Re: Dome design

This list is soooo cool!  I've worked a bit on parabolic domes, and sent
the following out 8/17/1999:

"For those interested, I've posted instructions on how to construct an
hexangonal parabolic dome along with pictures of my experimental parabolic
solar reflector at:

"Look under the 'Parabolic Domes' directory."

I read Fathy's _Architecture for the Poor_ (Chicago, University of Chicago
Press [1973]) with great interest.  A recent New York Times article, "Arts
Abroad: Honoring a Visionary If Not His Vision" (4/4/2000, Sec. E p.1),
details the general decay of his model village, New Gourna:

"Residents have plugged up the wind catches, drastically increasing the
indoor temperature in summer and lowering it in winter. They have covered
the courtyards, blocking out the sky. They have crammed concrete into the
windows. And whenever one of the signature Fathy domes collapses -- as
they tend to do from natural wear and a little help from the villagers --
the residents rebuild in reinforced concrete, mimicking the anonymous
urban housing blocks Fathy so detested."

So, it appears that parabolic geometry is the best for mud domes, but they
still require occasional maintenance.

Spencer W. Hunter, Library Specialist

p.s.  I've been working for the last few months on what I think is a novel
tensegrity structure to support a panel dome, inspired by the continuing
discussion in this list about flexible strut connectors.  The tensegrity
is meant to address those problems you mention, such as local buckling and
"pop-in."  I've built a few models, and just need to scan the photos and
write the text in the next couple of weeks (there--I gave myself a
deadline).  I'll post the results here when they're ready.

I have a question about tensegrities in general: does anyone have advice
on how to measure those # at $*!#$ tendons precisely?

On Wed, 2 Aug 2000, Charles J Knight wrote:

> The other day, I was reading a book on Middle Eastern architecture.  It 
> mentioned that with the use of mud brick, domes could be quickly and 
> easily built.
> BUT it also mentioned that all barrel vaults and domes had to posess 
> a parabolic shape, so that the forces involved would be purely 
> compressional, since mud bricks can't tolerate *ANY* tensile forces.
> Due to this, there is a unique and characteristic shape to all
> traditional
> buildings in the middle east, especially around Egypt.
> A modern renaissance in mud-brick design, spearheaded by Hassan 
> Fathy, started with his attempts to build spherical domes from mud 
> brick -- they failed miserably.  Only when he changed to the local 
> traditional shape, which happens to be parabolic, would his domes 
> remain standing.
> ("An Architecture for People:  The Complete Works of Hassan Fathy")
> Of course, I immediately started thinking about geodesic domes.  While 
> a sphere is indeed the most efficient way to enclose space, period, is 
> it the *best* way to enclose space in a gravity field?  Or would a
> parabolic 
> dome work even better in this application?
> We all know that spherical geodesics resist outside forces, such 
> as those encountered underwater, beautifully.  But those are not a 
> unidirectional force, like gravity is...
> We've heard about troubles with local buckling, etc, with high frequency
> spherical domes...could this be the result of choosing an incorrect 
> geometry -- one which isn't taking gravity into consideration?  Could it 
> be that the hubs aren't holding the struts into place as effectively as
> they
> could?  (Bucky's main complaint about rectilinear homes was that the
> corners held the struts rigidly into place, instead of using natural
> geometry
> to maintain the form)
> Has anyone ever studied this aspect of dome design?
>      -- Chuck Knight

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