Reasons for Collapse of Steel Silos for Wheat with 1600 M3 Capacity

In 2021, five silos for grain storage were ordered, delivered and mounted for expansion of a warehouse in southern Bulgaria. They were produced of thin-walled galvanized sheets. The sheets were corrugated to prevent local loss of stability. All elements were joined together with bolts to facilitate and speed up the mounting processes. After completion of the mounting works, all five silos were filled up to the roof with grains. Three were filled with wheat, and the remaining two with sunflower seeds. On August 16, 2021, at about 8:30 am, a few minutes after the beginning of the first unloading of one of them, its cylindrical shell had torn, and it collapsed. A team from the University of Architecture, Civil Engineering and Geodesy (UACEG) was invited to inspect the accident site and determine the causes of the collapse. For this purpose, the members of the team carefully inspected the structure of the collapsed silos, tested samples of the used material and made control calculations. Through these activities, they established the most likely causes for steel silos destruction.