Brittle Fracture and Collapse of Large Grain‐Storage Tank

Abstract

Failure of a poorly welded 2‐ft (0.61‐m) square cutout patch in the wall of a very large grain‐storage tank caused it to collapse. The tank split open first as a result of brittle fracture. The latter was affected by grain‐induced hoop tension and reduced fracture toughness in the steel caused by low temperature. An investigation was launched that included field observations of the fracture surface at the split wall, a structural review of the tank design, and laboratory determination of fracture toughness of the steel. Both Charpy and center‐cracked specimens were tested; the results indicated low fracture toughness in the steel and a small critical crack length. Answers are given to the following questions: Why hadn't the tank collapsed before? Why didn't it split open when the original cutout was made? How tough a steel would have prevented brittle fracture? Could vertical tube stiffeners have arrested the crack? Various conclusions that affect tank design are supported by the investigation.