RE: [PSUBS-MAILIST] Prestressed concrete pipe

["Brian Cox" <ojaivalleybeefarm@dslextreme.com>]

Marc,
       If you could figure out a system for connecting them and making end
caps you would have an instant submarine!  It could be done, but why?   The
reasoning behind my ferro hull is that I was able to make a freeform shape
which is hydrodynamically advantages.  My shape also doubles as a ballast
and a structure to carry the actual pressure hull (which is steel).  So mine
is sort of a hybrid.  In my sub the wieght of the ferro cement will
contribute to the wieght I will need anyway so I figured that would help me
in that regard.  But working with the concrete is very interesting,  I had
some minor damage to the egdes of my ferro structure when I had to flip it
over using the fork lift  - to repair it all I had to do was mix up a small
batch of my cement mix and it was like new!  I'm looking forward to epoxying
the whole thing and adding some color !!

Brian

-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Marc de
Piolenc
Sent: Wednesday, March 17, 2010 2:49 AM
To: Personal Submersibles; International Personal Subs & Minisubs
Subject: [PSUBS-MAILIST] Prestressed concrete pipe


I was recently reminded of my obsession with Eugène Freyssinet's
advocacy of prestressed concrete for ship and submarine hulls by coming
into possession of a copy of Nayyar's _Piping Handbook_. That book
includes a chapter on prestressed concrete pipe which includes some
information on its manufacture.

I compared the information in Nayyar's book to the prestress levels
mentioned in the Smith paper on concrete hulls. There are significant
differences.

For one, the commercial prestressed pipe uses only circumferential
preload provided by high-tensile wire wrapped around the pipe and
mortared in place. It makes sense: the pipe is designed to resist
internal pressure. Longitudinal strength is provided only by a thin
steel shell whose main purpose is to prevent leaks. Clearly, the product
cannot be used as is for a submarine. It does not, however, appear
impossible, or even especially difficult, to incorporate longitudinal
prestress into the manufacturing process - more specifically into the
manufacture of the (currently unreinforced) concrete core.

What really bugged out my eyes is the sizes of pipe that are
commercially available; one type is made in internal diameters up to
3600 mm - 12 feet!

Marc de Piolenc
Iligan City, Philippines




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