Behaviour of Silos Supported on Discrete Brackets

The controlling design condition in thin metal silos is generally buckling under axial compression. This compression is often assumed to be uniform but in many practical cases several failure modes interact as a result of a rather more complex pattern of stresses. Small silos are often supported on several columns with local brackets attached to the sides of the shell. Failure occurs with an interaction between buckling and yielding under a stress regime involving a combination of membrane and bending stresses developed by the applied loads. This paper firstly reviews the literature relevant to bracket supported silos and exposes the limitations in the available design guidance. The results of a series of finite element analyses are then presented to describe the underlying structural behaviour. It is shown that material and geometric non-linearity both play an important role in the behaviour of discretely supported silos. It is also established that the degree of bracket eccentricity is an important factor in determining the mechanism of failure and the associated strength of the silo. Finally, comparison is made between the numerical results and existing design guidelines.