Warehouse Floor Loading

[suqlainUK]

Many warehouse ground floor slabs on geotechnically poor sites are being constructed on piles due to the high specified loads of 50kN/sq.m being set in the Clients brief. This leads to expensive floor slab, or even shelving, ironically, of the whole project.
I presume that the basis of this hign load is BS6399:Table 1 which gives a UDL of "4.8kN/sq.m for each metre of storage height"....giving 48kN/sq.m (hence 50)for a 10m clear internal height of warehouse.
How realistic is this quoted figure of 50kN/sq.m.?

 

[JAE]

That seems quite high to me. In the US, codes typically require 125 psf (6 kn/m^2) for light storage and 250 psf (12 kn/m^2) for heavy storage. Now these are minimum code requirements and typically, you should ascertain what types of material is to be stored in the warehouse.

In a recent project, we were designing a covered overhead crane with a storage area beneath for structural steel shapes. The actual calculated load came out to be about 800 psf (38 kn/m^2) which was used. This was also on a very poor site with soil densities below approaching that of water. We used a reinforced mat slab but this was not technically within a warehouse building where slab settlements would be more of a concern.

Check on the basis of BS6399:Table 1 and what the 50 kn/m^2 is intended for. Perhaps the client could be consulted as to verifying the actual loading vs. some arbitrary code amount. It seems over-kill to design for 50 when you might be storing foam products or toilet paper.

 

[Imagineer]

JAE,
Just a note: paper products such as toilet paper have very high storage densities. Try lifting a box of copier paper, then remember that you can get 40 boxes on a pallet. Stack the pallets two or three high and you get a sizeable load. Each sheet doesn't weigh very much but they add up very quickly.


Imagineer

 

[JAE]

Imagineer,
You're right, I guess that real soft stuff my wife has been buying kinda skewed my thoughts.

 

[suqlainUK]

JAE,
Thanks for your viewpoint. These high UDL loadings are common in UK building specs, and stems from Property Developers wanting the flexibilibty for future use of the building as a high bay racking warehouse. Actual racking leg loads are rarely given at the outset.

Design for the high UDL on sites with say peat (reinforced water) layers have given piles@3m centres with enlarged heads, 300mm thk slabs with 85kg/m^3 mesh reinforcement quantity. The alternative to this slab is 250 thk fibremesh reinforced slab with 60kg/m^3 of steel fibres....solution which end up being too expensive.

Imagineer,
Your reply reminds me....which is heavier, a ton of feathers or a ton of steel?