Abstract: Kinetic energy transfer from an above failed floor slab to an impacted floor slab is theoretically analyzed for two extreme impact possibilities, namely fully plastic impact and fully rigid impact, and the influence of a ratio of the failed slab’s mass to the impacted slab’s mass on the kinetic energy transfer is discussed. Numerical simulations are also conducted for the kinetic energy transfer related to the two extreme impact possibilities. Then, a simplified evaluating method is proposed to assess the impacting effect between the failed and impacted slabs, including two stages: 1) nonlinear static analysis of the impacted floor slab, and 2) determination of the maximum acceptable gravity load of the failed floor slab using a simplified energy balance approach. It can be seen that: 1) in the case that the failed slab’s mass is equal to the impacted slab’s mass, the total kinetic energy transfer percentage and the impacted slab’s kinetic energy transfer percentage related to fully plastic impact are, respectively, 33.3% and 16.7%; 2) the impacted slab’s kinetic energy transfer percentage related to fully rigid impact is affected by velocity of the failed slab before impacting and edge velocity of the failed slab after impacting. In the case that the failed slab’s mass is equal to the impacted slab’s mass, the impacted slab’s kinetic energy transfer percentage related to fully plastic impact is range from 44.4% to 97.1%; and 3) the calculated impacted slab’s kinetic energy transfer percentages related to the two extreme impact possibilities using ABAQUS are close to the theoretically analyzing results on the whole.