled on-site. Single-layer structures made of lightweight concrete are widely used as envelopes of these buildings. In buildings operated under various climatic conditions, exterior wall panels, as well as other envelopes, are exposed to thermal deformations and, accordingly, changes in the stress-strain state. As the temperature changes, corresponding stresses and deformations occur across the thickness of the exterior panels. To analyze their values, the bending moments and support reactions of single-layer lightweight concrete panels of different length and thickness in the range of temperature differences from 0 °С to 65 °С have been calculated. It was found that the bending moments and support reactions of 1,500 mm long panels decrease as the thickness of the panels increases over the entire temperature gradient. The values of bending moments and support reactions of panels with length of 3,000, 4,500 and 6,000 mm decrease only when the temperature rises from 0 to 10 °С, in the rest of the range 15–65 °С – increase as the thickness of the panel increases due to the bending stiffness.
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Research Trends in the Mechanoactivation of Clay Minerals Used in Obtaining Geopolymers

https://doi.org/10.58224/2618-7183-2023-6-5-3
Аннотация
The article is an attempt to review scientific achievements in the field of obtaining aluminosilicate geopolymers and current research trends in the field of mechanical treatment (mechanical activation or mechanoactivation, as the term is used in the article) of their predecessors. A geopolymer, also referred to in the literature as geopolymer resin and geopolymer cement, is a mineral binder resulting from geopolymerization, the main step of which is the polymerization (or polycondensation) of precursors in an alkaline or acidic medium. This review focuses on geopolymers whose precursors are natural aluminosilicates, i.e., clay minerals, because, firstly, clay minerals are widespread and available worldwide, and secondly, geopolymers based on heat-treated kaolinite (or metakaolin) have a number of advantages that make kaolinite attractive for further study in terms of reducing energy consumption and carbon footprint in their manufacturing. On the other hand, the review considers the potential of mechanoactivation of clay minerals in an air medium and establishes that mechanoactivated kaolin clays have the potential to replace metakaolin.
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