Progressive collapse resistance of two-storey seismic configured steel sub-frames using welded connections

This paper presents the experimental and numerical investigation on resistance of two-storey steel sub-frames subjected to a middle column removal scenario. Two different types of 1/2 scaled steel sub-frames with seismic configuration were fabricated and tested, they are: (1) welded connections with gross beam section (GBS) and (2) welded connections with reduced beam section (RBS, typically used for energy dissipation in earthquake design). Based on the test results, finite element models using explicit software LS-DYNA which can accurately replicate the response of the frames were created and validated. Using the validated model, the parametric studies were also performed to investigate the effect of different parameters on the progressive collapse resistance of the frame. Base on the experimental and numerical studies, the failure mechanism and collapse resistance capacities of these two types of frame systems are first time investigated. The test results indicated that the welded connections with RBS exhibits better performance due to the guaranteed formation of plastic hinges at the location of reduced section, as well as the avoidance of welding heat effect and brittle weld fracture at beam to column connections. Thus, RBS exhibits larger deformation capacity which is favorable in mitigating the possible progressive collapse. (C) 2020 Elsevier Ltd. All rights reserved.