Progressive collapse resistance of post-fire cellular beam-column substructures with various web-opening shapes

The sudden column loss, which is caused by fire, is a unique illustration of a localized failure that can eventually lead to the progressive collapse of the entire steel-framed structures. To avoid high costs, as well as risks of testing progressive collapse under fire conditions, numerical simulation, which utilizes the finite element (FE) software, is essential to investigate the fire exposure influence on steel-framed structures. In this study, FE simulations using ABAQUS-Explicit are used to examine the resistance of the progressive collapse of beam-column substructures with a cellular opening in the web under fire or post-fire conditions. The FE models' ac-curacy and reliability are accordingly enhanced and validated by comparing the results with previous experi-mental test results. Twenty different types of cellular beams with differently sized (i.e., D = 75, 90, and 105 mm) and shaped web openings (i.e., circular, square, and hexagon holes) are numerically investigated. The failure mechanism, load-displacement behavior, and collapse mechanisms are assessed as well. The results showed that the load-carrying capacity and associated displacement are significantly reduced for fire-exposed specimens. The flexural action and catenary action mechanism resistances of the fire-exposed specimens are all lower than those of the non-fire-exposed specimens, which established that the fire exposure condition might have worsened the initial stiffness and ultimate capacity of the specimens.