Progressive collapse behaviour of endplate connections to cold-formed tubular column with novel Slip-Critical Blind Bolts

A novel blind bolt, named Slip-Critical Blind Bolt (SCBB), was recently invented at Tongji University to be used as slip-critical high strength bolt for moment connections with handy installation from outside of tubular column. This paper applied SCBBs in extended endplate connections to cold-formed Square Hollow Section (SHS) columns, and investigated this application in the beam-to-column assembly against progressive collapse. The performance of SCBBs at connection regions was evaluated in four full-scale specimens with different configurations. Four distinct failure modes were identified, including fracture at beam section, pull-out of bolts from column wall, plastic deformation of endplates and welded bottom flange fracture forcing the reinforcing component to work. Throughout the damage evolution, the SCBBs performed satisfactorily by clamping the connected plates firmly without slip occurring at the plate interface, showing a good mechanical property as being slip-critical high strength bolts. Under the progressive collapse scenario, SCBBs maintained the integrity of the blind bolted connection, thus facilitated the assembly to effectively develop the catenary mechanism which provided significant vertical resistance under large deflection. The considerable potential of SCBB to be applied into the blind bolted moment connections against progressive collapse and its effectiveness were further verified by comparison between the test specimens and other published moment-resisting beam-to-column assemblies.