The investigation of progressive collapse of steel structures considering physical nonlinearity

The article comprehensively analyzes the problems of research into the phenomenon of progressive collapse, defines the current stage of research, identifies key issues during the simulation of sudden removal of structures, gives the results of the study of sudden collapse of steel structures without taking into account and taking into account physical nonlinearity. A number of factors have been identified for the revival of interest in the topic of progressive collapse research, which began at the beginning of the new millennium and continues to this day. This includes the occurrence of world-famous cases of progressive collapse, a huge number of destroyed buildings and structures as a result of the full-scale invasion of the Russian Federation into Ukraine, a significant number of buildings and structures that, according to obvious signs, should have been completely destroyed due to the destruction of certain key load-bearing structures, but remained partially damaged, a low-income state regulatory framework regarding stability in the event of progressive collapse of buildings and structures, the emergence of technological possibilities for performing spatial calculations, etc. An approximate list of factors has been defined, the consideration of which at the stage of numerical modeling of the emergency situation of a progressive collapse can increase the stability and reserve of the load-bearing capacity of structures. The current regulatory requirements for taking into account the physical nonlinearity of steel structures are analyzed. In addition, the parameters of physical nonlinearity modeling were evaluated, namely the selection of the "stress-strain" diagram, the selection of the deformation limit, etc. Quasi-static and dynamic methods of modeling sudden collapse are compared, and the implementation algorithm of both methods is briefly analyzed. The scenarios according to which the simulation of the sudden collapse process took place are described.