PSI - Issue 48

G. Gusev et al. / Procedia Structural Integrity 48 (2023) 169–175 Gusev et al/ StructuralIntegrity Procedia 00 (2023) 000–000

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cause sinkhole. This study is described by Baryakh (2016, 2018). The danger is not that the building will suddenly fall into a sinkhole, but that it may cause critical deformations of the bearing elements of buildings from the slow process occurring in the near-surface soil layer. This study is described by Gusev (2021, 2022). Deformation processes in large-scale concrete structures under quasistatic loading are experimentally studied by Shardakov (2020) on the test stand. Deformation and failure of monolithic reinforced concrete frames under special actions is described by Fedorova (2019). Experimental studies on collapse of RC frame structures are described by Fan (2018) and Yi (2021). To ensure safe operation, instrumental observations and monitoring of deformation of soils, which may include the measurement of a large number of parameters that characterize the deformation of structures. It is also possible to estimate soil deformation using SAR interferometry, which is described in Samsonov (2018). At that, an important problem is the estimation of the current state and service life of structures on the basis of these measurements. Analysis of the publications shows that the issue of assessing the impact of ground undermining on modern monolithic structures is insufficiently studied, in contrast to panel buildings, for which numerical estimates of ultimate allowable deformations have been made. This study is described by Son (2013) and Gusev (2023). As for the variety of monolithic reinforced concrete structures located in the undermined area or planned for construction, it is relevant to conduct research aimed at the assessment of permissible and ultimate ground deformations causing potentially dangerous non-design deformation of buildings. Such estimations can be based on the analysis of the solution of the boundary value problem for the system "building - foundation - soil mass", focusing on the influence of soil deformation in the process of undermining on the structure. The models used should take into account not only the elastic properties of all the main elements of the system, but also their inelastic deformation behavior, which precedes failure. In the course of calculations, it is necessary to estimate the level of damage to the load-bearing elements in the building model at all stages of deformation. All this significantly increases the dimensionality of the problem, which is practically impossible to solve, even taking into account modern computing technologies. The approach proposed by the authors makes it possible to estimate the state of a structure by means of numerical simulation on different scales using different models. It should be noted that there are studies devoted to the strength of individual elements of reinforced concrete frames, but do not extend to the entire structure, taking into account the interaction with the soil base in a non-design combination of loads. The aim of the study is to create and improve algorithms for the assessment of the stress-strain state of building structures operated and under construction in undermined areas and in areas of man-made impact in order to predict the development of their pre-critical and critical deformation states. These problems are especially interesting because the stress-strain states of systems "building - foundation - soil mass" in such conditions are atypical and unpredictable at the design stage. The current regulatory documentation, which should regulate the issues of construction and operation of structures in such conditions is not without flaws and does not fully meet the current, modern technological solutions and conditions of construction and operation. Moreover, the current state of this issue both in Russia and in the world shows that most of the problems of the direction are not yet solved and it is new and not developed. Nomenclature  strain K relative stiffness of building fragment (relative to the maximum reaction obtained from the calculation in

the elastic formulation) U strain energy