Collapse and Repair of Tall Concrete Silos with Suspended Steel Hopper

Abstract

A tall reinforced‐concrete grain silo collapsed suddenly on a sunny, windless, day in the Midwest. Field observations and analysis showed that failure of the suspended steel hopper triggered the collapse. Attachment of the suspended hopper to the concrete wall of the silo had been designed awkwardly and was subject to substantial overstressing in service. The quality of fabrication and welding of the various components for the hopper‐supporting system was poor. The question of why it took four years of service before the silo collapsed but an adjacent, twin, silo remained standing, is answered. Design of the strengthening required for the remaining twin silo is also described. Advice to designers of suspended hoppers is also given at length.