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According to the Russian building codes, the numerical study of structures should be carried out taking into account the existing defects and damages. On the example of a U-shaped reinforced concrete frame containing damage, a comparative analysis of three cases of stress-strain state was carried out in comparison with the design scheme without damage. Also, a library of typical damages of reinforced concrete columns and proposed design models was compiled. The calculations were performed by the finite element method in LIRA-SAPR.

With the rapid development of engineering science and technology, tasks related to the calculation of wave processes in elastic medium are becoming more and more relevant. One of the important problems is the search for effective methods for calculating the propagation of harmonic oscillations in elastic mediums, in particular, in semi-infinite spaces. One of these methods is the use of asymptotic boundary conditions of the “radiation conditions” type, which allow us to describe the processes of wave propagation outside the computational domain. In this paper we consider the application of infinitesimal viscosity to derive an asymptotic boundary condition of the “radiation condition” type for the propagation of harmonic oscillations in a semi-infinite elastic space. The results of the study can be used in the design of various devices and structures subjected to the influence of wave processes in elastic mediums, in particular, in the field of soil mechanics.

The study of the implementation of the Saint-Venant principle for restrained rods of the I-section exposed to various loads at its free end is carried out. When using the program complex LIRA SAPR are defined zones of disturbance of normal stresses.

A method for calculation on the progressive collapse, in accordance with which the account of the fall of ceiling panels on the underlying floor when the loss of bearing capacity of vertical frame elements in the form of local impact determined by multiplying the weight plates on the dynamic coefficient determined by the drop height and static deflection. The calculation is carried out in several stages with the use of the LIRA SAPR software.

The limits of the applicability of the Saint-Venant principle are investigated while using the LIRA-CAD app. A large number of bars loaded at the end with different loads are considered. A graph of the distribution of the zones of influence of the Saint-Venant principle is plotted, depending on the size of the bars. It can be concluded that the stress-strain state near the perturbation zones can be represented by three components, two of which are linear, and the third is self-balanced in force and moment.