- STRUCTURAL MECHANICS
- Limit State of Building Structures and Critical Energy Levels
- UDC 624.046

**Leonid U. STUPISHIN**, e-mail: lusgsh@yandex.ru

Southwest State University, ul. 50 let Oktyabrya, 94, Kursk 305040, Russian Federation

**Abstract**. The concept of "limit state" for more than half a century is actively used by engineer-builders in project practice and entered into the normative documentation all over the world. Nevertheless, in engineering calculations and other areas of project activity, it has not become decisive. One of the reasons for this is the inadequate elaboration of the theoretical base connected with an attempt to cover a large number of phenomena that describe the loss of the bearing capacity of the structure. If we ask ourselves how many limit states can describe the load-bearing capacity of building structures, then it is hardly possible to expect the same responses from different specialists, not only in terms of their quantity, but also in content. This suggests that the formulation of limit states is based on hypotheses, the number of which can't be limited. This implies the complexity of the mathematical formalization of phenomena from a single point of view. The article proposes an approach to describing the limit state of structures as a phenomenological phenomenon on the basis of the criterion of critical energy levels. The problem of determining the extreme rigidity values of the system is formulated as an eigenvalue problem. An example of determining the main values of the rigidity of the truss and the corresponding vectors of external influences is presented. With the help of the considered criterion of critical energy levels, it is possible to build an algorithm for the study of complex systems with due regard for the issues of strength, stability and oscillations.

**Key words**: bearing capacity of structures, limit state of structure, criterion of critical energy levels, extreme states of structures, main directions of impacts on system. - REFERENCES

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