Difference between modelling quad fiber or tri fiber

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GianmarcoManzo
Posts: 19
Joined: Tue Sep 17, 2019 2:38 pm

Difference between modelling quad fiber or tri fiber

Post by GianmarcoManzo » Sun Jan 19, 2020 10:33 am

Hello,
I modeled a structure using triangular fiber discretization with STKO. Later I modified the section.tcl file inserting a quad fiber discretization. Unfortunately, the results of the two analyzes do not converge. Can you tell me how do I spot the error? Or if is it correct this difference? I tried to visualize the structure manually modeled with quad fibers in the STKO post-processor but I did not succeed. Place here a photo in which I compared the movement of a knot in the two different models:
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for example, how can I tell if the sections are rotated in the same way? Because I thought it could be a possible problem that causes me the difference. But graphically I can't see them.

NOTE: I have used this procedure viewtopic.php?f=27&t=73
But I can't see the sections. I only see the geometry without sections.

GianmarcoManzo
Posts: 19
Joined: Tue Sep 17, 2019 2:38 pm

Re: Difference between modelling quad fiber or tri fiber

Post by GianmarcoManzo » Sun Jan 19, 2020 5:31 pm

problem solved. the sections were rotated differently in the two models. following the instructions in the link posted in the previous message I solved it. in fact, by showing the fiber plot you can see the orientation of the section. now the difference is very little
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STKO Team
Posts: 220
Joined: Tue Oct 29, 2019 8:45 am

Re: Difference between modelling quad fiber or tri fiber

Post by STKO Team » Mon Jan 20, 2020 8:52 am

You already solved the problem. In fact whenever you see such a huge differnce between STKO-generated triangular fiber mesh, and a hand-written quad-fiber section, the only reason could be a different orientation.

Indeed there will always be a small difference, as the fiber-discretization is a numerical integration, thus only approximate. however the small difference will theoretically vanish in the limit of a finer mesh.

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