In this paper

finite element software SAP2000 was employed for nonlinear static analysis of a multi-story reinforced concrete（RC）planar frame under a middle column removal scenario

to investigate the load transfer mechanisms against progressive collapse.After the numerical model was validated by experimental results

the model was further extended to study the effect of loading pattern

boundary conditions

the number of frame spans and the isolation of typical sub-structures on the load transfer mechanisms of multi-story RC planar frames through the comparisons of structural resistances and internal forces of different frame models.The results showed that the loading pattern has little impact on internal forces of beams

but has evident impact on the internal forces of the columns above the removed one;the increase of the number of planar frame spans and the three dimensional skeleton frame models have little effect on the structural resistance curve

but evidently affect the internal forces of corresponding beams and columns;planar frame can reflect the load transfer mechanisms of actual structures to some extent

but still slightly differs from the planar part of three-dimensional structures in terms of the load transfer mechanisms.