Circular Tank: seismic load generation

[TSOFA]

Hi,

I modeled a circular tank in order to design the steel roof. My structure were modeled at "shell design" (structure type) and for the shell I loaded the respective thickness and material ( 8mm steel plate) as a panel. The problem is that when I ask the program to generate automatically the loads to masses for the seismic design, the self weight of the shell is not generated. I open the "mass table" and the self weight of the panes is nowhere! When I check the deformations, only the roof is deforming, when the rest of the structure (shell) is not. How is Robot generates the loads of plates (panels with thickness and material)  to masses?

Thank you in advance

Sofia

[TSOFA]

I deleted the FE of the roof but not the releases and the results were the same for the two models! That's great news, thanks for your support!