STUDY OF PROGRESSIVE COLLAPSE OF BUILDINGS AFTER DAMAGE OF MILITARY NATURE

Abstract

The aim of the study is to assess the stability of a monolithic reinforced concrete residential building against progressive collapse under an emergency scenario caused by local mechanical damage of a military nature, as well as to determine the redistribution patterns of internal forces in the load-bearing reinforced concrete elements of the frame after partial structural failure. An additional goal is to justify the feasibility of further operation and restoration of the building based on the results of numerical modeling. Methodology. The study was carried out using the finite element method in a physically nonlinear formulation. Calculations were performed taking into account the actual strength and deformation characteristics of concrete and reinforcement, as well as a realistic scenario of emergency failure of floor slabs, pylons, and diaphragm walls on levels 14–16. The spatial computational model of the building was created in the LIRA-SAPR software package. Special emergency load combinations and a dynamic coefficient were applied to simulate the sudden removal of individual structural elements. Results. The study revealed patterns of internal force redistribution in the vertical reinforced concrete elements of the frame following local damage. It was shown that in the zone of emergency impact, stresses in the pylons and diaphragm walls increase several times, forming local stress concentrations and pre-failure operating regimes. At the same time, in structural elements distant from the damaged area, stress increases are minor and do not lead to the loss of load-bearing capacity. Under the considered scenario, progressive collapse does not develop, and the overall spatial- rigid system of the building maintains its stability. Scientific novelty. The scientific novelty lies in the comprehensive physically nonlinear modeling of a real emergency scenario of military nature for a multi-story monolithic reinforced concrete building, taking into account the sequential removal of damaged elements and dynamic effects. New data were obtained regarding the localization of the stress-strain state and the mechanisms preventing the development of progressive collapse in such structural schemes. Practical relevance. The practical significance of the work lies in the possibility of using the obtained results to justify decisions on the further restoration and safe operation of damaged residential buildings. The proposed numerical analysis approach can be applied as an effective tool for assessing the survivability of buildings and structures in the absence or limitation of full-scale experimental studies. Keywords: progressive collapse, monolithic reinforced concrete frame, reinforced concrete structures, local damage, military impacts, finite element method, physical nonlinearity, stress redistribution, structural robustness.