I ran your file with the CONNECT edition (v6.0).
1. I’m not seeing anything that I would call excessive reinforcement around the innder triangular core, not parallel to the walls, nor perpendicular.
Since the slab terminates at the wall centerline and since the design strips also extend to the slab edge (rather than stopping at the wall face) it’s going to be hard to have bars with any development at all. One consequence of this is that the program bays may be anchored at the edges. I generally prefer to model the slab edges to the far side of the walls and strop my strips at the inside face to help alleviate this problem.
As sent, the walls are “compressible” and “not shear walls”. Compressible means that vertical deformation of the walls is possible (i.e. shortening of the walls under compression), it does not mean that the walls are compression only members (tension is still possible). Not shear walls means that the slab can slide around along the top of the walls, but not lift off.
The geometry is complicated enough with a triangle of walls that it’s difficult to say for sure why these settings make such a difference without looking at it strip by strip, comparing the envelope demand forces, etc.
2. AS 3600-2009 8.1.6.1 implementation notes are below:
Cross sections within 1/6 span from supports or 1/6 span from midspan are considered “at critical sections”.
- If the design section is not declared as post-tensioned in the design section or design strip segment, then the Pe/Ag and Pee terms of 8.1.6.1 are assumed to be zero (even if the cross section includes tendons), where Pe is the total effective prestress force considered.
- Cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section.
- See ““Cracking Moment” Used in Design Calculations” for a theoretical discussion of the “cracking load”.
It’s a little simplistic to say that 8.1.6.1 rebar indicates a need for more strands, but having more, or draping them to better balance the forces is the first solution I would consider so long as that’s practical and does not lead to an overbalancing of forces.
3. Triangles are really tricky because the strips in some direction always end up meeting at acute angles. Your strip layout seems quite clean in my opinion. For some strips, e.g. long. Strip 73-1, you may want to force the program to consider a support condition at the end of the first segment.
