[PSUBS-MAILIST] concrete

[Marc de Piolenc]

I don't have hard numbers, but remember that resistance to mostly 
compressive loading is a structural STABILITY problem. Most practical 
steel structures buckle under compression long before reaching their 
actual compression limit. Concrete has an advantage there due to its 
stiffness - the NCEL tests suggest that it comes much closer to using 
its full compressive strength.

That said, my primary interest in concrete is due to its cost and ease 
of maintenance.

Marc

PS. If anybody is interested, I will add the relevant reports that I 
have to my public Dropbox folder and post the link.

On 4/12/2014 3:15 AM, hank pronk wrote:
> A six foot od sphere built in 1.25in thick steel would be equal in weight to 4in thick concrete.  I would not ever expect 4in concrete to compare to 1.25 steel.  But, it would be interesting to know where the concrete stands in comparison.
> Hank
> --------------------------------------------
> On Fri, 4/11/14, Marc de Piolenc <piolenc at archivale.com> wrote:
>
>   Subject: Re: [PSUBS-MAILIST] concrete
>   To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
>   Received: Friday, April 11, 2014, 9:59 AM
>
>   A huge amount of work was done on
>   concrete for pressure-resisting structures, including long
>   term, deep exposure tests, by the US Naval Civil Engineering
>   Laboratory. Most of the reports are available for
>   downloading free of charge from DTIC.
>
>   Excellent results were achieved with concrete having NO
>   reinforcement. There has been limited work done with
>   prestressed concrete and even less done with reinforced
>   concrete and ferrocement, which can reasonably be expected
>   to give much more efficient and distortion-tolerant
>   structures.
>
>   Marc
>
>   On 4/11/2014 8:25 PM, hank pronk wrote:
>   > A cheap alternative to a super strong sphere hull is
>   re-enforced concrete. I feel like hiding under a blanket
>   while I say this,lol.  I know it is way out there, but
>   concrete is super strong under compression.  It is not
>   so good for impact resistance.  Concrete is a very easy
>   material to work with and form into a sphere shape.  I
>   have no idea what thickness would be needed.  Properly
>   engineered I would trust it.
>   > Hank
>   >
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