Experimental investigation of beam-column joints with cast steel stiffeners for progressive collapse prevention

A full-scale experimental study was carried out on a two-story steel frame to investigate the progressive collapse behavior of beam-column joints with cast steel stiffeners (CSS). The frame was divided into four vertical sections, and each section had a specific joint arrangement of (1) joints with CSS and (2) welded joints without stiffeners. Seven loads of increasing magnitude were applied to the frame. In each section, one of the columns had a device at the base that could be removed and replaced to simulate the failure and repair of this column; this column is referred to as an adjustable column. Strain changes and displacements were monitored during column removal. Moreover, three types of finite-element models were developed to simulate the test frame. The results showed that compared to a welded joint without stiffeners, joints with CSS reduced the strain change and deformation of the frame, as well as the dynamic strain magnification factor of strain change; concrete slabs played a significant role during the load redistribution in the sudden failure of the adjustable column.