Max displacements on a square vessel

[PeterWay]

Well, i'm new in this forum & and i'd like to ask some advice about the design of a square vessel.
This recipient normally doesn't work under pressure but i'll be submitted to 1psi test pressure. I'm running some simulations with a FEA program & i'd like to know which could be the allowable max displacement in the flat roof, 1/100 or 1/200?
Thanks in advance

 

[JStephen]

If it's not designed to any specific code, then limitations on deflection (if any) would be at the discretion of the designer.

When using standard flat-plate formulas, one of the limitations is that deflection should be small compared to the plate thickness, or else the formulas are invalidated due to the plate acting in tension rather than just in bending. You would need to confirm if this was an issue in your analysis as well.

 

[fegenbush]

I agree with JStephen on the deflection should be small in relation to the wall thickness.

In the ASCE 7-05 Commentary, it mentions L/360 as the historical allowable deflection for roofs subject to full live load. This is the criteria I typically design to.

Also, the Pressure Vessel Handbook 12th Edition by Megyesy has some great information on rectangular vessels.

 

[PeterWay]

Thanks JStephen and fegenbush!
Just in order to complete the info if someone needs, yesterday i was taking a look to the Megyesy, the suggested maximal allowable displacement for rectangular vessel is L/500 (length over 500), with L the maximal plate length.

 

[JStephen]

Just to clarify- the reason for the small-deflection criteria in many cases is because the design methods used in those cases assumed small deflections to simply the calculation. You may have applications where huge deflections are fine- a trampoline comes to mind- but your FEA model would need to be set up accordingly. Also, you may have some localized yielding that would be okay for a "test" case that wouldn't be acceptable under continued use.