FEA of Fixed-Roof Tank with out-of-plane Settlement

[femman]

Hello, I'm trying to model a tank with OOP settlement. The roof is fixed, with a beam structure that I find hard to model, as the roof plate is not welded to most beams, and the radial beams are free to slide over the circumferential beams, creating a lot of friction, and allowing some deformation modes on the top edge of the shell. However, as I understand it, the top edge is not quite free, as the roof is restraints elongations through tension. Anybody have a good reference for how to model this?

Another question, we only have data for settlement on the edge... is it possible to model the tank whitout knowing the settlement of the tank bottom?

Thanks a lot!

 

[Duwe6]

"is it possible to model the tank whitout knowing the settlement of the tank bottom?"

Unless the roof is attached to the bottom, Yes [sort of]. Unless the Center-post has sunk; unlikely - LARGE baseplate resting on floor in center of tank, the floor has no effect on the tank except at the edge [chime].

 

[JStephen]

I would be inclined to treat it assuming the top and bottom were held round. An analysis like that is going to be very approximate anyway, so I don't know that you could accomplish a lot by making more complicated assumptions.