[GSBN] earthquake-proof adobe walls (GSBN Digest, Vol 16, Issue 11)

Jeff Ruppert jeff at odiseanet.com
Mon Aug 17 13:52:59 CDT 2009


Rob,

My take on it is that the mat (it sounds like the mat is horizontal), or 
net, creates a bond because of it's width across the wall.  Any type of 
reinforcing in earth construction lacks the same magnitude of bond found 
between concrete and steel.  I think because the mat embodies a large 
surface area it has a bond with the blocks that develops the necessary 
capacity to actually work.  If the tensile forces are built-up one the 
edges and concentrated to the face of the wall then the bond to the 
masonry elements is reduced.  The nature of bales and earth blocks are 
different in that earth is very heavy and actually develops a small bond 
with whatever reinforcing you use within it.  The shear weight also 
creates more forces in earthquakes and maybe the mats increase friction 
between courses, holding things somewhat in-place.

Maybe this acts like the barbed wire in earthbag construction.

That said, reinforcing your plaster will also add capacity and both 
should be looked at in any particular design.

Jeff



RT wrote:
> On Mon, 17 Aug 2009 13:00:05 -0400, <gsbn-request at greenbuilder.com> 
> wrote:
>
>>    4. Re: earthquake-proof adobe walls (Lorenzo Robles)
>
>>  Many old constructions, as remote as colonial time, 3 or 4 centuries 
>> old, stood well after all the sismic activity.  Walls were built of 
>> adobe, with a wonderful reinforcement of cane, thin bamboo,  or split 
>> bamboo . It worked with the same logic as rebar and concrete.
>>
>>  I saw a  very  old house in the center of Lima, that had some walls 
>> pulled down for extension purposes, showing the long, hard and 
>> flexible strips holding like a wide net the core of the adobe wall.
>
>
> I don't know anything about earthbag nor adobe construction but 
> ignorance has never stopped me from shooting off my mouth in the past 
> so ...
>
> I would venture that the tensile reinforcement that Lorenzo mentions 
> as being useful in enhancing seismic resistance of adobe walls, would 
> be a lot more effective if moved out from the core of the wall, to the 
> extremities of the wall's cross section, for the same reason that 
> rebar in concrete construction isn't placed that the core of the 
> section ... and for the same reason why most people building with 
> straw bales these days know better than to whack a truck-load of rebar 
> pins into the core of an SB wall.
>
> The bamboo exoskeleton techniques that have been developed for SB 
> construction by YakWoman, Steens et al should be directly 
> transferrable to adobe & earthbag construction, or so one would suspect.
>
>



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