Load Capacity of a Concrete Warehouse Floor

[Beggar]

I'm an OEM who's shipping a heavy piece of equipment to China for installation in a warehouse. The original spec that my company provided (before I joined) called for floor loading of 9800 kg/m^2. Now, at the 11th hour, they're saying that the maximum floor loading is only 500 kg/m^2.

I just don't see how that could be accurate for it's such a small number. They're preparing to rework the floors at substantial expense but I don't think it's necessary. However, I don't have the expertise to determine it. I'm trying to rapidly find a CE that I can hire to advise me but until then I'm wondering if somebody can give me some guidance as to how to come up with an approximate loading (assuming good concrete, etc).

I'm told the floor is about 7" thick concrete over sand and stone. I do not know about rebar.

This is a large warehouse at a huge manufacturing facility whose other buildings have large equipment. This building has a 5-ton gantry crane in it so they obviously intended to move heavy things around.

My gut tells me the equipment is fine but I'd like to be able to calculate it within some safety factor.

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[pba]

First you need to confirm that this is a slab on ground rather than a suspended slab.

If it is a slab on ground, 500kg/m^2 is clearly wrong. However 9800kg/m^2 is quite heavy - Possible more than a 7 inch slab might have been designed for.

My guess (and it is purely a guess) is that they have lost a zero and the actual floor has been assessed as good for 5000kg/m^2.

In terms of how to assess the slab capacity, I'm of little help as I'm UK based.

 

[jheidt2543]

You should find a local Structural Engineer to help determine the floor capacity.

The load capacity of a slab-on-grade floor is determined by the floor thickness, concrete strength, the reinforcing steel, the subgrade materials, the layout of the storage system and the type of forklift wheel loading. So, there are many things to consider.

A usefull book that covers all of this is "Designing Floor Slabs on Grade", 2nd Edition, by Ringo and Anderson, The Aberdeen Group, 1996, ISBN 0-924659-75-0

 

[jjf1]

I agree with thte above + your gut feel may be correct. You may have already tried to obtain; but typically the floor design loading information is on the building drawings.

I would start there (you may have already) If they are running fork trucks (tow motors, lift trucks etc.) over the slab now, you may be okay.

You may want to talk to your installation contractor, there are a number of ways of spreading the loading when you are faced with limitiations.

Good Luck

jjf1

 

[ijdicer]

There are several methods of assessing the loading capacity of a concrete slab,beam etc via non destructive means, one of these is ultrasonic testing whereby ultrasonic beams are sent through the concrete and picked up by a reciever at the other end which measures the velocity of the passing beams and can get a good idea of density which can be translated to give an idea of loading capacity, this would be quite tricky to use on a slab, another way is by using a schmidt hammer which is a small relatively inexpensive tool which measures the reverberations through the concrete and gives a reading of pressure capacity, the only downside is that you need to take quite a lot of readings to get a reliable average.
The first step id take however is to see if the contractor who poured the slab has any cube test results for the concrete which were taken from the batch during construction, these will give you a much more accurate figure if you can obtain them.

 

[pba]

Strength of a slab on ground is almost certainly governed by the ground conditions rather than concrete quality (or more properly surface hardness - as recorded by a Schmidt hammer).