Study on progressive collapse behaviour of steel-framed substructures with sheathed CFS stud infill walls

Sheathed light-gauge steel walls (SLSW) made by cold-formed steel (CFS) studs and external sheathings have been widely applied as they possess many advantages such as flexible spatial layout and quick assembly on site. Previous studies have shown that SLSW can lead to an increase in structural resistance and stiffness when subjected to lateral load. However, influences introduced by SLSW on the progressive collapse resistance of steel-framed substructures have not been adequately investigated due to a deficiency of physical test data. Thus, this paper presents laboratory tests on two steel beam-to-column sub-assemblages, one skeleton frame (SF) and one SLSW infilled frame (IF), with an unsupported centre-column scenario. Comparison between two specimens suggests that additional infill walls can offer an alternative load path to the applied load and can lead to a considerable increase in progressive collapse resistance of the frame. An analytical approach based on the three-strut model is adopted to predict the structural resistance of the specimens. Finite element models are established to simulate the progressive collapse performance of the specimens based on the validated numerical modelling approach. The effects of key design variables on the progressive collapse resistance of the steel frame are further discussed based on parametric studies. The obtained results highlight that the effect introduced by the configuration of the sheathings on the load-carrying capacity of the steel frame is significant.