modeling a ribbed floor

[aliante]

Sorry, I posted this in another group . I'm new and I made a mistake. Perhaps this is the right place to post it.I beg pardon.

I'm trying to model a reinforced ribbed floor concrete and I've found the thread801-171434: Modelling Slabs and beams in SAP2000 very useful but I haven't understood when Stressed says "frames offset from the slab and connect them using joint constraints," . Which kind of constraints ? When we link the slab and the frames in the same node aren't they already constrained with "continuity" I would mean "congruence"?
I hope Stressed or whoever will help me clarifying it.

Furthermore, if I join the slab and the rib as beam in the midplane , I mean after I've calculated the real moment of inertia of the T-beam so the rib-beam plus the slab in their midplane have the same moment of inertia, what kind of physical entity would I lose?
Thank you very much in advance for your help.
Aliante

 

[mikyamero]

http://www.si-me.com/

 

[aliante]

Hi Mikyamero,
I've visited the site you adviced, but I haven't found the answer to my question or perhaps I haven't understood your suggestion. Please, could you explain more clearly.
Best regards,
Aliante

 

[stressed]

you can experiment with Assign>Frame>Insertion point by reviewing the difference in results between the default centroid and 8 Top center. By making insertion point assignments (aka cardinal points), SAP will automatically create internal constraints based on section and type of insertion point which will affect calculated moments.