Need help with placement of 50,000 lbsbulk tank on concrete slab
Need help with placement of 50,000 lbsbulk tank on concrete slab
(OP)
We currently have a HDPE vertical bulk tank that holds a surfactant. This tank is capable of holding 6,000 gallons. However, we have never filled this tank with more than half of its capacity because we are not sure if the concrete slab in which this tank is placed will support the weight. We would like to fill this tank up to 5,000 gallons, or 54,000 lbs. This bulk tank diameter is 8.5 feet, with a flat base area of 8,171 sq in. With 5,000 gallons, the product would exerts a pressure of 6.6 lbs per sq in onto this concrete slab. The concrete slab is 5 in thick without any rebar reinforcement. My question is: Will the slab hold such weight without cracking or settling? What is the theoretical pressure capacity of this slab? Are there any other factors that would affect the stability of this slab-other than pressure?
Note: This tank is vertical, and properly leveled. The weight of the tank is unknonw. However, it is calculated to be less than 1,000 lbs.
Thank you for your time and professional opinion on this subject.
Werner
Chemist
Note: This tank is vertical, and properly leveled. The weight of the tank is unknonw. However, it is calculated to be less than 1,000 lbs.
Thank you for your time and professional opinion on this subject.
Werner
Chemist





RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
Yes, indeed, there are other factors. Probably the most important one is the soil conditions under the slab. They will control the amount of settlement you get under load. That settlement in turn will determine if you have problems with the slab cracking, etc. Even with no rebar, a 5" slab might be sufficient for the loads you indicated, which translate to 0.95 ksf, are not really very high for "common" soil conditions. You need to investigate, probably by consulting with a geotechnical engineer, to confirm what soil conditions actually are.
Based on the iformation you provide, 6000 gal capacity, dia = 8.5', I'd say your tank must be about 14-15' high. I've not run any numbers on it, but wind might yield a large enough overturning to increase that bearing pressure some. I'd also suspect that wind on an empty tank might blow it over or away. I presume that the tank must be anchored to the foundation.
Regards,
chichuck
RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
If you want to be sure, hire a geotechnical and maybe a structural engineer to evaluate the conditions. Otherwise monitor the tank while you load it. Does the tank move? Does the slab move? If not you good to go, if it moves a little, keep watching, if it starts to move a lot, stop loading it.
RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
Also, the thickness of the bottom plate doesn't do much to alter the pressure distribution under the tank. In fact, I would argue the opposite - that a thicker steel plate would re-distribute the weight into hot spots, bridging over low spots or localized settled areas and create higher pressures around those low areas. A thin plate is just a bladder - the weight of the liquid directed onto the slab and the pressure is simply the height of the liquid times the density.
RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
I agree that ANYTHING could be under the slab, but if the tank has been in use for awhile at 1/2 full without problems, then it is unlikely there is very soft material under the slab. If the material under the slab is anything but very soft then 1,150 psf is not a significant pressure.
As for the bottom of the tank. You are of course correct that a thin bottom means that the contract pressure is the same everywhere. However, once you get the soil structure interface, the effect of the tank load under the center of the tank is greater if the structure is flexible. This is more of an issue the larger the tank, but true for a small tank as well.
RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
RE: Need help with placement of 50,000 lbsbulk tank on concrete slab
Again, thank you Gentleman. Your help in trully appreciated.
Sincerely,
Werner
Chief Chemist