CALCULATION OF INTERNAL AND EXTERNAL SILO LOADS

Bins and silos fail with a frequency much greater than that of any other industrial structure. One of the main reasons is that information in silo design codes on how to calculate silo loads is limited, difficult to follow, or incorrect.

For over 40 years our engineers have been actively involved in research on silo loads, and we have calculated loads acting on an extremely wide range of industrial bins and silos.  This includes: mass flow, funnel flow and expanded flow patterns; initial fill and flow loads; eccentric fill and discharge loading; loads on partition walls, gates and feeders; static, transient, dynamic and thermal loads; external loads due to wind or seismic activity.

Even the best silo design codes have limitations as to their application, but our engineers have developed methods to calculate loads for complex situations not covered by codes, such as: transition, chisel and asymmetric hoppers; inserts; non-free flowing materials.  We measure relevant material loading properties in our laboratories.

Typical loading scenarios:

• Solids induced loading (mass flow, funnel flow, eccentric discharge)
• External silo loads from wind, seismic, ancillary equipment
• Internal loading due to gas pressure

To accurately calculate silo loads one must first have appropriate material loading properties. While all codes contain a table of values of a few common materials, most bulk solids are not included. Even for those that are, the values provided are often of limited value, and the codes themselves recommend testing the actual bulk solid(s) whenever possible.

After measuring relevant material loading properties in our laboratories, we utilize the latest edition of silo design codes from around the world, as appropriate. Even the best silo design codes have limitations as to their application, but our engineers have developed methods to calculate loads for complex situations not covered by any code, including:

• Hopper geometries such as transition, chisel and asymmetric
• Multiple hoppers stacked one above the other
• Silos with an expanded flow pattern
• Inserts (inverted cone, pyramid, cone-in-cone, cross-beams)
• Non-free flowing bulk solids
• Localized effects of air cannons

We are also actively involved in ASME’s Structures for Bulk Solids committee, which is developing a silo design code.