A live bottom bin at an animal feed production plant became loose and fell 4 m, dragging along with it a 4 m³ storage bin containing crushed rapeseed, the piping and crusher associated with the storage bin, and a door and part of the building’s cladding. Another storage bin was also damaged by the falling equipment, spilling 30 t of maize draff onto the floor of the plant. The plant was not operating when the incident occurred.

According to the operator, arching inside the silo caused its contents to suddenly drop. The drop height created a dynamic effect that increased the actual load in the silo. This load then caused the bolts to be pushed through the panels of the live bottom bin (a phenomenon known as punching shear). The pushed-through bolts placed additional excess loads on the adjacent bolts, causing them to be pushed through as well. This domino effect therefore resulted in tensile stress failure of the bolts and led to the live bottom bin’s fall. In addition, the cyclic loading of the bin for more than 10 years weakened the materials and therefore reduced the strength of the bolt sections. The combination of these phenomena (dynamic force, domino-effect failure, weakening of the material due to cyclic loading) contributed to the equipment’s destruction.