[GSBN] Steel mesh in clay plaster + earthquake safe fire shelters

[John Swearingen]

I agree with Rub Tum, that 'staggered clums with alternating nodes or
collars is definitely the way to go, with chopped straw for T&S'.
However, we haven't done that. Our first try, we got the directions wrong,
drank too much, and ended up with several staggering clum chums with nudes
in collars eating chopped suet, flashing T&A, and blabbering about Bale
Bondage.  "Clum!" ~Chaucer

So we went with Centaflex, which is sized pretty well, and the plastic
coating tends promote bonding.  Our mesh is used to hold the bales
together, like a basket, and cheese cutting isn't an issue, as it might be
with cob.

It seems that metal in earth plaster can and does work, but under what
conditions would it fail?  The bond is important, and thin metal wires
cannot be considered sufficient unless they are very dense (notice that the
Our Troops recommended split bamboo over clums for better bonding). The
Japanese practice of coating metal with an alkaline plaster certainly
points the direction.

John







On Tue, Aug 27, 2013 at 9:55 AM, RT <archilogic at yahoo.ca> wrote:

> On Sun, 25 Aug 2013 18:52:24 -0400, <GSBN-request@**sustainablesources.com<GSBN-request at sustainablesources.com>>
> wrote:
>
>> Date: Sun, 25 Aug 2013 17:30:55 -0400
>> From: oasis at oasisdesign.netre: Steel mesh in clay plaster + earthquake
>> safe fireshelters
>>
>
>
>  it only takes a few hundred pounds of wire to reinforce a 100,000 lb cob
>> building.
>>
>
>  What is properly sized reinforcement?
>>
>
>  Still being worked out, but 1/8" wire mesh on 6" centers is abetter fit
>> to  cob than say, 3/8" rebar on 18" centers.
>>
>
>  (wire mesh) has a high likelhood of a) enabling the thing to get a permit
>> and be built
>>
>
> Y'all;
>
> It would seem that the third sentence (quoted above) negates the validity
> of the first sentence.
>
> I know nothing about designing/building with cob simply because its
> thermal performance makes it unsuitable for use for energy-efficient
> buildings in my climate (~8700 HDD/yr) so I've not looked at it in depth.
>
> However, I do know that in the design of reinforced concrete structures,
> 6" x 6" x 6 gauge welded wire mesh would be utilised only as secondary
> reinforcement to control temperature and shrinkage cracking.
>
> I also know that for reinforced concrete, the ratio of the cross sectional
> areas of reinforcment : concrete matters -- too much reinforcement can
> result in sudden destructive failure of the concrete -- too little
> reinforcement is essentially no reinforcement and can result in
> catastrophic failure of the structure.
>
> "A few hundred pounds" of wire mesh to reinforce 50 tons of cob whose
> thickness is presumably a foot or more sounds like a case of the latter --
> essentially a case of trying to use T&S reinforcement as primary
> reinforcement.
>
> Quite frankly, I suspect that straw or other fibre in the mix is probably
> more effective at the task of T&S than either 6x6 or chicken wire mesh and
> that a bamboo grid (whose spacing/placement/detailing has been properly
> designed) would be more appropriate for the primary reinforcement.
>
> I also suspect that in most jurisdictions when seeking plans approval,
> approaching the Chief Building Officer with alternative reinforcement
> strategies that were developed by the U.S. Army Corps of Engineers would be
> looked upon more favourably than a scheme with no engineering documentation
> and mostly anecdotal support.
>
> === * ===
> Rob Tom                                 AOD257
> Kanata, Ontario, Canada
>
> < A r c h i L o g i c  at  Y a h o o  dot  c a  >
> (manually winnow the chaff from my edress if you hit "reply")
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-- 
John Swearingen
Skillful Means Design & Construction
2550 9th Street   Suite 209A
Berkeley, CA   94710
510.849.1800 phone
510.849.1900 fax

Web Site:  http://www.skillful-means.com
Blog:         https://skillfulmeansdesign.wordpress.com
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