Concrete slab on grade
Concrete slab on grade
(OP)
I am designing some support stl for equipment that is going into an old warehouse.
This area covers about 30'x30' of this large warehouse.
Customer indicates that there is an existing 5" concrete slab on grade about 30 yrs old.
Within this are there will be about 12 conc loads from col's some ranging up to 7 kips load...Seismic, Cat B....max seismic uplift say 1.5 kips.
Obviously they do not want to put in new footings...
I am planning to use opost installed AB's..
I have the following concerns:
1 there is no guarantee that there stll is a good support for the slab due to soil settlement over time.
2 with no info on the reinforcement, I would expect cracks to develop in the slab..
3. post installed AB's..max effective depth 3 to 3 1/2" with 1" of grout..
I plan to make the base pl's as large as possible but I do not think this will
effectively address the introduction of all these conc loads over a defined area.
any suggestions would be welcome...thanks in advance
This area covers about 30'x30' of this large warehouse.
Customer indicates that there is an existing 5" concrete slab on grade about 30 yrs old.
Within this are there will be about 12 conc loads from col's some ranging up to 7 kips load...Seismic, Cat B....max seismic uplift say 1.5 kips.
Obviously they do not want to put in new footings...
I am planning to use opost installed AB's..
I have the following concerns:
1 there is no guarantee that there stll is a good support for the slab due to soil settlement over time.
2 with no info on the reinforcement, I would expect cracks to develop in the slab..
3. post installed AB's..max effective depth 3 to 3 1/2" with 1" of grout..
I plan to make the base pl's as large as possible but I do not think this will
effectively address the introduction of all these conc loads over a defined area.
any suggestions would be welcome...thanks in advance






RE: Concrete slab on grade
YOu will have difficulty anchoring anything to it if there is any uplift.
What type of loading? Static? Rotational? Vibratory?
How critical is his equipment to movement?
The spacing of loads can have an overall impact on the flexural stresses developed in the concrete.
What is the condition of the existing concrete?
Dik
RE: Concrete slab on grade
I also would not worry much about settlement below the slab, but can be checked with sounding if you think there are voids.
If you think you need footings, then recommend them. Just because the owner doesn't want them, doesn't mean they are not needed.
Don't count the grout in your AB embedment.
Check shear at the baseplate perimeter.
RE: Concrete slab on grade
RE: Concrete slab on grade
RE: Concrete slab on grade
BA
RE: Concrete slab on grade
a core sample to determine the depth certainly makes sense...
no major vibration issues and to some extend the equipment can handle differential settlement...
not very reassuring for uplift, even though seismic uplift is small..say 1 kip then add in the overstrength factor of 2...
I can make the base pl's rediculously large but it still does not address the potential flexural problem of the slab..
reading your replies, it seems individual footings would be the sensible way to go and I aggree...
the problem with using individual footings is by the time you pock-mark the slab with each footing and isolate them from the slab you are left with a compromised slab...which would lead one to a new slab in that area designed to take the individual conc loads...
RE: Concrete slab on grade
RE: Concrete slab on grade
It's only 30'x30'... may be consider re-constructing the area.
Dik