Fishy punching shear results from FEM 2

[milkshakelake]

I have two 8x36 "wallumns" next to two 12x24 columns. The FEM results show a massive overstress in punching shear due to the minor axis moment.

Can I pin these columns to remove the moment? Normally, I don't do this because it's very unconservative for punching shear. But my engineering gut is telling me that these wallumns are almost like shear walls, where I do release the moment. So if it works for shear walls, it should work for this. Visually and intuitively, they're taking quite small loads. But I don't want it to actually punch through in real life, especially when the overstress is this high.

That being said, I'd also like to check this by hand. I think my go-to, the direct design method, is out the window because it doesn't meet the conditions. Can someone guide me in the right direction for doing a secondary check?

The other option is to just remove these columns, but I don't like it. It's a 6' cantilever with heavy SDL (concrete pavers).

 

[milkshakelake]

I finally got back to this. I was able to fix the meshing, but it didn't change the result more than a few percent. I decided to go with KootK's method and check one way shear with a pin-pinned one way slab, and it works. I added a bunch of integrity steel and dowels. Even in the event of a concrete shear failure, I'll have rebar to hold it together. Thanks for all the suggestions!

@HTURKAK I would've tried that method, using more of those nodes, but threw in the towel and did a hand calculation. Good idea though.

@Tomfh SAFE doesn't use tributary area logic; it uses stiffness. I think tributary would actually be a lot better for this particular case, but it doesn't have the option.

@WinelandV @centondollar I did switch to a non-rectangular mesh but got almost the same result. I think in this case, for whatever reason, it wasn't affecting it too much. The software is SAFE. I will keep this in mind for the future. Shear walls are much easier to mesh and line with with rectangles; slabs are a bit more complicated.

@KootK Thanks for the nice explanation. I'm keeping that diagram handy.