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Elevated Tanks

Elevated Tanks

Elevated Tanks

(OP)
Hi, what are the main parameters that structural engineers require in designing foundations for elevated tanks? Also, assuming that it can be a pillar or multi-column tank. I expect that overturning and therefore uplift resistance may one of the controlling foundation requirements. The tank is most likely to be supported on shallow foundations with gravel soils as the bearing layer at GL -2 to 3 meters.

RE: Elevated Tanks

In addition to overturning, soil bearing and sliding resistance, as well as the design parameters of the material used, be it concrete, steel, or wood.

Mike McCann, PE, SE (WA)


RE: Elevated Tanks

Cyclical loading. Some soils are sensitive to this.

RE: Elevated Tanks

Allowable bearing, depth to that allowable bearing, factors of safety used for allowable bearing, estimated settlement or soil movement. If soil movement is excessive or allowable bearing is low, then allowable loads for drilled piers or piles. Soil classification for seismic loading. In high seismic regions, quite often there will be site-specific response spectra. If the foundation could bear at several different elevations, it would be helpful to show allowable bearing at each level with the designer picking the foundation depth.

RE: Elevated Tanks

(OP)
Thanks for the replies. Appears that only the typical requirements are required. Since this is my first tank, I was not sure that there may be special requirements.

Buggar, to address sensitive soils against cyclic loadings, we do not allow the 1/3 increase of allowable bearing pressure for short-term loading.

Thanks again !!

RE: Elevated Tanks

If the tank is full of lightweight material, or spends any considerable time empty, and if it is a tall tank, then you should also check it for dynamic (cyclical) wind forces. The combination of the tank and the footing together should be analyzed with regard to the soil stiffness under the mat footing.

Thaidavid

RE: Elevated Tanks

If this is an AWWA tank in the US, most often, the foundation will be designed by the tank contractor.
In that case, note that the AWWA specifications have some requirements for overturn criteria, seismic loading, wind loading, etc., that are different from ASCE 7.

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