[PSUBS-MAILIST] concrete

[Sean T. Stevenson]

The value used was an average for compressive strength only, which for a
featureless spherical shell is a pretty safe bet.  Once you start
putting holes in it, all bets are off, but this is a theoretical
exercise.  Such a hull would fail ABS anyway because it doesn't meet the
material requirements of 4/3.1, unless under 4/3.5 in conjunction with
extensive testing.  For the purpose of this exercise, buckling is less
of a concern with concrete due to the necessarily high t/D ratio.  This
applies exclusively to spheres.  Cylindrical hulls introduce tensile
loads, at which point the low tensile strength of concrete becomes a
problem without reinforcement.

Sean


On 2014-04-11 20:49, Marc de Piolenc wrote:
> Is that yield strength compression only, or tension and compression?
> If the latter, it is optimistic. The great weakness of un-reinforced
> Portland cement concrete is of course poor tensile strength. The
> stiffness, on the other hand, is high, and accounts for good
> structural stability in concrete structures due to buckling resistance.
>
> If it were possible to guarantee pure and consistent compressive
> stressing, then even sidewalk-grade concrete, with no steel, could be
> used at very great depths.
>
> Marc
>
> On 4/12/2014 10:34 AM, Sean T. Stevenson wrote:
>> Hank,
>>
>> There are countless varieties of concrete, all with different mechanical
>> properties, so it is difficult to make an effective comparison, but just
>> for fun, I ran your scenario (6' OD, 4in thick shell) with average
>> material properties for ordinary concrete, and it turns out it's good to
>> over 1000 fsw!  See below.
>>
>> Sean
>>
>>
>>
>>
>>
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>