topic Re: Gridshell model in Robot Structural Analysis Forum

Gridshell model

Anonymous — Thu, 21 May 2015 11:18:07 GMT

Hello!

I would like to ask for some help with my model. I’m working on a gridshell structure and I’m having some troubles rotating the bars in a way that it follows the inherent surface. The problem is that the rotation angles varies in length so if I rotate the whole lath that will not work… and I have almost 2000 little bars, it is crazy to rotate one by one… I’ve tried everything without success.

I attach a pic from the model in Rhino, with laths following the surface, and the robot model; As you can see, I already rotated some of the bars manually.

I hope I was clear with my question J

I want to thank you in advance!

Best regards,

David

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 12:51:28 GMT

Very hard to do it because the continuous beams are not even in a same plane. They are 3D.

And you´ll have an additional problem . The beams don´t cross each other at the same coordinate. There´s always a 5cm offset between them. If you mantain this geometry you´ll have to set some rigid links between these 2 "crossing" nodes.

How did you import this model from Rhino??

Maybe some of the file types that Robot can open are better suited for this import.Check if Rhino can export to one of these file types.

SSDNF files keep the original gamma angle . Even if robot doesn´t recognize the Rhino section , you can assign it later. The important thing is getting the correct gamma angle as you open the imported file in robot.

Re: Gridshell model

Anonymous — Thu, 21 May 2015 13:18:17 GMT

Thank you so much for your quick response!

I saved rhino model in a DWG file and then I assigned the section in Robot.

I was checking Rhino "Save as..." options and I could find the SSDNF file type. That would be great if I could keep gamma angle, the problem would be solved! Do you know if there is another file type which would be equivalent?

Re: Gridshell model

Rafal.Gaweda — Thu, 21 May 2015 13:34:21 GMT

The problem is that the rotation angles varies in length so if I rotate the whole lath that will not work… and I have almost 2000 little bars, it is crazy to rotate one by one… I’ve tried everything without success.

create node in the "dome center" \ "center" then Geometry \ Properties \ Gamma Angle -> Node and use this node number as a reference

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 13:47:37 GMT

Maybe .SAT file or CIS/2 format(.stp). Check the file formats that Robot can open on the picture I sent on the previous post!!!

This is what is supported by Rhinoceros

Or a triangular operation using Revit , or SketchUP .

Re: Gridshell model

Anonymous — Thu, 21 May 2015 13:47:29 GMT

Thank you so much for your suggestion Rafal.Gaweda!

When you say dome center do you mean the center point in the surface or taking the dome as a solid object and then the gravity center?

thanks!

Re: Gridshell model

Anonymous — Thu, 21 May 2015 13:53:56 GMT

In the last post, I forgot to tell you that I've tried all of the suported files in Robot... The best one is SAT. file, but still have the same problem.

Re: Gridshell model

Rafal.Gaweda — Thu, 21 May 2015 14:00:33 GMT

When you say dome center do you mean the center point

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 14:07:25 GMT

Rafal ,

I don´t think it is a sphere

Re: Gridshell model

Rafal.Gaweda — Thu, 21 May 2015 14:28:13 GMT

I don´t think it is a sphere

It does not matter sphere or elipsoid for my idea

It does matter that "beams" are wavy ; each meridian and parallel is not made in plane.

Good luck

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 15:04:45 GMT

Rafal ,

By the picture he sent on the 1st post , it seems that the beams are supposed to have one local axis perpendicular to the shell surface.

This gamma angle "node" solution " seems " to work for the higher " arches" but the below picture shows that it does not.

Re: Gridshell model

Anonymous — Thu, 21 May 2015 15:20:19 GMT

Rafacascudo,

When I initally applied Rafa.Gaweda solution I had the same problem, but then I understood why... As you can see in the pic I send, the original surface that generated this structure it is different. I used the center point of that big ellipsoid, applied gamma angle and then I just rotated 90º and now it's working!!! 🙂 there are some little errors but not relevant!

Thank you so much for your help Rafacascudo and Rafa.Gaweda!!

Best regards 😉

David

Re: Gridshell model

Anonymous — Thu, 21 May 2015 15:25:45 GMT

I forgot the picture!

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 15:54:26 GMT

David ,

The geometrical center of the big elipsoid as reference node for gamma angle will never give you the exact solution.

If your elipsoid approaches a sphere , it will " seem" that the bars orientations are correct.

It is clear by the picture below , that the shell surface will be perpendicular to the elipsoid center only at 0 , 90, 180 and 270 degrees

Re: Gridshell model

Anonymous — Thu, 21 May 2015 16:18:50 GMT

Rafacusdo,

I understand it now!! you're right... thats why I see some little errors! In this case it might be not relevant, but if I need to change the surface it can be important.

I was trying to understand by the image you sent me if there is other option...Any idea?

Thank you a lot,

David

Re: Gridshell model

Rafacascudo — Thu, 21 May 2015 16:53:36 GMT

I think the solutions within robot will be also aproximations. Best option ,in my opinion ,would still be getting the bars correct gamma angles through the imported file.

I see by the name of your Robot file , does it comes from SCIA enginneer software??If yes , can it export to one of the formats that Robot can open?

Re: Gridshell model

Anonymous — Thu, 21 May 2015 17:07:21 GMT

From what I can see now, central point it is not the solution at all...

Scia appears in the file name because after struggling so much with this problem in robot I tried Scia engineer but the problem is exactly the same...The original file was the same, it is a DWG file exported from Rhino... so forget the name, it might induce in error.

I'm gonna try to check more about importing files keeping the same gamma angle...

Thank you a lot Rafacascudo!

David

Re: Gridshell model

Anonymous — Fri, 17 Feb 2017 11:13:13 GMT

Hi,

I advice you to use grasshopper to solve your problem.

Here attached is a little definition which might help you.

First check on GHX that your angle are correct using SDL line.

Second copy/paste, or use API GHX/RSA to inform the angle in the bar tab,

Then chack visually on preview.

It should work fine. Tell me if you have any difficulty.

Once you've done it, there is another issue, getting the displacemnts into the local coordinates.

Here below an study cas on Bordeaux's Cité du Vin.

Global gamma orientation

Local Global orientation

Here another definition, maybe RSA could integrate it in RSA 2018 ?

Re: Gridshell model

Artur.Kosakowski — Fri, 17 Feb 2017 16:07:59 GMT

Bordeaux's Cité du Vin

Re: Gridshell model

Rafacascudo — Fri, 17 Feb 2017 22:54:18 GMT

Awesome!!!
Done in Robot??