Abstract.A study of the mechanical behavior of brick masonry vaults with cut aperture is presented. The vault in New Holland complex in St. Petersburg was assumed as an illustrative example. This vault was tested and simulated in order to evaluate its stress-strain state.Comparison of the results of numerical analysis and experimental test data has been performed. The optimal way to perform an aperture was defined: aperture should be cutting parallel to the lines of action of the principal stresses minimizing direction transversal to these lines. As a further development of the research, the investigation of the various types of aperture in vaults has been recommended to perform using different simulating models and methods.
The article considers the problem of the formation of temperature and cracks in a reinforced concrete floor in thin 400 mm, connected by reinforcing outlets with internal reinforced concrete walls and the outer ring wall of the core of a high-rise building. During the hardening of the laid concrete, the formation of through cracks in the overlapping, extending from the walls and located across the corridor formed by the walls, was observed. The paper analyzes the possible causes of cracking. Cracking occurs due to the restriction of free temperature and shrinkage deformation of the floor slab by a rigid connection with the walls. The direction of the cracks indicates that tensile shrink stresses act along the walls. Cracks form during the cooling of the concrete floor, when the directions of the vectors of shrinkage and thermal deformation coincide. The work gives recommendations for the care of concrete floor structures.
Introduction. The objects of the study are unheated stone buildings. Most of them are historical, including cultural heritage sites. The subject of the study is the analysis of the causes of cracks in the inner plaster layer. Damage of the internal plaster coating has a strong influence on the condition of wall paintings and artistic decoration of the exterior walls of preserved historical objects of cultural heritage. There is a lack of systematic studies of the causes of the damage on the walls. The scientific novelty of the work is the development of a finite element model. In this model, a fragment of masonry is considered together with a plaster coating. The practical significance of the study is to establish causal relationships between damage to load-bearing stone walls and internal plaster coatings. The study is aimed at identifying the most significant factors and impacts that influence the appearance of damage in the inner plaster layer of unheated stone buildings and religious buildings. Materials and methods. A detailed analysis of the stress state of the plaster layer during the course of shrinkage deformations in it was performed. Numerical research methods based on a finite element model of a fragment of masonry with a plaster layer were used. Results. The paper provides a graph of the dependence of the main tensile stresses on the ratio of the modulus of elasticity of the plaster mortar to the modulus of deformation of the masonry. With an increase in this ratio, the values of the main tensile stresses increase linearly. When they reach a value of 1.0 MPa, they become comparable to the limiting stresses at which a crack is formed. The obtained results are of great practical importance in the development of programs for the inspection, repair and restoration of historical cultural heritage sites. Conclusions. It is established that the values of the main tensile stresses practically do not depend on the thickness of the plaster layer. Humidity deformations of the plaster layer significantly exceed temperature ones and are the most significant factors for the appearance of cracks on the internal plaster coating of external walls in the absence of force cracks in the walls.
This paper presents the results of a study of the stress-strain state of a geodesic dome covering the planetarium designed in the city of Nizhny Novgorod. Four design schemes were created in the SCAD with different types of node modeling. A comparative analysis of the effect of the strain capacity of the “BrGTU” type unit on the stress-strain state of the dome cover has been carried out. The results are obtained on the change in the displacements of the structure nodes and internal forces in the dome bars, with rigid and hinged mates. The option of increasing the diameter of high-strength bolts to reduce the overall deformability of the system is considered. On the basis of the obtained results, it was concluded that it is necessary to take into account the strain capacity of the semirigid connections when designing mesh steel domes.
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