The loading history, including duration, stress level, number of cycles and environmental influences, also affects concrete performance by increasing strength while reducing deformability. Under long-term service, concrete can exhibit elastic behaviour until stresses in the order of 70-80% of the expected compressive strength are reached. The plastic and viscous properties of concrete play an important role under dynamic loading, determining its dynamic hardening capacity. Thus, long-term operation significantly alters the dissipative properties of concrete and affects its response under accidental dynamic effects. The aim of this study was to assess the extent to which the deformed state of the frame as a result of the erection sequence, creep and shrinkage strain accumulation influences the collapse resistance in an emergency situation.The process of deformation of reinforced concrete frame of a multi-storey building in an emergency design situation was modelled, taking into account the stage of construction and different age of concrete at the moment of load application. The computational analysis was performed in quasi-static formulation in Scad Office 21.1.9.9 using the ‘Assembly’ module.According to the results of the study, deformations and forces in the elements of the load-bearing system after the initial local collapse in it have been obtained and analysed. It is shown that when taking into account the sequence of building erection, accumulation of creep and shrinkage deformations, the building resistance to progressive collapse decreases.

Keywords: monolithic reinforced concrete frame, progressive collapse, creep, shrinkage, modulus of elasticity, modulus of deformation, static-dynamic loading