Most of our articles to-date pertain to testing and ensuring reliable bulk solids flow. Silos, bins, hoppers, bunkers, vessels, etc. can experience catastrophic failure if not designed and maintained properly.

There are many reasons why silos fail, usually due to loads applied to silo walls that are not capable of resisting them. Failures can consist of complete collapse of the structure, denting in a metal cylinder or cracking in a concrete wall.

Several areas of concern when dealing with silo structural considerations are: First is the design of the structure requires knowledge of the material's flow properties. Determining the type of flow pattern that will develop aids in the prediction of wall pressures while the material is stationary or flowing.

Non-uniform loads, caused by eccentric material withdrawal must be considered. If you design a silo, you must have a full appreciation of the loads that can be applied to the walls of the structure by the bulk solid flowing within. Some of these flow related loading conditions include:

1. bending of circular walls caused by eccentric withdrawal
2. nonsymmetrical pressure distributions caused by protrusions or even inserts
3. self induced vibrations

During the silo construction, there are two ways problems can arise:

1. uneven foundation settlement
2. faulty construction caused by inferior materials or the lack of enough rebar

A bulk material for which the silo was not designed may impose loads completely different from which the silo was originally designed. Your silo may be designed to handle material that has a bulk density of 50 lb./cu. ft. If all of a sudden you put much heavier material in the silo, the imposed loads will be greater that those for which the silo was designed.

If a side discharge or side port is put in a silo designed to discharge from the center, eccentric loads will develop due to the preferential flow channel that develops. The wall pressures developed by a preferential flow channel are less than those of the rest of the silo. The subsequent eccentric loads can cause dents to occur in the region of the preferential flow channel.