Tank Foundation Design

STAAD Foundation Advanced offers ringwall foundation design for self-anchored, non-refrigerated, above ground liquid storage tanks.

In most cases, a ring wall foundation is preferable for tanks more than 20 feet in diameter. A ringwall is also provided when significant soil or differential settlement is anticipated.

Ringwall size should be appropriately selected so that soil the bearing below ringwall equals the soil pressure under the confined earth at the same depth as the bottom of the ringwall. The program designs ringwall foundations per the following codes/guidelines:

API650- Appendix E
PIP STE03020
ACI 318, ASCE 7-05 for US Code design
IS 456, IS 875 III for Indian Code design

For ringwall minimum dimensions, refer to Section 5 from PIP STE03020 guideline.

Load Generation

For US code, Wind load is generated based on ASCE7-05

For IS code, Wind load is generated based on IS 875 III

Seismic load for both US and IS code is generated based on API650 Appendix E. Convective and impulsive portion of load is calculated separately and then combined using API 650 E.6.1.5

Design Philosophy

First, the tank stability is checked based on J factor specified in API 650.

Note: If the tank is determined to be unstable, you may need to design the tank as mechanically anchored tank.
Internal Soil bearing is checked for soil inside ringwall.
Ringwall soil bearing is checked based on PIP STE03020 and API 650 using following diagram,
If tank stability checks are selected as an input, slab moment generated based on API650 appendix E is used as disturbing force.
Forces for hoop steel and twist steel are calculated per PIP STE03020 and concrete design is performed per ACI 318.