Thin walled Section definition

[Anonymous]

Dear Robot support,

I have done a cross section as a thin walled section. I have the following few questions:

- The model is rather big (about 240 nodes) although I would not think it is extraordinary big. Neverthelss it takes 3 minutes to calculate. This is not quite handy as everytime I close the result window all the process as to take place once again (even if do not make any change and I want only to generate the calculation note). I was wondering whether the model is correct. I will have to investigate various section and make iterative changes hence it may get a little too time consuming..

- By mistake I accidentally draw two perfectly overlapping lines (by copying twice back and forth). That was noticed so it has not been a problem. Is there any check tool or any procdeure to make sure that overlapping lines are not considered?

- Is there any way to split one drawn line in two (equivalent of edge division for a contour)? That would be quite handy as I have to divide the structure in correspondance of the centroid which obviouly I know about only after result generation.

Model enclosed.

Thank you.

[Anonymous]

I kindly ask for the expert support. Just by comparing Areas I have noticed something which does not seem to be working fine. 

Model 1 A=0.71m2. I  know this is wrong by simple hand calc

I then separate the outer plates from the inner ones and run result again. It turns out that A=0.79m2. Again I have not done a single change besides translating the plates.

Can anybody solve this issue. It seems to be a severe bug?!?

Thank you.

[Artur.Kosakowski]

Make sure the outer lines connect with all intermediate points. The best is to define them as chains of lines rather than as "start point to end point clicks. 

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[Anonymous]

Dear Arthur thank you for your support but please note that your model has the calculation note "Separated section" meaning that the internal plates are not nicely connected (they should appear with a double line meaning that an enclosed area as been deifned and torsional properties are also found).

I have simplified the geoemtry to better takle the issue. I DO NOT know how to solve it (the error is not negligible and no matter what - there should not be any error at all). I think the section definition has issue with "inclined lines".

- To simplify the geometry I have considered only the upper plate and relative inner plates.
- I have been extremely cautios on line definition and following your suggestion I have modelled the upper plate snapping thorugh the inner plate points. Now the geometry is such that even if you increse the decimals the plate nodes and the inner plates notes match PERFECTLY to the first decimal (double check by copying and pasting node coorinated into Excel).
- In fact double ticking marking appear to all closed area.

-> Yet again the Area is not calculated correctly (calculated 177253mm2, target one 211825mm2. It turns out correctly only if the upper plate is fully separated to the the inner ones, below. 

The error is obviously remarkable and seems like all inner plates are consider to their half values in the former case. This is pretty scary as in the first case double ticking appear making you think everything is right.

Please I really wait for your help as this would be a huge shortcoming not making me able to use the software at ll. I enclosed models and excel table for node checking.

Regards.

[Artur.Kosakowski]

I can't tell what happened but it seems that the top line in the definition of the profile shape is somehow corrupted with some segments being recognized as having 0.6 cm thickness instead of 1.4 cm. I deleted it and created it again which resulted in obtaining the correct value of the area. 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.