Progressive collapse resistance of RC beam-column substructures under fire conditions

To better understand the performance of reinforced concrete (RC) structures subjected to fire under column-removal scenarios, 3D numerical models were established to analyze the structural behavior of pre-loaded beam-column substructures under elevated temperatures in this paper. The temperature-dependent thermal and mechanical properties of concrete and steel were adopted to perform the sequentially coupled thermal-mechanical analysis in an ABAQUS/Explicit solver in a quasi-static manner. To capture the damage evolution of concrete and steel rebar, the concrete damaged plasticity (CDP) and ductile damage for metals (DDM) models were calibrated in the numerical model. Existing experimental data under both ambient and high temperatures were used to validate the feasibility of the proposed numerical model. The structural performance of the RC substructure under the loading stage and heating stage was investigated and the contributions of the resisting mechanisms were quantified using the analytical method. The effects of structural design features, such as reinforcement ratios, concrete strengths, span-to-depth ratios, and fire curves, on the collapse-resisting performance were analyzed in the parametric study. The chord rotation limit criteria regulated by the US Department of Defense (DOD) were utilized to identify the failure of substructures under fire and middle column-removal scenarios.