[GSBN] earthquake-proof adobe walls
Bruce King
ecobruce at sbcglobal.net
Tue Aug 18 21:48:42 UTC 2009
Hi, everyone. I've been immersed in this subject for the past four
years as I've written an ASTM standard (now nearly complete), and
studied the large stack of technical papers and field reports by a
small group of engineers and builders from all over the world. I
generally agree with everything that's been said on this listserve,
with a few additions & corrections:
1) fibers make stronger bricks, but not necessarily better walls.
Weak bricks will ALWAYS give a weak wall, but a strong wall requires
strong bricks, thin, well-bonded mortar joints, and good workmanship.
2) fiber -- that is, tensile reinforcing -- is crucial to getting any
amount of seismic safety. You want reinforcing wherever the wall
tends to crack, especially wall corners and openings, and especially
around the top (the "crown beam" Lorenzo referred to, also called a
top beam, collar beam, bond beam, or ring beam)
3) mesh, whether outside or inside the wall, serves to hold everything
together even when it does crack, thus keeping pieces of wall from
falling off and bonking you in the head. The basket effect.
4) earthen buildings are really bad in earthquakes, because they are
heavy, soft, and brittle. Three things you don't want. But people
build with earth because it's cheap and available, so we're working
out how to make it safer -- primarily with tensile mesh and reinforcing.
5) the much-vaunted barbed wire reinforcing system for earthbag houses
is as yet completely unproven for carrying any, especially seismic,
loads, and in my opinion is just deceptively bad. I know this from
bitter experience, having gone over Nader Khalili's tests 12 years ago
in excruciating detail, and trying to get Nader, Iliona, or their
engineer to explain or fill in the missing parts. They couldn't, and
I see all of that earthbag testing as badly conceived, designed,
executed and reported. I don't want to posthumously slam Nader, just
suppress an overblown and unpromising technology. We could never get
our earthbag domes to stop leaking, either. Phooey.
So build with earth, baleheads, and enjoy it! But don't kid yourself
-- an earth wall is not a thermal insulator, and is very hard to make
safe in an earthquake.
Thanks,
Bruce "dirtbag" King
(415) 987-7271
bruce-king.com
On Aug 18, 2009, at 1:33 AM, Lorenzo Robles wrote:
> Hello Alex,
>
> yes I will try to give more detailed description _ but
> unfortunately no photos available from that beautifull old house, at
> the time the walls were opened., my long stay in Lima ended more
> than 25 years ago, though the memory is vivid. As attachment,
> there are a few photos found on the web, that illustrate somehow the
> system, an show comparison between reinforced and non-reinforced
> adobe walls.
>
> The old thick walls were about 70cm wide, and the bricks
> dismanteled by the workers looked hairy, like the handmade type
> including fiber. The fiber may have been straw, or drie local grass
> or fiber from plants ,lots of very tough growing on hillside and
> semi desertic near Lima _sorry again no botanical name to suggest.
>
> There were 2 bricks end to end across the wall,on cossing course;
> so each brick had a length of about 35 cm; the other dimensions I
> cant tell sure, perhaps like 20 and 10, .
> The netting was central, showing vertical cane sticks about 50 cm
> distant, less for the horizontal sticks, like 20 or 22cm, probably
> embracing one of every two courses of adobe bricks. As often ,
> the courses alterned parallel and transversal (crossing) layers of
> bricks. the canes were not tied, but webed _like in our grannies
> baskets.
> I remember well staying a long time to observe the dismantling
> job, and discussing with other, older people, who where
> commenting how strong ang good this netting was to help the wall
> against the hazard of collapsing after those earthquakes. A few
> weeks before, a strong shake had damagesd several houses in the area
> we lived, so these discussions ment something to everyone.
> At that time I wasnt involved in building, though feeling very
> concerned by earthquaques. I havn't had the opportunity to copy or
> adapt this combination of adobe/webed canes reinforcement, because
> my earth constructions werent really in sismical high risk areas.
>
> A tip from my humble experience:
> _for added strength, the choice of the mud or clay used for the
> adobes is very important, as they should not be able to "burst into
> dust" when dropped, once fully dried. The mud must be sticky enough,
> and a generous proportion of hcked straw or other fiber ("schaff")
> added when mixing, is structurally very good. A good test is to drop
> the dry brick from a meter hight. It should not break, or at least,
> give only 2 pieces.
>
> _think of a "crown beam" connecting from the top all 4 walls, and
> are the connection for roof or terrace beams.
>
>
> All the best,
>
> Lorenzo
>
>
>
> From: lotan-build at lotan.ardom.co.il
> To: lorobles55 at hotmail.com
> CC: jc10508 at windstream.net
> Subject: RE: [GSBN] earthquake-proof adobe walls
> Date: Mon, 17 Aug 2009 14:08:13 +0200
>
> Dear Lorenzo,
>
> The detail of the fiber net is, in your words, a critical element.
>
> Your explanation is not clear. You typed (there may be some
> incorrect letters):
> "The workers had to take brick by brick, an saw each cane to release
> de digged trough area. it took much more time than with simple
> adobe. "
>
> Please expand your description. Also, would you be able to send me,
> or post for all, some photographs of the net, a cross section of a
> wall that show the interplay between the adobe brick and the
> netting. Also, what size are the earth bricks, were they "hand"
> molded or compressed and do they have fibers (straw or other) in them?
>
> Thank you. This information is very important for our work, also a
> seismically active area, with low cost housing for Bedouins in
> southern Israel and Palestine.
>
> Alex
>
> Alex Cicelsky
> Center for Creative Ecology
> a non-profit education institute supported by
> Amuta Tzel Hatamar, Israel tax exempt no. 580347029
> Friends of Lotan, USA 501(c)(3), no. 17053031035036
> Kibbutz Lotan
> D.N. Eilot 88855 Israel
> Tel: +972-(0)54-979-9009
> Websites: www.kibbutzlotan.com
> www.birdingisrael.com
>
>
> Souhaitez vous « être au bureau sans y être » ? Oui je le veux !
> <Construction of Cane
> Reinforcement.doc>_______________________________________________
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