Data Center Equipment Access Walkway Live Load?

[Mike Mike]

Hi all, what is an appropriate live load for a data center walkway? Owner is adding large racks for servers, batteries, electrical, etc to an existing multi-story concrete building, and access is restricted to service technicians. I've already accounted for all the equipment. I just need to know the live load to apply to the walkways through the racks.

I read through the code and commentary and didn't see any guidance for my situation. ASCE-7 prescribes 40 psf / 300 lbs for maintenance access catwalks. 40psf makes sense for localized design, but I don't think a typical 20' x 20' bay is going to see more than a couple workers at a time.

 

[SlideRuleEra]

1} ...40psf makes sense for localized design, but I don't think a typical 20' x 20' bay is going to see more than a couple workers at a time.

2) Data Center Equipment Access Walkway Live Load

1) ...and those workers may (will) come with tools and carts carrying replacement servers, parts, (heavy) batteries, etc.

You can probably justify 60 PSF, if you add a 500 lb. concentrated load requirement:

2) Of course you could just go directly to the exact requirement per ASCE 7-10 (the most recent I have)...
100 PSF and 2000 lb concentrated load:

 

[Mike Mike]

Slide Ruler, it would seem the allowance for computer use access floor systems is intended to include the computers themselves.

60psf over a 20' x 20' bay is 24 kips, and forklifts don't fit on the elevators.

 

[OldDawgNewTricks]

For heavy equipment rooms in a new facility, I usually design the whole floor for the equipment load so the owner has flexibility to rearrange things later. For an existing facility, you could try to justify using a lower load for aisles between the equipment if you are having trouble getting existing framing to pencil out. But also consider whether the aisles could be used as travel paths for moving the equipment in and out. I typically try to use a minimum of 100 psf / 2,000 lb for this case.

 

[SlideRuleEra]

...it would seem the allowance for computer use access floor systems is intended to include the computers themselves.
60psf over a 20' x 20' bay is 24 kips, and forklifts don't fit on the elevators.

Take another look at ASCE 7, 60 PSF is not for computer access, it's just general purpose "walkways and elevated platforms". Also, a typical forklift (even a "small" one) would overload a 60 PSF floor, especially one without a concentrated load requirement. When a forklift is carrying a load, the majority of the total weight (forklift + load) is concentrated on the two front wheels.
I suggested the 60 PSF, with added 500 lb concentrated load, to cover workers pulling (by hand) loaded (four wheel} carts... a moving load (maybe like the one in your photo).

Also, note the wide aisle in your photo. If these isle were only for a couple of workers to walk through, perhaps making visual inspections... why is the isle so wide?

Take ODNT's comments seriously.

FWIW: 24 kips on a 20' square area are just numbers. Don't arbitrarily decide that 24 kips is "too high", then "fudge" the loading assumptions to come up with a number you consider acceptable. Use valid loading assumptions, then do the engineering to make it work.

 

[JLNJ]

Agreeing with the above...

I design the slab for worst case, the beams for the worst equipment/aisle arrangement, and the girders and columns for the likely overall equipment arrangement. I'd probably skinny it down to 40 psf in the aisles for the girders and columns, but the slab and individual beams could easily see more when they are staging equipment during install/changeout.

 

[bones206]

I agree the install/changeout scenario needs to be addressed. I would treat it as one overall equipment live load with varying patterns of load application to envelope worst case member stresses.

 

[Mike Mike]

JLN, old dawg, agreed, higher loads are in order for floor design, lower loads are in order for columns/footings

Slide Ruler, not sure we're speaking the same language here. The question is what's appropriate, what's likely, what's reasonable. If 60 psf or 24 kips is the correct answer, let's talk about why it's the correct answer. No one is suggesting fudging anything.

I just started reading through the Delphi method that the ASCE cites right now, and it does not seem like rigorous science, since data for extraordinary loading events is largely unavailable. I'll share if and when I finish.

 

[SlideRuleEra]

If 60 psf or 24 kips is the correct answer, let's talk about why it's the correct answer.

...higher loads are in order for floor design, lower loads are in order for columns/footings.

With ODNT and JLNJ's input, I think you are on the right track now.

The entire floor should be designed for "high" loading (per your photo, I agree with 100 PSF + concentrated load, not 60 PSF).
Total load on the floor at any given time would never be 100 PSF x 20' x 20'. It would be less, so lower column/footing loads.
I would base that column/footing loading on the details of the equipment being installed and credible assumptions on how installation would be done (e.g. path used to move equipment into place & type equipment used to do so).