Here's a situation that seems to come up frequently: I create a model in STAAD that includes a combination of linear elements (for things like beams, columns, etc.) and plate elements (to model surface elements like floors, roofs, etc.). When surface elements get meshed, the attached coplanar beams or columns get broken into many small segments, which is fine. The problem is that the attachment of each plate element to each linear element defaults to full fixity at all nodes. This has the effect of creating full composite action between the linear and surface elements. In many of my cases, the actual structure does not have full composite action between these elements (certainly not to the extent that generally happens in the model). As a result, my model is then un-conservative in this regard. I don't want to be selecting section sizes based upon the strength increase that comes from false composite action. Is there a slick way to somehow release the plates from the attached linear elements so that out-of-plane loads on the plates are still transferred to the linear elements, but shears and moments are not? I don't want to release shears and moments between pairs of adjacent plate elements - just between the plate elements and the attached linear elements. However, I also don't want to have to get too fussy with releases. Trying to figure out node numbering and plate orientation based upon the local axis seems like a royal pain in the neck. Is there a simple way to do this? If it's too complicated, I'll just stop using hybrid models. Anybody got a good solution for this?
Dave