Multiscale analysis of progressive collapse resistance in RC beam-slab sub-assemblages under tensile membrane action

The tensile membrane action (TMA) of reinforced concrete (RC) beam–slab sub-assemblages is a key mechanism for resisting progressive collapse following column removal. Most existing numerical studies, however, use simplified material models and purely macroscale finite element (FE) approaches, which have limited capability to represent concrete heterogeneity, localized cracking, and out-of-plane behavior at large deformations. This paper develops a multiscale FE framework to assess the progressive collapse resistance of RC beam–slab sub-assemblages under edge-column removal, with emphasis on TMA-related mechanisms. At the macroscale, FE models of three experimentally tested beam–slab sub-assemblages are validated against load–displacement responses, confirming that load transfer at large deflection is dominated by TMA after extensive slab cracking. Stress-critical regions are subsequently extracted as sub-models to examine crack initiation, propagation and fracture under TMA-dominated deformation and to evaluate how local failure influences the global response. Within these regions, heterogeneous 3D mesoscale concrete models are constructed using voxel- and Voronoi-based techniques to explicitly represent aggregates, mortar and the interfacial transition zone, and are compared with corresponding 2D mesoscale idealizations. For the studied column-removal scenario, the 3D mesoscale simulations capture out-of-plane responses and fracture processes more consistently with the macroscale behavior than the 2D models. By integrating validated macroscale models, stress-critical sub-modelling and voxel-/Voronoi-based 3D mesoscale simulations, the proposed framework directly links global TMA-dominated deformation to underlying 3D mesoscopic failure mechanisms, thereby extending existing multiscale FE approaches that have mainly focused on beam–column sub-assemblages under catenary action and addresses key limitations of progressive collapse studies based on purely global or mainly 2D models.