Circular Steel Silo – Part 4

Load calculation as per Indian standards

• Horizontal pressure calculation
• Gravitational forces on substances give rise to horizontal pressure. Pressure greater at bottom than the top. Pressure increases with depth
• If silos contain powdery materials. Homogenization as per IS 9178 considered.
• As per IS 9178 P-1, Variation of pressure along depth, PI (Z) = (Ph)_max * ( 1 – e-^Z/Zo )

• Wind load calculation
• Pressure coefficient around cylindrical structures, Table 19, IS 875 P-3, depending upon the h/d ratio (for the bin and cone wall)
• Coefficient for single frames for un-cladded buildings, Table 31 , IS 875 P-3 (for supporting system)

The wind load is generally considered critical when silo is empty and maximum possible wind load. The seismic load is generally considered critical when silo is full and maximum seismic load acts.

• Seismic load calculation
• Earthquake calculation as per IS 1893 PART 4: 2015
• The time period for stack like structure (silos) is adopted as per Clause 14.1

Design and detailing

The ring beam is generally welded to the supporting structure (tie beams and main beams)

Manhole is provided usually with small sensors at top.

The ring beam is rested on the main and tie beams.

Vertical stiffeners are generally provided to resist the bending caused in cone portion of silos

The supporting system (beam, column and bracing) generally designed as per IS 800 standards.