shell element types 1

[pirs]

Hello everyone,

I have tried to find some answers to this particular question in the theory manual/user manual, but I haven't been successful.

My issue lies with the modelling of a simple cold-formed steel structure, i.e. I used shell finite elements since the thickness is considerably smaller than the other 2 dimensions. I have tried to compare 2 geometrically identical models in a simple buckling analysis: the conventional shell element S4R and the continuum shell element SC8R. I have obtained significantly stiffer results with the SC8R model. Does anyone know why exactly does this happen?

Thanks in advance for any input,

PN

 

[IceBreakerSours]

If I remember correctly, nodes on one type have rotational degrees of freedom. Documentation talks about this in detail.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[pirs]

Yes, this is absolutely true.

S4R - nodes have rotational d.o.f.
SC8R - nodes have displacement d.o.f. only.

However, I don't think this explains the differences I am observing, since my mesh is significantly small (large number of elements) in the areas where deformation is expected to occur.

 

[burningDiesel]

Well, SC8R get the thickness from the nodal coordinates, and S4R from the thickness given, but I guess you made the mesh to have SC8R with the same thickness as S4R.
To be sure: use overlay plot to plot both outputs on the same screen and "render shell profiles"
Also check that the thickness reduction is limited for SC8R elements.