CAE has problems when you modify a part in different modules. Features will disappear and these parent/child problems appear. In general try and do all modifications in the part module and delete any features that have been lost. When you look in the feature list you should see a 'clean' list of features with no errors or suppression. That should give you fewer problems later on.

corus

Thank you for the response Corus,

Going even more fundamental than this...

Would you look to make it using the following methods :-

1. make each web and flange seperately as parts, then bring them into an assembly. Thus for an I beam, you'd have 3 "parts", and a 4 sided frame would have 12 parts.

2. Make each piece of metal as a seperate part, for an I beam, you'd have only 1 part. and a frame would have 4 parts.

3. Make the whole structure as a part? Thus having a single part in the assembly.

regards
Mikey

In case it makes any difference, it's a fabricated structure.

I would always try and make a single part as this avoids messy constraints to tie structures back together again. This gives a slight error at the connection between web and flange using shell elements but it's negligible.
For a 3D shell model you can sketch a wire drawing and extrude this to make up the I section in shells. Similarly for the frame. For more complicated 3D shapes, extrude edges from the basic shape you've defined.

corus

Cheers Corus,

Up and running

Mikey