I am modeling a concrete slab supported on concrete beams. The beams are "beam elements" given a defined width (ZD) and depth (YD). The slab is a plate element, sharing nodes with the beams. The slab and beam system share the same centerline (3D render). I use the "offset" command to drop the beam down a distance so top of beam is same as top of slab. In reality, the beam reinforcing will extend into the top of the slab.
My question: Should I reduce the depth of the beam (YD) so the plate (slab) depth will essentially "act" as the top portion of the beam, after "offset?" (Will the beam and slab elements automatically work together as a section)?
Or: Should I keep my beam defined as it's intended depth to model the actual beam stiffness? (in this case, after "offset" the slab-plate element will overlap the top portion of the beam, possibly giving an increased false stiffness).
Thanks!
Model the beam considering the full depth as YD and do not deduct the slab thickness from it because if you do so, when designing the beam reinforcement, the software would only use the provided YD for calculating the effective depth. It is true that the plate and the top of the beam would overlap but my personal opinion is, it is not a significant source of error and may be overlooked. I have seen much more complicated modeling being attempted by stopping the slab short of the beam centerline and then using rigid links to connect the slab to the beam centerline etc. just to avoid accounting for this additional stiffness, but these modeling techniques introduce more artificial stiffness in the model and is simply not worth it.