Sudden column removal in tall buildings with flat slabs supported on core and perimeter columns

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This paper focuses on robustness considerations of tall buildings with reinforced concrete flat slabs supported by a central core and one row of perimeter columns. This layout is commonly used in office and residential buildings to reduce storey height and maximise natural daylighting. The core and lateral bracing of tall buildings is generally less sensitive to local failure than the secondary load transfer system provided by the floors and perimeter columns, considering the high vulnerability of perimeter columns to accidental actions and punching of the slab around the supports. This paper analyses sudden corner and edge column removal situations in slab-core-perimeter column systems using dimensions and loading representative of current tall building design and construction, looking at potential punching at the connections and flexural failure in the slab. The dynamic punching model previously developed by the authors, was validated in this work for further cases of punching around edge columns and slabs with low amount of flexural reinforcement. The dynamic punching model is based on the Critical Shear Crack Theory for quasi-static punching and the Ductility-Centred Robustness Assessment method. A simplified level of approximation is proposed for a preliminary dynamic punching check during the conceptual design stage to optimise the position columns and level of flexural and punching reinforcement needed. The approaches proposed are consistent with Model Code 2010 and can be used to arrest the horizontal propagation of failure in the slab. The analyses of the case studies in this work showed that removal of an edge column adjacent to a corner column can be critical and alternative robustness design considerations are needed in this case.