We modeled a tunnel using two rings connected with links to simulate shear springs.
Increasing 10 shear springs to 180 increased the forces significantly. Increasing the number of springs shouldn’t increase the forces since the spring values with multilinear elastic stiffness ku2 and ku3. The stiffness is derived from the spring per unit length of the cross section. e.g. ku180 = 18 * Ku10.
We don't want additional links to transfer more forces, instead the idea was to distribute and reduce the forces.
I saw a similar post with a similar problem without decent answer: http://www.eng-tips.com/viewthread.cfm?qid=234314.
I tried changing the length of the link and the length dj. I obtained no change.
I tried frames instead of links. I tried this option by assigning a value 1 to the modifiers shear area 22 and shear area 33. I obtained the frames didn't transfer forces at all in any direction.
Any suggestion is welcomed.