Progressive collapse of 3D steel composite buildings under interior gravity column loss

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This paper presents a novel analytical framework on the quasi-static robustness assessment of 3D steel and concrete composite gravity framed buildings subjected to an interior gravity column loss scenario. The analytical method takes into consideration the two most presumable collapse mechanisms which can be activated in such a case, denoted as the yielding-type and the stability collapse mode. The proposed framework is formulated upon a series of elastic analyses on appropriately selected and accordingly modified structural idealizations of the building, allowing the method implementation by any structural engineering software regardless of the user experience. The method is capable of estimating the damage propagation path within the structural system, assess the gravity connections failure load including the influence of a failed connection to the system response, account for the transition from the composite to the membrane action, assess the potential for column instabilities, determine the gradual system stiffness degradation as the gravity load increases and finally calculate the ultimate collapse load and the corresponding characteristic vertical displacement on the onset of collapse. The analytical method is applied on a 9-story prototype structure performing 9 interior gravity column removal scenarios along the same column row, and the numerical validation of the method demonstrates the excellent agreement among the analytical and numerical results.