# Reinforced Concrete Beams in Karamba

Hello. I’ve just discovered this plug-in and giving it a spin. I’ve noticed that with Karamba3D it is not straightforward how one would use it for Reinforced concrete columns and beams (but it’s possible for slabs…? )

Is there a specific workflow for this, one that i am missing somehow, or is it simply outside the scope of the software?

at the moment (version 1.3.3) the design of reinforced concrete columns and beams is not directly possible in Karamba3D.
For the design of the concrete cross sections one can use the strength values of the concrete materials together with a reduced target utilization. The reinforcement design then needs to be done in a separate step based on the cross section forces and buckling length.
– Clemens

Thank you for your reply. Do you have an example of reinforcement design using karamba, or a demonstration?

Thank you

1 Like

Hi,
I’m struggling with the same problem. I designed a high rise precast concrete building in karamba. And with the help of mohr’s circle I calculated the normal stresses and shear stresses. But now I want to analyse these stresses and this analysis should lead to a reinforcement percentage in the shell elements. But I’m not sure how to make the connection her, because I understand that Karamba calculates this lineair-elastic and doesn’t take reinfocement into consideration when calculating stresses. How did you design this component to calculate the principal stresses and is there a way to influence the stresses by altering material properties?

Hi @anneholthaus,
the ‘OptiReinf’-component in Karamba3D calculates the reinforcement based on linear elastic cross sections forces assuming a cracked cross section (see here).
Alternatively you get the principal cross section forces via the ‘ShellForces’-component (see here) which can be used to determine reinforcement quantities.
– Clemens

Hi Clemens,

What I do not understand about designing shells in Karamba, is the following. In your example about the concrete slabs that were on youtube:

There is no reinforcement design yet. So what I do not understand it, how does Karamba know how thick the slab must be? Because without reinforcement, the tensile forces are going to be too high, so it will crack.
For my master thesis, I need to simply know how thick my slab is going to be, because I am making an environmental footprint calculation about the building. Calculating the slab thickness is the only thing I need, and exact amounts of reinforcement is not necessary for my footprint calculation.

Would the following work?

• set the concrete class to C30 for example
• connect a slider with the thickness of the slab to galapagos
• give a penalty to galapagos in case any of the compression stresses in the slab is more than 1.00
• then assume that all tension stresses higher than 1.00 can be taken up by reinforcement, so I will then just ignore too high tensile stresses.

But if you have any other ideas how I can estimate how thick my slab is going to need to be without reinforcement design, I would greatly appreciate your advice.

Kind regards,

Duco

Hi @ducoFR,
in reinforced concrete slabs without post tensioning cracking and creep usually cause a maximum displacement which is 3 to 4 times higher than that resulting from a linear elastic calculation. The exact factor depends on the load intensity.
Based on this you could optimize the cross section height of your slab with K3D’s CroSecOpti-component towards an adapted maximum displacement.
– Clemens