The paper presents the methodology and results of experimental studies of concrete strength under uniaxial and biaxial compression under dynamic impact. The research results are presented in the form of illustrative tables and graphs. The effect of loading rate and the second principal stress on concrete strength is assessed. Ways for further research development are proposed. The studies have shown that under both static and dynamic loading, the type of stress state and the stress level σ2 significantly affect the strength of concrete. The most noticeable increase in strength occurs during the transition from uniaxial compression to biaxial, even with a small value of the second principal stress σ2. With an increase in the level of lateral compression from 0.2Rb to 0.6Rb, the strength of concrete also increases. Thus, the increase in strength at σ2 = 0.6Rb both under statics and dynamics is more than 40% compared to the strength in uniaxial tests with the corresponding loading rate. The type of stress state and the level of lateral compression affect the dynamic hardening coefficient, but to a lesser extent than the loading rate. A slight increase in k_(b,v) (σ_2) compared to kb,v was observed under biaxial compression with a lateral compression level of 0.4Rb and 0.6Rb.

Keywords: concrete, strength, strength criterion, experimental study, uniaxial compression, biaxial compression, dynamic loading, dynamic hardening coefficient

The paper considers an example of solving a plane problem of the theory of plasticity as applied to concrete, which occurs when an absolutely rigid stamp acts on a concrete base. In this case, the solution was sought in the form of isolines of characteristics, the position of which made it possible to determine the stress state of the foundation. In this case, three areas were distinguished, differing in the stressed state. In the work, it was possible to analyze the effect of friction on the surface of the stamp on the boundaries of these regions and the isolines of stresses in them. Three conditions were considered: friction is absent, friction is constant, friction is proportional to the greater principal stress. The influence of various boundary conditions on the surface of the stamp on the stress state of the concrete base is revealed.

Keywords: concrete, theory of plasticity, plane problem, stress-strain state, stresses, friction, corner punch

The paper considers a structural model of a solid body. Yu. N. Malashkin proposed a structural model of concrete, the main idea of ​​which is an elementary volume in the form of a polyhedron formed from rod octahedra. When developing the model, only its analytical analysis was carried out. In this work, in the development of the model, its finite element analysis was carried out in the LIRA-SAPR software package. The study showed the coincidence of the qualitative and quantitative parameters of the model obtained by numerical and analytical calculations, confirmed its adequacy in relation to concrete.

Keywords: structural model, concrete, elementary volume, polyhedron, rod octahedron, finite element analysis, lira-sapr software package

The basis of the state policy of preservation of cultural heritage objects is the maintenance of the state register of such objects. The occasion for inclusion in the register are recorded in a special document . This document is The draft of the subject matter of protection (DSMP). The paper discusses the methodological issues of the development of this document. The principles that should be the basis for the formation of the project are formulated. In modern practice, the development of DSMP is carried out mainly by architects with the participation of art historians. At the same time, it is necessary to increase the role of the engineer-restorer in the research of features, authenticity, historical and cultural value of structures and other engineering aspects of the existence of the monument. This is confirmed in the analysis of literary sources, and follows from the practical experience of the authors. In conclusion, the article formulates proposals for the content of the work of the engineer-restorer and measures to enhance its role in developing the DSMP.

Keywords: draft subject of protection, cultural heritage, historical and cultural monument, engineer-restorer, historical constructions