Full-scale tests on two-story SCBFs with Through–Gusset Plate in brace-to-CFT column connections

Abstract

In Special Concentrically Braced Frames (SCBFs) with Concrete-Filled Tube (CFT) columns, brace force must be transferred through beam–brace–column joint and thereafter distributed between steel tube and concrete infill of column. In the common practice, gusset plates are directly welded to the steel tube of CFT columns where the majority of force is transferred to only a part of steel tube placed adjacent to the gusset plate resulting in distortion and fracture. Accordingly, Through–Gusset Plate (TGP) passing through CFT column is proposed for connecting brace to CFT column and distributing the brace force between steel tube and concrete infill. Moreover, the gusset plates in the braced frames may encounter pinching forces due to frame action. The current study resolves this problem through proposing a new method for connecting the beam to the gusset plate. In addition, beam–to–column connections in SCBFs tolerate large rotation demands due to frame action. Consequently, fracture and damage may occur at beam–to–column connections. This research considers moment connections between the beam and the column using a Through–Plate (TP) to evaluate their effects on the behavior of SCBFs. The cyclic performance of the proposed connections is experimentally assessed through full-scale tests conducted on two one-bay, two-story SCBFs with CFT columns and braces. The results showed desirable behavior of TGP connections that remained undamaged. The proposed method for beam-to-gusset plate connections eliminated the pinching force on the gusset plates. In addition, beam-to-column moment connections using TPs resulted in delaying brace fracture and strength degradation.