Investigation of the collapse resistance of concrete-filled square steel tubular column to H-beam connection with outer ring plate under exposure to high temperature

This study presents a numerical simulation examining the collapse load-carrying capacity of concretefilled square steel tubular column connected to H-beam with outer ring plate. This analysis considers material property damage sustained at varying temperatures in the event of a column's removal at a beam-column joint due to fire. Using the finite element ABAQUS/Standard numerical model, this study investigates the failure characteristics and mechanisms of this joints' progressive collapse after hightemperature material degradation. The results reveal that failure consistently initiates at the juncture between the ring plate and the flange of steel beam in the concrete-filled square steel tubular column to H-beam connection with outer ring plate (SJ-RP). Notably, damage patterns and trends remain relatively consistent across different temperature scenarios. However, as the temperatures rise, both the joint's ultimate collapse resistance and its post-damage ductility decrease significantly. Furthermore, leveraging this numerical model and geometric relationships, this paper delves into the joint's resistance mechanisms against progressive collapse. The results indicate that once the specimen SJ-RP enters the catenary mechanism phase, the entire steel beam section contributes to anti-collapse capacity. Interestingly, the higher damage temperatures correlate with a greater proportion of the steel beam's axial tensile force contributing to the overall collapse resistance.