ENHANCING COLLAPSE-RESISTANCE OF STEEL FRAME JOINTS BASED ON FOLDED AXILLARY PLATES

To address the limited anti-collapse ability of traditional rigid connections under progressive collapse, this study improves upon the traditional fully welded connection based on folded axillary plates.These folded axillary plates were arranged on the outer side of the beam-end flanges.The movement mechanisms of the tension and compression folded axillary plates under progressive collapse were revealed based on theoretical analysis.Using the validated numerical model, the performance against progressive collapse and key parameters of the improved connection were discussed in detail.No significant effects were observed on the stress of the structure, given the small deformation, and the ultimate deformation and resistance of the steel structure could be significantly improved in later stages.Subsequently, the catenary mechanism in the beam was fully developed, and the beam member was fully utilized.The failure sequence of the substructure with folded axillary plates first involved the folded axillary plate on the tension side gradually straightening, followed by the two plastic regions forming at the beam flange.Afterward, either the tension beam flange at the beam root and the folded axillary plate broke successively or the tension beam flange broke at the point where the plastic hinge moved outward.Additionally, the anti-progressive collapse design process for the folded axillary plate and the des ign parameters were suggested following theoretical and numerical analyses.