# Shell and beam joint

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hi i am new to karamba, i have question about shell and beam connection. as seen in the picture, i applied, 4 in plane tension on the shell and a point load. Shell structure is very thin ETFE film, and i want edges of shell the displace with the beam(stays on the beam).
1.i tried mesh brep after reading some discussion here, not helping
2.i also tried to input supports on the edges of the shell, but not helping when beam displaces shell edges stays unmoved
3.i tried beam joint agent. could not really understand how it really works

someone help me thanks

i am not a native speaker so, sorry if it is difficult to understand 11.17normal frame.gh (83.1 KB)

Hi @ayca5855, if you change the âgirderâ elements to the exact geometry of the mesh edges, you will then see that these elements are now connected to your mesh. This is because Karamba needs to know that the elements are geometrically connected at the nodes.

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thank you so much, can i ask you simple question again?thanks.
i wanna put initial load on the shell, tensile load on the edge of the shell. as you seen before, i made small mesh within the mesh surface and applied force in x,y direction. but tensile force supposed to stiffen it and decrease the displacement, but in my model mesh tensiles loads actually increases it.
i tried initial strain component, but only initial forces are know which is 10N/mm, hence i dont know eps0 and kappa0. help me pls, again sorry for asking such a basic question.

Hi @ayca5855,
if the membrane has a thickness of âtâ [cm], its material a Youngâ Modulus of âEâ [kN/cm2] and the prestress normal force shall be ânâ [kN/cm] then the strain you nee to apply is eps0 = n/(t*E). This is based on the assumption that the membrane is rigidly held at its perimeter. Since the edge beams will deform, eps0 needs to be increased accordingly.
If the membrane is very thin use membrane elements from Karamba3D 2.0.0 (see here, set âbendingâ to false at the âMeshToShellâ-component) otherwise you will face numerical problems in your calculation. Set a positive initial value for the membraneâs NII-force via the ModifyShell-component. In order to see the stiffening effect of in-plane forces use second order theory analysis.
â Clemens

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@karamba3d, Clemens, thank you so much

sorry for bothering you again and again i have been trying to solve this on my own but still facing problems.
i had installed Karamda3d 2.0.0 as you told me to, and set positive initial value for NII-force via the ModifyShell, as you instructed.

But i when i set âbendingâ to false at the âMesh to shellâ , i got warning in my analyze Th2 saying âThe structural system buckles in 256nodesâ etc. plus even i applied minus Zvector point load in the middle of the shell, it actually moves up.(i attached a pic)

if i set âbendingâ to âtrueâ, warning is gone plus, shell displace downward(like in the pic). Help me, spent days trying the solve this.

11.24normalframe.gh (77.7 KB)