## 2 Analysis of Previous Research  
The systematization, classification, and study of individual types of damage gives accurate quantitative estimates of the bearing capacities of damaged structural elements of buildings and structures. The study of the influences of various factors on bearing capacity saves a significant amount of material and technical resources when designing the necessary reinforcements and performing work on their reconstruction. One of the important points in the diagnosis of buildings and structures is the ability to identify concrete corrosion from mechanical damage and chemical attack. This is due to the fact that the outward signs are the same in both cases--concrete spalling, reinforcement rust, and cracks in the corners of the structure. [3; 4] Mechanical failure mainly includes two types of defects [5]. The first type includes internal or surface structural failures due to shrinkage or expansion, and the second, overvoltage caused by compressive, tensile, shear, and torsional forces. Chemical impacts are primarily present due to the operation of structures in aggressive environments that are not planned for by the design solution: the effects of various acids, alkalis, salts, gas vapors, and biological effects. The authors of [6] considered the classification of damage to concrete, as well as the prerequisites for assessing residual bearing capacity in building elements of concrete in the absence or presence of reinforcement with simple mechanical loading. The influence of the cross-section size [7] on the bearing capacity of a normal section of reinforced concrete column obtained using a theoretical analysis and generalization of experimental data was also considered. However, based on the studies highlighted in the article, the bearing capacity was greatly influenced by the combined effects of cross-sectional shape and flexibility of the columns with a noncentral load application [8; 9], as well as lower slenderness limits depending on the strength, stiffness, boundary conditions, and forces acting on the column. In their paper, the authors of [10] presented simplified analytical expressions for the lower slenderness limits of symmetrically reinforced rectangular columns. One of the important factors affecting the bearing capacity of reinforced concrete structures is the depth of damage and its combination with the shape of the columns; in works [11; 12], their combined effect on the bearing capacity was considered. In [13], the relationship of three factors affecting bearing capacity was considered, namely taking into account the influence of the loading option, the reinforcement method, and the level of preliminary damage. To study the bearing capacity, plasticity, and failure mode of reinforced concrete structures, it is necessary to analytically investigate the nonlinear behavior [14] of reinforced concrete structures. Therefore, in reinforced concrete structures, due to the importance of flexibility and bearing capacity under lateral loads, it is necessary to look for ways to increase plasticity and bearing capacity. Most damaged reinforced concrete (RC) frame structures still can be used after earthquakes. It is important to assess the residual performance of damaged structures, however, quantitatively evaluating the residual performances of damaged structures and taking into account the nonlinear behavior of the material [15; 16]. A significant part of reinforced concrete structures during operation is exposure to intense environmental influences [17]. This can cause the local destruction and failure of buildings if mandatory measures are not taken to protect them from corrosion [18]. Exposure to high temperatures can significantly affect the design characteristics and bear ing capacities of reinforced concrete elements and, therefore, lead to partial or complete destruction [19; 20].