Progressive collapse resistance of steel frame with beam to column transfer structure under a middle column-removal scenario

•The progressive collapse resistance of a steel sub-structure with beam to column transfer structure under a middle column-removal scenario is examined through numerical analysis.•The effect of the span to depth ratio and axial compression ratio of the beam to column transfer structure are investigated through parametric study.•The causations of different failure modes are discussed based on the parametric study.•Advice for the design of the span to depth ratio and axial compression ratio of the beam to column transfer structure is proposed.