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Re: Buoyancy factor of safety

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Doesn't the load combination 0.6D + H give you a "safety factor" of 1.0/0.6 = 1.67?

On 11/26/2012 2:03 PM, h.d.richardson wrote:
Tarek,

Whenever I've done these I've assumed the groundwater table for buoyancy calculations was at the surface due to rain saturating the backfill. I've also considered only the soil directly above the submerged tank (or footing extension for concrete cisterns); I've not considered the soil sloping away from the tank wall at 60 degrees or anything like that. I also consider the buoyancy acting on the concrete weights or the footing.

For safety factors (I prefer to call them ignorance factors) Canadian limit states codes would use 1.25 for the dead load (or other accurately determined load) being the force to be resisted and 0.85 for dead weights resisting the force. This results in 1.25/0.85 = 1.47, which is close to 1.5. I would not consider anything less than 1.5.

Regards,

H. Daryl Richardson


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