Maiboroda R. Ensuring the resistance of monolithic reinforced concrete buildings to progressive collapse caused by fire and deflagration explosion

This dissertation is devoted to solving an important scientific and practical problem in the field of fire safety – ensuring the resistance of monolithic reinforced The introduction presents a general overview of the dissertation. It substantiates the direction of the research, defines the aim of the work and the main objectives of the study, the object and subject of research, the scientific novelty, and the practical implementation. It also demonstrates the connection of the dissertation with scientific programmes. Information regarding the author’s personal contribution, the approbation of the research, and the related publications is provided. The first section analyses scientific sources and regulatory documents concerning the study of the problem of progressive collapse of monolithic reinforced concrete buildings as a result of emergency situations. The second chapter developed a mathematical model for predicting the behaviour of monolithic reinforced concrete structures under fire and deflagration explosion conditions, which, unlike existing models, takes into account the nonlinear thermophysical characteristics of materials, fire temperature regimes, the nonlinearity of the laws of deformation of structural materials, and the impact of deflagration explosion loads. A mathematical model of the distribution of temperature fields in the ‘reinforced concrete column-slab’ system during a fire has been developed, which is based on equations of unsteady heat conduction, thermal radiation, convective heat transfer, taking into account the spatial combined thermal interaction of structural elements, thermal contact in the node area, and the mechanism of mutual irradiation of surfaces. The third section developed a methodology based on the proposed mathematical models, which allows calculations to be made and the stability of monolithic reinforced concrete buildings to be predicted in terms of progressive collapse under conditions of high-temperature fire exposure and dynamic loading caused by an internal deflagration explosion. In the fourth section, the reliability of the developed mathematical models was verified by comparing the results of numerical calculations with experimental data from fire resistance tests of monolithic reinforced concrete structures. The scientific novelty of the results obtained lies in the fact that: 1. For the first time, a mathematical model has been developed to predict the behaviour of monolithic reinforced concrete structures in conditions of fire and deflagration explosion, which, unlike existing models, takes into account the nonlinear thermophysical characteristics of materials, temperature regimes of fires, the nonlinearity of the laws of deformation of structural materials, and the impact of loads from deflagration explosions. 2. For the first time, a mathematical model of temperature field distribution in a reinforced concrete column-slab system during a fire has been developed, based on equations of unsteady heat conduction, thermal radiation, convective heat transfer, taking into account the spatial combined thermal interaction of structural elements, thermal contact in the node area, and the mechanism of mutual irradiation of surfaces. 3. For the first time, a methodology has been developed to ensure the stability of monolithic reinforced concrete buildings against progressive collapse due to fire and deflagration explosion, which is based on developed mathematical models and provides for determining the stress-strain state of the structural system under the influence of fire and explosion, identifying destroyed elements, and implementing structural solutions or engineering and technical measures to prevent progressive collapse of buildings. 4. A computer model of the resistance of monolithic reinforced concrete buildings to progressive collapse has been improved, which ensures the software implementation of the developed methodology. The developed methodology for ensuring the resistance of monolithic reinforced concrete buildings to progressive collapse due to fire and deflagration explosion, which is based on the developed mathematical models, is a new approach that allows you to implement design strategies, make informed decisions on the choice of structural and engineering measures to ensure the structural integrity of buildings under conditions of combined emergency loads. The use of an improved computer model allows you to automate the process of assessing the stability of the structural system, carry out a phased study of the stress-strain state of the structural system and determine critical failure zones. This provides practical value both at the design stage of new facilities and during the inspection and reconstruction of existing structures, and can also be used in decision-making support systems in conditions of man-made and military emergencies.