Re: Concrete reinforcement

[DaveIrons@aol.com]

DaveIrons@aol.com wrote:

> At viewport  openings or other hull penetrations a steel ring can
>be imbedded in the  concrete.  The cable would be welded on
>each side of the opening and the  cable inside the opening cut
>away.

>If the inside is cut away, wouldn't that auotomatically distort the
hatch/dome
flange?  I imagine the pre-stress loads would have to be equal all
around.

A steel ring embedded in solid concrete shouldn't move a when the
cables are cut.  

>The embedded steel ring - are we talking a large flange similar to
a 360 deg. bib of, say, 6 in. (delta OD-ID x 0.5) or more (for stress
distribution)?  Or is it more of a flange of just a couple of inches?

Sounds like an excellent design.  It has the added advantage of
increasing the strength of the hull around the viewport openings. 
The viewport openings would be the weakest portion of the hull.  

>Would it make sense to form the flange as a circular "I"- beam to
resist inward deflection?  The top side of the "I" would rest on the
exterior of the hull and the bottom side would rest against the
inside of the hull.  Of course, the vertical bar of the "I" would be
bonded (welded or W.H.Y.) to the concrete edge.

>Or is that over. kill?

Sounds like overkill.  The concrete hull is much stronger that the
depth it is designed for.  The I beam method would involve
imbedding steel inside the concrete pressure hull.  It is possible
that a hidden pocket of rust could expand and damage the pressure
hull.

The embedded steel ring design makes sense.  If more strength
were needed, imbedding steel inside and outside the concrete hull
would increase the strength in the same way steel sandwich
construction increases compressive strength.  If additional strength
were needed to resist the inward pressure I would also increase the
thickness of the hull around the viewports.

The method you've brought up reminds me of the Seacon
experiment.  Seacon was a full sized concrete habitat.  The
viewport was surrounded by a massive steel structure.  The steel
structure acted as a viewport seat and a structural component.  The
design
rational was that the hole in the pressure hull would be
"structurally invisible."   

Please correct me if there is a flaw in my logic.  The acrylic
viewport compresses as the pressure increases and the viewport
slides further inside the viewport seat.  The viewport exerts
outward pressure on the viewport seat.  Wouldn't the pressure be
exactly the same as the pressure that the hull exerts on the viewport
seat?

Therefore, a massive viewport seat is unnecessary.

Have I made my point clearly?

David Irons