API 620 Seismic Calculations

[Muhammad Ijaz]

Please share step by step seismic calculations of tank per API 620.
Regards,
Ijaz

 

[Geoff13]

API 620 Annex L for seismic design is based on API 650 Annex E, as noted in clause L.1.

API 650 Annex EC has a number of sample problems you could review.

 

[MJCronin]

This might help, sir ...

https://letmegooglethat.com/?q=+seismic+calculations+of+tank+per+API+620

MJCronin
Sr. Process Engineer

 

[JStephen]

For flat-bottom cylindrical tanks, the seismic design will be very similar to API-650.
For "other" tanks, design may vary depending on details. Note that API-620 tanks can be large, small, skirt-supported, leg-supported, etc, so details will vary accordingly.
In the US, also refer to the applicable version of ASCE 7.

 

[Muhammad Ijaz]

We have a tank with 8 shell courses (SCs). 04 SCs (from bottom to top) are of different thicknesses (i.e. 11.3, 10.1, 8.8 and 7.6mm) and thickness of remaining top 04 SCs is 7.4 mm.
My questions is:
In API 650 Annex-E para E.6.2.2.2, maximum longitudinal shell compression stress (Sc) shall be calculated considering thickness of bottom shell course only i.e. 11.3mm or Sc must be calculated for every SC?

 

[Geoff13]

API wants you to check for the possibility of "elephant foot" buckling of the bottom shell ring. EDITED : Tanks do not experience this bucking on higher rings so a similar check of upper rings is not required. See correct information by JStephen below

Example : Elephant foot picture

 

[JStephen]

See the last paragraph in E.6.2.2.3.