What effect does the weight of a wall have on the steel in the reinforced concrete below?

Question

Considering the two options

1. build internal wall on top of 10 cm deep concrete slab reinforced with 7.7 mm smooth steel wire mesh
2. build internal wall on top of 30 cm deep concrete floor joist reinforced with a 24x24 cm steel cage made of 12 mm deformed steel rebar

What effect do

1. the deeper concrete
2. the greater amount of steel

in the floor joist have in supporting the weight of the wall (which I assume is treated as a compressive load)?

In both cases assume that the concrete used is the same grade. The wall is not load-bearing, as the overall structure is a reinforced concrete frame.

Answer 1

The first thing to note is that the wall will not act as a compressive load, but as a load which generates shear and bending on the supporting structure.

As such, the joist will undoubtedly be the stronger option. Both shear and bending strength are highly proportional to height, so the taller and better-reinforced joist will certainly have an easier time withstanding the wall's weight.

That being said, if there are architectural reasons such that the wall would be better-placed directly on the slab, without a supporting joist directly below, that's still fine. Just do the math and make sure the slab can take it (well, you should do the math for the joist too, of course).