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

[Rafal.Gaweda]

File please.

[TSOFA]

Because the file was too large, i erased all the load cases that don't take part to earthquake and I also erased the finite elements of the shell.

[TSOFA]

The file that I sent is also without results in order to be small. I run the analysis and I send you the mass table and pictures of deformation due to seismic loading. 

[Rafal.Gaweda]

Sofia,

I do not have such old robot version.

My results below:

[TSOFA]

I think that the new versions do open the old ones. It just open a note that the stucture is with an older version, but then it runs. Can I send you an exampe with robot 2010?

[TSOFA]

what version do you use? How 506 element appeared at mass table? You put it by hand? When I put it manually at the table and I run the analysis again, the element dissapeares from the mass table!! Is it a bug of the old versions? I also have robot 2010, but the files that creates are huge (1.6 GB without results), so I can't send it to you

[Rafal.Gaweda]

As you see there was no problem to open the File. I just can not compare my results with results of v21.
Check Total masses in your results and results from my screen capture

[Rafal.Gaweda]

what version do you use?

2014

How 506 element appeared at mass table?

Automatically

You put it by hand?

No, Automatically

When I put it manually at the table and I run the analysis again, the element dissapeares from the mass table!! Isit a bug of the old versions?

You can not put it manually there because this record is automatically generated.

Bug with displaying panel number in mass table was corrected in 2014.

I have checked masses in robot 2010, 2011, 2012, 2013, 2014 - in all robots  - 99277kg. If you have the same masses in v21 it means everything is correct.

I also have robot 2010, but the files that creates are huge (1.6 GB without results), so I can't send it to you

No way to have 1,6 GB data file without results. To have file without results please use "Save as" as "rtd without results" and specify NEW file name.

I do not need v2010 file.

[TSOFA]

In case of 2014 Robot, does the shell deforms under seismic loads? Can you send me a screen capture of deformation? what is the percentage of mass participation of modal analysis results? Also, when I ask the programm to display graphically the seismic masses, at the shell does not show any load. Is this the same case for you also? I am trying to make my file of 2010 smaller in order to send it

[Rafal.Gaweda]

The total mass is the same. The problem is that in my case element no 506 doesn't appear anywhere (i.e. mass table- see my excel file)! why?

Bug with displaying panel number in mass table was corrected in 2014.

[Rafal.Gaweda]

[TSOFA]

Thanks a lot for your answers. The problem is that if you check the deformation of seismic loadings (not the modal ones, I don't know why), the shell is without deformation. Do you think that this results can be right or there is a problem to my model? The deformation of 32cm under seismic loading along X axis looks too large.

[TSOFA]

I did the following test. Two identical structures, the one has a concrete panel of 0.8cm thickness and the other steel panel of the same thickness. I asked from the programm to generate the self weight of the structure to mass in order to calculate the seismic equivelant loads. As you can see, the reactions of the seismic load are the same (???) as well as the total mass at modal analysis. How is this possible? The self weights of the two structures are not the same! The results are changing if I replace the steel bars with much heavier ones.

[Rafal.Gaweda]

My results

[TSOFA]

In my case the reactions of seismic loading are the same for both structures!! 😞

Do you think that this is a problem of older versions?

[Rafal.Gaweda]

Load to mass conversion worked wrong on panles \ claddings with simplified loads generation.

Use Analytical. (Corrected in 2014)

[TSOFA]

I created a shell with analytical method for transfering loads. The problem is that I can't assign the new shell to my structure because it doesn't find contour. What I did to create the shell of the tank is to creat first a contour and then to extrude it. 

[Rafal.Gaweda]

Extruded objects or all complex elements are automatically "shells".