Movable filing cabinets 1

[strucguy]

I have a composite floor system that needs to be strengthened to accommodate high density filing area for movable cabinets. What typical load and deflection criteria should I be using for designing my floor framing. The owner hasn't picked a manufacturer yet. So, I am using a floor live load of 200 psf and a live load deflection limit of L/480. Let me know what your thoughts are? Thanks in advance.

- strucguy

 

[StructuralEngGuy]

I recently had to do the exact same thing. I think you'd be safer using a LL of 250 psf for heavy storage. However, keep in mind that movable storage units generally run on tracks (line loading) which will very likely be worse. The cut sheet I was given during construction listed a line loading of 750-800 lbs/ft and required live load deflections be limited to L/700. I was also given the attached document. You may find it helpful.

 

[PEinVA]

StructuralEngGuy,

The attached document you provided seems to only account for the file load in the example. This is nto true. You still need to account for a live load capacity of the area not occupied by the filing system. This is an engineering judgment call, but should we never use less than 30psf because if there is space to walk, there is typically space to store more boxes!
In these applications, we typically have a live load from the storage and a "walkway" live load.

Just my two cents.



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[jike]

My experience also says to use about 250 psf for the high density movable files. We do not typically add any extra in for personnel since when the files are separated and a person is accessing them, the file load is not on that portion of floor where the person is walking.

 

[strucguy]

Thanks so much!! I guess I am going to bump the live load to 250 psf. Any other thoughts on deflection criteria. Seems like L/700 for this kind of loading is very conservative. Any thoughts??

StructuralEngGuy -

That was very useful piece of information. I am going to ask the architect to get me something like that before I finalyze my design. Thanks again

-strucguy

 

[enginerding]

How much adjustment is available in the tracks?

 

[strucguy]

I don't have the manufacturer or model information yet. But, the owner wants to know the possibe impact on the framing. The architect has indicated that he has seen engineers using 200 psf live load in some of his previous projects. He couldn't provide anymore info than that.

- strucguy

 

[MiketheEngineer]

200 - 250 psf seems reasonable see IBC 2006 -- see table 1607.1 etc. - but it is your call. I think IBC also requires that the floor can handle a single 2,000 lb load.

Deflection of 1/700 seems a bit conservative unless you some special flooring needs - tile, marble ,etc. or the track system cannot take more than that....

Good Luck!!

 

[StructuralEngGuy]

The L/700 requirement is based on the fact that they want little deflection in the system I was designing for. The storage units roll on tracks and I'm assuming they don't want it to get stuck if the deflection is too high. I agree with Jike about not adding any other loading for people.

 

[vandede427]

unless you're able to allign the rails over the beams (highly unlikely) make sure you check the concrete deck for the loads, not just the beam framing.

 

[lkjh345]

The L/700 requirement is to limit the floor deflection under the track, otherwise, you will be trying to the roll the storage unit uphill.

vandede427 is correct. I've had to check existing floors for new high-density file systems many times. It is often the deck that is the problem. I have often had to add deck support from below ( when access to the underside is available) or place tubes under the rails that can span from beam to beam to take the deck out of the problem.

 

[JrStructuralEng]

I just did one of these. 200psf LL covers an average mobile storage unit when they are spread out over their operating distance. However, keep in mind that when all the units are rolled to one side the resulting area load is often much higher. I have found when all units are pushed to that typically results in the governing load case in many situations.

I agree L/700 seems very unrealistic. I have installed several at l/360. At L/700 a unit that covers 8.5ft would only allow for 3/32" deflection. That seems very conservative.