- 01Silo wall pressures are not hydrostatic — stored grain arches and transfers load to the walls (Janssen behaviour), so silos are designed to specialist silo codes, not tank rules.
- 02Flow pattern (mass flow vs funnel flow) governs both discharge behaviour and the asymmetric pressures that can cause structural failure.
- 03Discharge, filling, and thermal effects create load cases that dominate the design of the wall, hopper, and support structure.
- 04BIM detailing coordinates silo groups with their support steel, conveying galleries, and equipment for a buildable, clash-free package.
Silos look like simple cylinders, but they are one of the more failure-prone structures in industry when designed naively — because stored bulk solids do not behave like liquids. Grain arches internally and pushes outward on the walls, and the pressures during discharge can be dramatically higher and more asymmetric than during storage. Grain silo structural design is a specialist discipline governed by its own physics and codes.
Why silo pressures aren’t hydrostatic
In a liquid tank, wall pressure grows linearly with depth. In a silo, the stored grain develops internal friction and arching, so much of its weight is carried down to the walls by friction rather than pressing on the base — the classic Janssen behaviour. This means wall pressure rises with depth but then flattens toward a limiting value, and it changes significantly between filling and discharge.
Mass flow vs funnel flow
- Mass flow: all material moves whenever any is discharged (first-in, first-out). Requires steeper, smoother hoppers but gives predictable flow and no dead stock.
- Funnel flow: a central channel flows while surrounding material stays static (first-in, last-out). Cheaper hoppers but risks caking, and the flow channel drives asymmetric wall loads.
- The chosen flow pattern must match the material and the structural design — they cannot be decided independently.
Detailing silo groups in BIM
Commercial storage is rarely a single silo — it is a group of silos tied together by conveying galleries, elevators, and a distribution head, all on a support structure. BIM detailing coordinates the silo shells, hoppers, support steel, galleries, and conveying equipment into one model, so the connections and openings are right and the whole cluster is buildable.
Storage that stands up
Silo design rewards specialist knowledge and punishes shortcuts. Spetia Engineering designs and details grain silos and silo groups to the correct bulk-solids physics and codes, coordinated with conveying and support structure in one model — safe, efficient, and buildable.
