Allan,
As you know I would agree entirely with your first comment in your first reply.
Regarding more efficient load paths generated by FEM analysis, yes this is also correct. The important thing that is often missed by designers however is that the slab must be reinforced in a manner consistent with the load path generated by the FEM analysis. Reinforcement must be supplied in the slab to match the pattern of the bending momets, not based on averages etc.
If the reinforcement pattern does not match the FEM bending moments, redistribution will occur which could reduce the accuracy of the original analysis and load path. Obviously, minor variations to make a slab constructable are ok but the more irregular the slab, the more important it is to follow the FEM load path and this is dependent on the user knowing what he is doing, the software cannot do it for you.
Calculor
RE Thin slabs by FEM,
Designers must be aware of the calculations that are being done by the FEM software and the relative accuracy of the results. REM analysis does not mean that concrete design results reported are accurate. The "design" is a separate addon after the analysis.
For example, if you do a flat slab design in most (not all) FEM programs, the deflections reported will normally be based on uncracked sections and will not allow for long term effects. Some programs may apply a long term factor and some may attempt to fudge cracking effects and a couple actually try to allow for cracking and long term effects.
If the program is reporting short term uncracked deflections, the real deflection could be 6 to 10 times as large as this value.
The designer must be aware of what the software (not only FEM based) is doing and what its results really mean and how they should be modified to be used in design decisions.
I know of many cases where the designer didi not reralize this resulting in slabs with excessive deflections.