Stress Integration in a Shell


(Mathieu Côté) #1

Hi, I am trying to obtain the maximum tensile and compressive stress in a shell between randomly generated lines that are not intersecting each other. The goal is to limit both stresses to predefined and independent values in an optimization framework in which the number and position of lines would be allowed to change. How could I acheive that for a shell with an irregular shape?

Thank you,

Mathieu

Karamba 1.3.1
Rhinoceros 6


#2

Dear Mathieu,
are the lines intended to be ribs?
You can retrieve the cross section forces of each element of a shell. The tricky part will be to assign these results to the correct lines - but this would be rather a Grasshopper related issue.
Best,
Clemens


(Mathieu Côté) #3

Dear Clemens,
The lines are actually post-tensioning lines which will mimic post-tensioning with an upward distributed load. However, to obtain the equivalent load, maximum tensile and compressive stresses must be retrieved. I was curious to see if there was a way to obtain those values since the OptiReinf component is able to obtain the reinforcing steel which must use a similar technique.

Thank you,

Mathieu


#4

Dear Mathieu,
in the case of the OptiReinf-component the cross section forces get calculated at the face centers. Based on these reinforcement quantities can be calculated.
Did you think about applying Meshloads for simulating the effect of post-tensioning?
Best,
Clemens


(Mathieu Côté) #5

Dear Clemens,
I thought about using mesh loads but generating a mesh from two points selected by the optimizer to orient the post-tensioning line would have been more complicated than just generating a line. The main concern in both cases is to retrieve the section’s thickness, and its stress values (both tensile and compressive) to limit the post-tensioning forces. I am open to suggestions as to how to retrieve those or another approach to design the post-tension.
Thanks,
Mathieu


#6

Dear Mathieu,
at the moment Karamba3D only returns the cross section forces per shell element. In your case it would be necessary to get the cross section forces along sections through the shell. This not yet implemented in Karamba 1.3.1., but on my todo-list for the next release.
As a work-around you could try to retrieve the shell results per face and check which faces are crossed by the post-tensioning cables.
Best,
Clemens