Shell element degrees of freedom?

[illini8181]

Is it generally true that shell elements typically only have 3 DOF per node (rotation about x, rotation about y, transverse displacement) for bending applications, but can have 5 DOF per node (addition of displacement in x and y directions) if they are being used for both bending and membrane stress applications?

I am in a finite element class right now, and am trying to understand my notes... I have been falling into the trap of writing everything down during class, without understanding it. Now it's time to start deciphering

Thanks,

Andrew

 

[ukbridge]

Just curious, are you confusing plate elements and shell elements? Plate elements have 3 DOF thetaX,Y and dZ typically (notation depends on package) and cannot model membrane effects.

Shell elements have 5/6 degrees of freedom, modelling deflection and rotation in all 3 axes. Sometimes for shell elements rotation about the vertical axis can be turned off/on, which is why they usually have either 5/6 degrees of freedom.

You might want to use plate elements to model a floor slab, in which typically only dZ and Mx/My/Mxy are of interest. For modelling perhaps a plate girder for a buckling analysis, shell elements are appropriate as lateral deflections will clearly be of importance. In my industry (Civil/Structural) I typically just use shell elements for even complex models, as the analysis takes very little time these days with either element type.

I'm not a FE expert/pro, but hopefully some of this might be helpful to you.

 

[illini8181]

Thanks ukbridge, you are right. I was confusing the two.