sig-max[kN/cm2]values utilization of elements component in Karamba 3D

Hey there,

I’m having a tough time wrapping my head around the sig-max value from the utilization of elements component in Karamba 3D. Would be grateful if someone can help me out a bit. It seems that at the moment this value is calculated by adding σ = [N/A (axial dir) + M/W(of y) + M/W(of z)] (1) . Shouldn’t the bending stress values be of resultant of the stresses in the y and z direction instead of just adding them up?

Hello @r.hora,
the stresses N/A, My/Wy, Mz/Wz act on the same plane in the same direction. Therefore they can be added.
– Clemens

Hey there Clemens!

First of all thank you so much for this lovely software, have been testing it out and is extremely useful for my applications. Am extremely excited about the new release as well!

Secondly thanks for the quick reply! I do apologize for not giving you the full picture but I guess my doubt is to do with circular cross sections. I feel like in the case of circular cross sections where Wy=Wz, the max stress due to moment should be closer to Sqrt(My^2+Mz^2)/W. Adding My/Wz+Mz/Wz would jsut give a much larger value.

Regards

Hello @r.hora,
yes you are right. In the special case of circular cross sections one needs to form the resultant moment first, and then use it in the formula sigma = M/W. Adding the contributions of My/Wy and Mz/Wz is based on the assumption that the corresponding stresses act in the same point which is not the case for circular cross sections.
– Clemens

Understood, thanks for the quick reply!