To study the load redistribution capacity of reinforced concrete (RC) flat slab structures subjected to a middle column loss scenario, high fidelity finite element (FE) models were built using commercial software LS-DYNA. The numerical models were validated by experimental results. It is found that the continuous surface cap model (CSCM) with an erosion criterion considering both the maximum principal and shear strain could effectively predict the punching shear failure at slabcolumn connections. The validated FE models were employed to investigate the effect of boundary conditions, amount of integrity reinforcement, and slab thickness on the load redistribution capacity of flat slab structures. Furthermore, multi-story RC flat slab substructures were built to capture the load redistribution behavior of different floors. Parametric studies indicate that ignoring the constraints from surrounding slabs may underestimate the load redistribution capacity of the flat slab substructures. Therefore, it is suggested that in future numerical or experimental studies, rigid horizontal constraints should be applied at the slab edge of the substructure to well represent the constraints from surrounding slabs. In addition, it is also found that the amount of integrity reinforcement would significantly affect the post-punching performance of flat slab structures. It is suggested that the minimum integrity reinforcement ratio should be 0.63 %.

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Progressive collapse is a global failure for a multi-story building. All stories above the removed column will consequently deform and help redistribute the loads initially withstood by the removed column. However, due to cost and excessive time to be involved, the majority of existing experimental researches regarding progressive collapse rely on single-story beam-column substructures or sub-assemblages. To date, how to use the results from single-story substructures or sub-assemblages to fully or confidently study the behavior of multi-story building is still unclear. Thus, it is imperative to investigate the relationship between the results of single-story substructures and the real behavior of multi-story buildings. Thus, for this purpose, in the present study, a series of planar multi-story reinforced concrete (RC) beam-column substructures were modeled using high-fidelity finite element software LS-DYNA. Firstly, the numerical models were validated by the test results of two three-story planar substructures with different design spans. Secondly, the validated models were explored on various load resistance of each story in the investigated multi-story frame. In addition, the effects of boundary conditions, missing column locations, story numbers on the variation of load resistance were studied in detail using the models.

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