Stairway forces on Shell

[BR0]

Hi All,
I think this may be an easy answer for a tank designer. I found a few other threads with similar questions, but didn't see an answer.

On water tank projects, our company would typically provide the civil engineering and the foundation design. However, the tank design is a delegated design by the contractor/tank manufacturer.

The calculation submittal will have calculations for the various appurtenances, such as stairways and guardrails. They are usually very complete, but they never check the stress on the tank shell.

Is this just considered to be not required? Is this a case where the loads are so small compared to the normal loading on a tank that it doesn't need to be checked? Or have they checked it so many times before that they know it will work? I did look in AWWA D100 and API 650 and didn't see specific design guidance.

Does anyone know if there are simple checks for plate stress that can be done?

Thanks for any help.

 

[JStephen]

I think all of the above.
Normally, when I put together a calculation package, I include major items, but there are a lot of little items that I either know don't really need checking or that I have design spreadsheets for but don't include them in the package.
There are ways to check stresses under reinforcing pads and more approximately under linear clips. So if you really need to see that, let the designers know.
Keep in mind, that anything that can be analyzed can be analyzed to a greater or lesser extent, and that extent is usually adjusted based on the how major the component is. So in that knee brace, I would expect that the fixed joints would be treated as pinned, radial and vertical deflections in the tank shell would be neglected, wind and thermal effects neglected, etc.