File Storage?

[SteelPE]

I have a structure that I recently designed and is currently under construction. The building is a medical office and was designed using the IBC 2009 with a floor live load of 80psf (we use 80 vs 50 (live) + 20 (par)). There is now a tenant who would like to have a file storage room added to their layout (this after we specifically discussed file storage in meetings and how it wasn't needed). My question is how to figure out if the file storage overloads the floor.

If you figure the actual load of a cabinet on the floor we are talking about 200psf which is nowhere close to working. However, if you add up the total weight of the storage area and then divide it by the floor area it takes up you are looking at a load of 40psf. Now this doesn't figure for any LL around the cabinets which would need to be added.... say at 50psf. Floor construction consists of steel joists at roughly 2'-6" o.c.

How do others figure the effects of file storage on their floors?

 

[JedClampett]

Why don't you work backward and tell them how much the floor can take, post it for that (125 psf, 140 psf, etc.) and have them limit their files?
Once you call the place file storage, someone in the future might go up to the code limit.

 

[SteelPE]

Backwards isn't going to work. I tried having them reconfigure the area and they have refused. The next step is to reinforce the floor accordingly. I was thinking about making the area 125psf.... but wasn't sure if I was over reacting.

 

[kylesito]

We have had it a few times and looked at it as isolated line loads on the floor. This was probably the most conservative way to approach it. If I remember correctly, we also determined that the load / area was below the allowable floor load, but we determined that it was necessary to look at each storage rack as a line load. In the case I am remembering specifically, we ended up sistering up almost every joist and reinforcing each beam to get the load. It's amazing how heavy these things can get.

Is your case a moving storage system? We have had those too and it presented a very unique challenge to a building engineer.

PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi

 

[SteelPE]

The reason why I bring it up at meetings for medical office buildings is because of a project I did 5 years ago where the client wanted to add rolling storage to a floor we designed. It was a huge PITA and I ended up with some engineer who worked for the GC telling everyone I over designed the floor (I added joists into every other bay like you did). I told him that if he wanted to take responsibility for the floor he was more than welcome to approve the design which I would specifically exclude on my final report. Never heard from him again.

In this instance, it doesn't look like rolling storage at all. Just a bunch of cabinets of different sizes with isles in-between. It's kind of late to be bringing this up as the building is almost finished.

 

[Archie264]

There is a big difference between individual storage shelves and high-density, rolling storage shelves. Individual storage shelves have to be accessible so there is a practile requirement that the floor space in front of them remain empty. And in that case the average floor loading often falls within the design parameters, assuming the individual members underneath the load can handle it, through load sharing or otherwise. And remember to check for punching shear, if applicable.

Rolling high-density storage, on the other hand, can be bad news. They are called "high-density" for a reason. The equipment salesman will try to justify them claiming that while the floor in the storage area is loaded to, say, 200 psf, the remainder of the room is unloaded so it all evens out in the wash. Don't fall for it. Unless he plans to post a sentry there for as long as the storage equipment is there, at some point the remainder of the bay will also be loaded; nature abhors a vacuum. In short, it's ill-advised, in my opinion.

Also, ASCE-7 has some provision for allowing the overloading of one bay if the other bays are unloaded, but I'm of the opinion that that approach is hare-brained...er, ill-advised, I mean.

 

[dcarr82775]

When we have looked at adding file rooms (not rolling file systems) into existing buildings we have taken the approach Archie264 mentioned about accounting for the aisle space at a much lower load.

 

[JAE]

I think what you figured out above is a good approach. Calculate the actual weight of the cabinets and use 50 psf between them.

This might get your floor to work globally but you also need to look at the local issues with floor slab - or if individual joists are aligned with a line of cabinets where it gets the heavier load along its length.

Also be sure to determine whether the file cabinets are traditional types or if they are fire-safe cabinets which can be much heavier.

 

[SteelPE]

We were given the loads for the cabinets including the length and weight in a CAD file from the architect. After I looked at the floor again, it appears as if we have some additional capacity in the joists due to the fact that we used a 26K5 joist which is capable of supporting 419/165.

The cabinets run parallel with the joists. I also suggested turning them 90 degrees which was shot down by the owner. I guess if I suggest either adding additional joists in-between the existing or turning them 90 degrees which I can get to work.

I just wanted to make sure I wasn't being to harsh on the client.

 

[dik]

Depending on the type of storage, 125 psf may not be adequate. Many dedicated storage areas can have 200 to 400 psf loading... I've seen 8 drawer high filing cabinets on tracks so they can be compressed with no walking space between the cabinets and they are 'wheeled' out to provide drawer access...

Dik