Progressive collapse resistance of composite steel‐concrete structures following local damage due to fire

Abstract
Over the last decades, significant work has been developed worldwide into the field of structural robustness under extreme events. According to EN 1990, the design situations relevant to structural robustness refer to accidental actions, like blast, gas explosion, impact, fire, or localized failure. Although some of the results have been introduced into design practice codes and guidelines, there are still some gaps in knowledge and technical regulations. The study presented in the paper investigated the response of bare steel frames and steel frames with composite floor systems under column loss scenarios in the event of a localized fire. 3D models were calibrated against test data and employed in an extensive study using nonlinear static procedure. Two main parameters were employed, i.e., mechanical properties of beam‐to‐column joint (full‐strength, partial strength) and steel–concrete interaction. The results showed that two‐way bare steel systems with ductile behavior may provide alternative load paths and retain integrity in case of a localized fire. Also, special attention may be required for systems with composite floor deck and partial strength joints, due to the possible premature loss of steel‐concrete interaction.