Hi there,
First off, I’m a long time user and big fan of Karamba. Kudo’s for you guys!
There are three main things though that keep coming back.
Eccentricity of shell elements: I know this has been on the to do list for a while, is there any progress in this?
Assymmetric and custom profiles: Is there or will there be a way to generate U-, C- and L-profiles or even completely custom profiles?
Load combinations: Is this also on the to do list?
Regards,
Merijn
Hi Merijn,
thanks for your kind words!
Currently I am working on load- and result-combinations. They will be part of the next release.
The other two points are also on my TODO-list. Probably eccentric shells will come first, then asymmetric profiles.
Best,
Clemens
Thanks for the answer! Looking forward to the next release.
Regarding the asymmetric profiles, would it be possible to add them myself? Or are the needed calculations for it not in place?
There are two things which need to be taken into account in case of unsymmetric cross sections:
These two points are not taken care of in Karamba3D 1.3.2.
Best,
Clemens
Hi Clemens,
Did you confirm that asymmetric profiles (especially U-shape) are always not taken in Karamba 1.3.3 ?
I made a test with a U-profile beam, compared results with a handmade verification (here Maximum deflection of a beam) and results don’t match. After check, already inertia along weak axis (and strong axis ?) seems to be wrong, compared with values of ArcelorMittal catalog. Is it right ?
Thanks and I wish you the best for this year !
Alex
Hello @alex.macoen,
currently - version 1.3.3 - Karamba3D assumes that the principal axes of inertia of the cross sections coincide with the local beam axes and that the cross section centroid lies at the center of shear.
In situations where that does not lead to errors, one could use a box cross section and set ‘UpperThick’ to zero. The torsional stiffness will be wrong, the moments of inertia should be correct however.
Do you have a short definition regarding your U-profile that you could post?
– Clemens
Hi Clemens,
I continued my graduate work but I still have this questioning. It doesn’t have a big influence on my work but I am wondering about it. I left this out and then forgot about it.
I compared the inertia of the same section on 4 different software. Only Grasshopper gives a different answer. And the center of gravity looks good.
The results are in the PDF file.
I hope I’m not making a mistake and haven’t taken up your time unnecessarily. But your opinion will be interesting!
Sorry for the late reply,
Alex
Inertia comparison.pdf (305.4 KB)
Hi @Alex,
thanks for the pdf-file. I have to check what causes the difference. Maybe it is a bug in Karamba3D.
– Clemens
Hi @Alex,
there was a bug in the calculation of the ox-cross section in case of unsymmetric flange thickness. I removed it in the current build of Karamba3D 1.3.3 (see here). Now Iyy comes out correctly (see here: crosec_check_cp.gh (17.2 KB) ). The patch for Karamba3D 2.0.0 WIP will come next week.
– Clemens
Hello @karamba3d - interesting workaround. I had the same challenge on constructing U-profiles in karamba. so thx.
The U-profiles in our construction are actually standing upright. Using the Karamba orientation component and some tinkering with extracted z-axis from the elements seems to work. At least the structure gets assembled and analyzed and the Beam View component presents results. Im however not sure how valid the results are Ponton-carrier-U.gh (45.5 KB)
Hello @martin.tamke,
I could not run your definition, the input geometry is missing.
In the euphoria of getting the right values for Iyy and Izz I forgot about correcting the torsional moment of inertia when the cross section changes from a closed tube to an open profile. This is now corrected (see here).
One problematic thing remains: for U- and unsymmetric I-cross sections the center of gravity and center of shear do not coincide. In such a case, element loads in local Y-direction cause torsional moments. This is currently not accounted for in Karamba3D. I plan to add that in the coming days.
– Clemens
Hello @cp1 - ooops - her the gh definition with internalised geometry Ponton-carrier-U_internalised.gh (40.7 KB)
My case has a diagonal load along the lower inner edge of each of two interconnected u-beams. This makes surely for some interesting torsional moments. I wonder how valid the solution and the calculated values are. I wonder as well how to define in Karamba, where in the section of a profile forces are induced.
Thanks for the development - really cool to see karamba making continuously progress!
Great ! pleased to participate in the improvement of the program.
I really like your availability for the users, Thank you !
Alex
Hello @martin.tamke,
the element loads act at the centroid of the cross sections.
– Clemens