ABSTRACT
This paper investigates progressive collapse resistance of 3D steel portal frames exposed to fires. Explicit dynamic analyses are carried out to fully consider the post-buckling behavior of frames. A total of three portal frames with spans ranging 12–36 m are analyzed. The influence of fire protections on the collapse mode and resistance is studied. The collapse process of portal frames is defined by four warning times depending on the mid-span deflection of rafters, and horizontal and vertical displacements of columns. The results showed that these four warning times can be determined from the fire-resistant rating of protected columns. The findings in this study can be used to help firefighters to evacuate from a fire-exposed portal frame in time before its collapse.
