Field Investigation of a Failed Concrete Cone Spreader inside of a Cement Mixing Silo

Concrete silos with concrete cone spreaders are unique and complex reinforced concrete shell structures with relatively limited available design and case study literature. In 2013, the authors were retained by an insurance company to investigate the failure of a concrete cone spreader inside of a 66-m tall by 24-m diameter concrete silo located in Colombia, South America. The silo, which was used for raw meal mixing in the production of cement, remained intact while the cone and supporting perimeter ring beam inside the silo collapsed during normal operation of the plant. This paper discusses the unique aspects of this type of structure and describes the sequence of failures of the cone components. A literature review in relation to silos is provided for context, and conclusions of the forensic investigation by the authors are provided. The main purpose of this paper is to disseminate the factors of the failure of this unique structure and to present the findings of the collected field evidence, as opposed to providing a complex computational analysis. The case study presented in this paper will be of benefit to both designers and forensic engineers involved with concrete cone spreaders and silos.