Bulk storage improved — the 3/4 sphere Monolithic Dome

David B. SouthPublished Monolithic Dome Bulk Storage

Shapes and Strength

Generally, traditional bulk storages, such as grain silos, cement silos and vertical grain bins, are cylinders.  Sometimes they are rectangular, but usually such storages are silo shapes. There is a good reason for silo shape over the rectangular: For the same materials or cost, you get a far stronger shape with a cylindrical silo.

But the strength of a spherical shape beats both the cylindrical shape and the rectangular shape. In fact, the spherical shape is twice as strong as the cylindrical shape.


It’s simple math: The tension in the wall of the cylinder is equal to the radius of the cylinder times the pressure.  The tension in a sphere is the same, but divided by two — hence half as much. This means less steel reinforcing and less concrete is needed to contain the pressure from the product.

For any single point on a cylinder, there is one arch running through it. But for any single point on a sphere, there are two arches.

Hence: If both the cylinder and the sphere are made of the same material, the sphere is twice as strong as the cylinder.

Bulk Unloading

Unloading bulk stored materials can be a major problem.  Somehow the entire floor of the storage must be swept clear.

While different materials flow differently, most materials will flow to extraction holes in the the floor. From there, the material can be conveyed through tunnels to the load-out area.

The 3/4 Sphere

In a bulk storage that’s designed as a 3/4 sphere, the floor area is generally much smaller for the amount of material stored. The interior surface is sloped toward the center, hence concentrating the amount of area at floor level. In other words the area that needs to be swept to retrieve stored material is greatly reduced.

So, the 3/4 sphere is ideal for dropping the stored product into conveyors, and far fewer conveyors are needed.

And since the sphere is naturally stronger, you can reduce the amount of construction material needed to build it and still get the same amount of storage.

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