Abstract: To study the progressive collapse resistance of bolted beam-to-upright connections in steel storage racks, an experimental study was conducted on their double half-span substructures under a middle column removal scenario to explore the effects of no-load and half-load conditions on the internal force effects and resistance performance of the substructures. The full-range load-displacement curves and typical failure modes of the substructure specimens were provided, and it was found that the typical failure mode of the bolted beam-to-upright connections was the combination of tab crack and bolt bearing failure leading to tearing of beam-end-connector (T+B). A full-scale refined finite element model was constructed, and its reliability was validated by comparing with the experimental results. Furthermore, the effects of the number and positions of bolts on the progressive collapse resistance of the substructures were explored. The experimental results showed that compared with the beam-to-upright connection substructure specimen locked with one upper bolt under no-load, the pallet cargo load weakened the ultimate vertical resistance and deformation capacity of the bolted beam-to-upright connection substructures. Locking two bolts (upper and lower) significantly improved the ultimate vertical resistance of the substructures, but the ultimate deformation capacity was poor. Locking one lower bolt slightly improved the ultimate vertical resistance of the connection substructures, while the ultimate deformation capacity of the substructures significantly decreased. For the progressive collapse resistance design of beam-to-upright connections in steel storage racks, it was recommended to lock one upper bolt or two bolts (upper and lower) to improve the structural robustness against progressive collapse.

Key words: steel storage rack, progressive collapse, numerical simulation, beam-toupright connection substructure, flexural mechanism, catenary mechanism