steel structure joint, end plate

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bernd
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steel structure joint, end plate

Postby bernd » Fri Nov 02, 2018 4:13 pm

I did do a enplate of a steel structure joint with FreeCAD FEM and volume elements and nonlinear material. Attached the pics and the file ... cheers bernd


endplate.FCStd
(22.32 KiB) Downloaded 69 times

stress.jpg
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bernd
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Re: steel structure joint, end plate

Postby bernd » Fri Nov 02, 2018 4:21 pm

We had a disscussion about calculation of an enplate of steel beam cantilever which ist with bolts at work. The beam on the plate is a is a IPE 200. The plat itself is 30 mm thick. I just said let's do it with volume elements and nonlinear in FreeCAD.

The problem:
The yield point is 235 N/mm2, max sigma should be 223 N/mm2 according national standard, but it is impossible. If the steel starts to yield by 235 the max sigma is above 235. The picture shows any sigma above 240 N/mm2

How about the fixes. Is the fix wron and it should be on top of the plate for the tension bolt hole and on bottom of the plate for the pressure bolt hole.

cheers bernd
Jee-Bee
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Re: steel structure joint, end plate

Postby Jee-Bee » Fri Nov 02, 2018 4:25 pm

is the mesh added to the model. when opening the model the GMSH mesh was empty
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bernd
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Re: steel structure joint, end plate

Postby bernd » Fri Nov 02, 2018 4:42 pm

mesh is cleared, because it is huge. Double click on gmsh mehs object and recreate it.
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bernd
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Re: steel structure joint, end plate

Postby bernd » Fri Nov 02, 2018 4:43 pm

btw, nice FreeCAD colour! How to get them?
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HarryvL
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Re: steel structure joint, end plate

Postby HarryvL » Fri Nov 02, 2018 5:52 pm

bernd wrote:
Fri Nov 02, 2018 4:21 pm
We had a disscussion about calculation of an enplate of steel beam cantilever which ist with bolts at work. The beam on the plate is a is a IPE 200. The plat itself is 30 mm thick. I just said let's do it with volume elements and nonlinear in FreeCAD.

The problem:
The yield point is 235 N/mm2, max sigma should be 223 N/mm2 according national standard, but it is impossible. If the steel starts to yield by 235 the max sigma is above 235. The picture shows any sigma above 240 N/mm2

How about the fixes. Is the fix wron and it should be on top of the plate for the tension bolt hole and on bottom of the plate for the pressure bolt hole.

cheers bernd
Bernd, the Von Mises stress should not be above the values defined in the non-linear material object. But as I demonstrated in my knee joint analysis (https://forum.freecadweb.org/viewtopic.php?f=24&t=27431, the nodal values output to FRD are extrapolated from Gauss points and are not necessarily in line with the input values. You can only really rely on the Gauss point values in the DAT file. They will be perfectly in line with the values entered in the non-linear material object.
Last edited by HarryvL on Fri Nov 02, 2018 7:11 pm, edited 1 time in total.
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ppemawm
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Re: steel structure joint, end plate

Postby ppemawm » Fri Nov 02, 2018 6:23 pm

bernd wrote:
Fri Nov 02, 2018 4:13 pm
I did do a enplate of a steel structure joint with FreeCAD
Could you also attach a picture of the structure or the 3D model?
I am curious if you have included the bolt preload and how you handled it.
"It is a poor workman who blames his tools..." ;)
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HarryvL
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Re: steel structure joint, end plate

Postby HarryvL » Fri Nov 02, 2018 6:28 pm

Also, as explained in the same analysis, stress itself is a questionable indicator for failure. Local stress concentration on a sharp corner can in theory be infinite, while the structural detail is perfectly ok. What matters in statically loaded details is ductility (full plasticification of the detail - full yielding of the detail without the equivalent plastic strain coming close to the rupture value). This is recognised in design codes by allowing average stresses rather than stress concentrations to govern static design.
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HarryvL
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Re: steel structure joint, end plate

Postby HarryvL » Fri Nov 02, 2018 7:07 pm

I ran your example. It took 20 minutes to run. :shock: The output object reports a maximum von Mises stress of 292MPa and a maximum equivalent plastic strain (PEEQ) of 0.0091. Clearly these are not consistent with your input values, where at a PEEQ of 0.2 the stress should be 240 MPa. This is because of the extrapolation of stress and strain values to the nodes.

The DAT file is too big to load into my spreadsheet tool, but I am pretty sure that a bit of Python wizardry will show that the von Mises stress in the Gauss (integration) points (to be calculated from the formula below) is perfectly in line with the PEEQ (saved to file) in the same point.

Screenshot from 2018-11-02 20-04-04.png
Screenshot from 2018-11-02 20-04-04.png (6.98 KiB) Viewed 2325 times
Last edited by HarryvL on Sat Nov 03, 2018 1:21 pm, edited 1 time in total.
Jee-Bee
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Re: steel structure joint, end plate

Postby Jee-Bee » Fri Nov 02, 2018 8:09 pm

bernd wrote:
Fri Nov 02, 2018 4:43 pm
btw, nice FreeCAD colour! How to get them?
Screen Shot 2018-11-02 at 21.04.29.png
Screen Shot 2018-11-02 at 21.04.29.png (66.12 KiB) Viewed 2303 times
Over here i set to 2 color gradient.
Upper is grey scale 25% (the light color, don't know if it is system specific it could be reversed)
Lower is grey scale 75%