beam section dissappears when adding a shell

[pingus]

Hi,

I'm trying to model a 3D-frame with a slab on top for my master thesis. The frame is modeled with wire - B31 elements, and the slab with shell - S4R elements. The problem is when I draw the slab on top of the frame, all the elements in the same plane as the slab disappears. So the horisontal elements, functioning as supports to the slab, seems to be converted from wire to shell when I do this. Thus the frame effect is gone.

Pic. 1: frame[

http://files.engineering.com/getfile.aspx?folder=2ff4b6a0-2dbd-49d3-8615-8148008a8581&file=frame.png

]
Pic. 2: frame + slab [

http://files.engineering.com/getfil...3c-4f26-a1d8-3ff8a15e3310&file=frame+slab.png

]

It's a large model, so it will be time consuming to make the frame and slab as separate parts and then use constraints or connections to connect them.

Anyone got a proposal for a solution to my problem?

Thanks!