On Fri, 17 Aug 2007 08:52:17 -0400, "Roger Long"
wrote:

Does that sound like a way to build a boat? Worse the steel, which
should be the tensile material on a thin shell, was on the inside and the
concrete, a material most effective in compression, was on the outside.

That is why they invented prestressed concrete. Tension on the steel
keeps the concrete in compression. The design allowance for tensile
strength of concrete is zero. Opposite of chain, which has no
compressive strength. Materials science is a facinating field of
study. They generally cover steel building framing with concrete, but
it is just fireproofing for the metal. On the other hand, they do use
actual reenforced concrete for similar structures, and they can look
similar on the outside.reenforced concrete that looks about like the
covered steel.

For something more efficient consider the submarine, with two
concentric shells and all the frames between. Those things were strong
enough to handle any wave imaginable. Big waves just cover them and
then move on.They don't flood when they get swept, after all. Then
there is the other sub. the fabric one. Gunny sack, cat, and brick.
Just kidding, we love our four cats. We got them from a shelter that
doesn't kill animals, they will keep them forever.

Casady