Beam Offsets

[ULBsha]

Hi,

Regarding the beam offsets, in one of the Pro tutorials (AP1) related to V5 for which *.CL files were updated, it is shown that the finite element definition of the beam is updated when we change the reference plane from Centroid to Top or Bottom, by using Beam Offsets.

However, in V6.4, I have 3 questions about this Beam Offset:

1) Why the default option in the Reference Plane is set to "TOP", and not Centroid, whereas when I visualise the FEM in Patran, the beams are defined such that their centroid (and not top of them) are set on the nodes (grids) !?

2) When I try to change it, for instance, from 'top' to 'bottom', nothing happens... nothing in terms of final results when I re-analyse everything, nor when I visualise them (still at the same place).

3) I don't find the update in the FEM files either (which makes sense, since nothing happened in the analysis nor in the visualisation).  Where can I find this update in the FEM files please ?


Thanks a lot.

Regards

[Ryan]

1) I believe the default is set to TOP since most beams on an aeroshell will be attached on a skin. Unfortunately the offset definition is not imported from the FEM.

2, 3) When you change the beam offset, the updated FEM files will reflect the latest offsets. In Nastran, the offsets are found on the element definitions.

[ULBsha]

1) I believe the default is set to TOP since most beams on an aeroshell will be attached on a skin. Unfortunately the offset definition is not imported from the FEM.

Yes. That makes sense. But the fact is that it doesn't seem to work !
I attached a figure (FEM files visualized in Patran) that clearly shows the beams are not correctly set. In HyperSizer, the Reference Plane is set to 'Top', while in the figure it seems to be the centroid.

2, 3) When you change the beam offset, the updated FEM files will reflect the latest offsets. In Nastran, the offsets are found on the element definitions.

I was also expecting such a behaviour. However, once again, it doesn't seem to work. When I change the Reference Plane via the Option tab, nothing happens. I also analysed the component, group and the whole project to see if there is any update on the FEM files... but the beams are still like before (see figure)... !

[ULBsha]

Any suggestion... ?

Thanks a lot

[Ryan]

What do the updated CBAR entries look like per component? You should be able to change the offset style, update the FEM, and look at the CBARs in the *.CEL or _i.bdf file to see the offsets.

[ULBsha]

Dear Ryan,

The thing is that the _i.bdf file is not updated at all... therefore the CBAR entries are exactly the same...

I use the conventional Nastran entry for CBARs with 2 grid points and the orientation vector:
CBAR EID PID GA GB X1 X2 X3 OFFT
PA PB W1A W2A W3A W1B W2B W3B


Actually this is precisely the point: I'm not able to change the offset style, because apparently the FEM is not updated when I do it!

Maybe I'm not doing it correctly: I simply go to the Sizing Form, Options tab, and in the Reference Plane section, I change the 'Top' to 'Bottom' for instance, and I save it. Should I do something else ?

But the thing is that even at the beginning, when I import the FE model into HyperSizer and setup all the groups/components, by going into the Sizing Form window, Option tab, I see that the Reference Plane is set to Top (by default, as we already discussed). So, the reference plane of the beams should originally be set at the grids, right ? Unfortunately, this is not the case at all when I visualize them (see figures attached previously)... and it remains the same when I change it from Top to Bottom...


Regards

[Ryan]

After you save, are you updating the FEM? Click Update FEM on the Project or Sizing form.

[ULBsha]

Thanks a lot. That solved my problem.
I wasn't updating the FEM. I thought that saving it would also automatically update the FEM.