Very Heavy Load at First Floor vs. Roof Variation: Why Does ETABS Seem to Flip Moment and Axial Results?

[darrennthnl]

I have 2 variations of the same structure:
Variation 1: Very heavy live load (24 kN/m2) at the first floor (one floor above the base)
Variation 2: Very heavy live load (24 kN/m2) at the roof.

ETABS gives higher axial compression on variation 2, and higher moment on variation 1. Both maximum axial and moment happens on the same column (on the first floor) and due to the same load combinations.
However this does not make sense to me logically, as I think variation 2 should have lower axial compression because the load has more chance to redistribute the axial load, and variation 2 should have higher moment as the moment arm to the load is bigger.

What is the reason for this? Can anyone help the reasoning behind the results?

 

[human909]

Load paths, load paths, load paths. Chase you load paths.

You are looking at two scenarios and only look at one point. You are also giving us ZERO information to work with here.

Chase your load paths from the load to the multiple reaction points. You'll find an error or your answer.

 

[jayrod12]

Assuming, perhaps wrongly, that this is a concrete structure, the higher moments on the column in variation 1 make sense. It's due to the unbalanced slab moments.

The higher axial load is a bit odd to me, but as @human909 indicates, follow your load path. Run some numbers by hand, don't always blindly trust the answers coming from a program.