[GSBN] Catalan vaults

Tue Dec 13 05:54:11 UTC 2011

Hi

An interesting thread indeed.  A few thoughts, much as I love vaults and domes.

I share an instinctive concern about thin, highly stressed, brittle, heavy structures, which have little redundancy.

Here in New Zealand, in an area considered to have a relatively low risk of a having a major earthquake, we experienced  a shallow magnitude M6.3 earthquake near Christchurch which caused severe local peak ground accelerations of up to 1.4g horizontal and 2.2 g vertical. Modified Mercali intensities (MMI) of up to MMVIII were recorded in the area. Vertical acceleration of 2.2g is virtually unprecedented and was considerably more than the horizontal g forces.  The damage was huge.  Anything not really well tied down and tied together flew apart.

As we have learnt, having structures that can happily resist gravity loads is fine, but when gravity is effectively reversed in an earthquake, then brittle, unreinforced, or only horizontally reinforced, structures fail.

The good news is that earth buildings built in line with the NZ Earth Building Standards survived well, and the only strawbale building I saw in the affected area was also fine.

Where does this leave our earthbag dome friends with very heavy structures which are only horizontally reinforced?

And I am always mindful that 1970's owner builder guru Ken Kern died when one of his natural earth domes saturated in a storm, softened, and collapsed on him.  

Keeping away from raining bricks is a great idea.

Graeme
Graeme North Architects
49 Matthew Road
RD1
Warkworth
tel/fax +64 (0)9 4259305

graeme at ecodesign.co.nz
www.ecodesign.co.nz

On 13/12/2011, at 12:31 PM, Derek Roff wrote:

> It's great to see what people are doing with thin, low-arch vaults and domes.  Obviously things are working for them.  However, I am concerned about safety.  With every building material and design, as we push toward the extremes, the risk of failure increases.  And when failures occur, they are more likely to be catastrophic.  Traditional building forms, methods, and materials tend to have a lot of redundancy, and are usually quite fault tolerant.  More modern, optimized, resource minimizing designs and structures require everything to be done right, and run the risk of collapse from the failure of one or a few key elements.  
> 
> I feel concern about the Catalan arches in this regard.  Individual pieces of the arch are each in high stress.  The perimeter of the low-arch shell experiences forces many times the weight of the dome.  Small horizontal displacements can lead to structural failure and collapse across some or all of the dome.  Few of us have trained our intuitions sufficiently to make accurate judgements about many of the design and building details.  
> 
> I'm not suggesting that no one should experiment with these structures,  Rather, I am calling for us to take proportionately greater care and to pay substantially greater attention to design, materials, and construction details, when the risks are higher and harder to judge.  I wonder if Bruce, or other engineers on the list, would comment on building Catalan domes with unfired earthen materials.  
> 
> Trying to keep our heads in the clouds, and out from under the bricks,
> 
> Derelict
> 
> Derek Roff
> derek at unm.edu
> 
> 
> On Dec 12, 2011, at 12:02 PM, huffnpuff at q.com wrote:
> 
>> Chris and All,
>> 
>> I do remember perusing the info posted for the Catalan vaults and found it most interesting. About a year ago I had an opportunity to attend a charrette on Compressed Earth Blocks, hosted by Bernard Amadei at the U. of Colorado. These CEB builders were meeting to discuss similar issues that we SB builder types are/have experienced with acceptance, testing, codes etc. Two fellows of particular vision and spirit were Satprem Maini from the Auroville Institute, India http://www.earth-auroville.com/vaulted_structures_introduction_en.php and Jim Hallock, of icatis, USA http://www.icatis.org/, both NGO's building with CEB's and Vaults/domes. Both web sites are full of the work these two organizations have done and are eye candy for anyone interested in vaults. If you visit the icatis site you'll see they have teamed with George Nez and built at least one of his 'thin shelled latex concrete' roof systems.
>> 
>> Currently our local engineer and COSBA member Ian Smith and his wife (both engineers) are on their honeymoon in India at the Auroville Institute at a workshop on vaults. That's devotion...
>> 
>> Mark Schueneman
>> COSBA 
>> 
>> 
>> ----- Original Message -----
>> From: "Chris Magwood" <chris at chrismagwood.ca>
>> To: "with public archives) Global Straw Building Network (private" <GSBN at greenbuilder.com>
>> Sent: Sunday, December 11, 2011 9:55:05 AM
>> Subject: [GSBN] Catalan vaults
>> 
>> Hi all,
>> 
>> The mention on this list some months back about Catalan vaults (or 
>> Guastavino vaults) sparked my interest, and we've now decided to forge 
>> ahead and build one as the roof for a buried, earthbag root cellar at 
>> Trent University.
>> 
>> Does anybody have experience building these, or know of anybody who 
>> does. I'd like to try and hire in somebody to lead us in this build. 
>> It's a small structure (18 x 22 ft) so it won't be a long build, but I 
>> always like to have someone knowledgeable in charge when doing things I 
>> haven't done before.
>> 
>> The budget for the project is not high, but I would be willing to try 
>> and cover travel costs, food, lodging and a bit of cash for the right 
>> person.
>> 
>> Let me know!
>> 
>> Chris
>> 
>> -- 
>> www.chrismagwood.ca
>> www.endeavourcentre.org
> 
> 
> 
> 
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