Existing building equipment loads.

[SteelPE]

I designed a building a few years ago that was constructed and is currently occupied. The building is a 3 story office building with a design live load of 80psf. The building is currently occupied by medical offices.

Every few month I receive a call from the owner saying that their client would like to add x piece of equipment that weighs x lbs. I drag out the drawings and try to accommodate their wishes while maintaining the original design live load. We usually go back and forth until we settle on a placement.

My question is in regards to the design live load and applied equipment. Could the equipment be considered live load and therefore when checking the floor could I take a reduced live load on the floor? Every time someone adds a desk or a cabinet we don’t check the capacity of the floor. What do others do in this instance?

In this particular instance I have some additional floor capacity since office loading is typically 50psf and we have no corridors in the area in question… but this is beyond the point I am trying to ask.

 

[jike]

Depends what it is......

I assume you are asking about medical equipment hung from a ceiling or supported directly on the floor. Worst case might be rolling storage for X rays (typically these files exceed floor loadings and best to locate in basement if possible), although with the computer today I suspect they are using these files less and less. I assume also that you have a mechanical room for specific building HVAC equipment but your question is not about this type of equipment.

For floor supported medical equipment, I include the specific equipment weight plus the weight of a person on it plus 40 psf in the unloaded area around it (for personnel). For hanging loads, I include the specific equipment weight plus the weight of a person on it plus floor load above. Hopefully, this works out to the 80 psf or less.

 

[SteelPE]

Jike,

In this instance it is some sort of camera, will weigh 1800#, and be supported on the floor.... but could be anything. This camera is going in an exam room. I going to try to get the client to center it on a girder that is under the room, but I probably have a better chance of hitting the lottery than this happening. If they can do this than the floor will be fine, otherwise I have to find another way. Trying to keep the full 50psf plus the weight of the equipment seems a little conservative to me.

 

[jike]

I believe the unloaded part of the floor should have something.......for incidental live load. What is adequate? 20 psf, 25 psf, 40 psf or 50 psf?. I agree that 50 psf is too conservative. Obviously, do not include the incidental live load where the equipment footprint is located.

I would also have a dead load allowance for nearby walls.......10 psf, 20 psf?

This analysis often comes down to judgment.

 

[Triangled]

I'll dip into live loads without too much concern for floor mounted equipment. I figure that people and equipment will not likely occupy the same area, unless it's McDonalds Playland (in which case I'd quadruple everything and then multiply by 10, and perhaps after that consider a factor of safety of 2).
For limitations, I'd consider such things as existence of other equipment in area, likelihood of partitions, how much the live load may be reduced for girders and columns, the likelihood of all of the live load occurring at one time, maybe even a local seismic load resisting connection.
In one case much like yours, 80 psf live load, computer servers added, when I took some live load, the Building Depth said fine, after discussion, and required a placard mounted in the room stating "Live Load not to exceed xx psf in this room".