Progressive Failure and Imminent Collapse of a Steel Storage Silo

Two 9' diameter by 56' tall steel storage silos were moved 1,000 miles from an existing location to a manufacturing plant in 1985. The steel storage silos were filled pneumatically with small plastic pellets. A review of photographs taken after installation and prior repainting operations indicated the distress was not present at that time. During the fall of 2002, a "buckled" portion of the eastern silo was discovered requiring it to be temporarily supported and unloaded. It was theorized by the plant manager that the distress might be due to the nearby railroad trains approximately 80' away. Based upon our observations and later mathematical analysis, it was discovered that the shell plates of these silos were at or near the plastic buckling limit when this silo was fully loaded with pellets.