Concentrated load on continuous one-way slab near supporting beam

[CrabbyT]

I have a situation where I'm trying to shore up some concrete encased roof beams so that a contractor can use them to lift a tank. It's a 2-story building with a basement. The diaphragms are composed of one-way cast-in-place concrete slabs (~5" thick, no form deck). The building steel is encased in concrete, and the slabs are tied into the concrete that encases the steel.

The intent was to shore the roof beams all the way down the 1st floor where they would land on the concrete-encased beams that will support the tank. The contractor missed this detail, and now one of the shoring posts is sitting on the 1st floor slab, and not over the beam. The east edge of the base plate is aligned almost exactly over the top of the beam's west edge. Shoring down to the basement slab is not viable.

Before jumping straight to the "you guys need to re-position your shoring post" option, I'm trying to check whether or not this is going to work. You guys have any advice on how I might analyze this? Based on how close the concentrated load is relative to the underlying beam (the critical section perimeter around the base plate is partially sitting over the beam), are there any considerations regarding punching shear? Or, am I overthinking this and should I just check one-way shear with a 12" wide design strip and check punching shear based on the critical section perimeter? I'm thinking that the slab is basically in a "fixed-fixed" condition and in reverse bending at the beams, except the beams are like springs that would deflect a bit under load and I'm not sure what effect a large concentrated load would have in this area.

 

[KootK]

A punching shear check based on plain concrete would be my first stop. As you intimated, punching failure is likely to be a 3 sided thing in reality with the side closest to the beam delivering load straight to the beam more or less. It's tough to evaluate that benefit robustly however.