STEEL WATER TANK BASE 5

[Nisha1977]

Hello everyone.

can u please give me your thoughts on this concept for temporary placing this steel water tank for testing . we provided steel (UC ) ring beam sitting on the ground as per the sketch attached . height in between existing ground and the beam top flange will filled with compacted soil and this needs to have recommended bearing capacity. I would like to know that this type of temporary support will be recommended or not ? if there is any differential settlement will result in tank wall failure. (this tnk size is dia 15.6m and height 8.8m). thanks for your time in advanced.

 

[1503-44]

The idea to prevent differentia settlement should be to have equal soil bearing under every point. It looks like the bearing pressure under your steel ring beam will be considerably higher than the bearing pressure under the tank floor plate itsef. The loads from the tank wall and roof, if there is a roof, will be transmitted directly onto the ring and then add the weight of the ring to get the load placed onto the soil immediately below the ring, whereas only the water plus the weight of the floor plate will be supported by the compacted soil directly below that.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[dauwerda]

As long as your sub-grade is adequate differential settlement should not be an issue. It is very common to simply use gravel ring foundations for above grade tanks in the oil and gas industry. This is a 6" - 12" tall steel band that has a diameter slightly larger than the tank. This ring is filled with gravel and the tank is placed on top of the gravel and the steel ring contains the gravel.

Here is the first example that came up in a google search:

http://wrighttank.com/water-storage-tank-products/gravel-rings/

 

[HTURKAK]

The use of steel UC ring beam will complicate the behavior. Your sketch shows flat bottom ( for this size, tank bottom should slope downward toward the center ) Just use compacted sand 200 mm thk with gravel ring .

 

[1503-44]

BTW, isn't this tank a bit too big to be doing testing in a temporary location? If you move it, you'll have to dismantle it, move all the pieces and then weld/bolt it back together in its final position, at which time will you NOT need to do another hydrotest?

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[LittleInch]

This is one reason I hate the word "temporary" when it comes to design like this. It just encourages a lower standard of everything -design, construction and use.

This isn't some little water tank here - you've got 1500 cubic metres of water there and a ground bearing pressure of 80 KPa on the floor and probably 100 kPa on the ring beam.

Yet the "design" is some sketch in a note book?

You need to do this properly or not at all.

Most importantly get the ground level for a diameter of at least 20m.

Get some initial bearing capacity checks so you know where the soft or hard bits are. Get a geotech engineer involved

Then grade it all, fill it with 500mm known material on top of some geotex and then test the bearing capacity. Then build your ring beam and fill the inside and outside of the ring beam with the same stuff and compact and test.

Then build your tank.

Sorry if his comes across too strong, but strike the word temporary and then see if it works. Too many "temporary" things get left for years and years.

The words "but it was only meant to be temporary" won't work if it fails in service.



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Also: If you get a response it's polite to respond to it.

 

[1503-44]

Be careful with internet engineering. This tank is has 470,500 gal and is 24 X the biggest tank on that internet link, plus it's 3.3 times as tall. That little steel band-aide isn't going to work on this one.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[JStephen]

Normally, a tank of those dimensions would be built in place and hydrotested in place, not in a temporary location.
If the subgrade is adequate, you don't need the ring beam- normally checked with soil borings.
A concrete ringwall is commonly used, but that's more for long-term performance.
See the details in API-650, for example.

 

[1503-44]

For many tank applications of this size, hydrdotest just might be the largest load ever experienced, since many oils, petroleum products and chemicals stored in tanks typical of this size have specific densities less than water. In any case, if you're testing with water, future loads won't be worse than water. Hence even the very short term performance of the compacted fill may be the most CRITICAL case. That also means it really cannot be designed as the word "temporary" might suggest. Long term performance is with more of an eye towards controlling differential settlements, however it is possible that the product weight is far less. Design for the short term condition. It is likely to be the worst case ever.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[LittleInch]

Somehting like this?

Looks about 8m tall at least. And you want to guess about the foundations?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nisha1977]

Thank you everyone for all the replies. Helped me to proceed with the design and API-650 Appendix B is a good Source . Thanks a lot

 

[LittleInch]

Next time note that there is a specific storage tank forum.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.