Ключевые слова: stress

Stress-strain state and stability of hinged-supported constructions along the boundary of shallow reinforced concrete shells

https://doi.org/10.58224/2618-7183-2026-9-1-7
Аннотация
This article examines the performance of shallow reinforced concrete shells with hinged supports along their perimeter. The relevance of this topic stems from the widespread use of such structures in modern construction for covering large buildings, as well as the insufficient understanding of their behavior under non-ideal boundary conditions. The aim of the study is to evaluate the stress-strain state and stability of the shells, taking into account geometric and physical nonlinearity, as well as the effect of long-term loads (concrete creep). The modeling was performed using the finite element method in the Pascal programming language based on DELPHI-7. The calculations take into account the rheological properties of concrete, nonlinear stress-strain relationships, and various loading schemes. Linear and nonlinear stability analyses were performed, including those involving the possible failure of supporting elements. The results showed that, when supported by a hinge, the shell loses stability under loads significantly lower than the design value, especially under long-term loads. The formation of characteristic localized dents and a loss of overall spatial performance of the structure were also detected. These data highlight the need for more accurate consideration of boundary conditions and nonlinear effects in the design of shallow shells. Recommendations are proposed for optimizing the shell shape and reinforcing the contour to improve its stability. The obtained results can be used in engineering practice for the analysis, design, inspection and safety of similar structures.
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Molding properties of clay mixtures in the soft mud brick manufacture

https://doi.org/10.58224/2618-7183-2024-7-1-5
Аннотация
The article reveals physical and mechanical characteristics of clay mixtures in the soft mud brick manifacture. Considering that currently Russia has no advisory or regulatory documents on the selection of raw materials for soft mud bricks and requirements for their physical and mechanical properties, this issue is quite relevant. The authors, based on their extensive practical experience, present data on acceptable ranges of clay mixtures deformation and critical compressive stress in the soft mud brick manufacture, as well as the results of studies on the influence of electrolyte additives on these indicators. The findings of how the mineral composition of clay raw materials and moisture con-tent influence the critical compressive stress and stickiness of clay mixtures are also presented. Thus, it has been experimentally established that the critical compressive stress of clay mixtures for soft mud bricks should be in the range of 0.2 – 0.8 kg/cm2, and the deformation degree of raw bricks should be in the range of 3 – 5 units. Moreover, even within such narrow limits, depending on their variation as well as on the method of molding and the composition of clay mixtures, it is possible to obtain differ-ent structures of the brick front surface: granular, tuberculate, grooved, wavy, corrugated, spotted, scaly, and their combinations. The moisture content of clay mixtures, depending on the type of clay raw material, can vary within very wide limits: from 20 to 38 per cent. The data obtained will make it possible to develop methods for selecting raw materials for soft mud bricks, which in turn will con-tribute to the organization of its wide production in various regions.
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