I dont really understand what you mean by this. However, this is not an issue at the moment and I might contact you again regarding this later when I start working on the nonlinear model.

I mean that you can use the same strategy I used for connecting the walls (shell) and the podium (solid).

You keep 2 geometries detached (main structure and slabs), then you create an interaction between the slab's edges and the main structure's walls and columns (excluding the connecting beams). This interaction will have an equalDOF in all 6 DOFs. By doing so, the slabs and the structure will be effectively "linked" everywhere but in the connecting beams.

When I run the model I am getting this error.

TimeSeries *getTimeSeries(int tag) - none found with tag: 0

Yes, you need a timeSeries: OpenSees does not allow a loadPattern without a timeSeries. A timeSeries is what tells the load how should evolve in time.

The bodyForce only works with continuum (solid 3D or 2D) elements. It's directly input in the definition of the solid element, and it computes the vector of external forces given by the bodyForces when computing the unbalance vector.

Note: the bodyForce in the element definition is ALWAYS applied instantaneously (because it is not associated with a timeSeries, where you can instead use a linear timeSeries to make load grow linearly)

So you have 2 options:

**BodyForce(in solid element property) + FaceForce (in condition on faces, in a loadPattern before the gravity analysis)**

The BodyForce will be applied instantanously, while the FaceForce will follow the timeSeries you use in the loadPattern. So, if you want to be consistent, the loadPatterm should have a constant time as well.

Problem: both loads will be applies instantaneously. If they are large and trigger non-linear behaviors, it can give convergence issues that cannot be solved using adaptive time steps (because the timeSeries is constant!)
**VolumeForce (in condition on solids) and FaceForce (in condition on faces), both in a loadPattern**. In this way you can assign a linear TimeSeries and both will evolve incrementally (ideal for nonlinear analyses)

The two approaches are theoretically equivalent. VolumeForce is an STKO automation that takes a force-per-unit-volume from the users, and converts it into equivalent nodal forces using the shape functions of the solid element. Exactly as OpenSees's solid elements do with their own body forces