Hamidreza1973 said:
This is the sample that the Owner provides to us for your kind information.
I have no doubt that it's possible to make an FEM model that looks like a floating roof (FR). What I believe is very, very difficult is making a model that acts like a real floating roof.
I will note that I am not trained in how to make proper FEM models (we have a dedicated group for that), but I have worked with the group enough to understand the difficulties.
It is impossible to review the package you attached in any proper way without the FR drawings, as well as the FEM model and software. Nonetheless a few things jump out at me.
[ul]
[li]Clause 5.1.3 : Why are the buoyancy pressures for the intact roof different for the deck and pontoons? In my mind the buoyancy pressures are an output of the FEM analysis, not an input to the model. See also Figure 15 comment below.[/li]
[li]Figure 4 : I have never seen an FR with so many structural members. Perhaps this FR works differently than ones I am used to?[/li]
[li]Fig 6, 7 & 8 : I've never seen an FEM model with such large plates, and elongated elements. This generally results in poor modelling.[/li]
[li]Figure 11 : The number of boundary conditions should be the minimum to keep the model from translating. I would have used one or two X-direction springs and also one or two Y-direction springs. This many fixed X and Y constraints will hide the real roof action, particularly during the punctured deck and pontoon condition. If the roof weight and buoyancy loads are properly balanced the model should not need to be any Z boundary conditions, other than a light spring since the load balance can never be exactly zero.[/li]
[li]Figure 15 : The buoyancy load looks to be perfectly uniform on both the deck and pontoon. Depending on the pontoon rotation in operation there will be some variation.[/li]
[li]Figure 16 : With the centre deck and two pontoons punctured there will be notable global FR rotation, as well as varying circumferential rotations, resulting in differing buoyancy pressures both around the circumference and across the pontoon radial width. As noted above buoyancy pressure should be an output, not an input.[/li]
[li]Fig 35 & 36 : There is almost no change in the figures at the two punctured pontoons. In fact from these figures it's hard to guess which are the punctured pontoons. No doubt this is due to the problems noted above.[/li]
[/ul]
This report is about what I would expect. The customer is happy because they have an FEM report on file, but the contents of the report are utterly meaningless in terms of accurately modelling the real floating roof.
