RESEARCH ON THE METHODOLOGY FOR CALCULATING RESISTANCE TO PROGRESSIVE COLLAPSE OF BUILDINGS DUE TO FIRE AND EXPLOSION

The authors analyzed the current state of the ability to calculate the resistance of buildings to progressive collapse in the event of a fire and internal deflationary explosion. The analysis of the literature allowed to form the main principles and approaches used by leading countries of the world to calculate and prevent progressive collapse of buildings, such as the traction force method, the alternative load redistribution path method and the method of increasing local stability). It was determined that when calculating the resistance to progressive collapse, the conditional removal of key elements from the calculation model and further analysis is accepted, but the work of load–bearing structures according to the modified calculation scheme of buildings, the structural elements of which are operated under the influence of high–temperature factors of fire and internal deflagration load, and other responsible/load–bearing reinforced concrete elements of buildings, the destruction of which leads to the occurrence of progressive collapse, is not taken into account. Most calculations and studies have been conducted for buildings with steel structures, individual elements, and completely unstudied buildings made of reinforced concrete structures, which are quite common in Ukraine. Existing methods do not describe the probability of the simultaneous impact of fire and internal deflagration explosion at different time points as the root cause of progressive collapse. The authors of this work have developed and described an improved calculation method for the resistance to progressive collapse of reinforced concrete buildings due to fire and internal deflationary explosion, and have determined the criteria necessary for conducting the relevant calculations. The researchers note that the proposed method allows for the assessment of both individual building structures and the building as a whole in terms of resistance to progressive collapse, which differs from existing ones by taking into account the influence of different design values of high temperatures and internal explosive load.