Progressive collapse resistance of composite frame with concrete-filled steel tubular column under a penultimate column removal scenario

Abstract

In this study, static tests of six two-story three-span composite frames with concrete-filled steel tubular (CFST) column under a penultimate column removal scenario were carried out. The experimental phenomena, vertical resistance, strain and axial force of steel beams were presented. The internal force transmission path of composite frame under a penultimate column removal scenario was investigated. The effects of reinforced concrete (RC) slab and weld-bolted connection on the progressive collapse resistance of composite frame were analyzed and discussed. Consequently, the dynamic response prediction and dynamic amplification factor (DAF) were analytically studied by energy balanced method (EBM). Further, the numerical models of composite frames were calibrated by the test results in ABAQUS/Explicit. The results showed that serious torsion of steel beam at directly affected region (DAR) reduced the resistance for the CFST frames with bare steel beam. However, for the CFST frames with composite beam (i.e., with steel beam and RC slab), the RC slab improved the initial stiffness and peak resistance of composite frame and thus mitigated and even prevented the torsion of beam. The composite frames presented an asymmetric failure mode and internal force transmission path under a penultimate column removal scenario, which was different from that under a middle column removal scenario. The composite frames with weld-bolted connection presented a lower resistance than the composite frames with welded connection due to the premature fracture of welded flanges but possessed multi-protection measures to resist progressive collapse due to the intermittent failure modes.