topic Re: Problem calculating curved structure in Robot Structural Analysis Forum

Problem calculating curved structure

Anonymous — Wed, 10 Apr 2013 22:21:26 GMT

Hi!

I'm trying to model the structure of the model atached below, but I have a lot of errors when I try to run the calculations. I only would like to test the structure with the self weight. I've tried to solve changing the diferent options in "meshing" tab in job preferences, but it continues not working.

Thank you very much for your help.

Pd: I cant upload the file

Re: Problem calculating curved structure

HoshangMustafa — Thu, 11 Apr 2013 03:50:45 GMT

I ran the calculations. No error. Please find the attached file.

Re: Problem calculating curved structure

Anonymous — Thu, 11 Apr 2013 07:32:37 GMT

Hi Mustafa Thank you very much for your very fast answer.

I can't run the model and I don't know why. This is a capture of the errors and warnings that the program gives me.

Anything bad in my configuration?

Thank you

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 08:17:09 GMT

Before I write you what to do the question : is the model size correct? ~300 meters x ~500 meters?

Re: Problem calculating curved structure

Anonymous — Thu, 11 Apr 2013 08:37:54 GMT

No, there was a little 10 bigger scale factor error . I've scaled it, but i continue with the same errors and warnings..

Thank you for your patience with me

Re: Problem calculating curved structure

t.sautierr — Thu, 11 Apr 2013 08:54:19 GMT

As you scale error is fixed, you should look at your geometry -> pannels contour.

You've got a lot of "pannel out of plane". you need to divide them and of planar objects before meshing.

Attached : the list of the pannel out of plane + an image : when you cannot see the entire countour it shall ring a bell -> meshing problem are susceptible to occur (not always, it can also be from the point of view you are using (if the structure is very twisted) .

Read post on "flatness" to get the API I used to check the panarity of your pannels.

Nice shape by the way!

Re: Problem calculating curved structure

t.sautierr — Thu, 11 Apr 2013 08:54:52 GMT

Other attachement.

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 09:03:52 GMT

Thomas is right.

Due to this weird geometry these panels are not planar. Some of them is well meshed , some not.

All non-flat panels should be replaced by flat triangular panels. Luckily - some of them are well meshed so replace only some of them. Take a look at corrected model (rescaled). Check loads, support etc

(of course kinematic liink should be off ; correct meshing parameters in attached file)

Re: Problem calculating curved structure

t.sautierr — Thu, 11 Apr 2013 09:18:51 GMT

One sapre question Rafal as we are talking about meshing.

When is it useful to use cinematic links? For most topics about meshing problems, you and artur always recommend no to use this option, so what is the scope of it?

Thx

Re: Problem calculating curved structure

Anonymous — Thu, 11 Apr 2013 09:20:07 GMT

Sorry, but i continue having problems when i try to run the model...

do you have any idea?

Re: Problem calculating curved structure

t.sautierr — Thu, 11 Apr 2013 09:23:07 GMT

Correct your pannels before and come back after.

The analysis is telling you that you have got twisted pannels actually.

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 09:30:47 GMT

When is it useful to use cinematic links? For most topics about meshing problems, you and artur always recommend no to use this option, so what is the scope of it?

This option is for Revit users \ model - not to pay attention to meshing. It always connects "incoherent nodes" to the centers of elements by kind of full rigid links. So depending on size of FEs it may make your structure (esspecially walls) "over stiff".

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 09:37:45 GMT

Replace panels 818 and 13 by new triangular panels.

Model attached

Re: Problem calculating curved structure

t.sautierr — Thu, 11 Apr 2013 09:41:16 GMT

Ok I see the point.

If I get lazy one time, and I use this links, is it correct to say the following :

"the finer the mesh is, the better it is to avoid problems of over-estimated stifness"

In your example, we can suppose it : is the mesh is much smaller, then the rigid link will link element closer to the edge of the pannel and then reduced "translate" the a big scale problem to a more local disturbance?

thx

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 09:48:36 GMT

In your example, we can suppose it : is the mesh is much smaller, then the rigid link will link element closer to the edge of the pannel and then reduced "translate" the a big scale problem to a more local disturbance?

Exactly.

Re: Problem calculating curved structure

Anonymous — Thu, 11 Apr 2013 11:01:58 GMT

Ok, thank your very much for your help.

But I don't understand why Robot let me create not planar shapes, and when i have to calculate them, it gives me the error.

How i can create correctly the mesh and create planar shapes quickly?

There is anyway to divide not coplanary shapes (in general, quadrangular), in triangular shells (triangular, planar).

Thank you very much for your help!

Re: Problem calculating curved structure

Rafal.Gaweda — Thu, 11 Apr 2013 11:14:18 GMT

How i can create correctly the mesh and create planar shapes quickly?

Dwd / dxf backgroud with trangles already created. then click inside each triangle to create panel.

There is anyway to divide not coplanary shapes (in general, quadrangular), in triangular shells (triangular, planar).

No, draw them or write API macro doing that :-).