Can I add large UPS battery rack system to existing 2-way slab

[scb111]

Hi. I'm working in a university setting as a structural consultant. I have been asked to look into the possibility of adding a UPS system to a server room on the 4th floor of a relatively new (3 years) concrete building. The slab is 9" thick, f'c=4000 psi, and the design LL=100PSF. The bay (corresponds to room size) is about 20'x28' with 18" square columns-no beam framing. The UPS system comes in 3 pieces weighing 860 pounds (36"x32"), 2350 pounds (43"x32") and 4795 pounds (44"x32") and must be placed adjacent to each other. That largest unit is 492 pounds/square foot. And the whole room is on a raised floor. There are also numerous existing racks within the room weighing 400-800 pounds each and an AC unit weighing 1300 pounds. Should I be concerned about placing this UPS system within the room? What is the best way to analyze this?
Thanks for any help you can offer.

 

[kslee1000]

Looks like a good topic for "Senior Design" in the engineering department. Don't you have one there?

 

[jike]

Sum everything up in the room plus 50 psf on unloaded areas (aisles, etc.)and then divided by the total area. If those loads average out to less than 100 psf, it is probably OK.

You also, however, need to use some judgement, regarding heavy loads concentrated in one area only. You might need to calculate those also to make sure that you do not have one area overloaded.

 

[kslee1000]

Since you have many heavy equipment spread all over the place, I would consider them to produce effect similart to uniform load. I will sum the loads by "weight averaging method" (I hope I know what I am talking about), divide by the floor area, then compare the result with the original design load. If it is withing a few percentage (say 5-10%), I probably would give a green light. Otherwise, you have to perform a rigorous analysis.

 

[kslee1000]

"Weighted Averaging Method"?

 

[JAE]

[blue]Should I be concerned about placing this UPS system within the room? [/blue]

Answer: Yes, it should be checked with consideration for 1. Flexural moment (and how it is distributed across the floor between center and middle strips)
2. Shear through the slab (based on the placement of the applied units across the floor)
3. Punching Shear through the slab at the column (punching shear that is included with shear from unbalanced moments at the columns)
4. Potential column bending due to units placed near a column on one side of the column.

[blue]What is the best way to analyze this?[/blue]

Answer: If you don't know how to do any of this, see kslee1000's first response above.

 

[kslee1000]

JAE:

Wish you are still in the "Senior Class" to handle that .

 

[PEinc]

"And the whole room is on a raised floor." If the UPS is sitting on top of the raised floor, you need to check the both raised floor AND the concrete floor. Even though the concrete floor MAY hold the load (or even the averaged load), the proposed UPS equipment may crush the vertical supports for the raised floor.

I'm just curious; but if you are the "structural consultant," why are you asking this question of others?

 

[kslee1000]

Consultants do the talk, staff engineers do the work.
No offense intended. I have been both

 

[apsix]

There has to be a structural engineer involved to check the capacities.
That might be you, scb111, or bring in an external consultant.

 

[JAE]

...hey... I know - load test it till it fails!!






(sorry - just getting carried away)