Simple question on cylindrical support [solved]

Hi guys,
I'm really new to CAElinux so please forgive me if I'm going to post an elementary question.
I need to constraint a cylindrical surface to simulate a bearing support.
To this end, using Ansys, you should rotate the nodal coordinate systems of the nodes on the cylindrical surface into a previous created cylindrical csys and then set dx=0 (as x represents R in cylindrical csys) for these nodes. I guess Code Aster provides a similar procedure but I have no idea of what it is. Could someone give me suggestions for managing this problem?
Thanks in advance<br /><br />Post edited by: theCapitain, at: 2010/07/27 10:25

Thanks Claus for the prompt replay.
Maybe I haven't explained very well. I have a cylindrical surface (like a shaft) and I want to keep its rotation free, the axial displacement may be imposed or not, doesn’t matter. You must think in cylindrical coordinates: rot free; R=0; z as required.
I cannot impose X=0 and Y=0 on the face in global Cartesian csys because this prevent the shaft's rotary motion.

Hi Calus,
you are right, that's the case, I have to impose the displacement and imposing dx=0 and dy=0 results in preventing shaft's rotation.
Linking the cylindrical surface to a single node is an excellent solution that, among other things, doesn't stiffen the shaft on the bending plane (so you are that Claus huh? Congratulations men!).
Anyway, while I was trying to solve the problem reading the documentation (with extreme difficulties: my French is very basic) I've found a way similar to which I was thinking when I started this topic:

char=AFFE_CHAR_MECA(MODELE=mode,
FACE_IMPO=_F(GROUP_MA=bearing,
DNOR=0.0,),),);

so the tangential DOF of the surface's nodes (DTAN) should be free. Am I right?