A reduced-order finite element model for the analysis of RC floor buildings under column loss

Abstract

Progressive collapse is an exceptional event associated with the propagation of local damage to a structure, which results in damage disproportionate to the initial cause. Some design standards recommend the provision of alternative load paths along the structure based on nonlinear structural analysis. This paper presents a novel and simplified proposal for modeling the beam-column connection, which can be utilized in reduced-order finite element models to represent the load path of reinforced concrete structures up to collapse. The proposed methodology is validated using tests documented in the literature, covering plane frames, grids of beams, and floors with monolithic concrete slabs and beams. The results demonstrate that a reduced-order finite element model with a simplified beam-column connection can accurately represent the load paths of plane frames and reinforced concrete floors up to their collapse, including the contribution of the slab. A parametric analysis is conducted to identify the minimum stiffness of the transverse beams so that they contribute to the mechanism's resistance to progressive collapse. When applied to a concrete floor, the proposed reduced-order model shows that catenary action can form even when the rotations in the beam-column connections are less than 0.20 rad. Hence, the proposed reduced-order finite element model is a practical alternative to more complex finite element models for evaluating the resistance of reinforced concrete floors against column loss.