Concrete floor loading

[Dropout]

Hi All.

I'm trying to figure out where to start so I can figure out what I need to do to support some tanks on a warehouse floor.

It's an old Canadian military warehouse with a poured concrete floor and ceiling. Unfortunately we can't get any information on the floor since some of the original drawings are lost. I do know that it's about 7" thick.

The tanks we need to bring in weigh about 135,000 lbs each and sit on four 16" by 16" square pads. This would give a floor loading of just under 20,000 lbs. per square foot which I'm told is too high.

On the other hand, pallet racking with six 2,000 lb skids has a foot print of 0.38 square feet and a floor load of 30,000 pounds per square foot. We used to do that without thinking about it.

Where do I start?

 

[jdonville]

Dropout,

I don't get the reference to 0.38 ft2 from the description of your pallet racking.

If you mean that you are supporting the 135000 lb. tank on six skids, then your average contact pressure is 22,500 lb. per skid, divided by the overall area (not just the contact area) of an individual skid. The actual pressure may be larger near the middle of the tank than at the ends.

Of course, you need to make sure that your skids could handle the load - I am guessing that the 2000 lb. skid has a rated capacity of 2000 lb. only.

However, I digress.

In order to determine the thickness of the floor slab, you could core it in selected (unimportant) locations. I would imagine, however, that you could also back-calculate a minimum allowable pressure from what equipment/goods were actually stored at the site.

Other means of obtaining information include an electromagnetic survey to find where the rebar is in the slab. You could also have test borings performed outside the warehouse to develop design guidance for subgrade modulus for the surrounding soils.

I am sure that structural engineers will also have their own perspectives on this. You may wish to post this question in one of the structural fora on this site, or ask a structural colleague in your area for advice.

Jeff

 

[civilperson]

What is beneath the floor?

 

[pba]

There are too many unknowns to do acurate calcs so do lateral thinking instead - jdonville has the right idea. What has the building been used for in the past? Is the existing slab damaged?

Now what are you going to do if you decide the slab can't support the tanks? You could consider adding new foundations for the posts, putting spreader plates on top of the slab or taking the risk that you might damage the slab...

Ideally you strutural engineer could help you in assessing the loads - You would need one in all cases other than just putting the tanks straight on to the slab.

 

[csd72]

Dropout,

You are in over your head on this one.

This forum is not a free design service and you should really get a structural engineer involved.

We are cheap compared to you guys.

Regards

csd

 

[33530454]

Ikotun
Pls i want the review of software available for modelling of foundation and recent development

 

[CTW]

Are these tanks being stored in the warehouse temporarily or is the warehouse now being used for some other function?