Modelling contact using BSURFS

[kammieorama]

I am trying to run a SOL103 in NxNastran v 8.1.

In my model there is are Surface cards (BSURFS)

I have just mentioned BSURFS.

Now SOL103 is running error free but the parts on which i defined surfaces are not acting like surfaces.

I mean in the modal shapes i see them bend independent of each other.

I would like them to act as contacts (like in abaqus)

Is there any contact or surface parameter that i need to add to define the surface that should come in contact.

best regards
Kammieo