Hi,
I want to model a panel (wall) but for de modeling calculation I want to use a Membrane and not a shell. You know that a mambrane only allows deformation in the plane (XY), with out regard of the deformation in the perpendicular axis (Z), like the sheel does.
When I try to change it, in the panel calculation model, it only allows me to use shell, but when I use the help from the progam, it says that i could choose shell, membrane or plate.
Thanking you in advice,
Sebastián Navarro
As Rafal has written there are no tension only surface elements in Robot. The workaround I can think of is to try to reduce the value of IY using the coefficient or define a panel with small thickness. In addition (if needed) you may also freeze the mesh and delete the surface elements under compression after looking at the results of the analysis.
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Ok, I would try to reduce the IY. rigth now, I was trying to use a orthotropic material, but when I used it, with out changin any n factor, i I get insetability type I in all the nodes from the shell.
Why this happend?
I was trying to use a orthotropic material, but when I used it, with out changin any n factor, i I get insetability type I in all the nodes from the shell.
I'm not sure what modification you actually made as in Robot there is possibility to define the orthotropic material properties. If you just modified the stiffness matrix in the definition of the panel thickness then I assume that either the values you entered were incorrect or for such definition the obtained values of displacements were extremely large.
Actually I try to use a orthotropic thikness in any wall, and it gaves me inestabilities in all the internal nodes of the shell. When I use a Homogenus material there is no problem, but when I use Orthotropic, dosen't matter wich one (rib in one direction, slab with trapezoidal plate, etc) it allways give me inestabilities for walls...
The instability can also be caused by large difference in stiffness of elements.