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David Cohen"David Cohen (Baran Raviv)" <dcohen(--nospam--at)barviv.co.il> wrote:I have a 
 HDPE pipe for natural gas that i need to check the strength capacity when 
transferred by HDD beyound a standard Highway , 1.20m depth . The internal 
pressure will be about 4barg , and the pipe is PE100 -90mm diameter with a 
strength capacity of 8 Mpa. What is the methodology and the adequate 
equations to check this? Thanks

David Cohen

Tarek Mokhtar <Tarekmokhtar(--nospam--at)earthlink.net> כתב:
Thank you for all your responses, I guess I was trying to justify a lower
F.S than the 1.67, considering that the ground water will rise to the top
of grade, as Daryl suggests, and the water weights are pretty well
defined, I just do not see reducing the weight of concrete by 60%

Tarek Mokhtar, SE

> 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.
>> 

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