Energy-based assessment of the survivability of structural systems under accidental actions

Purpose. To develop an energy-based criterion for assessing the survivability of structural systems under accidental actions, taking into account the dynamic behavior of the structure and the mechanisms of energy dissipation. Methodology. The study was carried out using a discrete nonlinear model in which the structure is represented as a system of lumped masses and nonlinear connections. Geometric and material nonlinearities, the dynamic nature of loading, and contact interaction between elements were taken into account. The numerical implementation was performed using custom-developed Python scripts, with determination of the components of the system energy balance. The proposed approach was tested using a laboratory experiment on the dynamic behavior of a steel frame with diagonal bracing. Findings. The regularities of energy redistribution in a structural system under local damage were established, and the conditions for transition to progressive collapse were determined. It is shown that, according to conventional criteria such as displacement and stiffness, the system may formally remain serviceable, whereas according to the energy-based criterion, when the action intensity increases by a factor of 2‒2.5, the input energy exceeds the allowable level by more than 70 %. The governing factor is the nature of dissipation: under dry friction, energy losses amount to 5‒10 % per cycle and have an unstable character, whereas energy-absorbing elements increase dissipation to 20‒30 % per cycle and reduce vibration amplitudes by 30‒40 %. The results were confirmed by a laboratory experiment. Originality. An integral energy-based criterion for assessing the survivability of structural systems is proposed. In contrast to existing approaches, it takes into account the combined effect of dynamic phenomena, nonlinear material behavior, and contact interactions, and makes it possible to identify the transition point to progressive collapse. Practical value. The developed approach can be used in the practice of design and structural assessment of buildings and structures, in particular industrial facilities, to evaluate their survivability under accidental actions using SCAD Office and custom Python-based computational tools.