Dear Rhino/Karamba team,
For a project I am working with the ‘Optimize Reinforcement’ tool. My problem now is that the quantities of needed reinforcement given by this tool are around 3 times higher than the reinforcement calculated by hand. After comparing both models it turns out that the bending moments and internal forces are the same in hand calculations and in Karamba, but the ‘Shell line Results’ tool shows that the stress diagram is still linear, even though the tension strength of Concrete has long be surpassed. It would be expected that the concrete stress then becomes zero and the reinforcement takes over. This does however not show anywhere and stresses just keep increasing linearly.
My questions now are: 1) Is there an explanation for the high amount of reinforcement, and 2) how come the stress diagram is linear even after the concrete should have cracked?
SlabTest.gh (39.5 KB)
Thank you for your help.
Kind regards,
Victor
Dear VH Ghering,
Karamba3D is based on linear elastic material behavior - also in case of concrete. It is the cross section design procedure which takes into account cracking. The latter is based on a simplified procedure devised by Marti and Kaufmann (see the Karamba3D manual for details and references).
Thanks for your definition. You are right - for the moment of 50kNm/m the calculated reinforcement quantity should be smaller. I will check that and give you notice when I have located the problem.
Best,
Clemens
Dear VH Ghering,
there is a bug in the calculation of reinforcement quantities in Karamba3D 1.3.1: The ‘Optimize Reinforcement’ component in most cases returns too large reinforcement quantities in the presence of bending moments: The concrete cover is wrongly used as the distance between reinforcement layer and neutral plane.
I have corrected that in the current build and will send you the link for download.
Thanks for your bug report!
Best,
Clemens