Point loads on form deck/thin concrete

[Fatboycowen]

I have an office building currently being occupied by a hospital as a secondary building (not the main hospital). They want to put Hyperbaric chambers on the 3rd floor (moving them from the ground floor).

The chambers roll on 4 wheels, and weight 2500 lb with patient. The wheels are small (maybe 5" dia, 1" wide) hard rubber casters, so the loading area is small. Each wheel is about 633 lb. Spacing is not a problem.

The building was built in the late 80s, and built as an office building, not hospital. The floor is 9/16" 28ga deck with 2.5" total thickness NW conc, with 6x6 w1.4/1.4 wwf. Bar joists are 2'-6" o.c.

The beams and joist are found to be capable. However, i am having trouble justifying the point load on the slab. I used the SDI's suggested approach for equivalent distribution area for point loads. I am finding that punching shear is no problem, but bending is.

I am curious is my approach is correct. The SDI tables show a load capacity for the concrete slab, of 212 psf. I found the width of beam strip (effective width) to be about 6 inches based on the SDI formula. I am using the equivalent point load to convert the uniform (212 psf) to a midspan point load. I am getting very low numbers.

Am i using the correct approach for bending? Are there any other suggestions? 633 pounds does not seem significant, but the numbers just can't justify it. Any advice?

Thanks in advance.

 

[delagina]

you can use this program..

 

[Fatboycowen]

Thank you delagina!

Question: This program has 1.5" form deck in 22 gauge as the minimum. Does it seem appropriate to use this, plus 2 inch topping with my reinforcing for this problem? I selected to neglect the shear capacity of the deck.

This seems appropriate, as it states that the form deck does not add structural moment capacity to the slab.

Thanks again, this is awesome!

 

[a2mfk]

If that ends up not working I have had similar projects where we used steel plates on top of wood 8x8s and they very slowly moved the equipment down the hallways. If you can easily field locate the joists then you could place shim plates on top of the floor over the joists, and then bridge over top of these plates so you are not putting point loads into slabs.

Or just have them roll it REALLY fast!

 

[BAretired]

The part that confuses me most is that Fatboycowen considers this bit of information to be awesome. It is unclear to me how anything in this thread justifies the original design. Perhaps someone would be kind enough to explain it to me.

BA

 

[Fatboycowen]

@BAretired:

I found it awesome that this excel spread sheet was a way of confirming my original calculations. I was unsure if the approach i was taking was correct. This is the first time i have worked with the SDI equivalent distribution for thin slabs like this. I am thankful for these forums for this purpose.

@a2mfk:

This is the approach we are now shooting for. We will put down steel plates, possibly shimmed, to either spread the load onto the slab, or span between joists (still working on the solution). The room will then be partially built up to the level of the steel, so that the floor is uniform. The units will be moved on plates or large timbers.

Thanks again for everyone's help. I was simply looking to confirm the results of my calculations, which is exactly what this did.