Optimize Reinforcement - Quantity

Hi, I am using the OptiReinf component with the OptiCroSec component as suggested to obtain the optimized mass of concrete and reinforcing steel for a 10 meter by 10 meter shell supported on two sides, see attached file. Under conventional loading, the reinforcement ratio (mass of steel over mass of concrete) is about 0.34 which is incredibly high, what could be the cause of such high quantity of reinforcing steel?

Thank you,

Mathieu

Karamba 1.3.1
Rhinoceros 6

Optimize Reinforcement.gh (38.3 KB)

Dear Mathieu,
thanksfor your bug-report. In the calculation of the reinforcement mass there seems to be a factor 100 error. The layer thicknesses seem to be OK though (see attached file: Optimize Reinforcement_cp.gh (37.8 KB)
).
Best,
Clemens

Dear Mathieu,
instead of the mass in kilogram the weight of the reinforcement is output in Newton. This results in a factor 10 error. I have corrected it in the current build of Karamba3D.

Best,
Clemens

Dear Clemens,
After further testing the mass is indeed multiplied by the gravity.

However, when further testing, I noticed that when the mesh is exploded before feeding it to the MeshToShell component, the mass of steel is multiplied by a factor of approximately 30. Also, the thickness of the cross-section is doubled for each face as seen after the Disassemble component, however, the mass of concrete remains unchanged. What could explain this behaviour?

Mathieu
Optimize Reinforcement Exploded.gh (47.3 KB)

Dear Mathieu,
thanks for your bug report. I will have a look at that.
Best,
Clemens

Dear Mathieu,
there is a bug in Karamba3D 1.3.1: The ‘Mass’-output at the ‘Optimize Reinforcement’-component is wrong in case of uniform reinforcement throughout a shell. The concrete cross section is counted then as reinforcement in this case.
I have removed the bug in the current build.
Thanks again for your bug report! I am sorry for the inconvenience.

Best,
Clemens

I need to do something similar to this. Just a question for @karamba3d about the workflow i.e. OptiCroSec → OptiReinf. OptiCroSec uses EN 1993-1-1 which is for steel design, but here it is being used for a concrete structure; how is it possible to use OptiCroSec for concrete design?

Thanks,
Leo

Hi @leo.h.hyde,
when the OptiCroSec-component is applied to shells, a strength hypothesis is used to evaluate the material utilization. In Karamba3D 1.3.3. this is the Van Mises Stress. In Karamba3D 2.0.0 is it possible to define different strength criteria via the Material-component.
For designing reinforced concrete shells, the OptiCroSec-component can be used to get a suitable cross section height, so that in the following reinforcement design step the reinforcement quantities are not too large.
– Clemens

Hi Clemens

Have the different strength criteria been implemented yet?

I am using Karamba3D 2.0.0 210504 WIP for Rhino 7. I have tried to model a concrete shell with in plane loads, see attached file.

shellFailureCriteria.gh (72.7 KB)

I tried setting the shell material strength hypothesis to Rankine. However, the results I got still fit the von Mises criterion. I tried to do it both with and without OptiCroSec to see if that was causing issues, but it does not seem like that is the problem. Also, it seems that only the tensile strength is used regardless of the magnitude of the compressive strength. Is this correct?

Lastly, I have a question about using the OptiReinf component. If I understand it correctly, OptiCroSec does not consider reinforcement and will find a suitable shell thickness, such that the cross section satisfies the target utilization (without cracks?). But then what is the point in using reinforcement if the cross section has sufficient bearing capacity without?

Best regards,
Bjørn

Hi @bjoern-w,
thank you for your bug report!
Sorry for my late reply. There is a bug in the calculation of the utilization values. I am currently working to find it, but haven’t succeeded yet.
The ‘OptiCroSec’-component does not consider cracking. In case of concrete it can be used however to get a reasonable thickness for the concrete cross section. The amount of reinforcement then results from the ‘Optimize Reinforcement’-component, which uses linear elastic cross section forces and the assumption of cracked concrete.
– Clemens

1 Like

Hi @bjoern-w,
the problem with the utilization display should be solved in the current build, see Releases · karamba3d/K3D_NightlyBuilds · GitHub.
– Clemens

1 Like