Numerical simulations on three-dimensional composite structural systems against progressive collapse

In this paper, three-dimensional steel frame-composite slab systems (3-D composite floor systems) are simulated by verified macro-based models to investigate the structural performance under internal column removal scenarios. The authors have studied the load-transfer mechanisms of 3-D composite floor systems under internal column-removal scenarios, such as flexural action, compressive arch action, tensile membrane action and catenary action, and the final failure mode. In addition, both displacement-based and force-based dynamic increase factors (DIFs) are obtained and their applicability for predicting progressive collapse resistance is discussed. Moreover, the force-based increase factor (DIFp) for 3-D composite floor systems are compared with those for 2-D steel frames and also compared with the values calculated based on DoD design guide. Based on dynamic analyses, several conclusions are found. Firstly, the dynamic ultimate state does not correspond to the static ultimate state in terms of load and deformation. Secondly, the energy method can predict the maximum dynamic responses well but it does not give the failure mode for the dynamic ultimate limit state. Lastly, comparing a 3-D composite floor system with the corresponding 2-D steel frame system, the former requires more ductility, and the DIFp for the 3-D composite floor system is smaller than that for the 2-D steel frame.